Abstract: A subsea drilling, production or processing actuation system comprising a variable speed electric motor (10) adapted to be supplied with a current, a reversible hydraulic pump (8, 28) driven by the motor, a hydraulic piston assembly (92, 101, 111, 121, 131) connected to the pump and comprising a first chamber (2), a second chamber (3) and a piston (4) separating the first and second chambers and configured to actuate a valve (91) in a subsea system, a fluid reservoir (14) connected to the pump and the hydraulic piston assembly, the pump, hydraulic piston assembly and reservoir connected in a substantially closed hydraulic system, and a pressure compensator (13, 65) configured to normalize pressure differences between outside the hydraulic system and inside the hydraulic system.

Abstract: A subsea drilling, production or processing actuation system comprising a variable speed electric motor (10) adapted to be supplied with a current, a reversible hydraulic pump (8, 28) driven by the motor, a hydraulic piston assembly (92, 101, 111, 121, 131) connected to the pump and comprising a first chamber (2), a second chamber (3) and a piston (4) separating the first and second chambers and configured to actuate a valve (91) in a subsea system, a fluid reservoir (14) connected to the pump and the hydraulic piston assembly, the pump, hydraulic piston assembly and reservoir connected in a substantially closed hydraulic system, and a pressure compensator (13, 65) configured to normalize pressure differences between outside the hydraulic system and inside the hydraulic system.