| 摘要 |
A valve actuator with an emergency shutdown feature incorporates shutdown of the valve when a sensed line pressure is outside of high- and low-pressure trip points. The actuator can be manually tripped. The actuator can be tripped in the event of a fire or, incorporating a solenoid, a trip can be accomplished with an appropriate signal. Once tripped, the actuator requires manual reset. The normal open and closed operation of the valve cooperates with a clutching mechanism which is part of the trip system. The preferred embodiment of the clutching system is a torsion spring or springs which normally allow movement in one direction but not in the other unless acted upon by the tripping system. |
