# Linde Gas & Equipment Inc. — Hazardous Materials Safety Interpretation **Citation:** 22-0035 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2022-12-05 22-0035 response to Linde Gas & Equipment Inc. concerning 171.23, 173.301, 173.301b. ## Document text <<>> 1200 New Jersey Avenue, SE Washington, DC 20590 U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration December 5, 2022 Mr. Mike Stephens Manager Distribution Compliance Linde Gas & Equipment Inc. 217 Loren Street Washington, IL 61571 Reference No. 22-0035 Dear Mr. Stephens, This letter is in response to your March 29, 2022, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the transportation requirements for dual-marked Department of Transportation (DOT) 3AA and United Nations International Organization for Standardization (UN ISO) 9809 cylinders that are also pi-marked. Specifically, you state that your company fills and ships dual-marked, pi-marked cylinders, without pressure relief devices (PRDs), and with the valves protected by steel caps, which are secured to the cylinders. You have included a picture of the steel cap assembly that protects the valve in your email. We have paraphrased and answered your questions as follows: Q1. You ask whether pi-marked DOT 3AA/UN ISO 9809 cylinders meet the provisions in § 173.301(f)(5)(iv) in that a PRD is not required on these cylinders for domestic and foreign transportation. A1. Section 173.301(f)(5)(iv) states that a PRD is not required on a UN pressure receptacle transported in accordance with paragraph (k) or (l) of § 173.301. The reference to paragraphs (k) and (l) in § 173.301(f)(5) is incorrect. This appears to have been an oversight in a previous rulemaking and will be addressed in a future rulemaking. The provisions in § 173.301(k) and (l) are now found in § 171.23(a)(4) and (5). A PRD is not required on a UN pressure receptacle imported for discharge within a single port area, provided the conditions of § 171.23(a)(4)(i) through (iii) are met, or on a UN pressure receptacle filled with a gas and offered for transportation and transported for export, provided the conditions in § 171.23(a)(5)(i) through (iii) are met. Further, <<>> § 171.23(a)(6) specifies additional conditions for DOT specification and UN cylinders not equipped with PRDs provided they are offered for transportation and transported for export. These exceptions do not apply to cylinders offered for domestic transportation. Q2. You ask whether the use of a steel cap conforming to ISO 11117:2008 meets the requirements of § 173.301b(c)(2). A2. The answer is yes. In accordance with § 173.301b(c)(2)(ii), a UN pressure receptacle must have its valves protected from damage that could cause inadvertent release of the contents of the UN pressure receptacle by one of the methods listed in paragraphs (c)(2)(i) through (vi) of that section. One of the permitted methods listed in paragraph (c)(2)(ii) entails equipping the UN pressure receptacle with a valve cap conforming to the requirements in ISO 11117:2008(E) and Technical Corrigendum 1. Q3. You ask whether the use of a steel cap referenced in question Q2 is considered a “metal attachment,” as stated in § 173.301(k). A3. The answer is yes. As stated in § 173.301(k), metal attachments to cylinders must have rounded or chamfered corners, or be otherwise protected, to prevent the likelihood of causing puncture or damage to other hazardous materials packages. This requirement applies to anything temporarily or permanently attached to the cylinder, such as metal skids. The steel cap shown in your picture may meet this requirement. