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

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    Solutions and Preventive Measures for Water Leakage from the Pump Cover of High-Head Multistage Pumps

    Publication Date:

    2026-04-07

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    When high-head multistage pumps operate under high-pressure conditions, seal failure at the pump cover often leads to leakage—a common and persistent problem that plagues users. Although such leaks may appear minor, they can reduce pump efficiency and increase energy consumption; if ignored over the long term, they may even result in serious secondary issues, such as bearing damage and water ingress into the motor. To address this widespread industry challenge, the original manufacturer of multistage pumps Changsha Zoomlion Pump Industry Drawing on decades of field service experience and starting with root-cause analysis of failures, we have developed a comprehensive set of solutions and preventive measures for addressing and preventing leakage from the pump cover of high-head multistage pumps, helping users fundamentally resolve this issue.  

     

    Multistage pump

     

    I. Diagnosis of Leakage Causes

    1. Seal failure: Aging, deformation, or misalignment of the sealing gasket at the pump cover–pump housing interface is common in equipment that has been in operation for more than 10,000 hours. Particular attention should be paid to the hardness (Shore A 60–70) and compression set (0.5–1.5 mm) of nitrile rubber or fluororubber gaskets.

    2. Bolted-joint issues: High-strength bolts (grade 8.8 and above) may experience a reduction in preload due to vibration or thermal expansion and contraction, resulting in torque values that fall below the manufacturer’s specified range (typically 150–200 N·m).

    3. Pump body defects: casting porosity, sand holes, or weld cracks, which are commonly found in stress-concentrated areas of castings (such as the junction between the pump cover and the impeller), shall be located by hydrostatic pressure testing at 0.8 times the working pressure.

     

    II. Tiered Handling Plan

    1. Sealing System Repair: Gasket Replacement: Select metal spiral-wound gaskets that comply with GB/T 3922, and apply diagonal, evenly distributed torque in accordance with the assembly drawing requirements (it is recommended to calibrate the torque wrench to within ±5% accuracy). Seal Ring Repair: For O-ring seals, it is recommended to upgrade to PTFE material and use dedicated installation tools to prevent damage.

    2. Bolt Tightening Procedure: Perform secondary tightening using a torque multiplier, following the three-step procedure of “initial tightening → re-tightening → anti-loosening.” After re-tightening, conduct a 30-minute operational vibration test.

    3. Treatment of Pump Body Defects: For porosity ≤0.5 mm, argon arc welding repair shall be performed, followed by stress-relief annealing at 550±20℃; for cracks, the pump cover shall be replaced after full-circumference grinding, with preference given to castings made of QT450-10 material.

     

    III. Preventive Maintenance System

    1. Regular inspections: Perform ultrasonic thickness measurements quarterly (replace gaskets when their remaining thickness is ≥50% of the original design thickness), and conduct a seal-face roughness inspection annually (Ra ≤ 1.6 μm).

    2. Environmental Adaptation: The humidity in the installation area shall not exceed 65% RH; in corrosive environments, a pump cover made of 316L stainless steel must be used; when the temperature of the process fluid exceeds 150°C, a water-cooled jacket is recommended.

     

    IV. Technical Support and Security Standards

    If self-resolution proves difficult, please contact the Changsha Zoomlion Pump Industry Technical Service Center at 400-XXX-XXXX and provide the pump model, operating parameters, and photos of the fault for remote diagnostics. Prior to commencing work, the power supply must be disconnected and a “Do Not Start” sign hung; when using a torque wrench, impact-resistant safety goggles must be worn to prevent burns from high-temperature components. Through precise diagnosis, process optimization, and standardized maintenance, the failure rate of pump cover leakage can be reduced to below 0.3 incidents per 1,000 units per year, significantly lowering system energy consumption (approximately 5,000 kWh of annual energy savings per unit). It is recommended to establish a full lifecycle record for each piece of equipment, documenting all seal-system upgrades to serve as a reference for future operation and maintenance.

     

    In addition, Changsha Zoomlion Pump Industry emphasizes that, throughout the implementation of the aforementioned solutions and preventive measures, ongoing technical training and continuous enhancement of personnel capabilities are equally critical. At the same time, technical staff are encouraged to participate in industry forums and conferences to share real-world case studies and practical experience, thereby jointly exploring innovative approaches to addressing complex challenges. By establishing a comprehensive technical training system, not only can the overall technical competence of the team be elevated, but technological innovation can also be fostered, providing a more robust technical foundation for tackling the various pump-head leakage challenges that may arise in the future. In short, effectively resolving the issue of pump-head leakage in high-head multistage pumps depends not only on advanced technical solutions and preventive measures, but also on a highly qualified, specialized technical team serving as a strong supporting pillar.

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