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

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    Technical Causes of Water-Draw Interruption in Multistage Pumps and Preventive Measures

    Publication Date:

    2026-04-10

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    Technical Analysis and Countermeasures for Interruption of Water Pumping by Multistage Pumps at Changsha Zoomlion Pump Industry

    When a multistage pump experiences intermittent suction during operation, it is a failure that severely impacts productivity, according to the multistage pump manufacturer. Changsha Zoomlion Pump Industry Based on the experience of technical engineers, this fault phenomenon requires a multi-dimensional investigation to identify the underlying technical causes. The following is an analysis of common technical root causes for such faults, along with corresponding solutions:

     

    Multistage pump

     

    1. Power supply system abnormalities: Voltage fluctuations (e.g., three-phase imbalance exceeding 5%) or sudden power outages can cause the motor to lose speed and shut down. It is recommended to install a voltage-stabilizing power supply and a dual-circuit power supply system to minimize the impact of grid fluctuations. The motors supplied by Changsha Zhonglian Pump Industry feature an IP55 protection rating and can detect power supply abnormalities by monitoring the motor’s operating current, which should remain within a fluctuation range of ±10% of the rated value.

    2. Hydraulic System Blockage: Clogging of the inlet strainer (with a flow area reduced to less than 80%) or sand accumulation in the pipeline (particle size greater than 0.5 mm) can cause a sudden drop in pump inlet pressure. Changsha Zoomlion Pump Industry recommends the following: regularly clean the strainer at intervals of no more than 15 days, and use a 30-mesh stainless steel strainer to filter media with a sand content exceeding 30 mg/L; when conveying over long distances, install an accumulator tank to prevent cavitation (which is likely to occur when the pump inlet pressure falls below 3 meters of water column).

    3. Abnormal water-source water-level parameters: When the water level in the source falls below the pump suction inlet’s minimum allowable submergence depth (300 mm according to the Changsha Zhonglian Pump Industry standard), the available net positive suction head (NPSH) will be insufficient. It is recommended to install an automatic water-level monitoring system that automatically shuts down the pump when the water level drops to the alarm threshold.

    4. Mechanical Component Failures: Excessive bearing clearance (>0.3 mm) or excessive seal ring clearance (>0.5 mm) can lead to pump vibration exceeding 4.5 mm/s and internal leakage. Regular inspections (at intervals of no more than 3,000 hours) are required: Bearings shall be imported SKF units, with operating temperatures maintained below 75°C; the clearance between the impeller and guide vanes (factory standard: 0.2–0.3 mm) must be periodically calibrated using a dial indicator.

    5. Changes in the Physical Properties of the Fluid When the viscosity of the conveyed fluid exceeds 1,000 mPa·s or the solid content exceeds 5%, the pump’s effective power must be recalculated (N = KQH, where K is a correction factor). Changsha Zoomlion Pump Industry recommends selecting variable-frequency-driven multistage pumps for high-viscosity fluids.

    6. Operational and Maintenance Deficiencies Incorrect setting of the pump operating frequency (e.g., exceeding the rated speed by 15%) or failure to follow the prescribed warm-up procedure (cold-start interval less than 30 minutes) can lead to shaft bending. Key maintenance points: Implement a three-tier inspection system (daily, weekly, and monthly inspections), with particular emphasis on checking motor insulation resistance (≥100 MΩ); conduct impeller dynamic balancing verification once a year (accuracy class G6.3) to ensure vibration does not exceed 2.8 mm/s.

    Changsha Zoomlion Pump Industry recommends the following measures to prevent interruptions in pumping:

    1. Establish a remote monitoring system for pump units (monitoring parameters: flow rate, pressure, vibration, and temperature);

    2. Key components are made of wear- and corrosion-resistant materials (e.g., CD4MCu alloy impellers);

    3. Conduct regular reviews of the NPSH curve to ensure system compatibility.

    Through precise diagnostics and scientific maintenance, the mean time between failures of multistage pumps can be significantly increased, thereby substantially reducing the risk of pumping interruptions.

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