{"operation":"document","citation":"03-0011","title":"Mr. John L. Hoffer — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2003-06-20","effective_on":null,"summary":"03-0011 concerning 173.302a.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-03-0011.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-03-0011.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-03-0011","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2003/030011.pdf","body":"<<<PAGE 1>>>\n\nof Transportatior\nJ.S. Department\nJUN 20 2003\n400 Seventh St., S.W.\nWashington, D.C. 20590\nMr. John L. Hoffer\n5104 - 97th Street, S.W.\nReference No. 03-0011\nMukilteo, WA 98275\nDear Mr. Hoffer:\nThis is in reference to your inquiry concerning the requirements for marking a plus sign (+) on\nDOT 3A and 3AA cylinders as specified in §173.302a(b) of the Hazardous Materials Regulations\n(HMR; 49 CFR Parts 171-180). I apologize for the delay in responding.\nA DOT cylinder 3A or 3AA may be marked with a plus sign (+) and filled with a listed gas to 10\npercent above its marked service pressure if all requirements for testing and evaluation contained\nin §173.302a(b) are met. The plus sign is required to be marked on any cylinder, including a\nnew cylinder, when charged to 110 percent. Only a plus sign after the last (most recent) test or\nretest date applies. That is, as stated in your Interpretation A, the cylinder must have the plus\nsign stamped after each requalification retest if it is be filled to 110 percent. The requalification\nretest must be performed using the water jacket method.\nWith regard to the differences in wall stress limits, the wall stress limits prescribed in\n§ 178.37(f)(2) for the DOT 3AA cylinder must be met by the cylinder manufacturer at the time\nof construction. The wall stress limits prescribed in § 173.302a(b)(3) must be met at the time of\neach requalification retest. The HMR contain no limitations on the number of times a cylinder\nthat meets the requirements in § 173.302a(b) may be marked with a plus sign.\nI hope you find this information responsive and helpful. If you have further questions, please do\nnot hesitate to contact this office.\nSincerely,\nHothe 2. Mithe ll\nHattie L. Mitchell, Chief\nRegulatory Review and Reinvention\nOffice of Hazardous Materials Standards\n173.302a (b)/\n030011\n\n<<<PAGE 2>>>\n\nMilliol\nWetsb\n5104 - 97\" Street S.W.\n3173.302 a(b)\nMukilteo, WA 98275\nJanuary 7, 2002\nCulmders\n03-00.11\nMr. Edward T. Mazzullo, Director\nOffice of Hazardous Materials Standards\n400 Seventh Street S.W.\nU.S. DOT/RSPA (DHM-10)\nWashington, D.C. 20590-0001\nRe: SCUBA tank pressure ratings\nDear Mr. Mazzullo:\nI am a SCUBA diver with questions about the use of SCUBA diving tanks. I posed these\nI believe the dive industry suffers from much misinformation on this topic. Toward that\nquestions on behalf of myself. However, I intend to widely disseminate your answers, as\nend, your response may be posted on the world-wide-web and reproduced or quoted in\ndiving magazines or other periodicals.\n1. Background.\nSteel cylinders for use in SCUBA diving frequently have a \"t\" symbol stamped on the\ncylinder adjacent to the service pressure. For example, many cylinders are stamped with\n\"2400 +\" which in the dive industry are referred to as \"low pressure steel tanks\" to\ndistinguish them from steel tanks that have higher service pressures such as 3000 or 3500\npounds per square inch (psi).\nThese cylinders are subject to hydrostatic testing at least every five years. After the\ninitial hydrostatic test, these cylinders are typically not stamped with the \"+\" symbol\nwhen they pass hydrostatic tests.\nThe \"t\" stamp permits these cylinders to be \"overfilled\" with compressed gas by 10%\n....\nabove the service pressure. 49 C.F.R. $173.302a(b).\nIt is \"common knowledge\" in the dive industry that tanks that do not have the \"+\" stamp\nmay not be overfilled by 10%.\nIt is also \"common knowledge\" in the dive industry that tanks may not be stamped with\nthe \"+\" symbol after the initial five-year period after purchase. According to this\n\"common knowledge,\" a cylinder stamped \"2400 +\" may be filled to 2640 psi only\nmay be filled only to 2400 psi.\nduring its first five years. Thereafter, when the cylinder passes another hydrostatic test it\n\n<<<PAGE 3>>>\n\nOn account of this \"common knowledge,\" in the example above most dive shops are not\npractice, primarily in the state of Florida where cave diving is practiced. We need no\nwilling to fill a six-year old tank to 2640 psi. (There are some exceptions to this\nconcern ourselves with those practices for the purposes of this inquiry.)\nThere is a minority view which holds that a SCUBA tank may receive a \"+\" stamp after\npassing hydrostatic testing, even if the test is not the initial test. Because dive shops will\nnot permit any subsequent \"+\" rating after the initial five years, divers must take their\ntanks to some place other than a dive shop to have their tanks hydrostatic tested and re-\nstamped with the \"+\" symbol.\nThere is a second minority view, a much smaller minority view, which holds that once a\nSCUBA tank has been stamped with the \"f\" symbol, it may be overfilled by 10% so long\nas it continues to pass the same visual inspection and hydrostatic testing required of all\nSCUBA tanks. No special testing or stamping is required.\nI have called US Department of Transportation (DOT) Info Center Hotline 1-800-467-\n4922 and was informed that DOT's position is essentially that of the second minority\nview. Overfills are permitted without regard to subsequent \"+\" stamping, so long as\nfrom DOT consistent with this interpretation.