What Factors Can Cause A Decrease in The Head Of A Submersible Sewage Pump?

Sep 04, 2024

The decrease in head of sewage submersible pump may be caused by the following factors:
(1) Impeller flow channel blockage
If the flow channel of the impeller is blocked, it will affect the work of the impeller and cause a decrease in outlet pressure. Therefore, it is necessary to dismantle the submersible pump to inspect and remove foreign objects. To prevent the problem from happening again, a filtering device can be added before the inlet of the submersible pump if necessary.
(2) Internal leakage occurs
When the gap between the rotating and stationary parts inside the sewage submersible pump exceeds the design range, it will cause internal leakage, manifested as a decrease in the discharge pressure of the submersible pump, such as the clearance between the impeller mouth ring. At this time, corresponding disassembly and inspection should be carried out to repair or replace the parts that cause excessive clearance.
(3) Cavitation occurs at the entrance
If the suction pressure of the sewage submersible pump is too low, lower than the saturated vapor pressure of the pumping medium, cavitation will occur. At this time, it is necessary to check whether the inlet pipeline system is blocked or whether the inlet valve opening is too small, or to increase the liquid level of the suction water tank.
(4) Speed reduction
The important factors affecting the head of a sewage submersible pump are the outer diameter of the impeller and the pump speed. Under other constant conditions, the head of the submersible pump is directly proportional to the second power of the speed, indicating that speed has a significant impact on the head. Sometimes, if the pump speed decreases due to external reasons, the pump head will be correspondingly reduced. At this point, the speed of the submersible pump should be checked. If the speed is indeed insufficient, the cause should be investigated and resolved reasonably.
(5) Deviation of operating point towards high flow and low head
In general, sewage submersible pumps have a continuous downward performance curve, and the flow rate gradually increases with the decrease of head. During the operation process, due to some reasons, the back pressure of the pump decreases, and the working point of the submersible pump passively shifts towards the low head and high flow point along the device curve, which will cause a decrease in head. In fact, this is caused by external factors such as changes in the device, and has no special relationship with the submersible pump itself. At this point, simply increasing the pump back pressure, such as closing the outlet valve slightly, can solve the problem.
(6) Motor reversal
Due to wiring reasons, the direction of the motor may be opposite to the actual required direction of the sewage submersible pump. Therefore, when starting, it is generally necessary to observe the direction of the submersible pump first. If the direction is reversed, any two wires on the motor terminal should be exchanged.
Thank you very much for visiting Lutsee Pump Industry! The above is an introduction to the factors that can cause a decrease in the head of a submersible sewage pump. If you would like to further understand this issue or have any questions about other pump products, pump selection, pump models, or pump prices that need to be answered, please contact our pump manufacturer. We welcome your inquiries at any time.