Charging of cylinders with non-liquefied compressed gases.

(a) Detailed requirements. Nonliquefied compressed gases (except gas in solution) for which charging requirements are not definitely prescribed in § 173.304(a)(2) must be shipped, subject to § 173.301, and § 173.305 in specification containers as follows:

(1) Specification 3,1 3A, 3AA, 3B, 3C,1 3D,1 3E, 4,1 4A,1 4B, 4BA, 4BW, 4C,1 25,1 26,1 33,1 or 38,1 (§§ 178.36, 178.37, 178.38, 178.42, 178.50, 178.51, 178.61 of this subchapter). See §§ 173.34 and 173.301(e).

1 Use of existing cylinders authorized, but new construction not authorized.

Note 1: Authorized cylinders containing oxygen which is continuously fed to tanks containing live fish may be shipped irrespective of the provisions of § 173.24.

(2) Specification 3HT (§ 178.44 of this subchapter) cylinders for aircraft use only, having a maximum service life of 24 years. Authorized only for nonflammable gases. Cylinders must be equipped with safety relief devices only of the frangible disc type which meet the requirements of § 173.34(d). Each frangible disc must have a rated bursting pressure which does not exceed 90 percent of the minimum required test pressure of the cylinder. Discs with fusible metal backing are not permitted. Spec. 3HT cylinders may be shipped only when packed in strong outside packagings.

(3) Specification 3AX, 3AAX, or 3T (§§ 178.36, 178.37, 178,45 of this subchapter) cylinders are authorized only for the following nonliquefied gases: Air, argon, boron trifluoride, carbon monoxide, ethane, ethylene, helium, hydrogen, methane, neon, nitrogen, or oxygen, except that specification 3T is not authorized for hydrogen. As used in this paragraph methane is a nonliquefied gas which has a minimum purity of 98.0 percent methane and which is commerically free of corroding components.

(4) Specification 39 (§ 178.65 of this subchapter) cylinder. For flammable gases, internal volume may not exceed 75 cubic inches. Aluminum cylinders are authorized for oxygen only under the following conditions:

(i) Cylinder threads must be straight threads;

(ii) Cylinder must be equipped only with brass or stainless steel valve; and

(iii) Each cylinder must be cleaned in compliance with the requirements of Federal Specification RR-C-901c, dated January 15, 1981, paragraphs 3.7.2 and 3.8.2. Cleaning agents equivalent to those specified in RR-C-901c, may be used; however any cleaning agent must not be capable of reacting with oxygen. One cylinder selected at random from a group of 200 or less cleaned at the same time, must be tested for oil contamination in accordance with specification RR-C-901c, paragraph 4.4.2.3 and meet the standard of cleanliness specified.

(5) Specification 3AL (§ 178.46 of this subchapter) cylinders are authorized only for the following nonliquefied gases: air, argon, carbon monoxide, diborane, ethylene, helium, mercury free hydrogen, krypton, methane, nitrogen, neon, oxygen and xenon. Flammable gases shipped in 3AL cylinders are authorized only when transported by highway, rail and cargo-only aircraft. When used in oxygen service, aluminum cylinders must be in compliance with the following conditions:

(i) Cylinder must be equipped only with brass or stainless steel valve;

(ii) Cylinder must have only straight threads in the opening;

(iii) Each cylinder must be cleaned in compliance with the requirements of Federal Specification RR-C-901c, dated August 1, 1967, paragraphs 3.7.2, and 3.8.2. Cleaning agents equivalent to those specified in RR-C-901c may be used; however, any cleaning agent must not be capable of reacting with oxygen. One cylinder selected at random from a group of 200 or less, cleaned at the same time, must be tested for oil contamination in accordance with Specification RR-C-901c, paragraph 4.4.2.3, and meet the standard of cleanliness specified; and

(iv) The pressure in the cylinder may not exceed 3,000 psig at 70 °F.

(b) Filling limits. (See § 173.301(e).)

(c) Special filling limits for Specifications 3A, 3AX, 3AA, 3AAX, and 3T cylinders. Specifications 3A, 3AX, 3AA, 3AAX, and 3T (§§ 178.36, 178.37, 178.45 of this subchapter) cylinders may be charged with compressed gases, other than liquefied, dissolved, poisonous, or flammable gases to a pressure 10 percent in excess of their marked service pressure, provided:

(1) That such cylinders are equipped with frangible disc safety relief devices (without fusible metal backing) having a bursting pressure not exceeding the minimum prescribed test pressure.

