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, the steering of the pump should be observed 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, the pump back pressure is reduced for some reason, and the working point of the pump passively shifts to the low lift and large 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. The change caused by the pump 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.
(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 speed. The effect of the speed on the lift is very large, 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 properly.
(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, it will cause internal leakage, which is reflected by the discharge pressure of the pump, such as the impeller ring gap and the interstage gap of the multistage pump. At this time, the corresponding disassembly inspection should be carried out 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.
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