| 摘要 |
A subsurface safety valve has a tubular valve housing, a valve closure member movable between an open and a closed position, an axially movable opening flow tube for opening the valve closure member. Hydraulic pressure from a control line is used to move a first piston, which in turn moves the axially movable opening prong through the closure member. A balance line can be used to provide a hydrostatic pressure against a second piston. The first and second pistons are coupled to a sliding member within the valve housing. Thus, the opposed piston arrangement substantially offsets any downward force on the first piston.
|
