61 FR 8328 - Restructuring of Cylinder Specifications Requirements | Regulus

Passage 1[Federal Register Volume 61, Number 43 (Monday, March 4, 1996)] [Proposed Rules] [Pages 8328-8370] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-3554] _______________________________________________________________________ _______________________________________________________________________ Research and Special Programs Administration _______________________________________________________________________ Restructuring of Cylinder Specifications Requirements; Proposed Rule Federal Register / Vol. 61, No. 43 / Monday, March 4, 1996 / Proposed Rules Research and Special Programs Administration [Docket HM-220B; Notice No. 96-2] RIN 2137-AC81 Restructuring of Cylinder Specifications Requirements AGENCY: Research and Special Programs Administration (RSPA), DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: RSPA is proposing to revise the Hazardous Materials Regulations (HMR) by restructuring the cylinder specification requirements. The intended effect of this rulemaking is to reduce the size of the HMR through consolidation of repetitive requirements and other formatting changes. This action will eliminate pages of regulations without substantially changing the regulatory requirements or affecting safety. It is in response to President Clinton's March 4, 1995 Regulatory Reinvention Initiative memorandum to heads of departments and agencies calling for a review of all agency regulations. RSPA is also proposing to make corresponding reference changes throughout the HMR. DATES: Comments must be received on or before April 26, 1996. ADDRESSES: Please address written comments to the Dockets Unit (DHM- 30), Research and Special Programs Administration, U.S. Department of Transportation, 400 7th Street, SW., Washington, DC 20590-0001. Comments may also be faxed to (202) 366-3753. Comments should identify the docket (Docket No. HM-220B). The Dockets Unit is located in Room 8421 of the Nassif Building, 400 Seventh Street SW., Washington, DC 20590-0001. Office hours are 8:30 a.m. to 5:00 p.m., Monday through Friday, except on public holidays when the office is closed.#

Passage 2FOR FURTHER INFORMATION CONTACT: John A. Gale, (202) 366-8553; Office of Hazardous Materials Standards, RSPA, Department of Transportation, Washington, DC 20590-0001.#

Passage 3On March 4, 1995, President Clinton issued a Regulatory Reinvention Initiative memorandum to heads of departments and agencies calling for a review of all agency regulations and elimination or revision of those regulations that are outdated or in need of reform. RSPA has performed an extensive review of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) and associated procedural rules (49 CFR Parts 106 and 107) in response to the President's directive. The President also directed that front line regulators ``* * * get out of Washington and create grassroots partnerships'' with people affected by agency regulations. On April 4, 1995, RSPA published in the Federal Register (60 FR 17049) a Notice of Public Meetings and request for comment on its hazardous materials safety program. Comments were requested on ways to improve the HMR and the kind and quality of services its customers want. RSPA held seven public meetings and received over 50 comments in response to the notice. On July 28, 1995, RSPA published a second Notice of Public Meetings in the Federal Register (60 FR 38888) which announced five more public meetings that were held from September through January 1996. One area identified by RSPA in its review of the HMR was the need to reform the cylinder specifications in 49 CFR Part 178. RSPA estimates that by consolidating duplicative requirements in 23 cylinder specifications, that it will eliminate at least 40 pages from the CFR. By reformatting the specifications, RSPA proposes to eliminate over 450 sections from Part 178 of Title 49. The combined effect of these changes will be to make the regulations shorter and easier to use and help RSPA move toward a goal of being able to issue the HMR in one volume of the Code of Federal Regulations, rather than two. This rulemaking also serves as the model for a more comprehensive rulemaking, being developed by RSPA in cooperation with the Compressed Gas Association, for which a notice of proposed rulemaking is anticipated later this year. In this latter rulemaking, under Docket HM-220, RSPA intends to propose substantive changes to the cylinder specifications to accommodate contemporary manufacturing techniques, eliminate obsolete requirements, contemporize regulatory language and make safety enhancements to the regulations.#

Passage 4In this NPRM, RSPA is proposing to revise the HMR by restructuring the cylinder specification requirements in 49 CFR Part 178. The proposed restructuring of the cylinder specifications would: (1) consolidate similar sections; (2) reformat subpart C of Part 178 for consistency with the format of the rest of Part 178; and (3) revise section references throughout the HMR to correspond to the revised sections. RSPA intends to streamline the cylinder specification requirements without making substantive changes to them. Sections that have been identified by RSPA for consolidation are the sections of each specification addressing compliance, authorized inspectors, duties of the inspector, the inspector's report, record retention, defects, safety relief devices, and marking. These sections will be consolidated into a new Sec. 178.35. Proposed Sec. 178.35, entitled ``General requirements for all DOT specification cylinders'' will prescribe these general requirements for all DOT specification cylinders. However, because some of the duties of the inspector and marking requirements are specific to the individual cylinder design, some specifications would have additional marking and inspector requirements remaining in their sections. For the inspector's report, RSPA has proposed to adopt the inspector report formats in Compressed Gas Association (CGA) Pamphlet C-11, ``Recommended Practices for Inspection of Compressed Gas Cylinders at Time of Manufacture.'' The report formats can be modified to represent the inspection of specific cylinders. Additional information may be required as stated in each specification. Those sections remaining in each specification will be consolidated into a single section. Presently, each specification is set forth in approximately 22 different sections. Under this proposal, there would be only one section for each specification. For example, Specification 3B is currently set forth in 24 sections, Secs. 178.38 through 178.38- 23. In this NPRM, Specification 3B is set forth in one section, Sec. 178.38. Some of the requirements are relocated in Sec. 178.35. Sixteen of the old sections are converted to paragraphs (a) through (o) of Sec. 178.38. As an aid to the reader, the regulatory text in this notice includes all of the requirements for cylinders in the current Subpart C of part 178, even though not all of the requirements are changed. The p#

Passage 5urpose of this rulemaking action is to reduce the size of the HMR and make it easier to use. It is not intended to make substantive changes to regulatory requirements and no adverse impacts are anticipated on the regulated community. Executive Order 12866 and DOT Regulatory Policies and Procedures This proposed rule is not considered a significant regulatory action under section 3(f) of Executive Order 12866 and was not reviewed by the Office of Management and Budget. The rule is not considered significant under the regulatory policies and procedures of the Department of Transportation (44 FR 11034). The economic impact of this rule is minimal to the extent that the preparation of a regulatory evaluation is not warranted.#

Passage 6This proposed rule has been analyzed in accordance with the principles and criteria contained in Executive Order 12612 (``Federalism''). The Federal hazardous materials transportation law (49 U.S.C. 5101-5127) contains an express preemption provision that preempts State, local, and Indian tribe requirements on certain covered subjects. Covered subjects are: (i) the designation, description, and classification of hazardous material; (ii) the packing, repacking, handling, labeling, marking, and placarding of hazardous material; (iii) the preparation, execution, and use of shipping documents pertaining to hazardous material and requirements respecting the number, content, and placement of such documents; (iv) the written notification, recording, and reporting of the unintentional release in transportation of hazardous material; or (v) the design, manufacturing, fabrication, marking, maintenance, reconditioning, repairing, or testing of a package or container which is represented, marked, certified, or sold as qualified for use in the transportation of hazardous material. The Federal hazardous materials transportation law provides that if DOT issues a regulation concerning any of the covered subjects after November 16, 1990, DOT must determine and publish in the Federal Register the effective date of Federal preemption. 49 U.S.C. 5125(b)(2). That effective date may not be earlier than the 90th day following the date of issuance of the final rule and not later than two years after the date of issuance. This proposed rule deals with the packaging of compressed gases. Although this proposal does not contemplate substantive changes, RSPA solicits comments on whether the proposed rule would have any effect on State, local or Indian tribe requirements and, if so, the most appropriate effective date of Federal preemption. Because RSPA lacks discretion in this area, preparation of a federalism assessment is not warranted. I certify that this proposed rule will not have a significant economic impact on a substantial number of small entities. This proposed rule does not impose any new requirements on persons subject to the HMR. This proposed rule does not propose any new information collection requirements.#

Passage 7A regulation identifier number (RIN) is assigned to each regulatory action listed in the Unified Agenda of Federal Regulations. The Regulatory Information Service Center publishes the Unified Agenda in April and October of each year. The RIN number contained in the heading of this document can be used to cross-reference this action with the Unified Agenda. Exports, Hazardous materials transportation, Hazardous waste, Imports, Reporting and recordkeeping requirements. Hazardous materials transportation, Packaging and containers, Radioactive materials, Reporting and recordkeeping requirements, Uranium. Hazardous materials transportation, Packaging and containers, Reporting and recordkeeping requirements. In consideration of the foregoing, 49 CFR parts 171, 173, and 178 would be amended to read as follows: PART 171--GENERAL INFORMATION, REGULATIONS, AND DEFINITIONS 1. The authority citation for Part 171 would continue to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR part 1.53. 2. In Sec. 171.7(a)(3), in the table, under the entry ``Aluminum Standards and Data, Seventh Edition, June 1982'', the section reference ``178.65-5'' is revised to read ``178.65''; and under the entry Compressed Gas Association, Inc., a new entry is added in alpha- numerical order to read as follows: ------------------------------------------------------------------------ 49 CFR Source and name of material reference ------------------------------------------------------------------------ * * * * * CGA Pamphlet C-11, Recommended Practices for Inspection of Compressed Gas Cylinders at Time of Manufacture, 1993...... 178.35 * * * * * ------------------------------------------------------------------------ PART 173--SHIPPERS--GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS 3. The authority citation for Part 173 would continue to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR part 1.53.#

Passage 84. In Sec. 173.34, paragraph (h) would be amended by: a. Removing, in the first sentence, the phrase ``Secs. 178.36-9(a), 178.37-9(a), 178.38-9(a), and 178.40-9(a)'' and replacing it with the phrase ``Secs. 178.36(e), 178.37(e), 178.38(e), and 178.40(e)''. b. Removing, in the fourth sentence, the phrase ``Sec. 178.36-9(a), Sec. 178.37-9(a), Sec. 178.38-9(a), or Sec. 178.40-9(a)'' and replacing it with the phrase ``Sec. 178.36(e), Sec. 178.37(e), Sec. 178.38(e), or Sec. 178.40(e)''. 5. In Sec. 173.316, in paragraph (a)(8), the section reference ``178.57- 20(a)(4)'' would be revised to read ``178.35'' and in paragraph (c)(3)(ii) the section reference ``178.57-20'' would be revised to read ``178.35''. 6. The authority citation for Part 178 would continue to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR 1.53. 7. Subpart C of Part 178 would be revised to read as follows: Sec. 178.35 General requirements for specification cylinders. 178.36 Specifications 3A and 3AX seamless steel cylinders. 178.37 Specification 3AA and 3AAX seamless steel cylinders. 178.38 Specification 3B seamless steel cylinders. 178.39 Specification 3BN seamless nickel cylinders. 178.42 Specification 3E seamless steel cylinders. 178.44 Specification 3HT seamless steel cylinders for aircraft use. 178.45 Specification 3T seamless steel cylinder. 178.46 Specification 3AL seamless aluminum cylinders. 178.47 Specification 4DS welded stainless steel cylinders for aircraft use. 178.50 Specification 4B welded or brazed steel cylinders. 178.51 Specification 4BA welded or brazed steel cylinders. 178.53 Specification 4D welded steel cylinders for aircraft use. 178.55 Specification 4B240ET welded or brazed cylinders. 178.56 Specification 4AA480 welded steel cylinders. 178.57 Specification 4L welded insulated cylinders. 178.58 Specification 4DA welded steel cylinders for aircraft use. 178.59 Specification 8 steel cylinders with porous fillings for acetylene. 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. 178.61 Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam. 178.65 Specification 39 non-reusable (non-refillable) cylinders. 178.68 Specification 4E welded aluminum cylinders. Sec. 178.35 General requirements for specification cylinders.#

Passage 9(a) Compliance with the requirements of this subpart is required in all details. (b) Inspections and analyses. Chemical analyses and tests as specified must be made within the United States unless otherwise approved in writing by the Associate Administrator, in accordance with Sec. 173.300b of this subchapter. Inspections and verifications must be performed by-- (1) An independent inspection agency approved in writing by the Associate Administrator, in accordance with Sec. 173.300a of this subchapter; or (2) For DOT Specifications 3B, 3BN, 4B, 4BA, 4D (water capacity less than 1,100 cubic inches), 4B240ET, 4AA480, 4L, 8, 8AL, 4BW, 39 (marked service pressure 900 p.s.i.g. or lower) and 4E manufactured in the United States, a competent inspector of the manufacturer. (c) Duties of inspector. The inspector shall determine that each cylinder made is in conformance with the applicable specification. Except as otherwise specified in the applicable specification, the inspector shall perform the following: (1) Inspect all material and reject any not meeting applicable requirements. For cylinders made by the billet-piercing process, billets must be inspected and shown to be free from pipe, cracks, excessive segregation and other injurious defects after parting or, when applicable, after nick and cold break. (2) Verify the material of construction meets the requirements of the applicable specification by-- (i) Making a chemical analysis of each heat of material; (ii) Obtaining a certified chemical analysis from the material manufacturer for each heat of material (a ladle analysis is acceptable); or (iii) If an analysis is not provided for each heat of material by the material manufacturer, by making a check analysis of a sample from each coil, sheet, or tube. (3) Verify compliance of cylinders with the applicable specification by-- (i) Verifying identification of material is proper; (ii) Inspecting the inside of the cylinder before closing in ends; (iii) Verifying that the heat treatment is proper; (iv) Obtaining samples for all tests and check chemical analyses; (v) Witnessing all tests; (vi) Verify threads by gauge; (vii) Reporting volumetric capacity and tare weight (see report form) and minimum thickness of wall noted; and (viii) Verifying that each cylinder is marked in accordance with the applicable specification. (4) Furnish complete test reports required by thi#

Passage 10s subpart to the maker of the cylinder and, upon request, to the purchaser. The test report must be retained by the inspector for fifteen years from the original test date of the cylinder. (d) Defects. A cylinder may not be constructed of material with seams, cracks, laminations, or other injurious defects. (e) Safety devices and protection for valves, safety devices, and other connections, if applied, must be as required or authorized by the appropriate specification, and as required in Secs. 173.34 and 173.301 of this subchapter. (f) Markings. Markings on a DOT Specification cylinder must conform to applicable requirements. (1) Each cylinder must be marked with the following information: (i) The DOT specification marking must appear first, followed immediately by the service pressure. For example, DOT-3A1800. (ii) The serial number must be placed just below or immediately following the DOT specification marking. (iii) A symbol (letters) must be placed just below, immediately before or following the serial number. Other variations in sequence of markings are authorized only when necessitated by a lack of space. The symbol and numbers must be those of the manufacturer. The symbol must be registered with the Associate Administrator; duplications are not authorized. (iv) The inspector's official mark and date of test (such as 5-95 for May 1995) must be placed near the serial number. This information must be placed so that dates of subsequent tests can be easily added. An example of the markings prescribed in this paragraph (f)(1) is as follows: DOT-3A = specification number 1800 = service pressure 1234 = serial number xy = symbol of manufacturer AB = inspector's mark 5-95 = date of test#

Passage 11(2) Additional required marking must be applied to the cylinder as follows: (i) The word ``spun'' or ``plug'' must be placed near the DOT specification marking when an end closure in the finished cylinder has been welded by the spinning process, or effected by plugging. (ii) As prescribed in specification 3HT (Sec. 178.44) or 3T (Sec. 178.45), if applicable. (3) Marking exceptions. (i) A DOT 3E cylinder is not required to be marked with the inspector mark. (ii) An identifying lot number may be marked on the cylinder in place of a serial number for cylinders not over 2 inches outside diameter or for cylinders with a volumetric capacity not exceeding 60 cubic inches. Each lot shall not have over 500 cylinders. (4) Unless otherwise specified in the applicable specification, the markings on each cylinder must be stamped plainly and permanently on the shoulder, top head, or neck. (5) The size of each marking must be least 0.25 inch or as space permits. (6) Other markings are authorized provided they are made in low stress areas other than the side wall and are not of a size and depth that will create harmful stress concentrations. Such [[Page 8331]] marks may not conflict with any DOT required markings. (g) Inspector's report. Each inspector shall prepare a report containing, at a minimum, the applicable information listed in CGA Pamphlet C-11. Any additional information or markings that are required by the applicable specification must be shown on the test report. The signature of the inspector on the reports certifies that the processes of manufacture and heat treatment of cylinders were observed and found satisfactory. (h) Report Retention. The manufacturer of the cylinders shall retain the reports required by this subpart for 15 years from the original test date of the cylinder. Sec. 178.36 Specification 3A and 3AX seamless steel cylinders.#

Passage 12(a) Type size and service pressure. In addition to the requirements of Sec. 178.35, cylinders must conform to the following: (1) A DOT-3A cylinder is a seamless steel cylinder with a water capacity (nominal) not over 1,000 pounds and a service pressure of at least 150 pounds per square inch. (2) A DOT-3AX is a seamless stainless steel cylinder with a water capacity not less than 1,000 pounds and a service pressure of at least 500 pounds per square inch, conforming to the following requirements: (i) Assuming the cylinder is to be supported horizontally at its two ends only and to be uniformly loaded over its entire length consisting of the weight per unit of length of the straight cylindrical portion filled with water and compressed to the specified test pressure; the sum of two times the maximum tensile stress in the bottom fibers due to bending, plus that in the same fibers (longitudinal stress), due to hydrostatic test may not exceed 80 percent of the minimum yield strength of the steel at such maximum stress. Wall thickness must be increased when necessary to meet the requirement. (ii) To calculate the maximum longitudinal tensile stress due to bending, the following formula must be used: (iii) To calculate the maximum longitudinal tensile stress due to hydrostatic test pressure, the following formula must be used: S = tensile stress-p.s.i.; M = bending moment-inch pounds (wl\2\)/8; w = weight per inch of cylinder filled with water; l = length of cylinder-inches; c = radius (D)/(2) of cylinder-inches; I = moment of inertia-0.04909 (D\4\-d\4\) inches fourth; D = outside diameter-inches; d = inside diameter-inches; A1 = internal area in cross section of cylinder-square inches; A2 = area of metal in cross section of cylinder-square inches; P = hydrostatic test pressure-p.s.i.#

Passage 13(b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.55; phosphorous, 0.045; sulphur, 0.050. (c) Identification of material. Material must be identified by any suitable method, except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedures. (2) As permitted in paragraph (d) of this section. (3) Cylinders used solely in anhydrous ammonia service may have a \1/2\ inch diameter bar welded within their concave bottoms. (f) Wall thickness. For cylinders with service pressure less than 900 pounds, the wall stress may not exceed 24,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder over 5 inches outside diameter. Wall stress calculation must be made by using the following formula: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches.#

Passage 14(g) Heat treatment. The completed cylinder must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable methods, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus the test pressure cannot be maintained the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent, volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least 5/3 times service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to#

Passage 15[[Page 8332]] knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) Gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times thickness with width not over 6 times thickness is authorized when cylinder wall is not over \3/ 16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2-percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy the entire stress-strain diagram must be#

Passage 16plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation at least 40 percent for a 2-inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, the flattening test is not required. (2) An elongation at least 20 percent for a 2-inch gauge length or 10 percent in other cases and a yield strength not over 73 percent of tensile strength. In this instance, the flattening test is required, without cracking, to 6 times the wall thickness. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture subject to the following conditions and limitations: (1) Pressure, approximately the same as but no less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least 1 minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder that is leaking must be rejected. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylin#

Passage 17ders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provisions of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. Sec. 178.37 Specification 3AA and 3AAX seamless steel cylinders. (a) Type, size and service pressure. In addition to the requirements of Sec. 178.35, cylinders must conform to the following: (1) A DOT-3AA cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 1,000 pounds and a service pressure of at least 150 pounds per square inch. (2) A DOT-3AAX cylinder is a seamless steel cylinder with a water capacity of not less than 1,000 pounds and a service pressure of at least 500 pounds per square inch, conforming to the following requirements: (i) Assuming the cylinder is to be supported horizontally at its two ends only and to be uniformly loaded over its entire length consisting of the weight per unit of length of the straight cylindrical portion filled with water and compressed to the specified test pressure; the sum of two times the maximum tensile stress in the bottom fibers due to bending, plus that in the same fibers (longitudinal stress), due to hydrostatic test pressure may not exceed 80 percent of the minimum yield strength of the steel at such maximum stress. Wall thickness must be increased when necessary to meet the requirement. (ii) To calculate the maximum tensile stress due to bending, the following formula must be used: (iii) To calculate the maximum longitudinal tensile stress due to hydrostatic test pressure, the following formula must be used: S=tensile stress-p.s.i.; M=bending moment-inch pounds (wl\2\)/8; w=weight per inch of cylinder filled with water; l=length of cylinder-inches; c=radius (D)/(2) of cylinder-inches; I=moment of inertia-0.04909 (D\4\-d\4\) inches fourth; D=outside diameter-inches; d=inside diameter-inches; A\1\=internal area in cross section of cylinder-square inches; A\2\=area of metal in cross section of cylinder-square inches; P=hydrostatic test pressure-p.s.i. (b) Authorized steel. Open-hearth, basic oxygen, or electric steel of uniform#

