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

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    Technical Solution to Impurity Issues in the Packing Chambers of Multistage Centrifugal Pumps

    Publication Date:

    2026-03-28

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    Analysis of Impurity Accumulation in the Packing Chamber of Multistage Centrifugal Pumps at Changsha Zoomlion Pump Industry

    Multistage centrifugal pumps can be equipped with either packing seals or mechanical seals, depending on the specific operating conditions. When conveying particle-laden fluids, packing seals are prone to deposit accumulation in the stuffing box area. In this paper, Centrifugal pump Manufacturer Changsha Zoomlion Pump Industry This paper systematically analyzes, from the dual perspectives of fluid dynamics and mechanical design, the causes of impurity accumulation in the packing of multistage centrifugal pumps and proposes corresponding solutions for reference by user organizations.

     

     

    Multistage centrifugal pump

     

     

    I. Impurity Ingress Caused by Environmental Factors

    In industrial environments where dust concentrations exceed 5 mg/m³—such as mine dewatering and chemical feedstock conveying—the airborne dust particles entrained in the fluid (with particle sizes less than 50 μm) can be carried into the pump casing along with the process medium. According to GB/T 3215-2016, “Test Methods for Centrifugal Pumps, Mixed-Flow Pumps, and Axial-Flow Pumps,” when the solid content of the process medium exceeds 0.1%, impurities are prone to accumulate at the stuffing box. Changsha Zoomlion Pump Industry recommends installing a filter screen (with a mesh size of at least 80 mesh) at the pump inlet, combined with pre-treatment using a cyclone separator, which can reduce the ingress of impurities by more than 60%.

     

    II. Failure of the Packing System Itself

    1. Material Aging: When nitrile rubber packing is used in service conditions above 120°C—such as in hot-oil circulation pumps—the insufficient temperature resistance can lead to seal failure, allowing contaminants to penetrate along the sealing gaps. Changsha Zoomlion Pump Industry recommends using fluororubber V-shaped combined packing, which has a temperature range of –20°C to 200°C and a compression recovery rate of 92%, thereby extending the effective sealing life to more than 12 months.

    2. Geometric Deviation: If the clearance between packing rings during installation exceeds 0.3 mm (the standard value is 0.15 ± 0.05 mm), a vortex-induced deposition zone will form. According to ISO 13709, “Pump Shaft Seal Systems,” it is recommended to use a torque wrench to tighten the gland follower diagonally to a torque of 50 N·m, ensuring uniform radial loading on the packing.

     

    III. Fluid Quality Control Standards

    When the solid content of the conveyed medium exceeds 0.05%, pretreatment is required: Gravity sedimentation: This method is suitable for media with particle densities greater than 2.5 g/cm³; a inclined-plate settling tank should be installed upstream of the pump, with a detention time of no less than 30 minutes. Filter precision matching: The three-stage filtration system supplied by Changsha Zoomlion Pump Industry—comprising 100-mesh, 50-mesh, and 20-mesh filters—can capture more than 95% of suspended impurities.

     

    IV. Technical Specifications for Maintenance and Management  

    1. Daily inspection: Weekly monitoring of the stuffing box temperature (normal ≤65°C); if the temperature difference between the measured temperature and the ambient temperature exceeds 20°C as determined by an infrared thermometer, the equipment must be shut down for inspection.

    2. Cleaning Procedure: During disassembly and overhaul, use an ultrasonic cleaner (40 kHz) to clean the packing chamber, and inspect the inner wall for wear using an endoscope. If the wear depth exceeds 0.5 mm, replace the impeller shroud.

    3. Backup Plan: For critical applications such as municipal wastewater treatment, it is recommended to install a dual-pump switching system that leverages the downtime of the standby pump to perform cleaning operations.

     

    V. Typical Fault Diagnosis Cases

    A chemical enterprise’s D-type multistage pump manufactured by Changsha Zhonglian Pump Industry experienced a 15% reduction in head due to impurities trapped between the packing. The issue was resolved through the following steps:

    1. Disassembly revealed a 3.2 mm-thick calcium carbonate deposit inside the stuffing box.

    2. Replace the fluororubber packing with a polytetrafluoroethylene guide ring, and adjust the gland preloading force to 0.4 MPa;

    3. An online filtration system with a filtration accuracy of 30 μm was installed at the inlet; after three months of operation, the vibration level stabilized at 4.2 mm/s (in accordance with ISO 10816-3).

    Changsha Zoomlion Pump Industry consistently adheres to the principle of “prevention first, precision maintenance.” Through technological innovations such as optimizing packing materials (employing a carbon-fiber-reinforced composite structure) and improving the fluid inlet flow passage (by adopting S-shaped guide vanes), the incidence of impurity accumulation in the packing has been reduced to 0.8 occurrences per year per unit. Technical personnel are required to establish an electronic archive of pump operating parameters, recording the packing wear every 100 hours to provide data support for predictive maintenance.

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