What are the reasons for the lowering of the centrifugal pump outlet pressure? One or more of the following reasons may cause the centrifugal pump outlet pressure to decrease:
(1) Motor reversal
Due to the wiring, the steering of the motor will be reversed from the actual demand of the pump. In general, you should observe the steering of the pump first. If the steering is reversed, any two wires on the terminal on the motor should be exchanged.
(2) 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 the operation process, for some reason, the backpressure of the pump is reduced, and the working point of the pump passively shifts to the low-lift and large flow point of the device curve, which causes the head to decrease. In fact, this is due to external factors such as the device. The change caused by the pump has no special relationship with the pump itself. At this time, as long as the pump backpressure is increased, such as closing a little outlet valve, the problem can be solved.
(3) Reduced speed
The important factors affecting the pump head are the outer diameter of the impeller and the rotational speed of the pump. Under other conditions, the lift of the pump is proportional to the square of the velocity. However, the effect of the velocity on the lift is huge, sometimes because, For some reason externally, the speed of the pump is reduced, which will reduce the lift of the pump accordingly. In this case, check the speed of the pump. If the speed is not enough, check the cause and solve it reasonably.
(4) 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.
(5) Internal leakage
When the gap between the rotating part and the stationary part in the pump exceeds the design range, leakage will be caused inside, which is reflected by the pump's discharge pressure, such as the impeller ring gap and the interstage gap of the multistage pump. Therefore, at this time, you should carry out the corresponding disassembly inspection to repair or replace the parts that cause excessive clearance.
(6) Impeller flow channel blockage
If the flow path of the impeller is blocked, it will affect the work of the impeller, resulting in a drop in the outlet pressure. Therefore, it is necessary to remove the pump to check for foreign matter. To prevent this from happening again, a filter can be added before the pump inlet if necessary.
There are many reasons for the drop in the centrifugal pump outlet pressure. For the above reasons, please check the one by one.
Fuan Zhongzhi Pump Co., Ltd
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Contact Person: Ms. Semmy Wu