Reasons for the heating of the magnetic pump motor and countermeasures

Magnetic pumps are widely used in chemical, pharmaceutical, electronic, electroplating and other fields due to their good sealing performance, simple structure and no leakage characteristics. However, pump head heating is a common problem during the operation of magnetic pumps. Understanding the causes of heating is essential to effectively prevent equipment damage and safety accidents.

I. Four Major Causes of Heating

1. Dry running (operation without medium): Starting or running the pump when there is no liquid or the liquid level is too low causes the bearings to lose lubrication and cooling. The heat generated by the magnetic eddy current cannot be dissipated, resulting in a sudden temperature rise that can burn out the bearings or cause the isolation sleeve to crack.

2. Magnetic eddy current loss: This is an inherent cost of the structure. When the active rotor rotates, it generates an alternating magnetic field. When this field passes through the isolation sleeve, it induces a current (eddy current) inside the sleeve, causing the sleeve to heat up. The higher the rotational speed, the stronger the magnetic force, and the thicker the isolation sleeve, the more obvious the heating. Even if the medium is sufficient and the operating conditions are normal, the pump head (especially the isolation sleeve area) will still have a temperature rise, which is an inherent design characteristic.

3. Medium issues:

High viscosity liquids: Poor fluidity and high internal friction resistance (viscous shear heat generation), and more difficult to carry away the heat inside the pump.

Containing particle impurities: Aggravates the friction and wear of the flow components such as bearings, shaft sleeves, and impellers, generating additional heat.

High-temperature medium: High inlet temperature, further absorbing the heat generated by friction and eddy currents when flowing through the pump body, resulting in a higher outlet temperature.

Poor lubricity: Such as certain light hydrocarbons and ultra-pure water, which cannot effectively lubricate the bearings or carry away the heat.

4. Overload and cooling failure

Overload slippage: When overloaded, the magnetic rotor slips, causing a sharp increase in eddy current loss and high temperature.

Cooling interruption: Blockage of the auxiliary cooling/rinse pipeline, preventing heat dissipation (common in high-temperature and easily crystallizing media).

II. Practical Solutions

1. Preventing Idle Running: Ensure the pump is fully filled with liquid before startup and install a liquid level sensor for interlock protection.

2. Optimizing Operation: Avoid keeping the outlet valve closed for extended periods and regularly clean the cooling pipelines.

3. Precise Selection: For high-viscosity media, choose bearings with larger clearances; for high-temperature media, equip with a forced cooling system.

4. Daily Maintenance: Monitor the temperature of the bearing area (stop the machine if it exceeds 150°C), and regularly inspect the gap and wear of the magnetic rotor.

III. Safety Tips

1. High Temperature Burns: The pump head may be extremely hot during operation or immediately after shutdown. Do not touch it directly.

2. Medium Risks: Overheating of the pump head can significantly increase the risk of leakage of dangerous media (toxic, flammable, and explosive).

3. Electrical Safety: Overheating may damage seals or accessories, causing secondary risks such as short circuits.

The heating of the magnetic pump head is the result of multiple factors. From strictly prohibiting idle running, paying attention to the characteristics of magnetic eddy currents, to matching the medium and system design, each link must be treated with caution. The temperature rise caused by magnetic eddy currents (30-50°C) is a normal phenomenon, but abnormal heating requires immediate investigation. Understanding these principles and implementing scientific management and preventive maintenance can significantly enhance the reliability and service life of the equipment.