This book was written following an incident in 1992 that involved failure of a relief valve when a semi-pressurised LPG carrier was being loaded. The cargo being loaded was propane, and the pressure relief valves PRVs were set to operate at 11 bar gauge. During the final stages of loading at a pressure of 7 bar gauge, one of the pressure relief valves fitted to a cargo tank failed.
There were no guidelines available on board or at the terminal to provide any assistance in the emergency methods for closing the valve. The valve was eventually blanked off with the tank pressure reduced to 0.02 bar gauge, but by this time a large amount of the product had been lost into the atmosphere. The investigation that followed discovered that there was a failure of the pilot valve diaphragm, possibly due to the diaphragms being in service for too long.