Passage 18[[Page 8333]] quality must be used. A heat of steel made under the specifications in Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerance shown in Table 2 of this paragraph (b) are not exceeded. When a carbon-boron steel is used, a hardenability test must be performed on the first and last ingot of each heat of steel. The results of this test must be recorded on the Record of Chemical Analysis of Material for Cylinders required by Sec. 178.35. This hardness test must be made \5/16\-inch from the quenched end of the Jominy quench bar and the hardness must be at least Rc 33 and no more than Rc 53. The following chemical analyses are authorized:#

Passage 19Table 1.--Authorized Materials -------------------------------------------------------------------------------------------------------------------------------------------------------- Intermediate Designation 4130X (percent) NE-8630 (percent) 9115 (percent) (see 9125 (percent) Carbon-boron manganese (see Note 1) (see Note 1) Note 1) (see Note 1) (percent) (percent) -------------------------------------------------------------------------------------------------------------------------------------------------------- Carbon....................... 0.25/0.35.......... 0.28/0.33.......... 0.10/0.20.......... 0.20/0.30......... 0.27-0.37......... 0.40 max. Manganese.................... 0.40/0.90.......... 0.70/0.90.......... 0.50/0.75.......... 0.50/0.75......... 0.80-1.40......... 1.35/1.65 Phosphorus................... 0.04 max........... 0.04 max........... 0.04 max........... 0.04 max.......... 0.035 max......... 0.04 max. Sulfur....................... 0.05 max........... 0.04 max........... 0.04 max........... 0.04 max.......... 0.045 max......... 0.05 max. Silicon...................... 0.15/0.35.......... 0.20/0.35.......... 0.60/0.90.......... 0.60/0.90......... 0.3 max........... 0.10/0.30 Chromium..................... 0.80/1.10.......... 0.40/0.60.......... 0.50/0.65.......... 0.50/0.65......... .................. .................. Molybdenum................... 0.15/0.25.......... 0.15/0.25.......... ................... .................. .................. .................. Zirconium.................... ................... ................... 0.05/0.15.......... 0.05/0.15......... .................. .................. Nickel....................... ................... 0.40/0.70.......... ................... .................. .................. .................. Boron........................ ................... ................... ................... .................. 0.0005/0.003 .................. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note 1: This designation may not be restrictive and the commercial steel is limited in analysis as shown in this Table 1.#

Passage 20Table 2.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the Limit or maximum specified minimum limit Element (percent) ------------------------------- Under minimum Over maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon........................................ To 0.15 incl.................... 0.02 0.03 Over 0.15 to 0.40 incl.......... .03 .04 Manganese..................................... To 0.60 incl.................... .03 .03 Over 0.60 to 1.15 incl.......... .04 .04 Over 1.15 to 2.50 incl.......... .05 .05 Phosphorus \1\................................ All ranges...................... .............. .01 Sulphur....................................... All ranges...................... .............. .01 Silicon....................................... To 0.30 incl.................... .02 .03 Over 0.30 to 1.00 incl.......... .05 .05 Nickel........................................ To 1.00 incl.................... .03 .03 Chromium...................................... To 0.90 incl.................... .03 .03 0.90 to 2.90 incl............... .05 .05 Molybdenum.................................... To 0.20 incl.................... .01 .01 Over 0.20 to 0.40............... .02 .02 Zirconium..................................... All ranges...................... .01 .05 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus.#

Passage 21(c) Identification of material. Material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defects is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedure. (2) As permitted in paragraph (d) of this section. (f) Wall thickness. The thickness of each cylinder must conform to the following: (1) For cylinders with a service pressure of less than 900 pounds, the wall stress may not exceed 24,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder with an outside diameter of over 5 inches. (2) For cylinders with service pressure of 900 p.s.i. or more the minimum wall must be such that the wall stress at the [[Page 8334]] minimum specified test pressure may not exceed 67 percent of the minimum tensile strength of the steel as determined from the physical tests required in paragraphs (k) and (l) of this section and must be not over 70,000 p.s.i. (3) Calculation must be made by the formula:#

Passage 22S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches.#

Passage 23(g) Heat treatment. The completed cylinders must be uniformly and properly heat treated prior to tests. Heat treatment of cylinders of the authorized analyses must be as follows: (1) All cylinders must be quenched by oil, or other suitable medium except as provided in paragraph (g)(5) of this section. (2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1750 deg.F. (3) All steels must be tempered at a temperature most suitable for that steel. (4) The minimum tempering temperature may not be less than 1000 deg.F except as noted in paragraph (l)(vi) of this section. (5) Steel 4130X may be normalized at a temperature of 1650 deg.F instead of being quenched and cylinders so normalized need not be tempered. (6) Intermediate manganese steels may be tempered at temperatures not less than 1150 deg.F, and after heat treating each cylinder must be submitted to a magnetic test to detect the presence of quenching cracks. Cracked cylinders must be rejected and destroyed. (7) Except as otherwise provided in paragraph (g)(6) of this section, all cylinders, if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle, dye penetrant or ultrasonic method to detect the presence of quenching cracks. Any cylinder designed to the requirements for specification 3AA and found to have a quenching crack must be rejected and may not be requalified. Cylinders designed to the requirements for specification 3AAX and found to have cracks must have cracks removed to sound metal by mechanical means. Such specification 3AAX cylinders will be acceptable if the repaired area is subsequently examined to assure no defect, and it is determined that design thickness requirements are met. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of a length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) H#

Passage 24ydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least \5/3\ times the service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out of each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to the same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) Gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times the thickness with width not over 6 times thickness when the thickness of the cylinder wall is not over \3/16\ inch. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip e#

Passage 25nds may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. An acceptable result for physical and flattening tests is elongation at least 20 percent for 2#

Passage 26[[Page 8335]] inches of gauge length or at least 10 percent in other cases. Flattening is required without cracking to 6 times the wall thickness of the cylinder. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture. Pressure, approximately the same as but no less than the service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder must be rejected if there is any leaking. (1) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (2) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (3) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provision of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. Sec. 178.38 Specification 3B seamless steel cylinders.#

Passage 27(a) Type, size, and service pressure. A DOT 3B cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 1,000 pounds and a service pressure of at least 150 to not over 500 pounds per square inch. (b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: carbon, 0.55; phosphorus, 0.045; sulphur, 0.050. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses to be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedure. (2) As permitted in paragraph (d) of this section. (f) Wall thickness. The wall stress may not exceed 24,000 pounds per square inch. The minimum wall thickness is 0.090 inch for any cylinder with an outside diameter of 6 inches. Calculation must be made by the following formula: where: S=wall stress in pounds per square inch; P=at least two times service pressure or 450 pounds per square inch, whichever is the greater; D=outside diameter in inches; d=inside diameter in inches.#

Passage 28(g) Heat treatment. The completed cylinders must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads, conforming to the following, are required on all openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads when used, must be of a length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 4 engaged threads are authorized. Straight threads must have a tight fit, and calculated shear strength at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Cylinders must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to insure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) Each cylinder; to at least 2 times service pressure; or (ii) 1 cylinder out of each lot of 200 or less; to at least 3 times service pressure. Others must be examined under pressure of 2 times service pressure and show no defect. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment#

Passage 29as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following:#

Passage 30(i) Gauge length of 8 inches with a width of not over 1\1/2\ inches; or a gauge length of 2 inches with a width of not over 1\1/2\ inches; or a gauge length at least 24 times the thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation of at least 40 percent for a 2-inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, the#

Passage 31flattening test is not required. (2) An elongation of at least 20 percent for a 2-inch gauge length or 10 percent in other cases and yield strength not over 73 percent of tensile strength. Flattening is required, without cracking, to 6 times the wall thickness. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions and limitations: (1) Pressure, approximately the same as but no less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder must be rejected if there is any leaking. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, he should design his apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provisions of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. (o) Marking. Markings may be stamped into the sidewalls of cylinders having a service pressure of 150 psi if all of the following conditions are met: (1) Wall stress at test pressure may not exceed 24,000 psi. (2) Minimum wall thickness must be not less than 0.090 inch. (3) Depth of stamping must be no greater than 15 percent of the minimum wall thickness, but may not exceed 0.015 inch. (4) Maximum outside diameter of cylinder may not exceed 5 inches.#

Passage 32(5) Carbon content of cylinder may not exceed 0.25 percent. If the carbon content exceeds 0.25 percent, the complete cylinder must be normalized after stamping. (6) Stamping must be adjacent to the top head. Sec. 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water capacity (nominal) not over 125 pounds water capacity (nominal) and a service pressure at least 150 to not over 500 pounds per square inch. (b) Nickel. The percentage of nickel plus cobalt must be at least 99.0 percent. (c) Identification of material. The material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Cylinders closed in by spinning process are not authorized. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except that welding is authorized for the attachment of neckrings and footrings which are nonpressure parts, and only to the tops and bottoms of cylinders. Neckrings and footrings must be of weldable material, the carbon content of which may not exceed 0.25 percent. Nickel welding rod must be used. (f) Wall thickness. The wall stress may not exceed 15,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder over 5 inches in outside diameter. Wall stress calculation must be made by using the following formula: S=Wall stress in pounds per square inch; P=Minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=Outside diameter in inches; d=Inside diameter in inches. (g) Heat treatment. The completed cylinders must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge.#

Passage 33(2) Taper threads, when used, to be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least 2 times service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\ inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i)#

Passage 34A gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times the thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, and the strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation of at least 40 percent for a 2 inch gauge length or at least 20 percent in other cases and yield point not over 50 percent of tensile strength. In this instance, the f#

Passage 35lattening test is not required. (2) An elongation of at least 20 percent for a 2 inch gauge length or 10 percent in other cases and a yield point not over 50 percent of tensile strength. Flattening is required, without cracking, to 6 times the wall thickness. (m) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding is not authorized. Sec. 178.42 Specification 3E seamless steel cylinders.#

Passage 36(a) Type, size, and service pressure. A DOT 3E cylinder is a seamless steel cylinder with an outside diameter not greater than 2 inches nominal, a length less than 2 feet and a service pressure of 1,800 pounds per square inch. (b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.55; phosphorus, 0.045; sulphur, 0.050. (c) Identification of steel. Materials must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured by best appliances and methods. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. The thickness of the spun bottom is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thickness must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 4 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (f) Hydrostatic test. Cylinders must be tested as follows: (1) One cylinder out of each lot of 500 or less must be subjected to a hydrostatic pressure of 6,000 pounds per square inch or higher. (2) The cylinder referred to in paragraph (f)(1) of this section must burst at a pressure higher than 6,000 pounds per square inch without fragmenting or otherwise showing lack of ductility, or must hold a pressure of#

Passage 37[[Page 8338]] 12,000 pounds per square inch for 30 seconds without bursting. In which case, it must be subjected to a flattening test without cracking to six times wall thickness between knife edges, wedge shaped 60 degree angle, rounded out to a \1/2\ inch radius. The inspector's report must be suitably changed to show results of latter alternate and flattening test. (3) Other cylinders must be examined under pressure of at least 3,000 pounds per square inch and not to exceed 4,500 pounds per square inch and show no defect. Cylinders tested at a pressure in excess of 3,600 pounds per square inch must burst at a pressure higher than 7,500 pounds per square inch when tested as specified in paragraph (f)(2) of this section. The pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete examination. (g) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture subject to the following conditions and limitations: (1) A pressure, approximately the same as but not less than the service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Accept as provided in paragraph (h) of this section, a cylinder must be rejected if there is any leakage. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer shall design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (h) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the prov#

Passage 38isions of paragraph (g) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. (i) Marking. Markings required by Sec. 178.35 must be stamped plainly and permanently on the shoulder, top head, neck or sidewall of each cylinder. Sec. 178.44 Specification 3HT seamless steel cylinders for aircraft use. (a) Type, size and service pressure. A DOT 3HT cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 150 pounds and a service pressure of at least 900 pounds per square inch. (b) Authorized steel. Open hearth or electric furnace steel of uniform quality must be used. A heat of steel made under the specifications listed in Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 of this paragraph (b) are not exceeded. Grain size 6 or finer according to ASTM Spec. E19-46. Steel of the following chemical analysis is authorized: Designation................................................ AISI 4130 (percent) Carbon..................................................... 0.28/0.33 Manganese.................................................. 0.40/0.60 Phosphorus................................................. 0.040 maximum Sulfur..................................................... 0.040 maximum Silicon.................................................... 0.15/0.35 Chromium................................................... 0.80/1.10 Molybdenum................................................. 0.18/0.25.#

Passage 39Table 2--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the Limit or maximum specified minimum limit Element (percent) ------------------------------- Under minimum Over maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon..................................... Over 0.15 to 0.40 incl............. .03 .04 Manganese.................................. To 0.60 incl....................... .03 .03 Phosphorus \1\............................. All ranges......................... .............. .01 Sulphur.................................... All ranges......................... .............. .01 Silicon.................................... To 0.30 incl....................... .02 .03 Over 0.30 to 1.00 incl............. .05 .05 Chromium................................... To 0.90 incl....................... .03 .03 Over 0.90 to 2.10 incl............. .05 .05 Molybdenum................................. To 0.20 incl....................... .01 .01 Over 0.20 to 0.40 incl............. .02 .02 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus. (c) Identification of material. Material must be identified by any suitable method. Steel stamping of heat identifications may not be made in any area which will eventually become the side wall of the cylinder. Depth of stamping may not encroach upon the minimum prescribed wall thickness of the cylinder.#

Passage 40(d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished container appreciably. The general surface finish may not exceed a roughness of 250 RMS. Individual irregularities such as draw marks, scratches, pits, etc., should be held to a minimum consistent with good high stress pressure vessel manufacturing practices. If the cylinder is not originally free of such defects or does not meet the finish requirements, the surface may be machined or otherwise treated to eliminate these defects. The point of closure of cylinders closed by spinning may not be less than two times the prescribed wall thickness of the cylindrical shell. The cylinder end contour must be hemispherical or ellipsoidal with a ratio of major-to-minor axis not exceeding two to one and with the concave side to pressure. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited, except that welding by spinning is permitted to close the bottom of spun cylinders. Machining or grinding to produce proper surface finish at point of closure is required. (f) Wall thickness. (1) Minimum wall thickness for any cylinder must be 0.050 inch. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure may not exceed 75 percent of the minimum tensile strength of the steel as determined from the physical tests required in paragraph (m) of this section and may not be over 105,000 psi. (2) Calculations must be made by the formula: where: S=Wall stress in pounds per square inch; P=Minimum test pressure prescribed for water jacket test; D=Outside diameter in inches; d=Inside diameter in inches.#

Passage 41(3) Wall thickness of hemispherical bottoms only permitted to 90 percent of minimum wall thickness of cylinder sidewall but may not be less than 0.050 inch. In all other cases, thickness to be no less than prescribed minimum wall. (g) Heat treatment. The completed cylinders must be uniformly and properly heated prior to tests. Heat treatment of the cylinders of the authorized analysis must be as follows: (1) All cylinders must be quenched by oil, or other suitable medium. (2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1750 deg. F. (3) The steel must be tempered at a temperature most suitable for the particular steel analysis but not less than 850 deg. F. (4) All cylinders must be inspected by the magnetic particle or dye penetrant method to detect the presence of quenching cracks. Any cylinder found to have a quenching crack must be rejected and may not be requalified. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings: (1) Threads must be clean cut, even, without cracks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for National Gas Tapered Thread (NGT) as required by American Standard Compressed Gas Cylinder Valve Outlet and Inlet Connections. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear stress of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. Pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent of 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inc#

Passage 42h, which ever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least 5/3 times service pressure. (j) Cycling tests. Prior to the initial shipment of any specific cylinder design, cyclic pressurization tests must have been performed on at least three representative samples without failure as follows: (1) Pressurization must be performed hydrostatically between approximately zero psig and the service pressure at a rate not in excess of 10 cycles per minute. Adequate recording instrumentation must be provided if equipment is to be left unattended for periods of time. (2) Tests prescribed in paragraph (j)(1) of this section must be repeated on one random sample out of each lot of cylinders. The cylinder may then be subjected to a burst test. (3) A lot is defined as a group of cylinders fabricated from the same heat of steel, manufactured by the same process and heat treated in the same equipment under the same conditions of time, temperature, and atmosphere, and may not exceed a quantity of 200 cylinders. (4) All cylinders used in cycling tests must be destroyed. (k) Burst test. One cylinder taken at random out of each lot of cylinders must be hydrostatically tested to destruction. (l) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (m) Physical tests. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material , as follows: (1) Test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of cylinders. (2) Specimens must conform to the following: (i) A gauge length of at least 24 times the thickness with a width not over six times the thickness. The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. When size of#

Passage 43cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with the record of physical tests detailed information in regard to such specimens. (ii) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length.#

Passage 44(i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (n) Magnetic particle inspection. Inspection must be performed on the inside of each container before closing and externally on each finished container after heat treatment. Evidence of discontinuities, which in the opinion of a qualified inspector may appreciably weaken or decrease the durability of the cylinder, must be cause for rejection. (o) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by dry gas or dry air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions and limitations: (1) Pressure, approximately the same as but not less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (q) of this section, a cylinder must be rejected if there is leakage. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been eff#

Passage 45ected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (p) Acceptable results of tests. Results of the flattening test, physical tests, burst test, and cycling test must conform to the following: (1) Flattening required without cracking to ten times the wall thickness of the cylinder. (2) Physical tests: (i) An elongation of at least 6 percent for a gauge length of 24 times the wall thickness. (ii) The tensile strength may not exceed 165,000 p.s.i. (3) The burst pressure must be at least \3/4\ times the test pressure. (4) Cycling-at least 10,000 pressurizations. (q) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. For each cylinder subjected to reheat treatment during original manufacture, sidewall measurements must be made to verify that the minimum sidewall thickness meets specification requirements after the final heat treatment. (r) Marking. (1) Cylinders must be marked by low stress type steel stamping in an area and to a depth which will insure that the wall thickness measured from the root of the stamping to the interior surface is equal to or greater than the minimum prescribed wall thickness. Stamping must be permanent and legible. Stamping on side wall not authorized. (2) The rejection elastic expansion (REE), in cubic centimeters (cc), must be marked on the cylinder near the date of test. The REE for a cylinder is 1.05 times its original elastic expansion. (3) Name plates are authorized, provided that they can be permanently and securely attached to the cylinder. Attachment by either brazing or welding is not permitted. Attachment by soldering is permitted provided steel temperature does not exceed 500 deg.F. (s) Inspector's report. In addition to the requirements of Sec. 178.35, the inspector's report must indicate the rejection elastic expansion (REE), in cubic centimeters (cc). Sec. 178.45 Specification 3T seamless steel cylinder.#

Passage 46(a) Type, size, and service pressure. A DOT 3T cylinder is a seamless steel cylinder with a minimum water capacity of 1,000 pounds and a minimum service pressure of 1,800 p.s.i. Each cylinder must have integrally formed heads concave to pressure at both ends. The inside head shape must be hemispherical, ellipsoidal in which the major axis is two times the minor axis, or a dished shape falling within these two limits. Permanent closures formed by spinning are prohibited. (b) Material, steel. Only open hearth, basic oxygen, or electric furnace process steel of uniform quality is authorized. The steel analysis must conform to the following: Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Check analysis Element Ladle analysis ------------------------------- Under Over ---------------------------------------------------------------------------------------------------------------- Carbon..................................... 0.35 to 0.50....................... 0.03 0.04 Manganese.................................. 0.75 to 1.05....................... .04 .04 Phosphorus (max)........................... 0.035.............................. .............. .01 Sulphur (max).............................. .04................................ .............. .01 Silicon.................................... 0.15 to 0.35....................... .02 .03 Chromium................................... 0.80 to 1.15....................... .05 .05 Molybdenum................................. 0.15 to 0.25....................... .02 .02 ---------------------------------------------------------------------------------------------------------------- (1) A heat of steel made under the specifications in the table in this paragraph (b), the ladle analysis of which is slightly out of the specified range, is acceptable if satisfactory in all other aspects. However, the check#

