During the operation of the pipeline, some factors may reduce the head. The following are the six reasons.1. Impeller passage blockedThe blockage of impeller flow passage will affect the work done by the impeller, and the pressure at the outlet will drop. This problem can be prevented by removing the pump body, removing foreign matters, and installing a filter device at the pump inlet.2. Internal leakage occursThe clearance between the rotating part and the stationary part of the pump body is too large, which exceeds the design index, and internal leakage will occur. The phenomenon is that the discharge pressure of the pump decreases, such as the clearance between the impeller ring and the interstage clearance of multistage pump. At this time, the corresponding inspection and replacement of components should be carried out.3. Cavitation at inletWhen the inlet pressure of the pump is too low, lower than the saturated vapor pressure of the pumping ring, cavitation will occur. The solution is to check whether the inlet pipeline system is blocked, whether the opening of the inlet valve is too small, or increase the liquid level of the suction pool.4. Speed decreaseThe important factors for head reduction are the outer diameter of the impeller and the speed of the pump. Under the same conditions, the head is in direct proportion to the quadratic power of the speed, so the speed has a great impact on the head. Some reasons reduce the speed of the pump, which will affect the head. At this time, check the speed of the pump. If the speed is not enough, find out the cause and eliminate it.5. The operating point is shifted to large flow and low liftIn most cases, the interest energy has a continuous rural performance curve, and the flow increases as the head decreases. In use, if there is some factor that causes the back pressure of the pump to decrease, the working point of the pump will shift to the point with large head and flow along with the device curve, which will cause the head to decrease. This is mainly caused by the change of external factors, and has nothing to do with the pump itself. It can be solved by increasing the pump back pressure.6. Motor reverseImproper wiring results in the motor steering contrary to the actual requirements of the pump. Normally, observe the rotation direction of the pump when starting. If it reverses, exchange any two wires of the terminal on the motor.