How to achieve interlocked shutdown of a valve that is stuck open
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The existing main fan outlet butterfly valve is equipped with an electro-hydraulic actuator. To account for faults such as power loss to the actuator during normal operation and to ensure the proper functioning of the main fan, the valve is designed to be in the open position in fault conditions. However, if the main fan triggers an interlock, the interlock requires this valve to be closed. Could the instrument meet the above requirements? And how can these two requirements be fulfilled?
First, the valve should remain in its open position in the event of a power failure. If your system uses an electro-hydraulic converter along with a hydraulic actuator, you can choose a hydraulic actuator equipped with a spring, that is, a single-acting type set to the normally open configuration. I’m not sure about the specifics of your setup – does it have an electromagnetic directional control valve at the output of the oil pump, or is it an electro-hydraulic converter? Does the actuator come with feedback functionality? Is it continuously adjustable, or on/off two-position? Second, regarding the issue of the interlock valves for fans, it is simple to incorporate the interlock signal into the valve-shutting command within the upper-level control system.
Faulty operation is achieved through a spring, while interlocked shutdown is accomplished via an electromagnetic valve in the oil circuit; there is no conflict between the two, and it is entirely possible to implement this.