a safety control system for a pump and anti - surge valve protects the pump , the valve and the hydraulic main line system . the valve is controlled by a pressure responsive circuit and , via a limit switch on the valve , controls both the steady state running of the pump and the pump start . a timed start circuit allows pressure to build up sufficiently to operate the valve upon initiation of pump operation . the system automatically shuts down upon power , mechanical or hydraulic failure , and prevents continued operation of the pump control valve when the pump has lost suction or there is a decrease in pump discharge pressure .