Axial flow pump at zero flow conditions, the maximum shaft power, rated shaft power of 140% to 200%, so the axial flow pump start characteristic should be large flow start (ie, fully open valve start). Working principle: The control valve to meet the axial flow pump fully open valve to start the working principle is the centrifugal pump off the valve to start the reverse run, the solenoid valve first work, the valve fully open, the pump restart. See a), do not go into details. Axial flow pump before the start, when the valve inlet pressure is zero, the control valve using the valve outlet side of the media pressure valve opens, and start the centrifugal pump is the use of the valve inlet side of the medium pressure valve opens. One of the key features of the pump control valve is its ability to open or close the control valve at either end of the valve.