Subsea wellhead apparatus

摘要

There is disclosed a system for controlling the operation of a ram of a subsea blowout preventer connected to a piston shiftable between alternate positions within a cylinder. The system includes valve apparatus for so shifting the piston which includes an outlet connected to the cylinder, a first passageway through which hydraulic fluid may be supplied to the outlet, a second passageway through which hydraulic fluid may be vented from the outlet, and a valve member movable between positions alternately connecting the outlet with the first and second passageways, respectively, so as to selectively supply hydraulic fluid to or vent hydraulic fluid from the cylinder.