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

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    Causes of Pumping Interruption in DGP-Type Self-Balancing Multistage Boiler Feedwater Pumps

    Publication Date:

    2026-05-13

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    When the DGP-type self-balancing multistage boiler feedwater pump experiences flow interruption during operation, it directly affects the boiler’s thermal efficiency and safe operation. In such cases, the unit must be shut down promptly, and operation may resume only after the fault has been rectified. In this paper, Self-balancing multistage pump Manufacturer Changsha Zoomlion Pump Industry We will share the causes of pump suction interruptions in DGP‑type self‑balancing multistage boiler feedwater pumps, for reference by user organizations.

     

    DGP-type self-balancing multistage boiler feedwater pump

     

     

    I. Failure of the Pump’s Core Components

    1. Impeller damage: Cavitation, impact from foreign objects, or material fatigue can cause deformation of the blade passages, leading to a sudden reduction in the flow area. This results in deviations of the pump’s head–flow curve from the design operating conditions, potentially causing flow interruption.

    2. Wear of the balance disc/sleeve: In a self‑balancing design, if the clearance between the balance disc and the balance sleeve exceeds allowable limits, axial force imbalance can cause friction between the impeller and the guide vanes, potentially leading to severe seizing and shutdown.

    3. Seal leakage: Aging of the mechanical seal or O-ring can lead to cross‑flow between the high‑pressure and low‑pressure chambers, resulting in insufficient effective head. This risk is particularly pronounced under high‑head operating conditions, where flow interruption becomes more likely.

     

    II. Water Source and System Blockage

    1. Water Source Depletion: When the water level in the tank or reservoir falls below the minimum effective suction lift, a vicious cycle of cavitation and vaporization occurs at the pump inlet, causing the flow rate to plummet until flow is completely lost.

    2. Suction pipe blockage: The filter screen is clogged with debris (such as rust or scale), or misalignment of the pipe supports causes a reduction in pipe diameter, resulting in excessive local resistance.

    3. Pipeline leakage: Flange seals fail or welds crack, resulting in a static pressure loss exceeding 3% of the design value, and the pump’s actual head is insufficient to overcome the pipeline resistance.

     

    III. Electrical and Control System Faults

    1. Motor abnormalities: Bearing overheating can cause the motor bearing clearance to exceed allowable limits, or winding insulation aging may lead to speed fluctuations, resulting in a mismatch between the pump unit’s output power and its intended operating conditions.

    2. PLC control logic error: The DCS system erroneously issues an “overload” signal, or the frequency setpoint deviates from the safe range of 50 Hz (±1 Hz), causing the pump unit to shut down.

    3. Sensor drift: Distortion of data from the inlet pressure sensor (range ±0.2% FS) or the flow transmitter (accuracy class 0.5) can lead to misjudgments by the automatic control system.

    IV. Operations and Maintenance, and Environmental Factors

    1. Maintenance deficiencies: Quarterly disassembly inspections were not conducted in accordance with Changsha Zhonglian Pump Industry’s “DGP Pump Maintenance Procedure,” resulting in bearing clearance exceeding 0.15 mm (per the national standard GB/T 4952) and potential risks such as emulsification and degradation of the lubricating oil.

    2. Extreme operating conditions: When the ambient temperature falls below –15°C, the viscosity of the fluid in the pump increases to 1.5 times its design value, causing the suction performance curve to shift to the right and resulting in flow interruption at low speeds.

    3. Voltage Fluctuations: When the three-phase voltage imbalance exceeds 2%, or when the voltage momentarily drops below 90% of its rated value, the motor’s starting torque becomes insufficient, preventing the pump unit from establishing the initial head.

     

    Diagnosis and Recommended Actions: We recommend adopting the “Four-Quadrant Troubleshooting Method”: first, use vibration spectrum analysis (10–2000 Hz) to pinpoint bearing faults; then, employ an infrared thermal imager to measure the pump’s temperature differential (normal ≤5°C). Combined with a comparison against the flow‑head curve—using the dedicated diagnostic software provided by Changsha Zhonglian Pump Industry—this approach enables rapid identification of the fault source. In routine operations and maintenance, prioritize monitoring the balance disc wear (≤0.2 mm/year) and the seal ring clearance (≤0.3 mm) to ensure stable operation of the pump unit throughout its designed service life.

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    Corrosion Causes and Anti-Corrosion Technical Solutions for Impellers of DP-Type Self-Balancing Multistage Centrifugal Pumps

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