Passage 47[[Page 8341]] analysis tolerances shown in the table in this paragraph (b) may not be exceeded except as approved by the Department. (2) Material with seams, cracks, laminations, or other injurious defects is not permitted. (3) Material used must be identified by any suitable method. (c) Manufacture. General manufacturing requirements are as follows: (1) Surface finish must be uniform and reasonably smooth. (2) Inside surfaces must be clean, dry, and free of loose particles. (3) No defect of any kind is permitted if it is likely to weaken a finished cylinder. (4) If the cylinder surface is not originally free from the defects, the surface may be machined or otherwise treated to eliminate these defects provided the minimum wall thickness is maintained. (5) Welding or brazing on a cylinder is not permitted. (d) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure does not exceed 67 percent of the minimum tensile strength of the steel as determined by the physical tests required in paragraphs (j) and (k) of this section. A wall stress of more than 90,500 p.s.i. is not permitted. The minimum wall thickness for any cylinder may not be less than 0.225 inch. (1) Calculation of the stress for cylinders must be made by the following formula: S=Wall stress in pounds per square inch; P=Minimum test pressure, at least 5/3 service pressure; D=Outside diameter in inches; d=Inside diameter in inches. (2) Each cylinder must meet the following additional requirement which assumes a cylinder horizontally supported at its two ends and uniformly loaded over its entire length. This load consists of the weight per inch of length of the straight cylindrical portion filled with water compressed to the specified test pressure. The wall thickness must be increased when necessary to meet this additional requirement: (i) The sum of two times the maximum tensile stress in the bottom fibers due to bending (see paragraph (d)(2)(ii) of this section), plus the maximum tensile stress in the same fibers due to hydrostatic testing (see paragraph (d)(2)(iii) of this section) may not exceed 80 percent of the minimum yield strength of the steel at this maximum stress. (ii) The following formula must be used to calculate the maximum tensile stress due to bending:#

Passage 48S=Tensile stress in pounds per square inch; M=Bending moment in inch-pounds (wl2/8); I=Moment of inertia-0.04909 (D4-d4) in inches fourth; c=Radius (D/2) of cylinder in inches; w=Weight per inch of cylinder filled with water; l=Length of cylinder in inches; D=Outside diameter in inches; d=Inside diameter in inches. (iii) The following formula must be used to calculate the maximum longitudinal tensile stress due to hydrostatic test pressure: S=Tensile stress in pounds per square inch; A1=Internal area in cross section of cylinder in square inches; P=Hydrostatic test pressure in pounds per square, inch; A2=Area of metal in cross section of cylinder in square inches.#

Passage 49(e) Heat treatment. Each completed cylinder must be uniformly and properly heat treated prior to testing, as follows: (1) Each cylinder must be heated and held at the proper temperature for at least one hour per inch of thickness based on the maximum thickness of the cylinder and then quenched in a suitable liquid medium having a cooling rate not in excess of 80 percent of water. The steel temperature on quenching must be that recommended for the steel analysis, but it must never exceed 1750 deg.F. (2) After quenching, each cylinder must be reheated to a temperature below the transformation range but not less than 1050 deg.F., and must be held at this temperature for at least one hour per inch of thickness based on the maximum thickness of the cylinder. Each cylinder must then be cooled under conditions recommended for the steel. (f) Openings. Openings in cylinders must comply with the following: (1) Openings are permitted on heads only. (2) The size of any centered opening in a head may not exceed one half the outside diameter of the cylinder. (3) Openings in a head must have ligaments between openings of at least three times the average of their hole diameter. No off-center opening may exceed 2.625 inches in diameter. (4) All openings must be circular. (5) All openings must be threaded. Threads must be in compliance with the following: (i) Each thread must be clean cut, even, without any checks, and to gauge. (ii) Taper threads, when used, must be the American Standard Pipe thread (NPT) type and must be in compliance with the requirements of NBS Handbook H-28, Part II, Section VII. (iii) Taper threads conforming to National Gas Taper thread (NGT) standards must be in compliance with the requirements of NBS Handbook H-28, Part II, Sections VII and IX. (iv) Straight threads conforming with National Gas Straight thread (NGS) standards are authorized. These threads must be in compliance with the requirements of NBS Handbook H-28, Part II, Sections VII and IX. (g) Hydrostatic test. Each cylinder must be tested at an internal pressure by the water jacket method or other suitable method, conforming to the following requirements: (1) The testing apparatus must be operated in a manner that will obtain accurate data. Any pressure gauge used must permit reading to an accuracy of one percent. Any expansion gauge used must permit reading of the total expansion to an ac#

Passage 50curacy of one percent. (2) Any internal pressure applied to the cylinder after heat treatment and before the official test may not exceed 90 percent of the test pressure. (3) The pressure must be maintained sufficiently long to assure complete expansion of the cylinder. In no case may the pressure be held less than 30 seconds. (4) If, due to failure of the test apparatus, the required test pressure cannot be maintained, the test must be repeated at a pressure increased by 10 percent or 100 p.s.i., whichever is lower or, the cylinder must be reheat treated. (5) Permanent volumetric expansion of the cylinder may not exceed 10 percent of its total volumetric expansion at the required test pressure. (6) Each cylinder must be tested to at least 5/3 times its service pressure. (h) Ultrasonic examination. After the hydrostatic test, the cylindrical section of each vessel must be examined in accordance with ASTM Standard A-388-67 using the angle beam technique. The equipment used must be calibrated to detect a notch equal to five percent of the design minimum wall thickness. Any discontinuity indication greater than that produced by the five percent notch must be cause for rejection of the#

Passage 51[[Page 8342]] cylinder unless the discontinuity is repaired within the requirements of this specification. (i) Basic requirements for tension and Charpy impact tests. Cylinders must be subjected to a tension and Charpy impact as follows: (1) When the cylinders are heat treated in a batch furnace, two tension specimens and three Charpy impact specimens must be tested from one of the cylinders or a test ring from each batch. The lot size represented by these tests may not exceed 200 cylinders. (2) When the cylinders are heat treated in a continuous furnace, two tension specimens and three Charpy impact specimens must be tested from one of the cylinders or a test ring from each four hours or less of production. However, in no case may a test lot based on this production period exceed 200 cylinders. (3) Each specimen for the tension and Charpy impact tests must be taken from the side wall of a cylinder or from a ring which has been heat treated with the finished cylinders of which the specimens must be representative. The axis of the specimens must be parallel to the axis of the cylinder. Each cylinder or ring specimen for test must be of the same diameter, thickness, and metal as the finished cylinders they represent. A test ring must be at least 24 inches long with ends covered during the heat treatment process so as to simulate the heat treatment process of the finished cylinders it represents. (4) A test cylinder or test ring need represent only one of the heats in a furnace batch provided the other heats in the batch have previously been tested and have passed the tests and that such tests do not represent more than 200 cylinders from any one heat. (5) The test results must conform to the requirements specified in paragraphs (j) and (k) of this section. (6) When the test results do not conform to the requirements specified, the cylinders represented by the tests may be reheat treated and the tests repeated. Paragraph (i)(5) of this section applies to any retesting. (j) Basic conditions for acceptable physical testing. The following criteria must be followed to obtain acceptable physical test results: (1) Each tension specimen must have a gauge length of two inches with a width not exceeding one and one-half inches. Except for the grip ends, the specimen may not be flattened. The grip ends may be flattened to within one inch of each end of the reduced sectio#

Passage 52n. (2) A specimen may not be heated after heat treatment specified in paragraph (d) of this section. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gage length. (i) This yield strength must be determined by the ``offset'' method or the ``extension under load'' method described in ASTM Standard E8- 69. (ii) For the ``extension under load'' method, the total strain (or extension under load) corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gage length under appropriate load and adding thereto 0.2 percent of the gage length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. However, when the degree of accuracy of this method is questionable the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set with the specimen under a stress of 12,000 p.s.i. and the strain indicator reading set at the calculated corresponding strain. (iv) The cross-head speed of the testing machine may not exceed \1/ 8\ inch per minute during the determination of yield strength. (4) Each impact specimen must be Charpy V-notch type size 10 mm x 10 mm taken in accordance with paragraph 11 of ASTM Standard A-333-67. When a reduced size specimen is used, it must be the largest size obtainable. (k) Acceptable physical test results. Results of physical tests must conform to the following: (1) The tensile strength may not exceed 155,000 p.s.i. (2) The elongation must be at least 16 percent for a two-inch gage length. (3) The Charpy V-notch impact properties for the three impact specimens which must be tested at 0 deg. F may not be less than the values shown as follows:#

Passage 53------------------------------------------------------------------------ Average value for Minimum value (1 Size of specimen (mm) acceptance (3 specimen only of specimens) the 3) ------------------------------------------------------------------------ 10.0 x 10.0................... 25.0 ft. lbs...... 20.0 ft. lbs. 10.0 x 7.5.................... 21.0 ft. lbs...... 17.0 ft. lbs. 10.0 x 5.0.................... 17.0 ft. lbs...... 14.0 ft. lbs. ------------------------------------------------------------------------ (4) After the final heat treatment, each vessel must be hardness tested on the cylindrical section. The tensile strength equivalent of the hardness number obtained may not be more than 165,000 p.s.i. (Rc 36). When the result of a hardness test exceeds the maximum permitted, two or more retests may be made; however, the hardness number obtained in each retest may not exceed the maximum permitted. (l) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. However, each reheat treated cylinder must subsequently pass all the prescribed tests. Repair by welding is not authorized. (m) Markings. Marking must be done by stamping into the metal of the cylinder. All markings must be legible and located on a shoulder. (n) Inspector's report. In addition to the requirements of Sec. 178.35, the inspector's report for the physical test report, must indicate the average value for three specimens and the minimum value for one specimen for each lot number. Sec. 178.46 Specification 3AL seamless aluminum cylinders. (a) Size and service pressure. A DOT 3AL cylinder is a seamless aluminum cylinder with a maximum water capacity of 1000 pounds and minimum service pressure of 150 psig. (b) Authorized material and identification of material. The material of construction must meet the following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks, laminations, or other defects likely to weaken the finished cylinder may not be used. (3) Material must be identified by a suitable method that will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number and the lot number. (4) The material must be of uniform quality. Only the following heat treatable aluminum alloys in Tables 1 and 2 of this paragraph (b)(4) are permitted:#

Passage 54Table 1.--Chemical Composition Limits\1\ [Chemical composition (in weight percent)] -------------------------------------------------------------------------------------------------------------------------------------------------------- Other \2\ Aluminum Assoc. alloy Si Fe Cu Mn Mg Cr Zn Ti Pb Bi -------------- Al designation No. Each Total -------------------------------------------------------------------------------------------------------------------------------------------------------- 6351......................... 0.7-1.3 0.50 0.10 0.40-0.80 0.40-0.80 ......... 0.20 0.20 0.01 0.01 0.05 0.15 Remainder. 6061......................... 0.40-0.80 .70 0.15-0.40 0.15 0.80-1.20 0.04-0.35 .25 .15 .01 .01 .05 .15 Remainder. -------------------------------------------------------------------------------------------------------------------------------------------------------- \1\ ASTM B 221-76 Standard Specification for Aluminum Alloy Extruded Bars, Rods, Shapes, and Tubes, Table 1 Chemical Composition Limits, Except for Pb and Bi. Limits are in percent maximum unless otherwise indicated. \2\ Analysis is regularly made only for the elements for which specific limits are shown, except for unalloyed aluminum. If however, the presence of other elements is suspected to be, or in the course of routine analysis is indicated to be in excess of specified limits, further analysis is made to determine that these other elements are not in excess of the amounts specified. (Aluminum Association Standards and Data/6th Edition, 1979).#

Passage 55Table 2--Mechanical Property Limits ---------------------------------------------------------------------------------------------------------------- Tensile strength--PSI Elongation-- -------------------------------- percent Alloy and temper minimum for Ultimate-- Yield-minimum 2'' or 4D\1\ minimum size specimen ---------------------------------------------------------------------------------------------------------------- 6351-T6......................................................... 42,000 37,000 \2\ 14 6061-T6......................................................... 38,000 35,000 \2\ 14 ---------------------------------------------------------------------------------------------------------------- \1\ ``D'' represents specimen diameters. When the cylinder wall is greater than \3/16\-inch thick, a retest without reheat treatment using the 4D size specimen is authorized if the test using the 2 inch size specimen fails to meet elongation requirements. \2\ When cylinder wall is not over \3/16\-inch thick, 10 percent elongation is authorized when using a 24t x 6t size test specimen.#

Passage 56(5) All starting stock must be 100 percent ultrasonically inspected, along the length at right angles to the central axis from two positions at 90 deg. to one another. The equipment and continuous scanning procedure must be capable of detecting and rejecting internal defects such as cracks which have an ultrasonic response greater than that of a calibration block with a \5/64\-inch diameter flat bottomed hole. (6) Cast stock must have uniform equiaxed grain structure not to exceed 500 microns maximum. (7) Any starting stock not complying with the above must be rejected. (c) Manufacture. Cylinders must be manufactured in accordance with the following requirements: (1) Cylinder shells must be manufactured by the backward extrusion method and have a cleanliness level adequate to ensure proper inspection. No fissure or other defect is acceptable that is likely to weaken the finished cylinder below the design strength requirements. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise conditioned to eliminate these defects. (2) Thickness of the cylinder base may not be less than the prescribed minimum wall thickness of the cylindrical shell. The cylinder base must have a basic torispherical, hemispherical, or ellipsoidal interior base configuration where the dish radius is no greater than 1.2 times the inside diameter of the shell. The knuckle radius may not be less than 12 percent of the inside diameter of the shell. The interior base contour may deviate from the true torispherical, hemispherical or ellipsoidal configuration provided that-- (i) Any areas of deviation are accompanied by an increase in base thickness; (ii) All radii of merging surfaces are equal to or greater than the knuckle radius; (iii) Each design has been qualified by successfully passing the cycling tests in paragraph (c) of this section; and (iv) Detailed specifications of the base design are available to the inspector. (3) For free standing cylinders, the base thickness must be at least two times the minimum wall thickness along the line of contact between the cylinder base and the floor when the cylinders are in the vertical position. (4) Welding or brazing is prohibited. (5) Each new design and any significant change to any acceptable design must be qualified for production by testing prototype sampl#

Passage 57es as follows: (i) Three samples must be subjected to 100,000 pressure reversal cycles between zero and service pressure or 10,000 pressure reversal cycles between zero and test pressure, at a rate not in excess of 10 cycles per minute without failure. (ii) Three samples must be pressurized to destruction and failure may not occur at less than 2.5 times the marked cylinder service pressure. Each cylinder must remain in one piece. Failure must initiate in the cylinder sidewall in a longitudinal direction. Rate of pressurization may not exceed 200 psi per second. (6) In this specification ``significant change'' means a 10 percent or greater change in cylinder wall thickness, service pressure, or diameter; a 30 percent or greater change in water capacity or base thickness; any change in material; over 100 percent increase in size of openings; or any change in the number of openings. (d) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure will not exceed 80 percent of the minimum yield strength nor exceed 67 percent of the minimum ultimate tensile strength as verified by physical tests in paragraph (i) of this section. The minimum wall thickness for any cylinder with an outside diameter greater than 5 inches must be 0.125 inch. Calculations must be made by the following formula: S=Wall stress in pounds per square inch; P=Prescribed minimum test pressure in pounds per square inch (see paragraph (g) of this section); D=Outside diameter in inches; and d=Inside diameter in inches. (e) Openings. Openings must comply with the following requirements: (1) Openings are permitted in heads only.#

Passage 58(2) The size of any centered opening in a head may not exceed one- half the outside diameter of the cylinder. (3) Other openings are permitted in the head of a cylinder if: (i) Each opening does not exceed 2.625 inches in diameter, or one- half the outside diameter of the cylinder; whichever is less; (ii) Each opening is separated from each other by a ligament; and (iii) Each ligament which separates two openings must be at least three times the average of the diameters of the two openings. (4) All openings must be circular. (5) All openings must be threaded. Threads must comply with the following: (i) Each thread must be clean cut, even, without checks, and to gauge. (ii) Taper threads, when used, must conform to one of the following: (A) American Standard Pipe Thread (NPT) type, conforming to the requirements of Federal Standard H-28 (1978), Section 7; (B) National Gas Taper Thread (NGT) type, conforming to the requirements of Federal Standard H-28 (1978), Sections 7 and 9; or (C) Other taper threads conforming to other standards may be used provided the length is not less than that specified for NPT threads. (iii) Straight threads, when used, must conform to one of the following: (A) National Gas Straight Thread (NGS) type, conforming to the requirements of Federal Standard H-28, (1978), Sections 7 and 9; (B) Unified Thread (UN) type, conforming to the requirements of Federal Standard H-28, (1978), Section 2; (C) Controlled Radius Root Thread (UN) type, conforming to the requirements of Federal Standard H-28 (1978), Section 4; or (D) Other straight threads conforming to other recognized standards may be used provided that the requirements in paragraph (e)(5)(iv) of this section are met. (iv) All straight threads must have at least 6 engaged threads, a tight fit, and a factor of safety in shear of at least 10 at the test pressure of the cylinder. Shear stress must be calculated by using the appropriate thread shear area in accordance with Federal Standard H-28 (1978), Appendix A5, Section 3. (f) Heat treatment. Prior to any test, all cylinders must be subjected to a solution heat treatment and aging treatment appropriate for the aluminum alloy used. (g) Hydrostatic test. Each cylinder must be subjected to an internal test pressure using the water jacket equipment and method or other suitable equipment and method and comply with the following requirements:#

Passage 59(1) The testing apparatus must be operated in a manner so as to obtain accurate data. The pressure gauge used must permit reading to an accuracy of one percent. The expansion gauge must permit reading the total expansion to an accuracy of either one percent or 0.1 cubic centimeter. (2) The test pressure must be maintained for a sufficient period of time to assure complete expansion of the cylinder. In no case may the pressure be held less than 30 seconds. If, due to failure of the test apparatus, the required test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 psi, whichever is lower. If the test apparatus again fails to maintain the test pressure, the cylinder being tested must be rejected. Any internal pressure applied to the cylinder before any official test may not exceed 90 percent of the test pressure. (3) The minimum test pressure is the greatest of the following: (i) 450 psi regardless of service pressure; (ii) Two times the service pressure for cylinders having service pressure less than 500 psi; or (iii) Five-thirds times the service pressure for cylinders having a service pressure of at least 500 psi. (4) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (h) Flattening test. One cylinder taken at random out of each lot must be subjected to a flattening test as follows: (1) The test must be between knife edges, wedge shaped, having a 60 deg. included angle, and rounded in accordance with the following table. The longitudinal axis of the cylinder must be at an angle 90 deg. to the knife edges during the test. The flattening test table is as follows:#

Passage 60Table 3.--Flattening Test Table ------------------------------------------------------------------------ Radius Cylinder wall thickness in inches in inches ------------------------------------------------------------------------ Under .150.................................................... .500 .150 to .249.................................................. .875 .250 to .349.................................................. 1.500 .350 to .449.................................................. 2.125 .450 to .549.................................................. 2.750 .550 to .649.................................................. 3.500 .650 to .749.................................................. 4.125 ------------------------------------------------------------------------#

Passage 61(2) An alternate bend test in accordance with ASTM E 290-77 using a mandrel diameter not more than 6 times the wall thickness is authorized to qualify lots that fail the flattening test of this section without reheat treatment. If used, this test must be performed on two samples from one cylinder taken at random out of each lot of 200 cylinders or less. (3) Each test cylinder must withstand flattening to nine times the wall thickness without cracking. When the alternate bend test is used, the test specimens must remain uncracked when bent inward around a mandrel in the direction of curvature of the cylinder wall until the interior edges are at a distance apart not greater than the diameter of the mandrel. (i) Mechanical properties test. Two test specimens cut from one cylinder representing each lot of 200 cylinders or less must be subjected to the mechanical properties test, as follows: (1) The results of the test must conform to at least the minimum acceptable mechanical property limits for aluminum alloys as specified in paragraph (b) of this section. (2) Specimens must be 4D bar or gauge length 2 inches with width not over 1\1/2\ inch taken in the direction of extrusion approximately 180 deg. from each other; provided that gauge length at least 24 times thickness with width not over 6 times thickness is authorized, when cylinder wall is not over \3/16\ inch thick. The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. When the size of the cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When such specimens are used, the inspector's report must show that the specimens were so taken and prepared. Heating of specimens for any purpose is forbidden. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard B-557-79. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by ca#

