Abstract: A subsea actuator for operating a valve (20) or the like comprises a movable wall member (19) fixed to an axially slidable stem and separating a pressure chamber (2) from a space (3) which is subjected to the hydrostatic pressure of ambient seawater. A selector valve (11) is operable to connect the chamber (2) to a source of pressurised fluid, e.g. a source of pressurised gas (14), or to a drain e.g. connected to atmosphere by a pressure vessel (12) and pipe (15). A blowdown valve (16) and dump valve (13) are provided for ejecting liquid collected in the vessel (12). The space (3) may be connected to an open-bottomed container (17) to provide a gas barrier between the seawater and the interior of the actuator. Supply of pressurised gas to the chamber (2) causes the member (19) to be driven forwards, gas being allowed to flow past the member into the space (3) during this movement to assist the expulsion of water from the container (17) and the expulsion of any contaminants from within the actuator.

Abstract: An apparatus for pressurizing and purging the interior of an enclosure (1) comprises a purge valve (3) operable to admit gas to the enclosure either at a high flow rate or at a low flow rate, and a pneumatic control system for the purge valve including a purge/power selector module (6), a enclosure pressure module (4) and a timing module (5) mounted on respective faces of the purge valve body. The purge valve body serves as a manifold providing necessary connections of the control modules (4-6) with each other and the enclosure interior whereby pipe connections are minimized.

Abstract: A valve actuator for a subsea oil well installation includes a rotatable adjusting member (53) for engagement with the valve spindle, and a linear fluid actuator (17) coaxial with the adjusting member and operable by fluid pressure pulses to index the adjusting member around selectively in either direction. A mechanical movement converts linear motion of the actuator to rotary motion of the adjusting member. A fluid operated clutch selectively connects the fluid actuator to the adjusting member. A shaft (65) projects from the rear end of the actuator casing to permit manual adjustment as well. Position sensors (120) emit signals indicative of the valve position, and a pointer (123) at the rear of the casing provides a visual indication of the valve condition.