# Momentive Performance Materials — Hazardous Materials Safety Interpretation **Citation:** 21-0035 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2021-06-02 21-0035 response to Momentive Performance Materials concerning 173.32, 178.275. ## Document text <<>> U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Avenue, SE Washington, DC 20590 June 2, 2021 Kirsten Pink AMR Supply Chain Regulatory Leader Momentive Performance Materials 260 Hudson River Road Waterford, NY 12188 Reference No. 21-0035 Dear Ms. Pink: This letter is in response to your April 5, 2021, letter and subsequent email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the pressure relief device settings on a Department of Transportation (DOT) Specification 51 portable tank to be used in the transportation of “UN1993, Flammable liquids, n.o.s., 3, PG II.” Specifically, you state that it is your understanding that the requirements for the setting of pressure relief devices on DOT Specification 51 portable tanks are found in § 178.275(g)(6). You seek confirmation that the pressure relief device must be set to start to discharge at a nominal pressure of 264 psi (~18.2 bar) for a DOT Specification 51 portable tank with a test pressure of 360 psi (~24.8 bar). Paragraph (f)(2) of § 173.32 states that a hazardous material may not be loaded in a DOT Specification 51, DOT Specification 60, an IM or UN portable tank unless the portable tank has a pressure relief device that provides total relieving capacity meeting the requirements of the HMR. The requirements for the setting of pressure relief devices for portable tanks intended for the transportation of liquid and solid hazardous materials are specified in § 178.275(g)(6)(ii). This section states that for shells with a test pressure of more than 4.5 bar, the pressure relief device must be set to start to discharge at 110% of two-thirds of the test pressure. <<>> Therefore, the start to discharge setting on a pressure relief device would be 264 psig (~18.2 bar) for a DOT Specification 51 portable tank with a test pressure of 360 psig (~24.8 bar). 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: Momentive - LOI 49CFR Part 178.275 Date: Wednesday, April 7, 2021 10:02:03 AM Attachments: 2021-04-05_Momentive_LOI 49CFR Part 178.275.pdf 21-0035 Hi Alice, Please see the attached Letter of Interpretation request. Let us know if you need anything from us. Regards, -Breanna From: Pink, Kirsten [mailto:kirsten.pink@momentive.com] Sent: Monday, April 5, 2021 3:24 PM To: INFOCNTR (PHMSA) Cc: Pink, Kirsten Subject: Momentive - LOI 49CFR Part 178.275 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. Dear Sir or Madam, Please find the attached request for regulatory clarification. Please fee free to contact me should you require any additional information. Best Regards, Kirsten Pink AMR Supply Chain Regulatory Leader Momentive Kirsten.pink@momentive.com (m) 518-441-8998 This message, including attached files, is confidential and intended for the addressees. It may contain information that is proprietary, privileged or exempt for disclosure under applicable law. Any unauthorized use and dissemination of the information or copying of this message is strictly prohibited. Any views, opinions or conclusions expressed in this message are those of the individual sender and do not necessarily reflect the views of Momentive or its affiliates. If you received this message in error, please immediately advise the sender by reply email, delete all copies of this message and refrain from printing, copying, or disseminating this message or otherwise using the information in it. Thank you. Although Momentive routinely screens incoming and outgoing mail messages for viruses, addressees should scan this e-mail and any attachments for viruses themselves. Momentive does not guarantee in any way the absence of viruses in this e-mail or any attachments and disclaims any liability in case of security problem that this message may cause to any system. <<>> Momentive Performance Materials Inc. 260 Hudson River Road Waterford, NY 12188 momentive.com Larson 21-0035 (6) Setting of pressure relief devices. (i) Pressure relief devices must operate only in conditions of excessive rise in temperature. The shell must not be subject to undue fluctuations of pressure during normal conditions of transportation. (ii) The required pressure relief device must be set to start to discharge at a nominal pressure of five-sixths of the test pressure for shells having a test pressure of not more than 4.5 bar (450 kPa) and 110% of two-thirds of the test pressure for shells having a test pressure of more than 4.5 bar (450 kPa). A self-closing relief device must close at a pressure not more than 10% below the pressure at which the discharge starts. The device must remain closed at all lower pressures. This requirement does not prevent the use of vacuum-relief or combination pressure relief and vacuum-relief devices. Kirsten Pink ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `e2345e04dcccdc47323fead560fa3d24bfd02cc36ffd7dba9977189990d3f336` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-23T21:30:54.338Z - Document slug: `phmsa-interpretation-21-0035` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Momentive Performance Materials" ], "individuals": [ "Kirsten Pink" ], "refIds": [ "21-0035" ], "catalogDates": [ "2021-06-02" ], "catalogParts": [ 173, 178 ], "catalogRowCount": 2, "sourceRecordUrls": [ "https://www.phmsa.dot.gov/node/72696" ], "linkedAttachmentUrls": [], "unavailableResponseUrls": [], "duplicateRepresentationUrls": [], "citedSections": [ "173.32", "178.275", "178.275(g)(6)" ], "catalogPageUrls": [ "https://www.phmsa.dot.gov/regulations/title49/section/17332", "https://www.phmsa.dot.gov/regulations/title49/section/178275" ], "pdfUrls": [ "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/75101/210035.pdf" ], "representations": [ { "viewUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/75101/210035.pdf", "detailUrl": null, "detailHtmlPath": null, "pdfUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/75101/210035.pdf", "pdfArtifactPath": "data/sources/phmsa-interpretations/21-0035-69ed1b6815.pdf", "pdfArtifactSha256": "5136ff17ac5b4a9bf1c3ab728db58f34312d0d5ad1e13599a61c407f33bae2da", "extractedTextPath": "data/sources/phmsa-interpretations/21-0035-69ed1b6815.v2.txt", "extractedTextSha256": "cff0724039bab9db3073241988f98bcc7eb5a2e23eb94be86ab84c7ee5363068", "pageCount": 4, "extractionVersion": 2 } ], "caveat": "Interpretations apply regulations to the facts presented and do not create independently enforceable requirements.", "jurisdiction": "US" } ```