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, T. Glenn Foster Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division <<>> Larson From: INFOCNTR (PHMSA) To: Dodd, Alice (PHMSA) Cc: Hazmat Interps Subject: FW: Clarification of 173.301 Date: Wednesday, April 27, 2022 4:30:18 PM 22-0035 Hello Alice, Please see the below interpretation request. Should you have any questions, do not hesitate to reach out. Regards, -Breanna From: Mike R Stephens Sent: Wednesday, April 6, 2022 4:53 PM To: INFOCNTR (PHMSA) Cc: Mike R Stephens Subject: RE: Clarification of 173.301 CAUTION: This email originated from outside of the Department of Transportation (DOT). Do not click on links or open attachments unless you recognize the sender and know the content is safe. From: Mike R Stephens Sent: Tuesday, March 29, 2022 2:26 PM To: PHMSAPortal@dot.gov Subject: Clarification of 173.301(f)(5)(iv), 173.301 b(c)(ii) and 173.301 (k) To Whom it May Concern, In accordance with 49 CFR 105.20, I am writing to you seeking guidance regarding the below referenced regulations; We fill and ship dual marked DOT 3AA and UN ISO 9809 with Pi marked cylinders made in USA containing Compressed Gas UN 3309 and UN 3305 mixtures. These steel cylinders are not equipped with a PRD and the valve is protected by a steel cap that is secured to the cylinder. <<>> We would like to request an interpretation regarding 173.301(f)(5)(iv) regarding PRD requirements on dual marked DOT 3AA and UN 9809 Pi marked cylinders. 173.301 b(c)(ii) regarding Pressure receptacle valve protection and 173.301 (k) regarding the clarification of “Metal Attachments” Question 1: A). Does our dual marked DOT 3AA/ UN ISO 9809 Pi marked steel cylinders described above meet the requirement of 173.301(f)(5)(iv) in that no PRD is required on the cylinder in use for domestic and foreign shipment? B). Does the use of a steel cap that conforms to ISO 11117:2008 meet the requirement of 173.301 b (c)(2)? C). Is the use of a Cylinder cap on the cylinder considered a “Metal Attachment” in 173.301 (k)? (Picture of Cylinder cap device below) Question 2: Can I get an update of DOT SP-6349, tracking number 2021124691? Question 3: Can I get an update on the modification request for DOT SP-14163, tracking <<>> number 2022024604? Mike Stephens Manager Distribution Compliance Linde Gas & Equipment Inc. Mike.R.Stephens@LInde.com Cell 314-568-6764 The information contained in this email and any attachments may be confidential and is provided solely for the use of the intended recipient(s). If you are not the intended recipient, you are hereby notified that any disclosure, distribution, or use of this e-mail, its attachments or any information contained therein is unauthorized and prohibited. If you have received this in error, please contact the sender immediately and delete this e-mail and any attachments. No responsibility is accepted for any virus or defect that might arise from opening this e-mail or attachments, whether or not it has been checked by anti-virus software. ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `4f8e7d1f6a3ee40d65bbb866d486ecec6bf1fd8f074157d8b6943ff6a2f1c13b` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-22T17:27:26.780Z - Document slug: `phmsa-interpretation-22-0035` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Linde Gas & Equipment Inc." ], "individuals": [ "Mike Stephens" ], "refIds": [ "22-0035" ], "catalogDates": [ "2022-12-05" ], "catalogParts": [ 171, 173 ], "catalogRowCount": 3, "sourceRecordUrls": [ "https://www.phmsa.dot.gov/node/73431" ], "linkedAttachmentUrls": [], "unavailableResponseUrls": [], "duplicateRepresentationUrls": [], "citedSections": [ "171.23", "171.23(a)(4)", "173.301", "173.301(f)(5)(iv)", "173.301b", "173.301b(c)(2)" ], "catalogPageUrls": [ "https://www.phmsa.dot.gov/regulations/title49/section/17123", "https://www.phmsa.dot.gov/regulations/title49/section/173301", "https://www.phmsa.dot.gov/regulations/title49/section/173301b" ], "pdfUrls": [ "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/77006/220035.pdf" ], "representations": [ { "viewUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/77006/220035.pdf", "detailUrl": null, "detailHtmlPath": null, "pdfUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/77006/220035.pdf", "pdfArtifactPath": "data/sources/phmsa-interpretations/22-0035-62318b8a26.pdf", "pdfArtifactSha256": "9dffad6a5ca7d132de30fa7edc2c1790f305f03c52250358ce7f18db91df3fc5", "extractedTextPath": "data/sources/phmsa-interpretations/22-0035-62318b8a26.v2.txt", "extractedTextSha256": "1f973e719eb89656b99179f8e2340a381f05ec73ff4be5dd59318dd591cb3eed", "pageCount": 5, "extractionVersion": 2 } ], "caveat": "Interpretations apply regulations to the facts presented and do not create independently enforceable requirements.", "jurisdiction": "US" } ```