LOCK-UP RELAY
Definition
A <LOCK-UP RELAY> is a <PNEUMATIC RELAY> that is used when it is required that the air pressure to the actuator be automatically held on the same level, unchanged from the pressure prior to a pressure change in the air source. When supply pressure drops down past a preset value, the device automatically locks the air piping to the control valve, and causes the control valve to hold its position until the air failure is rectified