Comprehensive Troubleshooting Guide for Chemical and Industrial Applications
Magnetic drive pumps are widely used in chemical, pharmaceutical, and environmental industries for their leak-free operation and high safety. However, when a magnetic pump fails to deliver liquid (no discharge or “not pumping” problem), production efficiency and process stability can be severely affected.
This guide provides a detailed analysis of common causes and practical solutions to help you troubleshoot effectively.
1. Common Causes
A. Suction Line Problems
1. Air leakage in the suction pipeline
Aging or damaged seals, loose fittings, or cracks at welded joints can allow air to enter the suction line. This breaks the vacuum inside the pump and prevents proper suction pressure from forming, resulting in no liquid being drawn in.
2. Blockage in the suction line
Foreign particles, fibers, or sludge from the medium may clog the suction line, strainer, or impeller passages. This restricts fluid flow and prevents the medium from entering the pump body.
3. Excessive suction lift
If the installation height exceeds the pump’s rated suction lift, the pump cannot draw the liquid from the source, especially when handling viscous or high-temperature fluids.
B. Internal Pump Problems
1. Air trapped inside the pump (air binding)
Failure to properly fill and vent the pump before startup—or when the liquid contains volatile components—can lead to air pockets. These pockets occupy the internal volume of the pump and block normal liquid flow.
2. Impeller malfunction
A severely worn, broken, or jammed impeller cannot rotate smoothly, resulting in loss of pumping ability. Excessive clearance between the impeller and pump casing may also cause recirculation and pressure loss.
3. Magnetic coupling demagnetization
Long-term operation under high temperature or mechanical shock can cause magnet demagnetization, leading to transmission failure—the impeller no longer follows the motor rotation.
C. Operating Parameter Mismatch
1. Insufficient head (discharge height)
If the required head exceeds the pump’s rated head, the pump cannot deliver liquid to the desired height or distance.
2. Abnormal motor speed
Voltage instability (too high or too low), phase loss, incorrect wiring, or motor failure can cause reduced pump speed and insufficient hydraulic power.
2. Solutions
A. Inspect the Suction Line
Check for leaks: Replace aged or damaged gaskets and O-rings. Repair any cracked or poorly welded joints to ensure airtight connections.
Clean blockages: Dismantle the suction line, strainer, and impeller to remove debris. Replace damaged filters. For media prone to clogging, install a secondary filtration system before the pump.
Adjust suction lift: Reinstall the pump at a lower position to ensure the suction height is within the rated range (considering fluid density and temperature corrections).
B. Repair Internal Components
Prime and vent the pump: Before startup, close the discharge valve and open the vent valve. Slowly fill the pump with liquid until the vent releases bubble-free fluid, then close the vent and start the pump.
Repair or replace the impeller: Replace worn or broken impellers. If jammed, remove debris and ensure smooth rotation. Check that impeller clearance meets design requirements.
Replace magnetic coupling: Test magnetic strength. If demagnetized, replace the entire magnetic coupling assembly and ensure proper alignment and clearance.
C. Adjust Operating Conditions
Match the head: Choose a pump model with suitable head capacity or optimize the pipeline design (increase diameter, reduce bends, or shorten the pipeline) to reduce flow resistance.
Fix motor issues: Verify voltage stability within rated limits. Inspect for phase loss or incorrect wiring. Repair or replace faulty motors to restore normal rated speed.