(2) That the elastic expansion shall have been determined at the time of the last test or retest by the water jacket method.

(3) That either the average wall stress or the maximum wall stress does not exceed the wall stress limitation shown in the following table (see Notes 1, 2 and 3):

Type of steel Average wall stress limitation Maximum wall stress limitation Plain carbon steels over 0.35 carbon and medium manganese steels 53,000 58,000 Steels of analysis and heat-treatment specified in spec. 3AA 67,000 73,000 Steel of analysis and heat treatment specified in Spec. DOT-3T 87,000 94,000 Plain carbon steels less than 0.35 carbon made prior to 1920 45,000 48,000

Note 1: The average wall stress shall be computed from the elastic expansion data using the following formula: S = 1.7EE / KV − 0.4P where: S = wall stress, pounds per square inch; EE = elastic expansion (total less permanent) in cubic centimeters; K = factor×10−7, experimentally determined for the particular type of cylinder being tested, or derived in accordance with CGA Pamphlet C-5; V = internal volume in cubic centimeter (1 cubic inch=16.387 cubic centimeters); P = test pressure, pounds per square inch. Formula derived from formula of Note 2 and the following: EE = (PKVD 2) / (D 2 − d 2)

Note 2: The maximum wall stress shall be computed from the formula: S = (P(1.3D 2+0.4d 2)) / (D 2 − d 2) where: S = wall stress, pounds per square inch; P = test pressure, pounds per square inch; D = outside diameter, inches; d = D − 2t, where t= minimum wall thickness determined by a suitable method

Note 3: Compliance with average wall stress limitation may be determined through computation of the elastic expansion rejection limit in accordance with CGA Pamphlet C-5 or through the use of the manufacturer's marked elastic expansion rejection limit (REE) on the cylinder.

(4) That an external and internal visual examination made at the time of test or retest shows the cylinder to be free from excessive corrosion, pitting, or dangerous defects.

(5) That a plus sign (+) be added following the test date marking on the cylinder to indicate compliance with paragraphs (c) (2), (3), and (4) of this section.

(d) Fluorine. Fluorine must be shipped in Specification 3A1000, 3AA1000, or 3BN400 (§ 178.36, § 178.37 or § 178.39 of this subchapter) cylinders without safety relief device and equipped with valve protection cap. Such containers must not be charged to over 400 p.s.i.g. at 70 °F. and must not contain over 6 pounds of gas.

(e) Verification of container pressure. (1) Each day, the pressure in a container representative of that day's compression must be checked by the charging plant after the container has cooled to a settled temperature and a record of this test kept for at least 30 days.

(f) Carbon monoxide. Carbon monoxide must be shipped in a Specification 3A, 3AX, 3AA, 3AAX, 3AL, 3, 3E, or 3T, (§§ 178.36, 178.37, 178.46, 178.42, 178.45 of this subchapter) cylinder having a minimum service pressure of 1,800 psig. The pressure in the cylinder must not exceed 1000 psig at 70 °F. except that if the gas is dry and sulfur free, the cylinder may be charged to five-sixths of the cylinder service pressure or 2000 psig, whichever is the lesser. Specification 3AL cylinders are authorized only when transported by highway, rail and cargo-only aircraft.

(g) Diborane and diborane mixtures. Diborane and diborane mixed with compatible compressed gas in Specification 3AA1800 (§ 178.37 of this subchapter), cylinders. The maximum filling density of the diborane shall not exceed 7 percent. Diborane mixed with compatible compressed gas must not have a pressure exceeding the service pressure of the cylinder if complete decomposition of the diborane occurs. Cylinder valves must be protected either by metal caps or by over packing cylinder in strong wooden boxes.

(h) Poisonous mixtures. Cylinders containing poison gases and poison gas mixtures meeting Division 2.3 Hazard Zone A must conform to the requirements of § 173.40 of this part.

[29 FR 18743, Dec. 29, 1964. Redesignated at 32 FR 5606, Apr. 5, 1967]

Editorial Note: For Federal Register citations affecting § 173.302, see the List of CFR Sections Affected appearing in the Finding Aids section of this volume.