1.Common Issues and Solutions for Pipeline Pumps
1. Failure to Start
First, inspect the power supply: Check if the connectors are securely fastened; verify if the switch contacts are properly engaged; examine if the fuse has blown; and confirm if there is a phase loss in three-phase power supply. If an open circuit, poor contact, blown fuse, or phase loss is detected, identify the cause and repair promptly. Second, inspect for mechanical failures within the vertical pipeline pump itself. Common causes include: packing too tight or debris blocking the impeller-to-pump housing clearance; rusted pump shaft, bearings, or leak-reducing rings; severe shaft bending. Solutions: Loosen packing and clear the water guide groove; disassemble the pump housing to remove debris and rust; remove the pump shaft for straightening or replace it with a new one.
2. Overheating of Vertical Pipeline Pump
Causes: Damaged bearings; insufficient clearance between rolling bearings or bracket covers; bent pump shaft or misaligned shafts; excessively tight belt tension; insufficient or poor-quality lubrication; clogged balance holes on the impeller causing imbalance and increased thrust on one side. Solutions: Replace bearings; remove rear cover and add shims between bracket and bearing housing; inspect pump shaft or adjust shaft alignment; loosen belt tension appropriately; fill with clean grease to approximately 60% of bearing cavity volume; clear blockage from balance holes.
3. Insufficient Flow
Causes: Mismatched motor speed resulting in low rotational speed; Insufficient head, excessively long piping, or sharp bends in the pipeline; Partial blockage in the foot valve, piping, or impeller, or impeller damage; Severe leakage in the discharge pipe. Troubleshooting: Restore rated speed; Lower the vertical pipeline pump installation position, shorten the piping, or modify the piping curvature; Clear blockages and replace the impeller; Replace the leak-reducing ring and seal the leakage points.
4. Failure to Suck Water
Causes: Air trapped in the pump body or suction pipe, or incomplete priming due to poorly sealed foot valve. Solutions: First pressurize the water supply, then fill the pump body with water before starting. Simultaneously inspect the check valve for tightness and check pipes/connections for air leaks. If leaks are found, disassemble, apply lubricant or compound paint to joints, and tighten screws. Inspect the shaft oil seal ring of the vertical pipeline pump. Replace with a new part if severely worn. Pipeline water or air leakage. This may occur if nuts were not sufficiently tightened during installation. For minor leaks, apply cement or a mixture of asphalt oil and cement slurry to the leaking area. For temporary repairs, apply wet clay or soft soap. If leakage occurs at joints, tighten nuts with a wrench. For severe leakage, disassemble and reassemble, replacing cracked pipes; reduce head by submerging the pump outlet 0.5m underwater.
5. Severe Vibration in Vertical Pipeline Pump
Primary causes include: unbalanced electric rotor; Poor coupling alignment; bearing wear or bending; loose or fractured rotating components; unstable pipe supports. Address these issues through adjustment, repair, reinforcement, straightening, or replacement as applicable.
The above scenarios represent common causes of vertical pipeline pump failures, though not exhaustive. When troubleshooting in practice, conduct thorough analysis and follow the principle of addressing external factors before internal ones. Avoid blind operation.
6. Overheating of the Power Motor
There are four primary causes:
First, power supply issues: Voltage that is too high or too low. Under specific loads, if voltage fluctuations exceed the rated range of +10% to -5%, it can cause motor overheating. Asymmetrical three-phase voltage, where the imbalance between phases exceeds 5%, can lead to winding overheating. Phase loss operation: Experience shows that over 85% of motor burnouts result from phase loss. Install phase loss protection devices. Second, issues with the vertical pipeline pump: Mismatched power selection (overloading the motor) causes prolonged overload operation and excessive motor temperature. Excessive starting frequency or continuous operation of motors rated for short-time or intermittent duty cycles. Limit the number of starts, select appropriate thermal protection, and operate within the motor's rated specifications. Third, motor-related causes: Incorrect wiring (e.g., connecting a delta (△) configuration as a star (Y) connection) causes rapid temperature rise; stator winding phase-to-phase short circuits, turn-to-turn short circuits, or partial grounding result in localized overheating or severe insulation failure; Broken bars or defects in the squirrel-cage rotor cause rapid core temperature rise within 1-2 hours of operation. Ventilation system failures require checking fan damage, rotation direction, and duct blockages. Bearing wear or rotor eccentricity causing stator-rotor core contact produces metallic knocking sounds, rapid core temperature rise, and in severe cases, motor smoke or coil burnout. Fourth, environmental factors: Moisture in motor windings or accumulation of dust/oil contamination reduces insulation integrity. Measure insulation resistance and perform cleaning/drying procedures. Excessive ambient temperature: When ambient temperature exceeds 35°C, high intake air temperature causes motor overheating. Improve operating conditions (e.g., shade structures). Note: For electrical faults, only qualified electricians with professional certification should perform repairs. Individuals with limited knowledge should not attempt repairs to prevent personal injury.
