Trigger Valve

TRIGGER VALVE




This valve has a function of maintaining a proper level of pressure behind the vanes (vane back pressure) such that they can move easily upon start of the compressor. The trigger valve is incorporated in the front side block and its end opens to a cavity called "K-ditch" that is provided in the rotor side end of the side block. The valve consists of a check ball and a spring.
The vanes are prone to chatter if there is only small difference between the high- and low-pressures. This condition typically occurs when the compressor is started. In such a condition, the spring raises the ball to open the valve and allows the back pressure to act on the vanes, thereby ensuring smooth operation.




1. When compressor starts or when load is low:
When the compressor starts or when the load is low (the high-pressure level is low), the spring can raise the check ball clear of its seat, so the trigger valve is opened. The pressure of the high- pressure chamber then acts on the back end surface of each vane to prevent it from chattering.




2. When compressor is in regular operation:
When the pressure in the high-pressure chamber of the compressor increases, the pressure overcomes the spring tension and pushes the check ball against its seat, so the trigger valve closes. The oil port pressure coming through the side block is applied to the end surface of vane to maintain proper back pressure.