Passage 62lculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of#

Passage 63[[Page 8345]] 10,000,000 psi. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 6,000 psi, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed 1/8 inch per minute during yield strength determination. (j) Rejected cylinder. Reheat treatment of rejected cylinders is authorized one time. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. (k) Duties of inspector. In addition to the requirements of Sec. 178.35, the inspector shall: (1) Verify compliance with the provisions of paragraph (b) of this section by: (i) Performing or witnessing the performance of the chemical analyses on each melt or cast lot or other unit of starting material; or (ii) Obtaining a certified chemical analysis from the material or cylinder manufacturer for each melt, or cast of material; or (iii) Obtaining a certified check analysis on one cylinder out of each lot of 200 cylinders or less, if a certificate containing data to indicate compliance with the material specification is obtained. (2) The inspector shall verify ultrasonic inspection of all material by inspection or by obtaining the material producer's certificate of ultrasonic inspection. Ultrasonic inspection must be performed or verified as having been performed in accordance with paragraph (c) of this section. (3) The inspector must also determine that each cylinder complies with this specification by: (i) Selecting the samples for check analyses performed by other than the material producer; (ii) Verifying that the prescribed minimum thickness was met by measuring or witnessing the measurement of the wall thickness; and (iii) Verifying that the identification of material is proper. (4) Prior to initial production of any design or design change, verify that the design qualification tests prescribed in paragraph (c)(6) of this section have been performed with acceptable results. (l) Definitions. In this specification, a ``lot'' means of group of cylinders successively produced having the same: (i) Size and configuration; (ii) Specified material of construction; (iii) Process of manufacture and heat treatment; (iv#

Passage 64) Equipment of manufacture and heat treatment; and (v) Conditions of time, temperature and atmosphere during heat treatment. In no case may the lot size exceed 200 cylinders, but any cylinder processed for use in the required destructive physical testing need not be counted as being one of the 200. (m) Inspector's report. In addition to the information required by Sec. 178.35, the record of chemical analyses must also include the alloy designation, and applicable information on iron, titanium, zinc, magnesium and any other applicable element used in the construction of the cylinder. Sec. 178.47 Specification 4DS welded stainless steel cylinders for aircraft use. (a) Type, size, and service pressure. A DOT 4DS cylinder is either a welded stainless steel sphere (two seamless hemispheres) or circumferentially welded cylinder both with a water capacity of not over 100 pounds and a service pressure of at least 500 but not over 900 pounds per square inch. (b) Steel. Types 304, 321 and 347 stainless steel are authorized with proper welding procedure. A heat of steel made under the specifications in Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 of this paragraph (b) are not exceeded, except as approved by Associate Administrator. The following chemical analyses are authorized:#

Passage 65Table 1.--Authorized Materials ---------------------------------------------------------------------------------------------------------------- Stainless steels ------------------------------------------------------------------------ 304 (percent) 321 (percent) 347 (percent) ---------------------------------------------------------------------------------------------------------------- Carbon (max)........................... 0.08 0.08 0.08 Manganese (max)........................ 2.00 2.00 2.00 Phosphorus\1\ (max).................... .030 .030 .030 Sulphur (max).......................... .030 .030 .030 Silicon (max).......................... .75 .75 .75 Nickel................................. 8.0/11.0 9.0/13.0 9.0/13.0 Chromium............................... 18.0/20.0 17.0/20.0 17.0/20.0 Molybdenum............................. ....................... ...................... ...................... Titanium............................... ....................... (\1\) Columbium.............................. ....................... ...................... (\2\) ---------------------------------------------------------------------------------------------------------------- \1\ Titanium may not be than 5C and not more than 0.60%. \2\ Columbium may not be less than 10C and not more than 1.0%. Table 2.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the Limit or maximum specified minimum limit Element (percent) ------------------------------- Under minimum Over maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon..................................... To 0.15 incl....................... 0.01 0.01 Manganese.................................. Over 1.15 to 2.50 incl............. .05 .05 Phosphorus\1\.............................. All ranges......................... .............. .01 Sulphur.................................... All ranges......................... .............. .01#

Passage 66Silicon.................................... Over 0.30 to 1.00 incl............. .05 .05 Nickel..................................... Over 5.30 to 10.00 incl............ .10 .10 Over 10.00 to 14.00 incl........... .15 .15 Chromium................................... Over 15.00 to 20.00 incl........... .20 .20 Titanium................................... All ranges......................... .05 .05 Columbium.................................. All ranges......................... .05 .05 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus. (c) Identification of material. Materials must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably; a reasonably smooth and uniform surface finish is required. No abrupt change in wall thickness is permitted. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. All seams of the sphere or cylinder must be fusion welded. Seams must be of the butt type and means must be provided for accomplishing complete penetration of the joint. (e) Attachments. Attachments to the container are authorized by fusion welding provided that such attachments are made of weldable stainless steel in accordance with paragraph (b) of this section. (f) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure may not be over 60,000 psi. A minimum wall thickness of 0.040 inch is required for any diameter container. Calculations must be made by the following formulas: (1) Calculation for sphere must be made by the formula: S=Wall stress in pounds per square inch; P=Test pressure prescribed for water jacket test, i.e., at least two times service pressure, in pounds per square inch; D=Outside diameter in inches; t=Minimum wall thickness in inches; E=0.85 (provides 85 percent weld efficiency factor which must be applied in the girth weld area and heat zones which zone must extend a distance of 6 times wall thickness from center of weld); E=1.0 (for all other areas).#

Passage 67(2) Calculation for a cylinder must be made by the formula: S=Wall stress in pounds per square inch; P=Test pressure prescribed for water jacket test, i.e., at least two times service pressure, in pounds per square inch; D=Outside diameter in inches; d=Inside diameter in inches.#

Passage 68(g) Heat treatment. The seamless hemispheres and cylinders may be stress relieved or annealed for forming. Welded container must be stress relieved at a temperature of 775 deg.F 25 deg. after process treatment and before hydrostatic test. (h) Openings in container. Openings must comply with the following: (1) Each opening in the container must be provided with a fitting, boss or pad of weldable stainless steel securely attached to the container by fusion welding. (2) Attachments to a fitting, boss, or pad must be adequate to prevent leakage. Threads must comply with the following: (i) Threads must be clean cut, even, without checks, and tapped to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the container; gaskets required, adequate to prevent leakage. (i) Process treatment. Each container must be hydraulically pressurized in a water jacket to at least 100 percent, but not more than 110 percent, of the test pressure and maintained at this pressure for a minimum of 3 minutes. Total and permanent expansion must be recorded and included in the inspector's report. (j) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each container must be tested to at least 2 times service pressure. (5) Container must then be inspected. Any wall thickness lower than that required by paragraph (f) of this section must be cause for rejection. Bulges and cracks must be cause for rejection. Welded joint defects exceeding requirements of paragraph (k) of this se#

Passage 69ction must be cause for rejection. (k) Radiographic inspection. Radiographic inspection is required on all welded joints which are subjected to internal pressure, except that at the discretion of the disinterested inspector, openings less than 25 percent of the container diameter need not be subjected to radiographic inspection. Evidence of any defects likely to seriously weaken the container is cause for rejection. Radiographic inspection must be performed subsequent to the hydrostatic test. (l) Burst test. One container taken at random out of 200 or less must be hydrostatically tested to destruction. Rupture pressure must be included as part of the inspector's report. (m) Flattening test. A flattening test must be performed as follows:#

Passage 70(1) For spheres the test must be at the weld between parallel steel plates on a press with welded seam at right angles to the plates. Test one sphere taken at random out of each lot of 200 or less after the hydrostatic test. Any projecting appurtenances may be cut off (by mechanical means only) prior to crushing. (2) For cylinders the test must be between knife edges, wedge shaped, 60 deg. angle, rounded to \1/2\-inch radius. Test one cylinder taken at random out of each lot of 200 or less, after the hydrostatic test. (n) Acceptable results for flattening and burst tests. Acceptable results for flattening and burst tests are as follows: (1) Flattening required to 50 percent of the original outside diameter without cracking. (2) Burst pressure must be at least 3 times the service pressure. (o) Rejected containers. Repair of welded seams by welding prior to process treatment is authorized. Subsequent thereto, containers must be heat treated and pass all prescribed tests. (p) Duties of inspector. In addition to the requirements of Sec. 178.35, the inspector must verify that all tests are conducted at temperatures between 60 deg. F and 90 deg. F. (q) Marking. Markings must be stamped plainly and permanently on a permanent attachment or on a metal nameplate permanently secured to the container by means other than soft solder. Sec. 178.50 Specification 4B welded or brazed steel cylinders. (a) Type, size, and service pressure. A DOT 4B is a welded or brazed steel cylinder with longitudinal seams that are forged lap- welded or brazed and with water capacity (nominal) not over 1,000 pounds and a service pressure of at least 150 but not over 500 pounds per square inch. Cylinders closed in by spinning process are not authorized. (b) Steel. Open-hearth, electric or basic oxygen process steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.25; phosphorus, 0.045; sulphur, 0.050. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hotdrawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform s#

Passage 71urface finish is required. Exposed bottom welds on cylinders over 18 inch long must be protected by footrings. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. Seams must be made as follows: (1) Welded or brazed circumferential seams. Heads attached by brazing must have a driving fit with the shell, unless the shell is crimped, swedged, or curled over the skirt or flange of the head, and be thoroughly brazed until complete penetration by the brazing material of the brazed joint is secured. Depth of brazing from end of shell must be at least four times the thickness of shell metal. (2) Longitudinal seams in shells. Longitudinal seams must be forged lap welded, by copper brazing, by copper alloy brazing, or by silver alloy brazing. Copper alloy composition must be: Copper, 95 percent minimum; Silicon, 1.5 percent to 3.85 percent; Manganese, 0.25 percent to 1.10 percent. The melting point of the silver alloy brazing material must be in excess of 1000 deg. F. When brazed, the plate edge must be lapped at least eight times the thickness of plate, laps being held in position, substantially metal to metal, by riveting or electric spot- welding; brazing must be done by using a suitable flux and by placing brazing material on one side of seam and applying heat until this material shows uniformly along the seam of the other side. (e) Welding or brazing. Only the attachment of neckrings, footrings, handles, bosses, pads, and valve protection rings to the tops and bottoms of cylinders by welding or brazing is authorized. Such attachments and the portion of the container to which they are attached must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedure. (f) Wall thickness. The wall thickness of the cylinder must comply with the following requirements: (1) For cylinders with outside diameters over 6 inches the minimum wall thickness must be 0.090 inch. In any case, the minimum wall thickness must be such that calculated wall stress at minimum test pressure (paragraph (i)(4) of this section) may not exceed the following values: (i) 24,000 pounds per square inch for cylinders without longitudinal seam. (ii) 22,800 pounds per square inch for cylinders having copper brazed or silver alloy brazed longitudinal seam. (iii) 18,00#

Passage 720 pounds per square inch for cylinders having forged lapped welded longitudinal seam. (2) Calculation must be made by the formula: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches. (g) Heat treatment. Cylinder body and heads, formed by drawing or pressing, must be uniformly and properly heat treated prior to tests. (h) Opening in cylinders. Openings in cylinders must conform to the following: (1) Each opening in cylinders, except those for safety devices, must be provided with a fitting, boss, or pad, securely attached to cylinder by brazing or by welding or by threads. Fitting, boss, or pad must be of steel suitable for the method of attachment employed, and which need not be identified or verified as to analysis except that if attachment is by welding, carbon content may not exceed 0.25 percent. If threads are used, they must comply with the following: (i) Threads must be clean cut, even without checks, and tapped to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the cylinder; gaskets required, adequate to prevent leakage. (iv) A brass fitting may be brazed to the steel boss or flange on cylinders used as component parts of hand fire extinguishers. (2) The closure of a fitting, boss, or pad must be adequate to prevent leakage. (i) Hydrostatic test. Each cylinder must withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be#

Passage 73[[Page 8348]] maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) At least one cylinder selected at random out of each lot of 200 or less must be tested as outlined in paragraphs (i)(1), (i)(2), and (i)(3) of this section to at least two times service pressure. (ii) All cylinders not tested as outlined in paragraph (i)(4)(i) of this section must be examined under pressure of at least two times service pressure and show no defect. (j) Flattening test. After the hydrostatic test, a flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from 1 cylinder, or part thereof heat-treated as required, taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times the thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by#

Passage 74blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, and strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation of at least 40 percent for a 2 inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, a flattening test is not required. (2) When cylinders are constructed of lap welded pipe, flattening test is required, without cracking, to 6 times the wall thickness. In such case, the rings (crop ends) cut from each end of pipe, must be tested with the weld 45 deg. or less from the point of greatest stress. If a ring fails, another from the same end of pipe may be tested. (m) Rejected cylinders. Reheat treatment is authorized for rejected cylinder. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair of brazed seams by brazing and welded seams by welding is authorized. (n) Markings. Markings must be st#

Passage 75amped plainly and permanently in any of the following locations on the cylinder: (1) On shoulders and top heads when they are not less than 0.087- inch thick. (2) On side wall adjacent to top head for side walls which are not less than 0.090 inch thick. (3) On a cylindrical portion of the shell which extends beyond the recessed bottom of the cylinder, constituting an integral and non- pressure part of the cylinder. (4) On a metal plate attached to the top of the cylinder or permanent part thereof; sufficient space must be left on the plate to provide for stamping at least six retest dates; the plate must be at least \1/16\ inch thick and must be attached by welding, or by brazing. The brazing rod must melt at a temperature of 1100 deg.F. Welding or brazing must be along all the edges of the plate. (5) On the neck, neckring, valve boss, valve protection sleeve, or similar part permanently attached to the top of the cylinder. (6) On the footring permanently attached to the cylinder, provided the water capacity of the cylinder does not exceed 25 pounds. Sec. 178.51 Specification 4BA welded or brazed steel cylinders.#

Passage 76(a) Type, size, and service pressure. A DOT 4BA cylinder is a cylinder, either spherical or cylindrical in shape, with a water capacity of 1,000 pounds or less and a service pressure of at least 225 and not over 500 pounds per square inch. Closures made by the spinning process are not authorized. (1) Spherical type cylinders must be made from two seamless hemispheres joined by the welding of one circumferential seam. (2) Cylindrical type cylinders must be of circumferentially welded or brazed construction. (b) Steel. The steel used in the construction of the cylinder must be as specified in Table 1 of Appendix A to this part. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hotdrawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. (1) Seams must be made as follows: (i) Minimum thickness of heads and bottoms must be not less than 90#

Passage 77[[Page 8349]] percent of the required thickness of the side wall. (ii) Circumferential seams must be made by welding or by brazing. Heads must be attached by brazing and must have a driving fit with the shell, unless the shell is crimped, swedged or curled over the skirt or flange of the head and must be thoroughly brazed until complete penetration by the brazing material of the brazed joint is secured. Depth of brazing from end of the shell must be at least four times the thickness of shell metal. (iii) Longitudinal seams in shells must be made by copper brazing, copper alloy brazing, or by silver alloy brazing. Copper alloy composition must be: Copper 95 percent minimum, Silicon 1.5 percent to 3.85 percent, Manganese 0.25 percent to 1.10 percent. The melting point of the silver alloy brazing material must be in excess of 1,000 deg.F. The plate edge must be lapped at least eight times the thickness of plate, laps being held in position, substantially metal to metal, by riveting or by electric spot-welding. Brazing must be done by using a suitable flux and by placing brazing material on one side of seam and applying heat until this material shows uniformly along the seam of the other side. Strength of longitudinal seam: Copper brazed longitudinal seam must have strength at least \3/2\ times the strength of the steel wall. (2) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Welding and brazing. Only the welding or brazing of neckrings, footrings, handles, bosses, pads, and valve protection rings to the tops and bottoms of cylinders is authorized. Provided that such attachments and the portion of the container to which they are attached are made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedures. (f) Wall thickness. The minimum wall thickness of the cylinder must meet the following conditions: (1) For any cylinder with an outside diameter of greater than 6 inches, the minimum wall thickness is 0.078 inch. In any case the minimum wall thickness must be such that the calculated wall stress at the minimum test pressure may not exceed the lesser value of any of the following: (i) The value shown in Table I of Appendix A to this part, for the particular material under consideration; (ii) One-half of the minimum tensi#

Passage 78le strength of the material determined as required in paragraph (j) of this section; (iii) 35,000 pounds per square inch; or (iv) Further provided that wall stress for cylinders having copper brazed longitudinal seams may not exceed 95 percent of any of the above values. Measured wall thickness may not include galvanizing or other protective coating. (2) Cylinders that are cylindrical in shape must have the wall stress calculated by the formula: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test; D=outside diameter in inches; d=inside diameter in inches. (3) Cylinders that are spherical in shape must have the wall stress calculated by the formula: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test; D=outside diameter in inches; t=minimum wall thickness in inches; E=0.85 (provides 85 percent weld efficiency factor which must be applied in the girth weld area and heat affected zones which zone must extend a distance of 6 times wall thickness from center line of weld); E=1.0 (for all other areas).#

Passage 79(4) For a cylinder with a wall thickness less than 0.100 inch, the ratio of tangential length to outside diameter may not exceed 4.1. (g) Heat treatment. Cylinders must be heat treated in accordance with the following requirements: (1) Each cylinder must be uniformly and properly heat treated prior to test by the applicable method shown in Table I of Appendix A to this Part. Heat treatment must be accomplished after all forming and welding operations, except that when brazed joints are used, heat treatment must follow any forming and welding operations, but may be done before, during or after the brazing operations. (2) Heat treatment is not required after the welding or brazing of weldable low carbon parts to attachments of similar material which have been previously welded or brazed to the top or bottom of cylinders and properly heat treated, provided such subsequent welding or brazing does not produce a temperature in excess of 400 deg.F in any part of the top or bottom material. (h) Openings in cylinders. Openings in cylinders must comply with the following requirements: (1) Any opening must be placed on other than a cylindrical surface. (2) Each opening in a spherical type cylinder must be provided with a fitting, boss, or pad of weldable steel securely attached to the container by fusion welding. (3) Each opening in a cylindrical type cylinder must be provided with a fitting, boss, or pad, securely attached to container by brazing or by welding. (4) If threads are used, they must comply with the following: (i) Threads must be clean-cut, even, without checks and tapped to gauge. (ii) Taper threads must be of a length not less than that specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water jacket, or other suitable method, operated so as to obtain accurate data. A pressure gauge must permit reading to an accuracy of 1 percent. An expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently l#

Passage 80onger to ensure complete expansion. Any internal pressure applied after heat treatment and previous to the official test may not exceed 90 percent of the test pressure. (3) Permanent volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) At least one cylinder selected at random out of each lot of 200 or less must be tested as outlined in paragraphs (i)(1), (i)(2), and (i)(3) of this section to at least two times service pressure. (ii) All cylinders not tested as outlined in paragraph (i)(4)(i) of this section must be examined under pressure of at least two times service pressure and show no defect. (j) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from one cylinder or part thereof having passed the hydrostatic test and heat-treated as required, taken at random out of each lot of 200 or less. Physical tests for spheres are required on 2 specimens cut from flat representative sample plates of the same heat taken at random from the steel used#

Passage 81[[Page 8350]] to produce the spheres. This flat steel from which 2 specimens are to be cut must receive the same heat treatment as the spheres themselves. Sample plates must be taken from each lot of 200 or less spheres. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, or a gauge length of 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times the thickness is authorized when a cylinder wall is not over \3/ 16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of the cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load''), corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain reference must be set while the specimen is under a stress of 12,000 pounds per square inch, and the strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed 1/8 inch per minute during yield strength determination. (k) Elongat#

Passage 82ion. Physical test specimens must show at least a 40 percent elongation for a 2-inch gauge length or at least 20 percent in other cases. Except that these elongation percentages may be reduced numerically by 2 for 2-inch specimens, and by 1 in other cases, for each 7,500 pounds per square inch increment of tensile strength above 50,000 pounds per square inch to a maximum of four such increments. (l) Tests of welds. Except for brazed seams, welds must be tested as follows: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less, or welded test plate. The welded test plate must be of one of the heats in the lot of 200 or less which it represents, in the same condition and approximately the same thickness as the cylinder wall except that in no case must it be of a lesser thickness than that required for a quarter size Charpy impact specimen. The weld must be made by the same procedures and subjected to the same heat treatment as the major weld on the cylinder. The specimen must be taken from across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. Should this specimen fail to meet the requirements, specimens may be taken from two additional cylinders or welded test plates from the same lot and tested. If either of the latter specimens fail to meet the requirements, the entire lot represented must be rejected. (2) Guided bend test. A root bend test specimen must be cut from the cylinder or welded test plate, used for the tensile test specified in paragraph (l)(1) of this section. Specimens must be taken from across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (3) Alternate guided-bend test. This test may be used and must be as required by CGA Pamphlet C-3. The specimen must be bent until the elongation at the outer surface, adjacent to the root of the weld, between the lightly scribed gage lines a to b, must be at least 20 percent, except that this percentage may be reduced for steels having a tensile strength in excess of 50,000 pounds per square inch, as provided in paragraph (k) of this section. (m) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair of brazed seams by brazing and wel#

