What causes head of the water pump to decrease?

Aug,10,2023

(1) The impeller flow passage is blocked

If part of the flow passage of the impeller is blocked, it will affect the work of the impeller and cause the outlet pressure to drop. Therefore, it is necessary to disassemble the pump to check and remove foreign objects. In order to prevent this problem from recurring, a filter device can be added before the pump inlet if necessary.

(2) Internal leakage occurs

When the gap between the rotating part and the static part in the pump exceeds the design range, it will cause internal leakage, which is reflected in the drop of the discharge pressure of the pump, such as the gap between the impeller orifice ring and the inter-stage gap of the multi-stage pump. At this time, the corresponding disassembly and inspection should be carried out to repair or replace the parts that cause excessive clearance.

(3) Cavitation occurs at the inlet

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 whether the opening of the inlet valve is too small, or increase the liquid level of the suction pool.

(4) Speed reduction

The important factors that affect the head are the outer diameter of the impeller and the speed of the pump. Under the condition that other conditions remain unchanged, the head is proportional to the square of the speed. It can be seen that the speed has a great influence on the head. For some external reason, the speed of the pump is reduced, and the head of the pump will be correspondingly reduced. At this time, the speed of the pump should be checked. If the speed is not enough, the reason should be checked and a reasonable solution should be made.

(5) The operating point shifts to the large flow and low head

In general, centrifugal pumps have a continuous downward performance curve, and the flow gradually increases as the head decreases. During the operation process, the back pressure of the pump is reduced due to some reason, and the working point of the pump is passively shifted to the low-lift and high-flow point with the device curve, which will cause the lift to decrease. In fact, this is due to external factors such as the device It is caused by the change of the pump and has no special relationship with the pump itself. At this time, as long as the pump back pressure is increased, such as closing a little outlet valve, the problem can be solved.