| 摘要 |
The improvement in a hydraulic actuator for actuating a subsurface safety valve having a metal piston connected to and actuating the valve and movable in a cylinder in which the cylinder is connected at one end to a hydraulic control fluid passageway and on the second end to pressure in the safety valve. The cylinder includes metal valve seats and metal valve elements are connected to the piston for seating on the valve seats for providing positive seals. A universal connection may be provided between the pistons and the valve elements. The piston seal may be opposing metal cups or a labyrinth seal.
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