Passage 83ded seams by welding is authorized. (n) Markings. Markings must be stamped plainly and permanently in one of the following locations on the cylinder: (1) On shoulders and top heads not less than 0.087 inch thick. (2) On side wall adjacent to top head for side walls not less than 0.090 inch thick. (3) On a cylindrical portion of the shell which extends beyond the recessed bottom of the cylinder constituting an integral and non- pressure part of the cylinder. (4) On a plate attached to the top of the cylinder or permanent part thereof; sufficient space must be left on the plate to provide for stamping at least six retest dates; the plate must be at least \1/16\ inch thick and must be attached by welding, or by brazing at a temperature of at least 1100 deg. F., throughout all edges of the plate. (5) On the neck, neckring, valve boss, valve protection sleeve, or similar part permanently attached to the top of the cylinder. (6) On the footring permanently attached to the cylinder, provided the water capacity of the cylinder does not exceed 25 pounds. Sec. 178.53 Specification 4D welded steel cylinders for aircraft use. (a) Type, size, and service pressure. A DOT 4D cylinder is a welded steel sphere (two seamless hemispheres) or circumferentially welded cylinder (two seamless drawn shells) with a water capacity not over 100 pounds and a service pressure of at least 300 but not over 500 pounds per square inch. Cylinders closed in by spinning process are not authorized. (b) Steel. Open-hearth or electric steel of uniform and weldable quality must be used. Content may not exceed the following: Carbon, 0.25; phosphorus, 0.045; sulphur, 0.050, except that the following steels commercially known as 4130X and Type 304, 316, 321, and 347 stainless steels may be used with proper welding procedure. A heat of steel made under Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 of this paragraph (b) are not exceeded, except as approved by the Associate Administrator. The following chemical analyses are authorized:#

Passage 84Table 1.--4130X Steel ------------------------------------------------------------------------ 4130X Percent ------------------------------------------------------------------------ Carbon......................................... 0.25/0.35. Manganese...................................... 0.40/0.60. Phosphorus..................................... 0.04 max. Sulphur........................................ 0.05 max. Silicon........................................ 0.15/0.35. Chromium....................................... 0.80/1.10. Molybdenum..................................... 0.15/0.25. Zirconium...................................... None. Nickel......................................... None. ------------------------------------------------------------------------#

Passage 85Table 2.--Authorized Stainless Steels ---------------------------------------------------------------------------------------------------------------- Stainless steels ---------------------------------------------------------------------------------- 347 304 (percent) 316 (percent) 321 (percent) (percent) ---------------------------------------------------------------------------------------------------------------- Carbon (max)................. 0.08................. 0.08................. 0.08................ 0.08 Manganese (max).............. 2.00................. 2.00................. 2.00................ 2.00 Phosphorus1 (max)............ .030................. .045................. .030................ .030 Sulphur (max)................ .030................. .030................. .030................ .030 Silicon (max)................ .75.................. 1.00................. .75................. .75 Nickel....................... 8.0/11.0............. 10.0/14.0............ 9.0/13.0............ 9.0/13.0 Chromium..................... 18.0/20.0............ 16.0/18.0............ 17.0/20.0........... 17.0/20.0 Molybdenum................... ..................... 2.0/3.0.............. .................... ............. Titanium..................... ..................... ..................... (\1\)............... ............. Columbium.................... ..................... ..................... .................... (\2\) ---------------------------------------------------------------------------------------------------------------- \1\ Titanium may not be less than 5C and not more than 0.60%. \2\ Columbium may not be less than 10C and not more than 1.0%.#

Passage 86Table 3.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the minimum limit Element Limit or maximum specified (percent) --------------------------- Under minimum Over maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon............................. To 0.15 incl................................... 0.01 0.01 Over 0.15 to 0.40 incl......................... .03 .04 Manganese.......................... To 0.60 incl................................... .03 .03 Over 1.15 to 2.50 incl......................... .05 .05 Phosphorus\1\...................... All ranges..................................... ............ .01 Sulphur............................ All ranges..................................... ............ .01 Silicon............................ To 0.30 incl................................... .02 .03 Over 0.30 to 1.00 incl......................... .05 .05 Nickel............................. Over 5.30 to 10.00 incl........................ .10 .10 Over 10.00 to 14.00 incl....................... .15 .15 Chromium........................... To 0.90 incl................................... .03 .03 Over 0.90 to 2.10 incl......................... .05 .05 Over 15.00 to 20.00 incl....................... .20 .20 Molybdenum......................... To 0.20 incl................................... .01 .01 Over 0.20 to 0.40 incl......................... .02 .02 Over 1.75 to 3.0 incl.......................... .10 .10 Titanium........................... All ranges..................................... .05 .05 Columbium.......................... All ranges..................................... .05 .05 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus.#

Passage 87(c) Identification of material. Material must be identified by any suitable method except that plates and billets for hotdrawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished container appreciably. A reasonably smooth and uniform surface finish is required. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Wall thickness. The wall stress at the minimum test pressure may not exceed 24,000 pounds per square inch, except where steels commercially known as 4130X, types 304, 316, 321, and 347 stainless steels are used, stress at the test pressures may not exceed 37,000 pounds per square inch. The minimum wall thickness for any container having a capacity of 1,100 cubic inches or less is 0.04 inch. The [[Page 8352]] minimum wall thickness for any container having a capacity in excess of 1,100 cubic inches is 0.095 inch. Calculations must be done by the following: (1) Calculation for a ``sphere'' must be made by the formula: Where: S=wall stress in pounds per square inch; P=test pressure prescribed for water jacket test, i.e., at least two times service pressure, in pounds per square inch; D=outside diameter in inches; t=minimum wall thickness in inches; E=0.85 (provides 85 percent weld efficiency factor which must be applied in the girth weld area and heat affected zones which zone must extend a distance of 6 times wall thickness from center line of weld); E=1.0 (for all other areas). (2) Calculation for a cylinder must be made by the formula: S=wall stress in pounds per square inch; P=test pressure prescribed for water jacket test, i.e., at least two times service pressure, in pounds per square inch; D=outside diameter in inches; d=inside diameter in inches.#

Passage 88(f) Heat treatment. The completed cylinders must be uniformly and properly heat-treated prior to tests. (g) Openings in container. Openings in cylinders must comply with the following: (1) Each opening in the container, except those for safety devices, must be provided with a fitting, boss, or pad, securely attached to the container by brazing or by welding or by threads. If threads are used, they must comply with the following: (i) Threads must be clean cut, even, without checks, and tapped to gauge. (ii) Taper threads must be of a length not less than that specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, must have a tight fit and calculated shear strength of at least 10 times the test pressure of the container. Gaskets, adequate to prevent leakage, are required. (2) Closure of a fitting, boss, or pad must be adequate to prevent leakage. (h) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. A pressure gauge must permit a reading to an accuracy of 1 percent. An expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Containers must be tested as follows: (i) Each container to at least 2 times service pressure; or (ii) One container out of each lot of 200 or less to at least 3 times service pressure. Others must be examined under pressure of 2 times service pressure and show no defects. (i) Flattening test for spheres and cylinders. Spheres and cylinders must be subjected to a flattening test as follows: (1) One sphere taken at random out of each lot of 200 or less must be subjected to a flattening test as follows: (i) The test must be performed aft#

Passage 89er the hydrostatic test. (ii) The test must be between parallel steel plates on a press with a welded seam at right angles to the plates. Any projecting appurtenances may be cut off (by mechanical means only) prior to crushing. (2) One cylinder taken at random out of each lot of 200 or less must be subjected to a flattening test, as follows: (i) The test must be performed after the hydrostatic test. (ii) The test must be between knife edges, wedge shaped, 60 deg. angle, rounded to \1/2\ inch radius. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to the same heat treatment as the finished cylinder. (j) Physical test and specimens for spheres and cylinders. Spheres and cylinders must be subjected to a physical test as follows: (1) Physical test for spheres are required on 2 specimens cut from a flat representative sample plate of the same heat taken at random from the steel used to produce the sphere. This flat steel from which the 2 specimens are to be cut must receive the same heat-treatment as the spheres themselves. Sample plates must be taken for each lot of 200 or less spheres. (2) Specimens for spheres must have a gauge length 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times the thickness is authorized when a wall is not over \3/16\ inch thick. (3) Physical test for cylinders is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to the same heat treatment as the finished cylinder. (4) Specimens for cylinders must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, or a gauge length of 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times the thickness is authorized when a cylinder wall is not over \3/ 16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. Heating of the specimen for any purpose is not authorized. (5) The yield strength in tension must be the stress corresponding to a permanent strain of#

Passage 900.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (k) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An Elongation of at least 40 percent for a 2 inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, the flattening test is not required. (2) An elongation of at least 20 percent for a 2 inch gauge length or 10 percent in other cases. Flattening is required to 50 percent of the original outside diameter without cracking. (l) Rejected cylinders. Reheat-treatment is authorized for rejected cylinders. Subsequent thereto, containers must pass all prescribed tests to be acceptable. Repair of welded seams by welding prior to reheat-treatment is authorized. (m) Marking. Marking on each container by stamping plainly and permanently are only authorized where the metal is at least 0.09 inch thick, or on a metal nameplate permanently secured to the container by means other than soft solder, or by means that would not reduce the wall thickness. Sec. 178.55 Specification 4B240ET welded or brazed cylinders.#

Passage 91(a) Type, spinning process, size and service pressure. A DOT 4B240ET cylinder is a brazed type cylinder made from electric resistance welded tubing. The maximum water capacity of this cylinder is 12 pounds or 333 cubic inches and the service must be 240 pounds per square inch. The maximum outside diameter of the shell must be five inches and maximum length of the shell is 21 inches. Cylinders closed in by a spinning process are authorized. (b) Steel. Open-hearth, basic oxygen, or electric steel of uniform quality must be used. Plain carbon steel content may not exceed the following: Carbon, 0.25; phosphorus, 0.045; sulfur, 0.050. The addition of other elements for alloying effect is prohibited. (c) Identification of material. Material must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Heads may be attached to shells by lap brazing or may be formed integrally. The thickness of the bottom of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell. Such bottom thicknesses must be measured within an area bounded by a line representing the points of contact between the cylinder and the floor when the cylinder is in a vertical position. Seams must conform to the following: (1) Circumferential seams must be by brazing only. Heads must be attached to shells by the lap brazing method and must overlap not less than four times the wall thickness. Brazing material must have a melting point of not less than 1000 deg. F. Heads must have a driving fit with the shell unless the shell is crimped, swedged, or curled over the skirt or flange of the head and be thoroughly brazed until complete penetration of the joint by the brazing material is secured. Brazed joints may be repaired by brazing. (2) Longitudinal seams in shell must be by electric resistance welded joints only. No repairs to longitudinal joints is permitted. (3) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Welding or brazing. Only the attachment, by welding or brazing, to the tops an#

Passage 92d bottoms of cylinders of neckrings, footrings, handles, bosses, pads, and valve protection rings is authorized. Provided that such attachments and the portion of the container to which they are attached are made of weldable steel, the carbon content of which may not exceed 0.25 percent. (f) Wall thickness. The wall stress must be at least two times the service pressure and may not exceed 18,000 pounds per square inch. The minimum wall thickness is 0.044 inch. Calculation must be made by the following formula: S=wall stress in pounds per square inch; P=2 times service pressure; D=outside diameter in inches; d=inside diameter in inches.#

Passage 93(g) Heat treatment. Heads formed by drawing or pressing must be uniformly and properly heat treated prior to tests. Cylinders with integral formed heads or bases must be subjected to a normalizing operation. Normalizing and brazing operations may be combined, provided the operation is carried out at a temperature in excess of the upper critical temperature of the steel. (h) Openings in cylinders. Openings in cylinders must comply with the following: (1) Each opening in cylinders, except those for safety devices, must be provided with a fitting, boss, or pad, securely attached to the cylinder by brazing or by welding or by threads. A fitting, boss, or pad must be of steel suitable for the method of attachment employed, and which need not be identified or verified as to analysis, except that if attachment is by welding, carbon content may not exceed 0.25 percent. If threads are used, they must comply with the following: (i) Threads must be clean cut, even without checks, and tapped to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the cylinder; gaskets required, adequate to prevent leakage. (2) Closure of a fitting, boss, or pad must be adequate to prevent leakage. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) At least one cylinder sel#

Passage 94ected at random out of each lot of 200 or less must be tested as outlined in paragraphs (i)(1), (i)(2), and (i)(3) of this section to at least two times service pressure. (ii) All cylinders not tested as outlined in paragraph (i)(4)(i) of this section must be examined under pressure of at least two times service pressure and show no defect. (5) Each 1000 cylinders or less successively produced each day must constitute a lot. One cylinder must be selected from each lot and hydrostatically tested to destruction. If this cylinder bursts below five times the service pressure, then two additional cylinders must be selected and subjected to this test. If either of these#

Passage 95[[Page 8354]] cylinders fails by bursting below five times the service pressure then the entire lot must be rejected. All cylinders constituting a lot must be of identical size, construction heat-treatment, finish, and quality. (j) Flattening test. Following the hydrostatic test, one cylinder taken at random out of each lot of 200 or less, must be subjected to a flattening test that is between knife edges, wedge shaped, 60 deg. angle, rounded to \1/2\ inch radius. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from 1 cylinder, or part thereof heat-treated as required, taken at random out of each lot of 200 or less in the case of cylinders of capacity greater than 86 cubic inches and out of each lot of 500 or less for cylinders having a capacity of 86 cubic inches or less. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times the thickness is authorized when a cylinder wall is not over \3/ 16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating t#

Passage 96he elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed 1/8 inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Acceptable results for the physical and flattening tests are an elongation of at least 40 percent for a 2 inch gauge length or at least 20 percent in other cases and a yield strength not over 73 percent of tensile strength. In this instance the flattening test is required, without cracking, to six times the wall thickness with a weld 90 deg. from the direction of the applied load. Two rings cut from the ends of length of pipe used in production of a lot may be used for the flattening test provided the rings accompany the lot which they represent in all thermal processing operations. At least one of the rings must pass the flattening test. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions: (1) Pressure, approximately the same as but no less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least 1 minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, cylinders which are leaking must be rejected. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the ma#

Passage 97nufacturer elects to make this test before the hydrostatic test, he should design his apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Repairs of rejected cylinders is authorized. Cylinders that are leaking must be rejected, except that: (1) Spun cylinders rejected under the provisions of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping, and plugging. (2) Brazed joints may be rebrazed. (3) Subsequent to the operations noted in paragraphs (n)(1) and (n)(2) of this section, acceptable cylinders must pass all prescribed tests. (o) Marking. Markings on each cylinder must be by stamping plainly and permanently on shoulder, top head, neck or valve protection collar which is permanently attached to the cylinders and forming an integral part thereof, provided that cylinders not less than 0.090 inch thick may be stamped on the side wall adjacent to top head. Sec. 178.56 Specification 4AA480 welded steel cylinders.#

Passage 98(a) Type, size, and service pressure. A DOT 4AA480 cylinder is a welded steel cylinder having a water capacity (nominal) not over 1,000 pounds water capacity and a service pressure of 480 pounds per square inch. Closures welded by spinning process not permitted. (b) Steel. The limiting chemical composition of steel authorized by this specification must be as shown in Table I of Appendix A to this part. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hotdrawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. Minimum thickness of heads and bottoms may not be less than 90 percent of the required thickness of the side wall. Seams must be made as follows: (1) Circumferential seams must be welded. Brazing is not authorized. (2) Longitudinal seams are not permitted. (3) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Welding. Only the welding of neckrings, footrings, bosses, pads, and valve protection rings to the tops and bottoms of cylinders is authorized. Provided that such attachments are made of weldable steel, the carbon content of which does not exceed 0.25 percent. (f) Wall thickness. The wall thickness of the cylinder must conform to the following: (1) For cylinders with an outside diameter over 5 inches, the minimum wall thickness is 0.078 inch. In any case, the minimum wall thickness must be such that the calculated wall stress at the minimum test pressure (in paragraph (i) of this section) may not exceed the lesser value of either of the following: (i) One-half of the minimum tensile strength of the material determined as required in paragraph (j) of this section; or (ii) 35,000 pounds per square inch. (2) Calculation must be made by the formula: Where: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test; D=outside diameter in inches; d=inside diameter in inches.#

Passage 99(3) The ratio of tangential length to outside diameter may not exceed 4.0 for cylinders with a wall thickness less than 0.100 inch. (g) Heat treatment. Each cylinder must be uniformly and properly heat treated prior to tests. Any suitable heat treatment in excess of 1100 deg. F is authorized except that liquid quenching is not permitted. Heat treatment must be accomplished after all forming and welding operations. Heat treatment is not required after welding weldable low carbon parts to attachments of similar material which have been previously welded to the top or bottom of cylinders and properly heat treated, provided such subsequent welding does not produce a temperature in excess of 400 deg. F., in any part of the top or bottom material. (h) Openings in cylinders. Openings in cylinders must conform to the following: (1) All openings must be in the heads or bases. (2) Each opening in the cylinder, except those for safety devices, must be provided with a fitting boss, or pad, securely attached to the cylinder by welding or by threads. If threads are used they must comply with the following: (i) Threads must be clean-cut, even without checks and cut to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads having at least 6 engaged threads, must have a tight fit and a calculated shear strength at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (3) Closure of a fitting, boss or pad must be adequate to prevent leakage. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds or sufficiently longer to assure complete expansion. Any internal pressure applied after heat-treatment and before the official test may not exceed 90 percent of the test pressure. If, due to failure of test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is lower. (3) Perman#

Passage 100ent volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) At least one cylinder selected at random out of each lot of 200 or less must be tested as described in paragraphs (i)(1), (i)(2), and (i)(3) of this section, to at least two times service pressure. If a selected cylinder fails, then two additional specimens must be selected at random from the same lot and subjected to the prescribed test. If either of these fails the test, then each cylinder in that lot must be so tested; and (ii) Each cylinder not tested as prescribed in paragraph (i)(4)(i) of this section must be examined under pressure of at least two times service pressure and must show no defect. A cylinder showing a defect must be rejected unless it may be requalified under paragraph (m) of this section. (j) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from one cylinder having passed the hydrostatic test, or part thereof heat-treated as required, taken at random out of each lot of 200 or less. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times the thickness with a width not over 6 times thickness is authorized when the cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' metho#

Passage 101d as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load''), corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain reference must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (k) Elongation. Physical test specimens must show at least a 40 percent elongation for 2-inch gauge lengths or at least a 20 percent elongation in other cases. Except that these elongation percentages may be reduced numerically by 2 for 2-inch#

Passage 102[[Page 8356]] specimens and by 1 in other cases for each 7,500 pounds per square inch increment of tensile strength above 50,000 pounds per square inch to a maximum of four such increments. (l) Tests of welds. Welds must be tested as follows: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less, or a welded test plate. The welded test plate must be of one of the heats in the lot of 200 or less which it represents, in the same condition and approximately the same thickness as the cylinder wall except that it may not be of a lesser thickness than that required for a quarter size Charpy impact specimen. The weld must be made by the same procedures and subjected to the same heat treatment as the major weld on the cylinder. The specimens must be taken across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. Should this specimen fail to meet the requirements, specimens may be taken from two additional cylinders or welded test plates from the same lot and tested. If either of the latter specimens fail to meet the requirements, the entire lot represented must be rejected. (2) Guided bend test. A root bend test specimen must be cut from the cylinder or a welded test plate, used for the tensile test specified in paragraph (l)(1) of this section. Specimens must be taken from across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (3) Alternate guided-bend test. This test may be used and must be as required by CGA Pamphlet C-3. The specimen must be bent until the elongation at the outer surface, adjacent to the root of the weld, between the lightly scribed gage lines-a to b, is at least 20 percent, except that this percentage may be reduced for steels having a tensile strength in excess of 50,000 pounds per square inch, as provided in paragraph (k) of this section. (m) Rejected cylinders. Reheat treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair of welded seams by welding is authorized. (n) Markings. Markings must be stamped plainly and permanently in one of the following locations on the cylinder: (1) On shoulders and top heads not less than 0.087 inch thick. (2) On neck, valve boss, valve protection sleeve, or similar pa#

