Excerpt from MSIB Number 004-17 published 03/07/2017
Due to a mishap from improper testing of a vapor safety relief valve on a compressed air system, the Coast Guard Office of Commercial Vessel Compliance (CG-CVC) reminds all those concerned of the risks and best practices in conducting or witnessing the testing of relief valves. While this information is based on testing compressed air systems using vapor relief valves, the guidance is also relevant to safety valves in other pressure systems, except boilers.