 ESD valves are required by law on any equipment placed on an offshore drilling rig to prevent catastrophic events like the BP Horizon explosion in the Gulf of Mexico in 2010.A safety shutoff valve should be fail-safe, that is close upon failure of any element of the input control system (such as temperature controllers, steam pressure controllers), air pressure, fuel pressure, current from a flame detector, or current from other safety devices such as low water cutoff, and high pressure cutoff.A blowdown valve (BDV) is a type of shutdown valve designed to depressurize a pressure vessel by directing vapour to a flare, vent or blowdown stack in an emergency.