Passage 103rt permanently attached to top end of cylinder. (3) On a plate attached to the top of the cylinder or permanent part thereof: sufficient space must be left on the plate to provide for stamping at least six retest dates: the plate must be at least \1/16\ inch thick and must be attached by welding or by brazing at a temperature of at least 1100 deg. F, throughout all edges of the plate. (4) Variations in location of markings authorized only when necessitated by lack of space. Sec. 178.57 Specification 4L welded insulated cylinders. (a) Type, size, service pressure, and design service temperature. A DOT 4L cylinder is a fusion welded insulated cylinder with a water capacity (nominal) not over 1,000 pounds water capacity and a service pressure of at least 40 but not greater than 500 pounds per square inch conforming to the following requirements: (1) For liquefied hydrogen service, the cylinders must be designed to stand on end, with the axis of the cylindrical portion vertical. (2) The design service temperature is the coldest temperature for which a cylinder is suitable. The required design service temperatures for each cryogenic liquid is as follows: ------------------------------------------------------------------------ Cryogenic liquid Design service temperature ------------------------------------------------------------------------ Argon............................ Minus 320 deg. F or colder. Helium........................... Minus 452 deg. F or colder. Hydrogen......................... Minus 423 deg. F or colder. Neon............................. Minus 411 deg. F or colder. Nitrogen......................... Minus 320 deg. F or colder. Oxygen........................... Minus 320 deg. F or colder. ------------------------------------------------------------------------#

Passage 104(b) Material. Material use in the construction of this specification must conform to the following: (1) Inner containment vessel (cylinder). Designations and limiting chemical compositions of steel authorized by this specification must be as shown in Table 1 in paragraph (o) of this section. (2) Outer jacket. Steel or aluminum may be used subject to the requirements of paragraph (o)(2) of this section. (c) Identification of material. Material must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart and to the following requirements: (1) No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. The shell portion must be a reasonably true cylinder. (2) The heads must be seamless, concave side to the pressure, hemispherical or ellipsoidal in shape with the major diameter not more than twice the minor diameter. Minimum thickness of heads may not be less than 90 percent of the required thickness of the sidewall. The heads must be reasonably true to shape, have no abrupt shape changes, and the skirts must be reasonably true to round. (3) The surface of the cylinder must be insulated. The insulating material must be fire resistant. The insulation on non-evacuated jackets must be covered with a steel jacket not less than 0.060-inch thick or an aluminum jacket not less than 0.070 inch thick, so constructed that moisture cannot come in contact with the insulating material. If a vacuum is maintained in the insulation space, the evacuated jacket must be designed for a minimum collapsing pressure of 30 psi differential whether made of steel or aluminum. The construction must be such that the total heat transfer, from the atmosphere at ambient temperature to the contents of the cylinder, will not exceed 0.0005 Btu per hour, per Fahrenheit degree differential in temperature, per pound of water capacity of the cylinder. For hydrogen, cryogenic liquid service, the total heat transfer, with a temperature differential of 520 Fahrenheit degrees, may not exceed that required to vent 30 SCF of hydrogen gas per hour. (4) For a cylinder having a design service temperature colder than minus 320 deg. F, a calculation of the maximum weight of conte#

Passage 105nts must be made and that weight must be marked on the cylinder as prescribed in Sec. 178.35. (5) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. In addition, an impact test of the weld must be performed in accordance with paragraph (l) of this section as part of the qualification of each welding procedure and operator. (e) Welding. Welding of the cylinder must be as follows: (1) All seams of the cylinder must be fusion welded. A means must be provided for accomplishing complete penetration of the joint. Only butt or joggle butt joints for the cylinder seams are authorized. All joints in the cylinder must have reasonably true alignment. (2) All attachments to the sidewalls and heads of the cylinder must be by fusion welding and must be of a weldable material complying with the impact requirements of paragraph (l) of this section. (3) For welding the cylinder, each procedure and operator must be qualified in accordance with the sections of CGA Pamphlet C-3 that apply. In addition, impact tests of the weld must be performed in accordance with paragraph (l) of this section as part of the qualification of each welding procedure and operator. (4) Brazing, soldering and threading are permitted only for joints not made directly to the cylinder body. Threads must comply with the requirements of paragraph (h) of this section. (f) Wall thickness. The minimum wall thickness of the cylinder must be such that the calculated wall stress at the minimum required test pressure may not exceed the least value of the following: (1) 45,000 pounds per square inch. (2) One-half of the minimum tensile strength across the welded seam determined in paragraph (l) of this section. (3) One-half of the minimum tensile strength of the base metal determined as required in paragraph (j) of this section. (4) The yield strength of the base metal determined as required in paragraph (l) of this section. (5) Further provided that wall stress for cylinders having longitudinal seams may not exceed 85 percent of the value in paragraph (f)(4) of this section, whichever applies. (6) Calculation must be made by the following formula: S=Wall stress in pounds per square inch; P=Minimum test pressure prescribed for pressure test in pounds per square inch; D=Outside diameter in inches; d=Inside diameter in inches.#

Passage 106(g) Heat treatment. Heat treatment is not permitted. (h) Openings in cylinder. Openings in cylinders must conform to the following: (1) Openings are permitted in heads only. They must be circular and may not exceed 3 inches in diameter or one third of the cylinder diameter, whichever is less. Each opening in the cylinder must be provided with a fitting, boss or pad, either integral with, or securely attached to, the cylinder body by fusion welding. Attachments to a fitting, boss or pad may be made by welding, brazing, mechanical attachment, or threading. (2) Threads must comply with the following: (i) Threads must be clean-cut, even, without checks and cut to gauge. (ii) Taper threads to be of a length not less than that specified for NPT. (iii) Straight threads must have at least 4 engaged threads, tight fit and calculated shear strength at least 10 times the test pressure of the cylinder. Gaskets, which prevent leakage and are inert to the hazardous material, are required. (i) Pressure test. Each cylinder, before insulating and jacketing, must be examined under a pressure of at least 2 times the service pressure maintained for at least 30 seconds without evidence of leakage, visible distortion or other defect. The pressure gauge must permit reading to an accuracy of 1 percent. (j) Physical test. A physical test must be conducted to determine yield strength, tensile strength, and elongation as follows: (1) The test is required on 2 specimens selected from material of each heat and in the same condition as that in the completed cylinder. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with width not over 1\1/2\ inches, or a gauge length at least 24 times thickness with a width not over 6 times thickness (authorized when cylinder wall is not over \3/16\ inch thick). (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of the cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such#

Passage 107specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load''), corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic expansion of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on the elastic modulus of the material used. In the event of controversy, the entire stress- strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain reference must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (k) Acceptable results for physical tests. Physical properties must meet the limits specified in paragraph (o)(1), Table 1, for the particular steel in the annealed condition. The specimens must show at least a 20 percent elongation for a 2-inch gage length. Except that the percentage may be reduced numerically by 2 for each 7,500 pounds per square inch increment of tensile strength above 100,000 pounds per square inch to a maximum of 5 such increments. Yield strength and tensile strength must meet the requirements of paragraph (o)(1), Table 1, of this section. (l) Tests of welds. Welds must be tested as follows: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less, or welded test plate. The welded test plate must be of one of the heats in the lot of 200 or less which it represents, in the same condition and approximately the same thickness as the cylinder wall except that it may not of a lesser thickness than that required for a quarter size Charpy impact specimen. The weld must be made by the same procedures and subjected to th#

Passage 108e same heat treatment as the major weld on the cylinder. The specimen must be taken across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. Should this specimen fail to meet the requirements, specimens may be taken from two additional cylinders or welded test plates from the same lot and tested. If either of the latter specimens fails to meet the requirements, the entire lot represented must be rejected. (2) Guided bend test. A ``root'' bend test specimen must be cut from the cylinder or welded test plate, used for the tensile test specified in paragraph (l)(1) of this section and from any other seam or equivalent welded test plate if the seam is welded by a procedure different from that used for the major seam. Specimens must be taken across the particular seam being tested and#

Passage 109[[Page 8358]] must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (3) Alternate guided-bend test. This test may be used and must be as specified in CGA Pamphlet C-3. The specimen must be bent until the elongation at the outer surface, adjacent to the root of the weld, between the lightly scribed gage lines-a to b, is at least 20 percent, except that this percentage may be reduced for steels having a tensile strength in excess of 100,000 pounds per square inch, as provided in paragraph (c) of this section. (4) Impact tests. One set of three impact test specimens (for each test) must be prepared and tested for determining the impact properties of the deposited weld metal-- (i) As part of the qualification of the welding procedure. (ii) As part of the qualification of the operators. (iii) For each ``heat'' of welding rodor wire used. (iv) For each 1,000 feet of weld made with the same heat of welding rod or wire. (v) All impact test specimens must be of the Charpy type, keyhole or milled U-notch, and must conform in all respects to Figure 3 of ASTM E-23-60T. Each set of impact specimens must be taken across the weld and have the notch located in the weld metal. When the cylinder material thickness is 2.5 mm or thicker, impact specimens must be cut from a cylinder or welded test plate used for the tensile or bend test specimens. The dimension along the axis of the notch must be reduced to the largest possible of 10 mm, 7.5 mm, 5 mm or 2.5 mm, depending upon cylinder thickness. When the material in the cylinder or welded test plate is not of sufficient thickness to prepare 2.5 mm impact test specimens, 2.5 mm specimens must be prepared from a welded test plate made from \1/8\ inch thick material meeting the requirements specified in paragraph (o)(1), Table 1, of this section and having a carbon analysis of .05 minimum, but not necessarily from one of the heats used in the lot of cylinders. The test piece must be welded by the same welding procedure as used on the particular cylinder seam being qualified and must be subjected to the same heat treatment. (vi) Impact test specimens must be cooled to the design service temperature. The apparatus for testing the specimens must conform to the requirements of ASTM Standard E-23-60T. The test piece, as well as the handling tongs, must be cooled for a length of time sufficien#

Passage 110t to reach the service temperature. The temperature of the cooling device must be maintained within a range of plus or minus 3 deg. F. The specimen must be quickly transferred from the cooling device to the anvil of the testing machine and broken within a time lapse of not more than six seconds. (vii) The impact properties of each set of impact specimens may not be less than the values in the following table: ------------------------------------------------------------------------ Minimum impact Minimum value impact required value for avg. permitted Size of specimen of each on one set of only of a three set of specimens three (ft.-lb.) (ft.- lb.) ------------------------------------------------------------------------ 10 mm x 10 mm................................... 15 10 10 mm x 7.5 mm.................................. 12.5 8.5 10 mm x 5 mm.................................... 10 7.0 10 mm x 2.5 mm.................................. 5 3.5 ------------------------------------------------------------------------#

Passage 111(viii) When the average value of the three specimens equals or exceeds the minimum value permitted for a single specimen and the value for more than one specimen is below the required average value, or when the value for one specimen is below the minimum value permitted for a single specimen, a retest of three additional specimens must be made. The value of each of these retest specimens must equal or exceed the required average value. When an erratic result is caused by a defective specimen, or there is uncertainty in test procedure, a retest is authorized. (m) Radiographic examination. Cylinders must be subject to a radiographic examination as follows: (1) The techniques and acceptability of radiographic inspection must conform to the standards set forth in CGA Pamphlet C-3. (2) One finished longitudinal seam must be selected at random from each lot of 100 or less successively produced and be radiographed throughout its entire length. Should the radiographic examination fail to meet the requirements of paragraph (m)(1) of this section, two additional seams of the same lot must be examined, and if either of these fail to meet the requirements of (m)(1) of this section, only those passing are acceptable. (n) Rejected cylinders. Reheat treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Welds may be repaired by suitable methods of fusion welding. (o) Authorized materials of construction. Authorized materials of construction are as follows: (1) Inner containment vessel (cylinder). Electric furnace steel of uniform quality must be used. Chemical analysis must conform to ASTM A240, Type 304 Stainless Steel. A heat of steel made under Table 1 and Table 2 of this paragraph (o)(1) is acceptable, even though its check chemical analysis is slightly out of the specified range, if it is satisfactory in all other respects, provided the tolerances shown in Table 3 of this paragraph (o)(1) are not exceeded. The following chemical analyses and physical properties are authorized:#

Passage 112Table 1.--Authorized Materials ------------------------------------------------------------------------ Chemical analysis, Designation limits in percent ------------------------------------------------------------------------ Carbon1........................................ 0.08 max. Manganese...................................... 2.00 max. Phosphorus..................................... 0.045 max. Sulphur........................................ 0.030 max. Silicon........................................ 1.00 max. Nickel......................................... 8.00-10.50 Chromium....................................... 18.00-20.00 Molybdenum..................................... None. Titanium....................................... None. Columbium...................................... None. ------------------------------------------------------------------------ 1 The carbon analysis must be reported to the nearest hundredth of one percent. Table 2.--Physical Properties ------------------------------------------------------------------------ Physical properties (annealed) ------------------------------------------------------------------------ Tensile strength, p.s.i. (minimum)......................... 75,000 Yield strength, p.s.i. (minimum)........................... 30,000 Elongation in 2 inches (minimum) percent................... 30.0 Elongation other permissible gauge lengths (minimum) percent................................................... 15.0 ------------------------------------------------------------------------#

Passage 113Table 3.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance over the maximum Elements Limit or specified range (percent) limit or under the minimum limit ---------------------------------------------------------------------------------------------------------------- Carbon............................... To 0.030, incl............................................. 0.005 Over 0.30 to 0.20, incl.................................... 0.01 Manganese............................ To 1.00 incl............................................... .03 Over 1.00 to 3.00, incl.................................... 0.04 Phosphorus \1\....................... To 0.040, incl............................................. 0.005 Over 0.040 to 0.020 incl................................... 0.010 Sulphur.............................. To .40 incl................................................ 0.005 Silicon.............................. To 1.00, incl.............................................. 0.05 Nickel............................... Over 5.00 to 10.00, incl................................... 0.10 Over 10.00 to 20.00, incl.................................. 0.15 Chromium............................. Over 15.00 to 20.00, incl.................................. 0.20 ---------------------------------------------------------------------------------------------------------------- 1 Rephosphorized steels not subject to check analysis for phosphorus.#

Passage 114(2) Outer jacket. (i) Nonflammable cryogenic liquids. Cylinders intended for use in the transportation of nonflammable cryogenic liquid must have an outer jacket made of steel or aluminum. (ii) Flammable cryogenic liquids. Cylinders intended for use in the transportation of flammable cryogenic liquid must have an outer jacket made of steel. (p) Markings. (1) Markings must be stamped plainly and permanently on shoulder or top head of jacket or on a permanently attached plate or head protective ring. (2) The letters ``ST'', followed by the design service temperature (for example, ST-423F), must be marked on cylinders having a design service temperature of colder than minus 320 deg. F only. Location to be just below the DOT mark. (3) The maximum weight of contents, in pounds (for example, ``Max. Content 51 #''), must be marked on cylinders having a design service temperature colder than minus 320 deg. F only. Location to be near symbol. (4) Special orientation instructions must be marked on the cylinder (for example, THIS END UP), if the cylinder is used in an orientation other than vertical with openings at the top of the cylinder. (5) If the jacket of the cylinder is constructed of aluminum, the letters ``AL'' must be marked after the service pressure marking. Example: DOT-4L150 AL. (6) Except for serial number and jacket material designation, each marking prescribed in this paragraph (p) must be duplicated on each cylinder by any suitable means. (q) Inspector's report. In addition to the information required by Sec. 178.35, the inspector's reports must contain information on: (1) The jacket material and insulation type; (2) The design service temperature ( deg. F); and (3) The impact test results, on a lot basis. Sec. 178.58 Specification 4DA welded steel cylinders for aircraft use.#

Passage 115(a) Type, size, and service pressure. A DOT 4DA is a welded steel sphere (two seamless hemispheres) or a circumferentially welded cylinder (two seamless drawn shells) with a water capacity not over 100 pounds and a service pressure of at least 500 but not over 900 pounds per square inch. (b) Steel. Open-hearth or electric steel of uniform quality must be used. A heat of steel made under Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 of this paragraph (b) are not exceeded except as approved by the Associate Administrator. The following chemical analyses are authorized: Table 1.--Authorized Materials ------------------------------------------------------------------------ 4130 Percent ------------------------------------------------------------------------ Carbon......................................... 0.28/0.33. Manganese...................................... 0.40/0.60. Phosphorus..................................... 0.040 max. Sulfur......................................... 0.040 max. Silicon........................................ 0.15/0.35. Chromium....................................... 0.80/1.10. Molybdenum..................................... 0.15/0.25. ------------------------------------------------------------------------#

Passage 116Table 2.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the minimum limit Element Limit or maximum specified (percent) ------------------------- Under Over minimum maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon.............................. Over 0.15 to 0.40 incl.......................... .03 .04 Manganese........................... To 0.60 incl.................................... .03 .03 Phosphorus \1\...................... All ranges...................................... ........... .01 Sulphur............................. All ranges...................................... ........... .01 Silicon............................. To 0.30 incl.................................... .02 .03 Over 0.30 to 1.00 incl.......................... .05 .05 Chromium............................ To 0.90 incl.................................... .03 .03 Over 0.90 to 2.10 incl.......................... .05 .05 Molybdenum.......................... To 0.20 incl.................................... .01 .01 Over 0.20 to 0.40, incl......................... .02 .02 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus.#

Passage 117(c) Identification of material. Materials must be identified by any suitable method except that plates and billets for hot-drawn containers must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured in accordance with the following requirements: (1) By best appliances and methods. No defect is acceptable that is likely to weaken the finished container appreciably. A reasonably smooth and uniform surface finish is required. No abrupt change in wall thickness is permitted. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (2) All seams of the sphere or cylinders must be fusion welded. Seams must be of the butt or joggle butt type and means must be provided for accomplishing complete penetration of the joint. (e) Welding. Attachments to the container are authorized by fusion welding provided that such attachments are made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130 steel. (f) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure may not exceed 67 percent of the minimum tensile strength of the steel as determined from the physical and burst tests required and may not be over 70,000 p.s.i. For any diameter container, the minimum wall thickness is 0.040 inch. Calculations must be made by the formulas in paragraph (f)(1) or (f)(2) of this section: (1) Calculation for a sphere must be made by the following formula: S=Wall stress in pounds per square inch; P=Test pressure prescribed for water jacket test, i.e., at least 2 times service pressure, in pounds per square inch; D=Outside diameter in inches; t=Minimum wall thickness in inches; E=0.85 (provides 85 percent weld efficiency factor which must be applied in the girth weld area and heat affected zones which zone must extend a distance of 6 times wall thickness from center line of weld); E=1.0 (for all other areas). (2) Calculation for a cylinder must be made by the following formula: S=wall stress in pounds per square inch; P=test pressure prescribed for water jacket test, i.e., at least 2 times service pressure, in pounds per square inch; D=outside diameter in inches; d=inside diameter in inches.#

Passage 118(g) Heat treatment. The completed containers must be uniformly and properly heat-treated prior to tests. Heat-treatment of containers of the authorized analysis must be as follows: (1) All containers must be quenched by oil, or other suitable medium except as provided in paragraph (l)(iv) of this section. (2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1,750 deg. F. (3) The steel must be tempered at the temperature most suitable for the analysis except that in no case shall the tempering temperature be less than 1,000 deg. F. (4) The steel may be normalized at a temperature of 1,650 deg. F instead of being quenched, and containers so normalized need not be tempered. (5) All cylinders, if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle or dye penetrant method to detect the presence of quenching cracks. Any cylinder found to have a quench crack must be rejected and may not be requalified. (h) Openings in container. Openings in the container must comply with the following requirements: (1) Each opening in the container must be provided with a fitting, boss, or pad of weldable steel securely attached to the container by fusion welding. (2) Attachments to a fitting, boss, or pad must be adequate to prevent leakage. Threads must comply with the following: (i) Threads must be clean cut, even, without checks, and tapped to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the container; gaskets required, adequate to prevent leakage. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the offici#

Passage 119al test may not exceed 90 percent of the#

Passage 120[[Page 8361]] test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each container must be tested to at least 2 times service pressure. (j) Burst test. One container taken at random out of 200 or less must be hydrostatically tested to destruction. The rupture pressure must be included as part of the inspector's report. (k) Flattening test. Spheres and cylinders must be subjected to a flattening test as follows: (1) Flattening test for spheres. One sphere taken at random out of each lot of 200 or less must be subjected to a flattening test as follows: (i) The test must be performed after the hydrostatic test. (ii) The test must be at the weld between the parallel steel plates on a press with a welded seam, at right angles to the plates. Any projecting appurtenances may be cut off (by mechanical means only) prior to crushing. (2) Flattening test for cylinders. One cylinder taken at random out of each lot of 200 or less, must be subjected to a flattening test as follows: (i) The test must be performed after the hydrostatic test. (ii) The test must between knife edges, wedge shaped, 60 deg. angle, rounded to \1/2\ inch radius; test (l) Radiographic inspection. Radiographic examination is required on all welded joints which are subjected to internal pressure, except that at the discretion of the disinterested inspector, openings less than 25 percent of the sphere diameter need not be subjected to radiographic inspection. Evidence of any defects likely to seriously weaken the container must be cause for rejection. (m) Physical test and specimens for spheres and cylinders. Spheres and cylinders must be subjected to a physical test as follows: (1) A physical test for a sphere is required on 2 specimens cut from a flat representative sample plate of the same heat taken at random from the steel used to produce the sphere. This flat steel from which the 2 specimens are to be cut must receive the same heat- treatment as the spheres themselves. Sample plates to be taken for each lot of 200 or less spheres. (2) Specimens for spheres have a gauge length 2 inches with a width not over 1\1/2\ inches, or a#

