Thickness test of a nurse tank
Pipeline and Hazardous Materials Safety Administration · Nov 27, 2007 · Reference No. 07-0197
Interprets: 49 CFR § 180.407
Reggie’s quick take
A company asked whether the actual wall thickness of a nurse tank used to carry anhydrous ammonia must be recorded after a thickness test. The agency said no. Thickness testing under § 180.407 applies to unlined DOT specification cargo tanks that carry materials corrosive to the tank. A nurse tank is a non-DOT specification cargo tank that only has to meet § 173.315(m). So the thickness testing and recording rules in § 180.407 do not apply to it.
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.
This is in response to your request for a clarification of the nurse tank provisions in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask if the actual thickness of a nurse tank, used to carry anhydrous ammonia, must be recorded following a thickness test.
The answer is no. A thickness test is required for unlined DOT specification cargo tanks used to transport materials corrosive to the tank as specified in paragraphs (c) and (i) of § 180.407. A nurse tank is a non-DOT specification cargo tank that must only meet the provisions in § 173.315(m). Therefore, the thickness testing and recording provisions in § 180.407 do not apply.
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.