| 摘要 |
A safety valve apparatus body defining a flow chamber having a side outlet, a control adjustable to move lengthwise in the chamber, a first valving part carried by the control and movable to advance and retract relative to a second valve part on the body, thereby to provide a first check valve to block reverse flow of fluid through the chamber, and a second check valve proximate the outlet to pass forward fluid flow from the chamber and to block reverse flow of fluid to the chamber, via the side outlet.
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