Passage 121gauge length at least 24 times thickness with a width not over 6 times thickness is authorized when wall of sphere is not over \3/16\ inch thick. (3) A physical test for cylinders is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. (4) Specimens for cylinder must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with a width not over 1\1/2\ inches, a gauge length at least 24 times thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) Heating of a specimen for any purpose is not authorized. (5) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (n) Acceptable results for physical, flattening, and burst tests. The following are acceptable results of the physical, flattening and burst test: (1) Elongation must be at least 20 percent for a 2-inch gauge length or 10 percent in other cases. (2) Flattening is required to 50 percent of the original outside diameter without cracking. (3) Burst p#

Passage 122ressure must be at least 3 times service pressure. (o) Rejected containers. Reheat-treatment of rejected cylinders is authorized. Subsequent thereto, containers must pass all prescribed tests to be acceptable. Repair of welded seams by welding prior to reheat-treatment is authorized. (p) Marking. Markings on each container must be stamped plainly and permanently on a permanent attachment or on a metal nameplate permanently secured to the container by means other than soft solder. Sec. 178.59 Specification 8 steel cylinders with porous fillings for acetylene. (a) Type and service pressure. A DOT 8 cylinder is a seamless cylinder with a service pressure of 250 pounds per square inch. The following steel is authorized: (1) A longitudinal seam if forge lap welded; (2) Attachment of heads by welding or by brazing by dipping process; or (3) A welded circumferential body seam if the cylinder has no longitudinal seam. (b) Steel. Open-hearth, electric or basic oxygen process steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.25; phosphorus, 0.045; sulphur, 0.050. (c) Identification of steel. Materials must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is acceptable that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Exposed bottom welds. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. (f) Heat treatment. Body and heads formed by drawing or pressing must be uniformly and properly heat treated prior to tests. (g) Openings. Openings in the cylinders must comply with the following: (1) Standard taper pipe threads are required; (2) Length may not be less than as specified for American Standard pipe threads; tapped to gauge; clean cut, even, and without checks.#

Passage 123(h) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) One cylinder out of each lot of 200 or less must be hydrostatically tested to at least 750 pounds per square inch. Cylinders not so tested must be examined under pressure of between 500 and 600 pounds per square inch and show no defect. If hydrostatically tested cylinder fails, each cylinder in the lot may be hydrostatically tested and those passing are acceptable. (i) Leakage test. Cylinders with bottoms closed in by spinning must be subjected to a leakage test by setting the interior air or gas pressure to not less than the service pressure. Cylinders which leak must be rejected. (j) Physical test. A physical test must be conducted as follows: (1) The test is required on 2 specimens cut longitudinally from 1 cylinder or part thereof taken at random out of each lot of 200 or less, after heat treatment. (2) Specimens must conform to a gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with width not over 1\1/2\, or a gauge length at least 24 times thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating t#

Passage 124he elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per-minute during yield strength determination. (4) Yield strength may not exceed 73 percent of tensile strength. Elongation must be at least 40 percent in 2 inch or 20 percent in other cases. (k) Rejected cylinders. Reheat treatment of rejected cylinder is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding is authorized. (l) Porous filling. (1) Cylinders must be filled with a porous material in accordance with the following: (i) The porous material may not disintegrate or sag when wet with solvent or when subjected to normal service; (ii) The porous filling material must be uniform in quality and free of voids, except that a well drilled into the filling material beneath the valve is authorized if the well is filled with a material of such type that the functions of the filling material are not impaired; (iii) Overall shrinkage of the filling material is authorized if the total clearance between the cylinder shell and filling material, after solvent has been added, does not exceed \1/2\ of 1 percent of the respective diameter or length, but not to exceed \1/8\ inch, measured diametrically and longitudinally; (iv) The clearance may not impair the functions of the filling material; (v) The installed filling material must meet the requirements of CGA Pamphlet C-12; and (vi) Porosity of filling material may not exceed 80 percent except that filling material with a porosity of up to 92 percent may be used when tested with satisfactory results in accordance with CGA Pamphlet C-12. (2) When the porosity of each cylinder is not known, a cylinder taken at random from a lot of 200 or less must be tested for porosity. If the test cylinder fails, each cylinder in the lot may be tested individu#

Passage 125ally and those cylinders that pass the test are acceptable. (3) For filling that is molded and dried before insertion in cylinders, porosity test may be made on a sample block taken at random from material to be used. (4) The porosity of the filling material must be determined. The amount of solvent at 70 deg. F for a cylinder: (i) Having shell volumetric capacity above 20 pounds water capacity (nominal) may not exceed the following: ------------------------------------------------------------------------ Maximum acetone solvent Percent porosity of filler percent shell capacity by volume ------------------------------------------------------------------------ 90 to 92................................................... 43.4 87 to 90................................................... 42.0 83 to 87................................................... 40.0 80 to 83................................................... 38.6 75 to 80................................................... 36.2 70 to 75................................................... 33.8 65 to 70................................................... 31.4 ------------------------------------------------------------------------ (ii) Having volumetric capacity of 20 pounds or less water capacity (nominal), may not exceed the following: ------------------------------------------------------------------------ Maximum acetone solvent Percent porosity of filler percent shell capacity by volume ------------------------------------------------------------------------ 90 to 92................................................... 41.8 83 to 90................................................... 38.5 80 to 83................................................... 37.1 75 to 80................................................... 34.8 70 to 75................................................... 32.5 65 to 70................................................... 30.2 ------------------------------------------------------------------------#

Passage 126(m) Tare weight. The tare weight is the combined weight of the cylinder proper, porous filling, valve, and solvent, without removable cap. (n) Duties of inspector. In addition to the requirements of Sec. 178.35, the inspector is required to-- (1) Certify chemical analyses of steel used, signed by manufacturer thereof; also verify by, check analyses of samples taken from each heat or from 1 out of each lot of 200 or less, plates, shells, or tubes used. (2) Verify compliance of cylinder shells with all shell requirements; inspect inside before closing in both ends; verify heat treatment as proper; obtain all samples for all tests and for check analyses; witness all tests; verify threads by gauge; report volumetric capacity and minimum thickness of wall noted. (3) Prepare report on manufacture of steel shells in form prescribed in Sec. 178.35. Furnish one copy to manufacturer and three copies to the company that is to complete the cylinders. (4) Determine porosity of filling and tare weights; verify compliance of marking with prescribed requirements; obtain necessary copies of steel shell reports; and furnish complete reports required by this specification to the person who has completed the manufacture of the cylinders and, upon request, to the purchaser. The test reports must be retained by the inspector for fifteen years from the original test date of the cylinder. (o) Marking. (1) Marking on each cylinder must be stamped plainly and permanently on or near the shoulder, top head, neck or valve protection collar which is permanently attached to the cylinder and forming integral part thereof. (2) Tare weight of cylinder, in pounds and ounces, must be marked on the cylinder. (3) Cylinders, not completed, when delivered must each be marked for identification of each lot of 200 or less. Sec. 178.60 Specification 8AL steel cylinders with porous fillings for acetylene.#

Passage 127(a) Type and service pressure. A DOT 8AL cylinder is a seamless steel cylinder with a service pressure of 250 pounds per square inch. However, the attachment of heads by welding or by brazing by dipping process and a welded circumferential body seam is authorized. Longitudinal seams are not authorized. (b) Authorized steel. The authorized steel is as specified in Table I of Appendix A to this part. (c) Identification of steel. Material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Footrings. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. (f) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) The attachment to the tops or bottoms of cylinders of neckrings, footrings, handlers, bosses, pads, and valve protecting rings is authorized provided that such attachments and the portion of the container to which they are attached are made of weldable steel, the carbon content of which may not exceed 0.25 percent. (2) Heat treatment is not required after welding or brazing weldable low carbon parts to attachments, specified in paragraph (f)(1) of this section, of similar material which have been previously welded or brazed to the top or bottom of cylinders and properly heat treated, provided such subsequent welding or brazing does not produce a temperature in excess of 400 deg. F in any part of the top or bottom material. (g) Wall thickness; wall stress. The wall thickness/wall stress of the cylinder must conform to the following: (1) The calculated wall stress at 750 pounds per square inch may not exceed 35,000 pounds per square inch, or one-half of the minimum ultimate strength of the steel as determined in paragraph (l) of this section, whichever value is the smaller. The measured wall thickness may not include galvanizing or other protective coating. (i) Calculation of wall stress must be made by#

Passage 128S=Wall stress in pounds per square inch; P=750 pounds per square inch (minimum test pressure); D=Outside diameter in inches; d=Inside diameter in inches.#

Passage 129(ii) Either D or d must be calculated from the relation D=d + 2t, where t=minimum wall thickness. (2) Cylinders with a wall thickness less than 0.100 inch, the ratio of straight side wall length to outside diameter may not exceed 3.5. (3) For cylinders having outside diameter over 5 inches, the minimum wall thickness must be 0.087 inch. (h) Heat treatment. Each cylinder must be uniformly and properly heat treated, prior to tests, by any suitable method in excess of 1100 deg. F. Heat treatment must be accomplished after all forming and welding operations, except that when brazed joints are used, heat treatment must follow any forming and welding operations but may be done before, during, or after the brazing operations. Liquid quenching is not authorized. (i) Openings. Standard taper pipe threads required in all openings. The length of the opening may not be less than as specified for American Standard pipe threads; tapped to gauge; clean cut, even, and without checks. (j) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows; (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) One cylinder out of each lot of 200 or less must be hydrostatically tested to at least 750 pounds per square inch. Cylinders not so tested must be examined under pressure of between 500 and 600 pounds per square inch and show no defect. If a hydrostatically tested cylinder fails, each cylinder in the lot may be hydrostatically tested and those passing are acceptable. (k) Leakage test. Cylinders with bottoms closed in by spinning must be leakage tested by setting the interior air or gas pressure at not less than the service pressure. Any cylinder that leaks must be rejected. (l) Physical test. A physical test must be conducted as follows; (1) The test is required on 2#

Passage 130specimens cut longitudinally from 1 cylinder or part thereof taken at random out of each lot of 200 or less, after heat treatment. (2) Specimens must conform to a gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy,#

Passage 131[[Page 8364]] the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed 1/8 inch per minute during yield strength determination. (m) Elongation. Physical test specimens must show at least a 40 percent elongation for a 2 inch gauge length or at least a 20 percent elongation in other cases. Except that these elongation percentages may be reduced numerically by 2 for 2 inch specimens and 1 in other cases for each 7,500 pounds per square inch increment of tensile strength above 50,000 pounds per square inch to a maximum of four such increments. (n) Weld tests. Specimens taken across the circumferentially welded seam must be cut from one cylinder taken at random from each lot of 200 or less cylinders after heat treatment and must pass satisfactorily the following tests: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less, or welded test plate. The specimen must be taken from across the major seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. Should this specimen fail to meet the requirements, specimens may be taken from two additional cylinders or welded test plates from the same lot and tested. If either of the latter specimens fail to meet the requirements, the entire lot represented must be rejected. (2) Guided bend test. A root bend test specimen must be cut from the cylinder or welded test plate, used for the tensile test specified in paragraph (n)(1) of this section. Specimens must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (3) Alternate guided-bend test. This test may be used and must be as required by CGA Pamphlet C-3. The specimen must be bent until the elongation at the outer surface, adjacent to the root of the weld, between the lightly scribed gage lines--a to b, must be at least 20 percent, except that this percentage may be reduced for steels having a tensile strength in excess of 50,000 pounds per square inch, as provided in paragraph (m) of this section. (o) Rejected cylinders. Rehe#

Passage 132at treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding is authorized. (p) Porous filling. (1) Cylinders must be filled with a porous material in accordance with the following: (i) The porous material may not disintegrate or sag when wet with solvent or when subjected to normal service; (ii) The filling material must be uniform in quality and free of voids, except that a well drilled into the filling material beneath the valve is authorized if the well is filled with a material of such type that the functions of the filling material are not impaired; (iii) Overall shrinkage of the filling material is authorized if the total clearance between the cylinder shell and filling material, after solvent has been added, does not exceed \1/2\ of 1 percent of the respective diameter or length but not to exceed \1/8\ inch, measured diametrically and longitudinally; (iv) The clearance may not impair the functions of the filling material; (v) The installed filling material must meet the requirements of CGA Pamphlet C-12; and (vi) Porosity of filling material may not exceed 80 percent except that filling material with a porosity of up to 92 percent may be used when tested with satisfactory results in accordance with CGA Pamphlet C-12. (2) When the porosity of each cylinder is not known, a cylinder taken at random from a lot of 200 or less must be tested for porosity. If the test cylinder fails, each cylinder in the lot may be tested individually and those cylinders that pass the test are acceptable. (3) For filling that is molded and dried before insertion in cylinders, porosity test may be made on sample block taken at random from material to be used. (4) The porosity of the filling material must be determined; the amount of solvent at 70 deg. F for a cylinder: (i) Having shell volumetric capacity above 20 pounds water capacity (nominal) may not exceed the following:#

Passage 133------------------------------------------------------------------------ Maximum acetone solvent Percent porosity of filler percent shell capacity by volume ------------------------------------------------------------------------ 90 to 92................................................... 43.4 87 to 90................................................... 42.0 83 to 87................................................... 40.0 80 to 83................................................... 38.6 75 to 80................................................... 36.2 70 to 75................................................... 33.8 65 to 70................................................... 31.4 ------------------------------------------------------------------------ (ii) Having volumetric capacity of 20 pounds or less water capacity (nominal), may not exceed the following: ------------------------------------------------------------------------ Maximum acetone solvent Percent porosity of filler percent shell capacity by volume ------------------------------------------------------------------------ 90 to 92................................................... 41.8 83 to 90................................................... 38.5 80 to 83................................................... 37.1 75 to 80................................................... 34.8 70 to 75................................................... 32.5 65 to 70................................................... 30.2 ------------------------------------------------------------------------#

Passage 134(q) Tare weight. The tare weight is the combined weight of the cylinder proper, porous filling, valve, and solvent, but without removable cap. (r) Duties of inspector. In addition to the requirements of Sec. 178.35, the inspector shall-- (1) Certify chemical analyses of steel used, signed by manufacturer thereof; also verify by check analyses, of samples taken from each heat or from 1 out of each lot of 200 or less plates, shells, or tubes used. (2) Verify compliance of cylinder shells with all shell requirements, inspect inside before closing in both ends, verify heat treatment as proper; obtain all samples for all tests and for check analyses, witness all tests; verify threads by gauge, report volumetric capacity and minimum thickness of wall noted. (3) Report percentage of each specified alloying element in the steel. Prepare report on manufacture of steel shells in form prescribed in Sec. 178.35. Furnish one copy to manufacturer and three copies to the company that is to complete the cylinders. (4) Determine porosity of filling and tare weights; verify compliance of marking with prescribed requirements; obtain necessary copies of steel shell reports prescribed in paragraph (b) of this section; and furnish complete test reports required by this specification to the person who has completed the manufacture of the cylinders and, upon request, to the purchaser. The test reports must be retained by the inspector for fifteen years from the original test date of the cylinder. (s) Marking. (1) Tare weight of cylinder, in pounds and ounces, must be marked on the cylinder. (2) Cylinders, not completed, when delivered must each be marked for identification of each lot of 200 or less. (3) Markings must be stamped plainly and permanently in locations in accordance with the following: (i) On shoulders and top heads not less than 0.087 inch thick; or (ii) On neck, valve boss, valve protection sleeve, or similar part permanently attached to the top end of cylinder; or (iii) On a plate of ferrous material attached to the top of the cylinder or permanent part thereof; the plate must be at least \1/16\ inch thick, and must be attached by welding, or by brazing at a temperature of at least 1,100 deg.F throughout all edges of the plate. Sufficient space must be left on the plate to provide for stamping at least four (4) retest dates.#

Passage 135Sec. 178.61 Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam.#

Passage 136(a) Type, size and service pressure. A DOT 4BW cylinder is a welded type steel cylinder with a longitudinal electric-arc welded seam, a water capacity (nominal) not over 1,000 pounds and a service pressure at least 225 and not over 500 pounds per square inch gauge. Cylinders closed in by spinning process are not authorized. (b) Authorized steel. Steel used in the construction of the cylinder must conform to the following: (1) The body of the cylinder must be constructed of steel conforming to the limits specified in Table I of Appendix A to this part. (2) Material for heads must meet the requirements of paragraph (a) of this section or be open hearth, electric or basic oxygen carbon steel of uniform quality. Content percent may not exceed the following: Carbon 0.25, Manganese 0.60, Phosphorus 0.045, Sulfur 0.050. Heads must be hemispherical or ellipsoidal in shape with a maximum ratio of 2.1. If low carbon steel is used, the thickness of such heads must be determined by using a maximum wall stress of 24,000 p.s.i. in the formula described in paragraph (f)(1) of this section. (c) Identification of material. Material must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart and the following: (1) No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface is required. Exposed bottom welds on cylinders over 18 inches long must be protected by footrings. Minimum thickness of heads may not be less than 90 percent of the required thickness of the sidewall. Heads must be concave to pressure. (2) Circumferential seams must be by electric-arc welding. Joints must be butt with one member offset (joggle butt) or lap with minimum overlap of at least four times nominal sheet thickness. (3) Longitudinal seams in shells must conform to the following: (i) Longitudinal electric-arc welded seams must be of the butt welded type. Welds must be made by a machine process including automatic feed and welding guidance mechanisms. Longitudinal seams must have complete joint penetration, and must be free from undercuts, overlaps or abrupt ridges or valleys. Misalignment of mating butt edges may not exceed \1/6\ of nominal sheet thickness or \1/32\ inch whichever is less#

Passage 137. All joints with nominal sheet thickness up to and including \1/8\ inch must be tightly butted. When nominal sheet thickness is greater than \1/8\ inch, the joint must be gapped with maximum distance equal to one-half the nominal sheet thickness or \1/ 32\ inch whichever is less. Joint design, preparation and fit-up must be such that requirements of this paragraph (d) are satisfied. (ii) Maximum joint efficiency must be 1.0 when each seam is radiographed completely. Maximum joint efficiency must be 0.90 when one cylinder from each lot of 50 consecutively welded cylinders is spot radiographed. In addition, one out of the first five cylinders welded following a shut down of welding operations exceeding four hours must be spot radiographed. Spot radiographs, when required, must be made of a finished welded cylinder and must include the girth weld for 2 inches in both directions from the intersection of the longitudinal and girth welds and include at least 6 inches of the longitudinal weld. Maximum joint efficacy of 0.75 must be permissible without radiography. (4) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (e) Welding of attachments. The attachment to the tops and bottoms only of cylinders by welding of neckrings, footrings, handles, bosses, pads and valve protection rings is authorized provided that such attachments and the portion of the container to which they are attached are made of weldable steel, the carbon content of which may not exceed 0.25 percent. (f) Wall thickness. For outside diameters over 6 inches the minimum wall thickness must be 0.078 inch. For a cylinder with a wall thickness less than 0.100 inch, the ratio of tangential length to outside diameter may not exceed 4 to 1 (4:1). In any case the minimum wall thickness must be such that the wall stress calculated by the formula listed in paragraph (f)(4) of this section may not exceed the lesser value of any of the following: (1) The value referenced in paragraph (b) of this section for the particular material under consideration. (2) One-half of the minimum tensile strength of the material determined as required in paragraph (m) of this section. (3) 35,000 pounds per square inch. (4) Stress must be calculated by the following formula:#

