When the pipe line pressure is lower than the setting value, low-pressure pilot opens, and the check valve is closed to isolate actuator and pressure source. The pressure in the actuator escapes automatically, and then the valve is closed.

When the line pressure exceeds the setting value, the high-pressure pilot opens. The check valve is closed to isolate the actuator and pressure source. The pressure in the actuator escapes automatically, and then the valve is closed. (The installed pilot in the prototype is the low pilot, and also we can install the high pressure pilot according to customers' requirements. )