| 摘要 |
<p>A subsurface safety valve for wells, including a ball valve closed by well fluid pressure and opened by control fluid pressure supplied from the surface. The ball valve includes a control fluid pressure responsive balancing valve for equalizing pressure across the closed ball valve to relieve the ball valve seating pressure. The ball valve is rotatable on support pins carried by the control fluid pressure responsive piston. A spring acts upwardly on the piston to assist well fluid pressure in overcoming control fluid pressure to close the ball valve.</p> |