Passage 138S=wall stress, p.s.i.; P=service pressure, p.s.i.; D=outside diameter, inches; d=inside diameter, inches; E=joint efficiency of the longitudinal seam (from paragraph (d) of this section). (g) Heat treatment. Each cylinder must be uniformly and properly heat treated prior to test by the applicable method referenced in paragraph (b) of this section. Heat treatment must be accomplished after all forming and welding operations. Heat treatment is not required after welding or brazing of weldable low carbon parts to attachments of similar material which have been previously welded to the top or bottom of cylinders and properly heat treated, provided such subsequent welding or brazing does not produce a temperature in excess of 400 deg. F in any part of the top or bottom material. (h) Openings in cylinders. Openings in the cylinder must conform to the following: (1) All openings must be in the heads or bases. (2) Openings in cylinders must be provided with adequate fittings, bosses, or pads, integral with or securely attached to the cylinder by welding. (3) Threads must comply with the following: (i) Threads must be clean cut and to gauge. (ii) Taper threads must be of length not less than as specified for American Standard Taper Pipe threads. (iii) Straight threads, having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the cylinder; gaskets required, adequate to prevent leakage. (4) Closure of fittings, boss or pads must be adequate to prevent leakage. (i) Hydrostatic test. Cylinders must withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit readings to an#

Passage 139[[Page 8366]] accuracy of 1 percent. The expansion gauge must permit readings of total volumetric expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat treatment and previous to the official test may not exceed 90 percent of the test pressure. (3) Permanent volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) At least 1 cylinder selected at random out of each lot of 200 or less must be tested as outlined in paragraphs (i)(1), (i)(2), and (i)(3) of this section to at least two times service pressure. (ii) All cylinders not tested as outlined in paragraph (i)(4)(i) of this section must be examined under pressure of at least two times service pressure and show no defect. (5) One finished cylinder selected at random out of each lot of 500 or less successively produced must be hydrostatically tested to 4 times service pressure without bursting. (j) Physical tests. Cylinders must be subjected to a physical test as follows: (1) Specimens must be taken from one cylinder after heat treatment and chosen at random from each lot of 200 or less, as follows: (i) Body specimen. One specimen must be taken longitudinally from the body section at least 90 degrees away from the weld. (ii) Head specimen. One specimen must be taken from either head on a cylinder when both heads are made of the same material. However, if the two heads are made of differing materials, a specimen must be taken from each head. (iii) If due to welded attachments on the top head there is insufficient surface from which to take a specimen, it may be taken from a representative head of the same heat treatment as the test cylinder. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with a width not over 1\1/2\ inches, or a gauge length at least 24 times thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) When size of the cylinder does not permit securin#

Passage 140g straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows when specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``off-set'' method or the ``extension under load'' method as prescribed in ASTM Standard E8-78. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load''), corresponding to the stress at which the 0.2-percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2- percent offset. (iii) For the purpose of strain measurement, the initial strain reference must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (k) Elongation. Physical test specimens must show at least a 40 percent elongation for a 2-inch gauge length or at least a 20 percent elongation in other cases. Except that these elongation percentages may be reduced numerically by 2 for 2-inch specimens and by 1 in other cases for each 7,500 pounds per square inch increment of tensile strength above 50,000 pounds per square inch to a maximum of four increments. (l) Tests of welds. Welds must be subjected to the following tests: (1) Tensile test. A specimen must be cut from one cylinder of each lot of 200 or less. The specimen must be taken from across the longitudinal seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (2) Guided bend test. A root test specim#

Passage 141en must be cut from the cylinder used for the tensile test specified in paragraph (l)(1) of this section. Specimens must be taken from across the longitudinal seam and must be prepared and tested in accordance with and must meet the requirements of CGA Pamphlet C-3. (3) Alternate guided bend test. This test may be used and must be as required by CGA Pamphlet C-3. The specimen must be bent until the elongation at the outer surface, adjacent to the root of the weld, between the lightly scribed gauge lines a to b, must be at least 20 percent, except that this percentage may be reduced for steels having a tensile strength in excess of 50,000 pounds per square inch, as provided in paragraph (k) of this section. (m) Radiographic examination. Welds of the cylinders must be subjected to a radiographic examination as follows: (1) Radiographic inspection must conform to the techniques and acceptability criteria set forth in CGA Pamphlet C-3. When fluoroscopic inspection is used, permanent film records need not be retained. (2) Should spot radiographic examination fail to meet the requirements of paragraph (m)(1) of this section, two additional welds from the same lot of 50 cylinders or less must be examined, and if either of these fail to meet the requirements, each cylinder must be examined as previously outlined; only those passing are acceptable. (n) Rejected cylinders. (1) Unless otherwise stated, if a sample cylinder or specimen taken from a lot of cylinders fails the prescribed test, then two additional specimens must be selected from the same lot and subjected to the prescribed test. If either of these fails the test, then the entire lot must be rejected. (2) Reheat treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair of welded seams by welding is authorized provided that all defective metal is cut away and the joint is rewelded as prescribed for original welded joints. (o) Markings. Markings must be stamped plainly and permanently in any of the following locations on the cylinder: (1) On shoulders and top heads when they are not less than 0.087- inch thick. (2) On a metal plate attached to the top of the cylinder or permanent part thereof; sufficient space must be left on the plate to provide for stamping at least six retest dates; the plate must be at#

Passage 142[[Page 8367]] least \1/16\-inch thick and must be attached by welding, or by brazing. The brazing rod is to melt at a temperature of 1100 deg. F. Welding or brazing must be along all the edges of the plate. (3) On the neck, valve boss, valve protection sleeve, or similar part permanently attached to the top of the cylinder. (4) On the footring permanently attached to the cylinder, provided the water capacity of the cylinder does not exceed 25 pounds. (p) Inspector's report. In addition to the information required by Sec. 178.35, the inspector's report must indicate the type and amount of radiography. Sec. 178.65 Specification 39 non-reusable (non-refillable) cylinders. (a) Type, size, service pressure, and test pressure. A DOT 39 cylinder is a seamless, welded, or brazed cylinder with a service pressure not to exceed 80 percent of the test pressure. Spherical pressure vessels are authorized and covered by references to cylinders in this specification. (1) Size limitation. Maximum water capacity may not exceed: (i) 55 pounds (1,526 cubic inches) for a service pressure of 500 p.s.i.g. or less, and (ii) 10 pounds (277 cubic inches) for a service pressure in excess of 500 p.s.i.g. (2) Test pressure. The minimum test pressure is the maximum pressure of contents at 130 deg. F or 180 p.s.i.g. whichever is greater. (3) Pressure of contents. The term ``pressure of contents'' as used in this specification means the total pressure of all the materials to be shipped in the cylinder. (b) Material; steel or aluminum. The cylinder must be constructed of either steel or aluminum conforming to the following requirements: (1) Steel. (i) The steel analysis must conform to the following: ------------------------------------------------------------------------ Ladle Check analysis analysis ------------------------------------------------------------------------ Carbon, maximum percent....................... 0.12 0.15 Phosphorus, maximum percent................... 0.04 0.05 Sulfur, maximum percent....................... 0.05 0.06 ------------------------------------------------------------------------#

Passage 143(ii) For a cylinder made of seamless steel tubing with integrally formed ends, hot drawn, and finished, content percent for the following may not exceed: Carbon, 0.55; phosphorous, 0.045; sulfur, 0.050. (iii) For non-heat treated welded steel cylinders, adequately killed deep drawing quality steel is required. (iv) Longitudinal or helical welded cylinders are not authorized for service pressures in excess of 500 p.s.i.g. (2) Aluminum. Aluminum is not authorized for service pressures in excess of 500 p.s.i.g. The analysis of the aluminum must conform to the Aluminum Association standard for alloys 1060, 1100, 1170, 3003, 5052, 5086, 5154, 6061, and 6063 as specified in its publication entitled ``Aluminum Standards and Data'' (7th edition dated June 1982). (3) Unauthorized material. Material with seams, cracks, laminations, or other injurious defects not permitted. (4) Identification. Material used must be identified by any suitable method. (c) Manufacture. (1) General manufacturing requirements are as follows: (i) The surface finish must be uniform and reasonably smooth. (ii) Inside surfaces must be clean, dry, and free of loose particles. (iii) No defect of any kind is permitted if it is likely to weaken a finished cylinder. (2) Requirements for seams: (i) Brazing is not authorized on aluminum cylinders. (ii) Brazing material must have a melting point of not lower than 1,000 deg. F. (iii) Brazed seams must be assembled with proper fit to ensure complete penetration of the brazing material throughout the brazed joint. (iv) Minimum width of brazed joints must be at least four times the thickness of the shell wall. (v) Brazed seams must have design strength equal to or greater than 1.5 times the minimum strength of the shell wall. (vi) Welded seams must be properly aligned and welded by a method that provides clean, uniform joints with adequate penetration. (vii) Welded joints must have a strength equal to or greater than the minimum strength of the shell material in the finished cylinder. (3) Attachments to the cylinder are permitted by any means which will not be detrimental to the integrity of the cylinder. Welding or brazing of attachments to the cylinder must be completed prior to all pressure tests. (4) Welding procedures and operators must be qualified in accordance with CGA Pamphlet C-3. (d) Wall thickness. The minimum wall thickness must be such that t#

Passage 144he wall stress at test pressure does not exceed the yield strength of the material of the finished cylinder wall. Calculations must be made by the following formulas: (1) Calculation of the stress for cylinders must be made by the following formula: S=Wall stress, in p.s.i.; P=Test pressure; D=Outside diameter, in inches; d=Inside diameter, in inches. (2) Calculation of the stress for spheres must be made by the following formula: Where: S=Wall stress, in p.s.i.; P=Test pressure; D=Outside diameter, in inches; t=Minimum wall thickness, in inches. (e) Openings and attachments. Openings and attachments must conform to the following: (1) Openings and attachments are permitted on heads only. (2) All openings and their reinforcements must be within an imaginary circle, concentric to the axis of the cylinder. The diameter of the circle may not exceed 80 percent of the outside diameter of the cylinder. The plane of the circle must be parallel to the plane of a circumferential weld and normal to the long axis of the cylinder. (3) Unless a head has adequate thickness, each opening must be reinforced by a securely attached fitting, boss, pad, collar, or other suitable means. (4) Material used for welded openings and attachments must be of weldable quality and compatible with the material of the cylinder. (f) Pressure tests. (1) Each cylinder must be tested at an internal pressure of at least the test pressure and must be held at that pressure for at least 30 seconds. (i) The leakage test must be conducted by submersion under water or by some#

Passage 145[[Page 8368]] other method that will be equally sensitive. (ii) If the cylinder leaks, evidences visible distortion, or any other defect, while under test, it must be rejected (see paragraph (h) of this section). (2) One cylinder taken from the beginning of each lot, and one from each 1,000 or less successively produced within the lot thereafter, must be hydrostatically tested to destruction. The entire lot must be rejected (see paragraph (h) of this section) if: (i) A failure occurs at a gage pressure less than 2.0 times the test pressure; (ii) A failure initiates in a braze or a weld or the heat affected zone thereof; (iii) A failure is other than in the sidewall of a cylinder longitudinal with its long axis; or (iv) In a sphere, a failure occurs in any opening, reinforcement, or at a point of attachment. (3) A ``lot'' is defined as the quantity of cylinders successively produced per production shift (not exceeding 10 hours) having identical size, design, construction, material, heat treatment, finish, and quality. (g) Flattening test. One cylinder must be taken from the beginning of production of each lot (as defined above) and subjected to a flattening test as follows: (1) The flattening test must be made on a cylinder that has been tested at test pressure. (2) A ring taken from a cylinder may be flattened as an alternative to a test on a complete cylinder. The test ring may not include the heat affected zone or any weld. However, for a sphere, the test ring may include the circumferential weld if it is located at a 45 degree angle to the ring, +/-5 degrees. (3) The flattening must be between 60 degrees included-angle, wedge shaped knife edges, rounded to a 0.5 inch radius. (4) Cylinders and test rings may not crack when flattened so that their outer surfaces are not more than six times wall thickness apart when made of steel or not more than ten times wall thickness apart when made of aluminum. (5) If any cylinder or ring cracks when subjected to the specified flattening test, the lot of cylinders represented by the test must be rejected (see paragraph (h) of this section). (h) Rejected cylinders. Rejected cylinders must conform to the following requirements: (1) If the cause for rejection of a lot is determinable, and if by test or inspection defective cylinders are eliminated from the lot, the remaining cylinders must be qualified as a new lot under p#

Passage 146aragraphs (f) and (g) of this section. (2) Repairs to welds are permitted. Following repair, a cylinder must pass the pressure test specified in paragraph (f) of this section. (3) If a cylinder made from seamless steel tubing fails the flattening test described in paragraph (g) of this section, suitable uniform heat treatment must be used on each cylinder in the lot. All prescribed tests must be performed subsequent to this heat treatment. (i) Markings. (1) The markings required by this section must be durable and waterproof. The requirements of Sec. 173.24 (c)(1) (ii) and (iv) of this subchapter and Sec. 178.35(h) do not apply to this section. (2) Required markings are as follow: (i) DOT-39. (ii) NRC. (iii) The service pressure. (iv) The test pressure. (v) The registration number (M****) of the manufacturer. (vi) The lot number. (vii) The date of manufacture if the lot number does not establish the date of manufacture. (viii) The following statement: Federal law forbids transportation if refilled-penalty up to $500,000 fine and 5 years imprisonment (49 U.S.C. 5124). (3) The markings required by paragraphs (i)(2)(i) through (i)(2)(v) of this section must be in numbers and letters at least \1/8\ inch high and displayed sequentially. For example: (4) No person may mark any cylinder with the specification identification ``DOT-39'' unless it was manufactured in compliance with the requirements of this section and its manufacturer has a registration number (M****) from the Associate Administrator. Sec. 178.68 Specification 4E welded aluminum cylinders. (a) Type, size and service pressure. A DOT 4E cylinder is a welded aluminum cylinder with a water capacity (nominal) of not over 1,000 pounds and a service pressure of at least 250 to not over 500 pounds per square inch. The cylinder must be constructed of not more than two seamless drawn shells with no more than one circumferential weld. The circumferential weld may not be closer to the point of tangency of the cylindrical portion with the shoulder than 20 times the cylinder wall thickness. Cylinders or shells closed in by spinning process and cylinders with longitudinal seams are not authorized. (b) Authorized material. The cylinder must be constructed of aluminum of uniform quality. The following chemical analyses are authorized:#

Passage 147Table 1.--Authorized Materials ------------------------------------------------------------------------ Chemical analysis--limits Designation in percent 5154 \1\ ------------------------------------------------------------------------ Iron plus silicon............................ 0.45 maximum. Copper....................................... 0.10 maximum. Manganese.................................... 0.10 maximum. Magnesium.................................... 3.10/3.90. Chromium..................................... 0.15/0.35. Zinc......................................... 0.20 maximum. Titanium..................................... 0.20 maximum. Others, each................................. 0.05 maximum. Others, total................................ 0.15 maximum. Aluminum..................................... Remainder. ------------------------------------------------------------------------ \1\ Analysis must regularly be made only for the elements specifically mentioned in this table. If, however, the presence of other elements is indicated in the course of routine analysis, further analysis should be made to determine conformance with the limits specified for other elements.#

Passage 148(c) Identification. Material must be identified by any suitable method that will identify the alloy and manufacturer's lot number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. All welding must be by the gas shielded arc process. (e) Welding. The attachment to the tops and bottoms only of cylinders by welding of neckrings or flanges, footrings, handles, bosses and pads and valve protection rings is authorized. However, such attachments and the portion of the cylinder to which it is attached must be made of weldable aluminum alloys. (f) Wall thickness. The wall thickness of the cylinder must conform to the following: (1) The minimum wall thickness of the cylinder must be 0.140 inch. In any case, the minimum wall thickness must be such that calculated wall stress at twice service pressure may not exceed the lesser value of either of the following: (i) 20,000 pounds per square inch. (ii) One-half of the minimum tensile strength of the material as required in paragraph (m) of this section. (2) Calculation must be made by the following formula: S=Wall stress in pounds per square inch; P=Minimum test pressure prescribed for water jacket test; D=Outside diameter in inches; d=Inside diameter in inches.#

Passage 149(3) Minimum thickness of heads and bottoms may not be less than the minimum required thickness of the side wall. (g) Opening in cylinder. Openings in cylinders must conform to the following: (1) All openings must be in the heads or bases. (2) Each opening in cylinders, except those for safety devices, must be provided with a fitting, boss, or pad, securely attached to cylinder by welding by inert gas shielded arc process or by threads. If threads are used, they must comply with the following: (i) Threads must be clean-cut, even, without checks and cut to gauge. (ii) Taper threads to be of length not less than as specified for American Standard taper pipe threads. (iii) Straight threads, having at least 4 engaged threads, to have tight fit and calculated shear strength at least 10 times the test pressure of the cylinder; gaskets required, adequate to prevent leakage. (3) Closure of a fitting, boss, or pad must be adequate to prevent leakage. (h) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit a reading of the total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure of 2 times service pressure must be maintained for at least 30 seconds and sufficiently longer to insure complete expansion. Any internal pressure applied previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent over the pressure otherwise specified. (3) Permanent volumetric expansion may not exceed 12 percent of total volumetric expansion at test pressure. (4) Cylinders having a calculated wall stress of 18,000 pounds per square inch or less at test pressure may be tested as follows: (i) At least one cylinder selected at random out of each lot of 200 or less must be tested in accordance with paragraphs (h)(1), (h)(2), and (h)(3) of this section. (ii) All cylinders not tested as provided in paragraph (h)(4)(i) of this section must be examined under pressure of at least 2 times service pressure and show no defect. (5) One finished cylinder selected at random out#

Passage 150of each lot of 1,000 or less must be hydrostatically tested to 4 times the service pressure without bursting. Inability to meet this requirement must result in rejection of the lot. (i) Flattening test. After hydrostatic testing, a flattening test is required on one section of a cylinder, taken at random out of each lot of 200 or less as follows: (1) If the weld is not at midlength of the cylinder, the test section must be no less in width than 30 times the cylinder wall thickness. The weld must be in the center of the section. Weld reinforcement must be removed by machining or grinding so that the weld is flush with the exterior of the parent metal. There must be no evidence of cracking in the sample when it is flattened between flat plates to no more than 6 times the wall thickness. (2) If the weld is at midlength of the cylinder, the test may be made as specified in paragraph (i)(1)(i) of this section or must be made between wedge shaped knife edges (60 deg. angle) rounded to a \1/ 2\-inch radius. There must be no evidence of cracking in the sample when it is flattened to no more than 6 times the wall thickness. (j) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from one cylinder or part thereof taken at random out of each lot of 200 or less. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width not over 1\1/2\ inches, a gauge length of 2 inches with a width not over 1\1/2\ inches. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows; when specimens are so taken and prepared, the inspector's report must show in connection with record of physical test detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by the ``offset'' method as#

Passage 151prescribed in ASTM Standard E8-78. (ii) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (k) Acceptable results for physical tests. An acceptable result of the physical test requires an elongation to at least 7 percent and yield strength not over 80 percent of tensile strength. (l) Weld tests. Welds of the cylinder are required to successfully pass the following tests: (1) Reduced section tensile test. A specimen must be cut from the cylinder used for the physical tests specified in paragraph (j) of this section. The specimen must be taken from across the seam, edges must be parallel for a distance of approximately 2 inches on#

Passage 152[[Page 8370]] either side of the weld. The specimen must be fractured in tension. The apparent breaking stress calculated on the minimum wall thickness must be at least equal to 2 times the stress calculated under paragraph (f)(2) of this section, and in addition must have an actual breaking stress of at least 30,000 pounds per square inch. Should this specimen fail to meet the requirements, specimens may be taken from 2 additional cylinders from the same lot and tested. If either of the latter specimens fails to meet requirements, the entire lot represented must be rejected. (2) Guided bend test. A bend test specimen must be cut from the cylinder used for the physical tests specified in paragraph (j) of this section. Specimen must be taken across the seam, must be 1\1/2\ inches wide, edges must be parallel and rounded with a file, and back-up strip, if used, must be removed by machining. The specimen must be bent to refusal in the guided bend test jig illustrated in paragraph 6.10 of CGA Pamphlet C-3. The root of the weld (inside surface of the cylinder) must be located away from the ram of the jig. No specimen must show a crack or other open defect exceeding \1/8\ inch in any direction upon completion of the test. Should this specimen fail to meet the requirements, specimens may be taken from each of 2 additional cylinders from the same lot and tested. If either of the latter specimens fail to meet requirements, the entire lot represented must be rejected. (m) Rejected cylinders. Repair of welded seams is authorized. Acceptable cylinders must pass all prescribed tests. (n) Inspector's report. In addition to the information required by Sec. 178.35, the record of chemical analyses must also include applicable information on iron, titanium, zinc, and magnesium used in the construction of the cylinder. Issued in Washington, DC on February 12, 1996, under authority delegated in 49 CFR Part 106. Alan I. Roberts, Associate Administrator for Hazardous Materials Safety. [FR Doc. 96-3554 Filed 3-1-96; 8:45 am] BILLING CODE 4910-60-P#