| 摘要 |
A sealing system for a flow tube to keep cement from getting around it to the flapper when the safety valve is in the open position is disclosed. Seals are provided at opposed ends of the flow tube so that the power spring and the flapper will not get fouled with cement pumped through the flow tube in wells that are completed through a production string with the safety valve in place. The seals may be mounted to the flow tube or the surrounding body. A unique seal construction is also disclosed. The force acting on the flow tube to hold the valve open also helps to apply a force against the lower seal adjacent the flapper.
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