Centrifugal pumps in the zero-flow conditions, the minimum shaft power for the rated shaft power of 30% - 90%, so the starting characteristics of the centrifugal pump is zero flow start (ie, off the valve start). After the pump reaches the rated speed, the control valve slowly opens at the set speed. Working principle: When the pump is started (before), the pressure water flows through the solenoid valve with delay to the upper chamber of the piston in the cylinder, while the lower chamber of the piston opens to the atmosphere through the solenoid valve at the lower end of the cylinder. At this time, the control valve is in the closed state. Motor compensation start over, the pump is running, the solenoid valve to perform commutation command, cut off the pressure on the piston cavity, close the lower end of the cylinder to the atmosphere loop, while the pressure water through the solenoid valve into the cylinder piston lower chamber, open the piston Upper chamber open to the atmosphere of the loop, the piston cavity of the water through the solenoid valve discharge valve, the control valve at a set speed slowly open to complete and meet the centrifugal pump at zero flow axis power minimum starting characteristics to ensure that the pump unit Safe operation.
