What Is The Reason For The Pressure Drop in Multi-stage Centrifugal Pumps

Jan 09, 2026

A multi-stage centrifugal pump is a combination of two or more centrifugal pumps with the same function. In terms of fluid channel structure, the medium pressure relief port of the stage is connected to the inlet of the second stage, and the medium pressure relief port of the second stage is connected to the inlet of the third stage. This series connection mechanism forms a multi-stage centrifugal pump.

Reasons for pressure drop in multi-stage centrifugal pumps:

1. Motor reversal

Due to wiring reasons, the direction of the motor may be opposite to the actual required direction of the centrifugal pump. Therefore, when starting, it is generally necessary to observe the direction of the pump first. If the direction is reversed, any two wires on the motor terminal should be exchanged.

2. Deviation of operating point towards high flow and low head

In general, multi-stage centrifugal 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 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 nothing to do with the pump itself. At this point, simply increasing the pump back pressure, such as closing the outlet valve slightly, can solve the problem.

3. Speed reduction

The important factors affecting the head of a multi-stage centrifugal pump are the outer diameter of the impeller and the speed of the pump. Under other constant conditions, the head of the pump is directly proportional to the second power of the speed. It can be seen that the influence of speed on the head is very significant. Sometimes, due to external reasons, the speed of the pump decreases, which will correspondingly reduce the head of the pump.

 

 

At this point, the pump speed should be checked. If the speed is indeed insufficient, the cause should be investigated and resolved reasonably.

4. Cavitation occurs at the entrance

If the suction pressure of a multi-stage centrifugal pump is too low, below the saturated vapor pressure of the pumped 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.

5. Internal leakage occurs

When the clearance between the rotating and stationary parts inside the pump exceeds the design range, it will cause internal leakage, manifested as a decrease in the discharge pressure of the pump, such as the clearance between the impeller mouth ring and the inter stage clearance of multi-stage pumps. At this time, corresponding disassembly and inspection should be carried out to repair or replace the parts that cause excessive clearance.

6. 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 pump for inspection and removal of foreign objects. To prevent the problem from happening again, a filtering device can be added before the pump inlet if necessary.

 

Multi stage centrifugal pumps have the advantages of energy saving, wide performance range, safe and stable operation, low noise, long service life, and easy installation and maintenance; By changing the material and sealing form of the pump and adding a cooling system, it can transport hot water, oil, corrosive and abrasive media, etc.