| 摘要 |
<p>A safety valve 18 includes a flow passage 16, closure mechanism 22, opening prong or sleeve 32 repeatedly displaceable to thereby repeatedly operate the closure mechanism, and a latching device 50 initially maintaining the opening prong positioned so as to isolate the closure mechanism from the flow passage. Releasing the latching device permits the opening prong to open and close the closure mechanism while it is exposed to the flow passage. The valve may be a flapper valve 24 and the latching device may include an interference fit. The latching device may be released in response to a pressure differential between the flow passage and an internal gas chamber. The opening prong may be displaceable to a third position to open the closure mechanism after the latching device is released. A method includes the steps of; latching an opening prong so that a closure mechanism is open and is isolated from a flow passage; releasing the opening prong so that the closure mechanism is closed and is exposed to the flow passage; and displacing the opening prong to a position in which the closure mechanism is open and is exposed to the flow passage.</p> |
