SUMMARY:RSPA was recently advised of the use of aluminum pressure relief valves on portable tanks and cargo tanks that are used for the transportation of anhydrous ammonia which is not authorized by the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180). The intent of this notice is to ensure safety and facilitate compliance with the HMR by clarifying applicable regulatory requirements pertaining to aluminum pressure relief valves.

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