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What Should I Do if the Outlet Pressure of The Split Case Pump Drops?

September 12,2023

(1) The Motor Reverses

Due to wiring reasons, the direction of the motor may be opposite to the actual direction required by the  pump. Generally, when starting, you must first observe the direction of the pump. If the direction is reversed, you should exchange any two wires on the terminals on the motor.

(2) The Operating Point Shifts to High Flow and Low Lift

In general,  split case pumps  have a continuously downward performance curve, and the flow rate gradually increases as the head decreases. During the operation, if the back pressure of the pump decreases for some reason, the working point of the pump will passively shift along the device curve to the point of low lift and large flow, which will cause the lift to decrease. In fact, this is due to external factors such as the device. It is caused by changes and has no special relationship with the pump itself. At this time, the problem can be solved by simply increasing the pump back pressure, such as closing a little outlet valve, etc. 


(3) Speed Reduction

The important factors that affect the pump lift are the impeller outer diameter and the pump speed. When other conditions remain unchanged, the pump lift is proportional to the square of the speed. It can be seen that the impact of speed on the lift is very large. Sometimes because If some external reason reduces the pump speed, the pump head will be reduced accordingly. At this time, the speed of the pump should be checked. If the speed is indeed insufficient, the cause should be checked and solved reasonably. the

(4) Cavitation Occurs at the Inlet

If the suction pressure of the split case pump is too low, lower than the saturated vapor pressure of the pumped medium, cavitation will form. At this time, you should 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. the

(5) Internal Leakage Occurs

When the gap between the rotating part and the stationary part in the pump exceeds the design range, internal leakage will occur, which is reflected in a drop in the discharge pressure of the pump, such as the gap between the impeller mouth ring and the inter-stage gap in a multi-stage pump. At this time, corresponding disassembly and inspection should be carried out, and the parts causing excessive gaps should be repaired or replaced. the

(6) The Impeller Flow Passage is Blocked

If part of the flow path 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 dismantle the split case pump to check and remove foreign matter. To prevent this problem from recurring, a filtering device can be installed before the pump inlet if necessary.

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