7. Vertical Pipeline Pump Fails to Draw Water or Has Low Flow Rate
First, compare the current drawn by the vertical pipeline pump during operation with its normal operating current. If the current is lower than normal (typically around 2/3 of the usual current), this indicates issues such as impeller wear or blockage in the check valve above the pump head. If the current remains the same as normal, it points to problems like leaks in the pipe gasket, pipes, or pump body. If the current is higher than normal, it is likely due to wear and tear of the pump's wear parts.
2.Common Issues and Solutions for Pipeline Pumps
(1) Basic Principles for Diagnosing Pipeline Pump Failures
All equipment experiences failures during operation, and pipeline pumps are no exception. Without specialized diagnostic equipment, pipeline pump users should adapt their troubleshooting approach to the specific circumstances. This means most assessments should be based on the current operational context—such as whether the pump was recently serviced, is undergoing a switchover, has been idle for an extended period, or is in the midst of operational adjustments. Additionally, the location and symptoms of the malfunction should be considered. The recommended troubleshooting sequence follows the principle of “Listen, Observe, Feel, Measure, and Determine”:
1. Listen: Check if the pump's operational sounds are normal.
2. Observe: Monitor whether the pump's current fluctuates or shows abnormalities, inspect for seal leaks, and verify if parameters like pressure are within normal ranges.
3. Feel: Assess whether the pump's temperature and vibration levels are normal.
4. Measure: Determine if the pump's operational vibration exceeds acceptable limits.
5. Diagnose: Compare findings against established standards to identify potential faults.
Common Cavitation Damage in Closed Centrifugal Pumps
(2) Selection of Vibration Measurement Parameters for Pipeline Pumps
When testing pipeline pump vibrations, the primary basis for selecting measurement parameters is the frequency range of the vibration signal. Generally, parameters can be chosen according to the following conditions:
1. For low frequencies below 10 Hz, use displacement measurement. For medium frequencies between 10 and 1000 Hz, use velocity measurement. For high frequencies above 1000 Hz, use acceleration measurement.
2. For centrifugal pump rotor assemblies, the most common faults are forced vibrations caused by imbalance, misalignment, or looseness, which predominantly occur at medium frequencies. Measuring velocity is recommended.
3. Rolling bearing faults often manifest as impact-like vibrations with natural frequencies exceeding several thousand Hz. Therefore, measuring acceleration is generally the most sensitive approach.
4. Pump cavitation occurs at frequencies between 6-20 kHz, also making acceleration measurement appropriate.
(3) Common Methods for Diagnosing Pipeline Pump Failures
Distinguishing pipeline pump failures: For a pump confirmed to have a fault, first determine whether it is mechanical or electrical to narrow the diagnostic scope. A simple method is to disconnect the motor and observe whether the vibration meter reading rapidly drops to zero. If it does, the fault is electrical; if it declines slowly, a mechanical fault is likely. If the pump cannot be stopped, perform frequency analysis on the vibration signal for determination. Prominent peaks at 1x or 2x the power supply frequency indicate electrical faults. Otherwise, it is a mechanical fault.
Parameter Directional Characteristics: Different fault types exhibit varying vibration magnitudes at different measurement points. In many cases, high horizontal vibration indicates imbalance, while high axial vibration suggests misalignment. For more detailed diagnosis, spectral analysis can be employed—e.g., pronounced double-frequency peaks indicate parallel misalignment, etc. (Further details omitted). High vertical vibration often indicates loose footings.
