| 摘要 |
There is disclosed a surface controlled, subsurface tubing safety valve having a tubular body with a bore therethrough disposable in a tubing string, and a flapper which is movable within-the body between open and closed positions and yieldably urged toward its closed position. The flapper is adapted to be opened by a flow tube which is vertically reciprocable within the body between upper and lower positions. The flow tube is yieldably urged to its upper position to permit the flapper to close, and is lowered to open the flapper by a flexible bellows which has a well pressure on one side and a pressure chamber on one side containing hydraulic fluid which is displaced to cause the bellows to move between expanded and contracted positions in response to the exhaust or supply of control fluid from a source at the surface, the bellows being connected to the flow tube to lower it as the bellows is moved to one position and to permit it to rise as the bellows moves to the other position.
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