1. air leakage of centrifugal pump or suction pipe; 2. the suction pipeline or centrifugal pump inlet is blocked, and the suction resistance is too large; 3. the wear clearance of impeller ring is too large; 4. the impeller is blocked or severely worn and corroded; 5. the rotation direction of the centrifugal pump is wrong or the impeller is installed reversely; 6. the outlet valve of the centrifugal pump is not opened or cannot be opened; 7. the motor speed is not allowed; 8. the selection or function of centrifugal pump is inconsistent. Treatment method: 1. check and clean the suction valve and pipeline; 2. remove impeller blockage or replace impeller; 3. replace the impeller sealing ring; 4. check and eliminate air leakage; 5. open the outlet valve of the pump and adjust the valve opening; 6. adjust the rotation direction of the pump; 7. increase the motor speed; 8. check whether the functional parameters of the pump meet the working conditions and adjust them.