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.