| 摘要 |
<p>A fail-safe closure system comprises two control valves (122, 124), a piston actuator (126), a solenoid (147) for operating the control valves and an accumulator module (150). Supply pressurized fluid is applied to an opening chamber of one or a plurality of process valve actuators while a flow path is opened to a vent from a closing chamber of the one or more actuators. Control valves are arranged so that if or when they fail, they fail in a position which allows the process valve actuators to be closed.</p> |
