Changsha Zoomlian Pump Co., Ltd. 长沙中联泵业股份有限公司

language
    language

    Does a vertical long-shaft pump have axial displacement?

    Publication Date:

    2025-06-19

    Author:

    Source:

    Facebook Linkedin Twitter Tumblr Pinterest

     

    Vertical Long Shaft Pump Axial displacement occurs during normal operation, which is determined by its structural characteristics and working principle. The following explains the causes, influencing factors, and control methods of axial displacement:

    1. Causes of Axial Displacement

    Effect of Axial Force

    When the vertical long shaft pump operates, the impeller rotation generates axial force (caused by the pressure difference on both sides of the impeller, directed towards the suction end), pushing the pump shaft to move axially. In addition, the reaction force of fluid flow and impeller manufacturing errors may also exacerbate the impact of axial force.

    Thermal Expansion Effect

    During pump operation, components such as the shaft and bearings generate heat due to friction or changes in medium temperature, causing thermal expansion that leads to slight changes in shaft length, resulting in axial displacement.

    Assembly and Installation Errors

    Clearances between the pump shaft and components like bearings and impellers, or coaxiality deviations during overall installation, may cause unexpected axial displacement during operation.

    2. Effects of Axial Displacement

    Positive Effects

    Axial displacement within a reasonable range can prevent the shaft from being "stuck" due to thermal expansion or axial force, ensuring flexible relative movement between components.

    Negative Effects

    If axial displacement is excessive, it may cause friction between the impeller and pump casing, shaft seals, and other parts, increasing wear and even causing vibration, noise, or seal failure;

    Under long-term axial force, bearing load increases, potentially shortening bearing life and, in severe cases, causing bearing burnout.

     

    [For more information on vertical long shaft pump models, parameters, selection, and quotation plans, please click the image above]

    3. Control and Limitation of Axial Displacement

    Structural Design Optimization

    Balancing Devices: By setting balance holes, balance discs, or balance drums, part of the axial force is offset to reduce axial displacement. For example, the balance disc can generate reverse thrust by adjusting the clearance to balance the axial force;

    Thrust Bearings: Installing high-precision thrust bearings (such as thrust ball bearings or tapered roller bearings) directly limits the axial displacement of the shaft while bearing axial force.

    Clearance Control

    Strictly control the axial clearance between the shaft and bearings, and between the impeller and pump casing during assembly (usually 0.1~0.5mm, depending on the pump model and working conditions), adjusting clearance accuracy with shims, positioning sleeves, and other parts.

    Monitoring and Maintenance

    During operation, sensors monitor axial displacement. When displacement exceeds the allowable value (e.g., 1.5 times the design value), alarms trigger for timely inspection of bearing wear, balance device status, or installation accuracy.

    4. Typical Cases and Industry Standards

    In large vertical long shaft condensate pumps (such as those used in thermal power plants), axial displacement is usually controlled within 0.2~0.3mm to ensure stable axial clearance between the impeller and guide vane casing, avoiding efficiency loss caused by excessive displacement;

    Industry standards (such as GB/T 5657-2019 "Technical Conditions for Centrifugal Pumps") clearly specify allowable ranges for axial displacement. Pumps under different working conditions must be designed and accepted according to these standards.

    Summary

    Vertical Long Shaft Pump Axial displacement is an unavoidable physical phenomenon but can be controlled within a safe range through reasonable structural design, precise assembly, and real-time monitoring. If abnormal vibration, increased noise, or elevated bearing temperature occurs during pump operation, it may be caused by excessive axial displacement and requires timely inspection and adjustment.

     

    Previous:

    Lubrication device of vertical long-shaft multistage pump

    Next:

    Why does 130° high-temperature soft water need to be delivered by a sub-high-pressure boiler feed pump?

    Related Products