| 摘要 |
<p>A double block valve is actuated by a single actuator (30) and includes a valve body housing a cavity (11) and a seating assembly (60). An enclosed space (70) with a finite volume is defined between a first blocking element (42) and a second blocking element (52) when the blocking elements contact the seating assembly. A proving system (210) connects to an enclosed space established between two safety shut-off valves (VI, V2) and includes a pair of three-way valves (V3, VX), oppositely balanced pressure switches (SW1, SW2) and a pump (P) to determine the integrity of the two safety shut-off valves.</p> |