\nhydrostatic test is current. I have read on the Internet of others who have received advice\n2. First Question.\nFirst, assume facts that give your agency jurisdiction to regulate the filling of the\ncylinder. That is to say, interstate transportation by a common carrier is involved. Dive\nshops do not know how tanks will be used. As a practical matter they must assume that\nintermittently.\nyour agency has jurisdiction to regulate every fill, even if that conclusion is valid only\nSecond, assume that the cylinder is stamped \"2400+\" because that is the most common\ntank that presents the issue.\nThird, assume that the cylinder has passed visual inspection and hydrostatic testing at the\nsuch tests again in the fifth year after the retail sale, but no \".\" symbol was stamped at\ntime of its initial retail sale to the end user, a SCUBA diver. Also, assume that it passed\nthat time.\nair to 2640 psi?\nMay the cylinder described above legally be filled with compress air or oxygen enriched\nOr, to state the question in more generic terms, once a cylinder has been stamped with the\n\"+\" symbol, is anything special needed (in the way of inspecting, testing, stamping, or\notherwise) to retain the ability to legally overfill the cylinder by 10%?\n3. Analysis.\n• Page 2 of 5\n\n<<<PAGE 4>>>\n\nIn reviewing the regulations, I note that 49 C.F.R §173.302a(b) permits the 10% overfill.\nThere are five requirements in 49 C.F.R §173.302a(b):\n(1) A frangible disc pressure relief device must be installed on the cylinder, which\nin the dive industry is known as a burst disc. No sane diver uses SCUBA\ntanks without one.\n(2) 'The cylinder's elastic expansion was determined at the time of the last test or\nretest by the water jacket method.\" (Emphasis added.) I believe from\ninformation available on the Internet that the water jacket method is used\nindustry wide for hydrostatic testing of SCUBA tanks.\n(3) Average or maximum wall stress cannot exceed certain limitations.\nCompliance with the average wall stress computation may be determined\nthrough a variety of methods, including the manufacturer's marked elastic\nPamphlet C-5.\nexpansion rejection limit (REE) on the cylinder or in accordance with CGA\n(4) The cylinder must pass visual inspection.\n(5). A plus sign (+) \"is added following the test date marking on the cylinder to\nindicate compliance with\" the other four requirements above. I note that 49\nC.F.R §173.34(c)(7) requires date markings on the cylinder after it\nsuccessfully passes a hydrostatic retest.\nInterpretation A: If \"the test date marking on the cylinder\" in requirement (5) refers to\nthe test date for the instant hydrostatic test, then clearly SCUBA tanks must have the \"t\"\nstamped after every hydrostatic test in order to be overfilled 10%.\nInterpretation B: If the \"test date marking on the cylinder\" in (5) refers to the test date\nof the cylinder's initial hydrostatic test, then SCUBA tanks need not have the \"+\" stamp\nafter every hydrostatic test in order to be overfilled by 10%.\nThe use of the word \"last\" in requirement (2) lends support to Interpretation A.\nRequirement (3), regarding wall stress, does not clarify when the limitation applies: at the\nof each hydrostatic test and retest.\ntime of the initial hydrostatic test or subsequent retests. Presumably it applies at the time\n49 C.F.R §173.34(e), regarding periodic qualification and marking of cylinders, does not\nhave been met.\nPage 3 of 5\n\n<<<PAGE 5>>>\n\nI conclude that the \"+\" symbol must be stamped on the cylinder after every hydrostatic\ntest in order to be overfill the cylinder by 10% because of the different wall stress\nlimitations imposed by 49 C.F.R §173.302a(b)(3). Unfortunately, my conclusion\nconflicts with the verbal conclusion given to me by your agency via the US Department\nof Transportation (DOT) Info Center Hotline, 1-800-467-4922.\n4. Second Question.\nAssuming my conclusion to the first question is correct, is the hydrostatic test used for\ncylinders to be stamped with the\nthe essential differentiating factor in determining whether the cylinder qualifies for the\n\"f\" stamp?\n5. Analysis. I could find no regulations describing a different method for hydrostatic\n\"4\" stamped cylinders are hydrostatic tested the same as other 3AA cylinders used for\nSCUBA tanks. In the SCUBA industry, n0 tank will not pass \"hydro\" unless the burst\nlescribed in 49 C.F.R. §173.302a(b)(2).. Only the wall stress calculations in 49 C.F.R\ndisc is in place, the tank passes visual inspection, and the tank passes the hydrostatic test\nhydrostatic test is the same.\n6. Third Question.\nIs there any truth to the SCUBA industry's \"common knowledge\" that no cylinder may\nbe stamped with the \"t\" symbol after its second hydrostatic testing becomes due?\n7. Analysis.\nIndeed, all of the regulations discussed above are premised on the proposition that\nI could find no support in the Code of Federal Regulations for this second proposition.\noverfilling is permitted indefinitely, so long as the regulations are met.\nConclusion.\nI am unschooled in DOT regulations and may have misread or incompletely read them.\nYour opinion addressing these questions would be greatly appreciated. No matter which\ninterpretation you embrace, many in the diving community will be surprised. A\ndefinitive answer is sorely needed.\nIf you have questions, please feel free to contact me.\nPage 4 of 5\n\n<<<PAGE 6>>>\n\nThank you for your attention to this matter.\nSincerely,\n_John L. Hoffer\n425-315-1734\nPage 5 of 5","truncated":false,"body_characters":10586}