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    What is the function of the balance pipe in a horizontal multistage centrifugal pump?

    Publication Date:

    2025-09-25

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    After prolonged use, do the bearings of a horizontal multistage centrifugal pump consistently overheat, with vibrations steadily increasing—and even causing the impeller to wear out rapidly? Many people assume it’s a quality issue, but in fact, the problem might stem from the balance pipe not functioning properly. Today, we’ll explore this common issue further, brought to you by a manufacturer of multistage centrifugal pumps. China United Pump Industry Let’s talk about this unassuming yet crucial component in horizontal multistage centrifugal pumps—what exactly is the role of the balance pipe?

     

    Horizontal Multistage Centrifugal Pump

     

    A horizontal multistage centrifugal pump operates by having multiple impellers arranged in series. Water enters the first-stage impeller and is discharged after being pressurized at each subsequent stage. However, the pressure generated on either side of the impellers differs: the inlet pressure is low, while the outlet pressure is high. This pressure difference creates a "thrust" directed toward the suction inlet—professionally known as axial force. The more stages there are, the greater the axial force becomes, much like being pushed from one direction by several people: the stronger the force, the less stable you’ll feel standing.

    What happens if this axial force isn't addressed? The pump shaft will be pushed toward the suction inlet side, placing extra stress on the bearings—resulting in overheating and unusual noises at best, or even wear and eventual burnout in severe cases. Meanwhile, the impeller may start rubbing against the pump casing, leading to seal failure, reduced efficiency, and potentially causing the unit to jam completely. That’s exactly when the balance pipe comes into play.

    The balance pipe is connected at one end to the balance chamber located behind the last-stage impeller (where the balance disc or balance drum is situated), and at the other end, it leads back to either the pump inlet or the suction line. Its primary function is "relieving axial force": the high-pressure water exiting the last-stage impeller flows through the balance pipe, returning to a low-pressure area. This action helps equalize the pressure in the balance chamber with the inlet pressure. As a result, the pressure difference across the impeller is significantly reduced, effectively neutralizing most of the axial force—much like when two people exert nearly equal force on either side, preventing you from being pushed over.

    In short, the balance tube ensures that the pump shaft of a horizontal multistage centrifugal pump remains stably centered, relieving the bearings from directly bearing the thrust. As a result, heat generation and vibration are naturally reduced, preventing abnormal friction between the impeller and pump casing, thereby extending the lifespan of the seals—and ultimately enabling smoother, more reliable, and longer-lasting pump operation.

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