US Patent 7637474 Fluid saving blowout preventer operator system

A hydraulic blowout preventer operator comprises a piston rod having one end coupled to a closure member. The operator further comprises an operator housing having one end coupled to a bonnet and a second end coupled to a head. The piston rod extends through the bonnet into the operator housing where it is coupled to a piston that is disposed within the operator housing. The piston comprises a body and a flange. A flange seal is disposed on the flange and is sealingly engaged with the operator housing. A body seal is disposed on the body and is sealingly engaged with the operator housing. The flange seal has a sealing diameter greater than a sealing diameter of the body seal.