Introduction to the Design & Maintenance of Pressure Relief Valves Onboard Gas Carriers

There was an incident during the loading of propane into a semi-pressurised LPG carrier. Pressure Relief Valves (PRV's) were set to operate at 11 bar gauge. At a pressure of 7 bar gauge one of the two PRV's fitted to a cargo tank lifted and failed to re-seat. There were no guidelines on board, or in the terminal, to describe or suggest emergency methods of closing the valve. This guide advises on types of PRV's maintenance and testing, emergency closure and operating problems and faults.