摘要 |
<p>A fail-safe closure system for one or a plurality of springless process valve actuators is disclosed. An accumulator is provided with an urging means, such as a spring for pressurizing fluid stored therein. A source of pressurized fluid is also provided. 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 the closing chamber of the one or more actuators. For closing the actuator or actuators, a flow path is established by which pressurized fluid from the accumulator is applied to the closing chamber of the actuator or actuators while the opening chamber is vented. Control valves are arranged so that if or when they fail, they fail in a position which allows the process valve actuators to close as described.</p> |