Common causes of excessive bearing temperature

(1) Poor lubrication, such as insufficient or excessive lubrication, the quality of the lubricating oil does not meet the requirements, deterioration or foreign matter;

(2) Insufficient cooling, such as pipe blockage, inappropriate cooler selection, and poor cooling effect;

(3) Bearing abnormality, such as bearing damage, poor bearing assembly process, and the clearance adjustment of the bearing box does not meet the requirements;

(3) Large vibration, such as poor coupling alignment process does not meet the requirements, the rotor has dynamic and static imbalance, poor foundation rigidity, weak foundation, rotation stall and surge.

Solutions

When the bearing temperature is high, the following problems should be solved first:

1) Improper oiling amount, too little or too much lubricating grease

The bearing box should be oiled regularly according to the work requirements. Sometimes the bearing temperature will be high after oiling, mainly due to excessive oiling. At this time, the phenomenon is that the temperature continues to rise, and after reaching a certain point (generally about 10℃~15℃ higher than the normal operating temperature), it will remain unchanged and then gradually decrease. 2) The grease applied to the bearing does not meet the requirements or is contaminated.

Improper grease selection makes it difficult to form a uniform lubricating film, failing to reduce internal bearing friction and wear. This results in insufficient lubrication and increased bearing temperature. When different types of grease are mixed, chemical reactions may occur, causing the grease to deteriorate and clump, reducing lubrication effectiveness. Grease contamination can also increase bearing temperature. Dust introduced during greasing can contaminate the grease, causing grease deterioration within the bearing housing and disrupting bearing lubrication, leading to increased temperatures.

For this reason, the appropriate grease should be selected. During maintenance, the bearing housing and bearings should be cleaned, and the oil lines should be inspected and unblocked. Different types of grease should not be mixed. When switching to a different type of grease, the original grease should be cleaned first. Regular grease application should be performed during operation and maintenance, and the grease should be properly stored and protected from moisture and dust.

3) Inadequate cooling:

Check the pipes for blockages and the oil inlet and return water temperatures for any excesses. If the cooler is inappropriate, cooling performance is poor, and it cannot meet operating requirements, it should be replaced or a new cooler installed in parallel. For axial-flow induced draft fans, the insulation and sealing of the core tube should also be checked.

4) After confirming that the above issues are not present, check the coupling.

Alignment of the coupling must meet process standards. When aligning axial-flow induced draft fans and hydraulic couplings, thermal expansion of the equipment during operation should also be considered. Thermal expansion on the impeller side of an induced draft fan causes the bearing housing to rise. During operation, the temperature of the hydraulic coupling rises, causing the bearing housing to expand and the bearing to rise. Therefore, the motor should be positioned higher during alignment. The amount of allowance should be determined based on the characteristics of the equipment and the operating temperature parameters.