The pump head is reduced, what are the reasons?
(1) Impeller flow path blockage
If the flow path of the impeller is blocked, it will affect the operation of the impeller, resulting in a drop in the outlet pressure. Need to remove the pump to check for foreign matter. To prevent this from happening again, a filter can be added to the pump inlet.
(2) Internal leakage
When the gap between the rotating part and the stationary part in the pump exceeds the design range, it will cause leakage inside. The discharge pressure of the pump is reduced. Such as the impeller ring gap, the interstage gap of the multi-stage pump. At this point, the corresponding disassembly should be carried out. Repair or replace parts that cause excessive clearance.
(3) Cavitation at the entrance
If the suction pressure of the pump is too low, below the saturated vapor pressure of the pumped medium, cavitation will form. At this time, check whether the inlet piping system is blocked or the inlet valve opening is too small, or increase the liquid level of the suction pool.
(4) Reduced speed
Important factors affecting the pump head are the outer diameter of the impeller and the speed of the pump. In the case where other conditions do not change, the lift of the pump is proportional to the square of the speed. Sometimes the pump's speed is reduced due to external reasons, which will reduce the pump's head. In this case, check the speed of the pump. If the speed is not enough, check the cause and solve it reasonably.
(5) The operating point is shifted to the high flow and low lift
In general, centrifugal pumps have a continuous downward performance curve, and the flow rate gradually increases as the lift is reduced. During operation, the pump back pressure is reduced for some reason.The pump's operating point passively moves to low lift and large flow points.This will cause the head to decrease. This is caused by changes in external factors and has no special relationship with the pump itself. At this time, as long as the pump back pressure is increased, the problem can be solved.
(6) Motor reversal
The steering of the motor is reversed from the actual demanding of the pump due to wiring. When starting the pump, first observe the steering of the pump. If the steering is reversed, you should exchange any two wires on the terminal on the motor.
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