Combining Pre-approved Thermal Protection Systems To Repair A Tank Car Thermal Protection System
Pipeline and Hazardous Materials Safety Administration · Mar 28, 2024 · Reference No. 23-0102
Interprets: 49 CFR § 179.18, 49 CFR § 179.18(a), 49 CFR § 179.18(a)(1), 49 CFR § 179.18(a)(2), 49 CFR § 179.18(b)(1)
Reggie’s quick take
A company asked whether it can repair an installed thermal protection system on a rail tank car by using a different system from PHMSA's list of pre-approved systems, where the list does not name the two systems as a pair. The asker thought this would be fine and that no new testing was needed, since each system no longer needs test verification on its own. PHMSA disagrees. Pieces of two or more listed systems combined together must be tested under § 179.18(a)-(b), because the listed systems were not tested in combination. Listed systems can be used as complete units without that extra testing.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
March 28, 2024
Reference No. 23-0102
This letter is in response to your November 28, 2023, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to thermal protection systems on rail tank cars. You ask whether thermal protection systems included among the Department’s list of thermal protection systems that comply with the requirements of Part 179, Appendix B—and no longer require test verification per § 179.18(c) —can be combined. Specifically, you ask whether a different thermal protection system on the list may be used to repair a thermal protection system on the list that has already be installed on a tank car if the list does not specifically identify the two systems in use together. It is your understanding that it would be permissible to use one listed thermal protection system to repair another listed thermal protection system provided the tank car still meets the required performance standards set forth in the HMR, and that further test verification of the combined system would be unnecessary because separately both systems no longer require test verification.
Based on the information in your letter and the included plans for repair of the thermal protection system, it is the opinion of this Office that your understanding is incorrect. The thermal protection systems that comply with Part 179, Appendix B and no longer require test verification per § 179.18(c), provide readily available options to be used wholly. Combining pieces of two or more systems from the thermal protection systems list will require test verification in accordance with the requirements of § 179.18(a)-(b), as the systems on the list were not tested in combination.
I hope this information helpful. Please contact us if we can be of further assistance.
Sincerely,
Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division
179.18(c), 179.18(a)-(b)
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.