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Bearing is hot again, how to do?
Feb 01, 2018

    High bearing temperature is a common and harmful fault of rotating equipment, which will reduce the service life of bearing and increase the maintenance cost. When the temperature rises faster and the temperature exceeds the standard value, it will easily lead to the unplanned shutdown or load reduction of the unit. Therefore, it is the guarantee of the continuous safe operation of the equipment to judge the cause of the failure quickly and take appropriate measures to solve it.

 

     Common causes of excessive bearing temperature

1) Poor lubrication, such as insufficient or excessive lubrication; lubricating oil quality does not meet the requirements; deterioration or debris.

2) The cooling is not enough; the pipe is blocked; the cooler is not suitable, and the cooling effect is poor.

3) Abnormal bearings, such as bearing damage, poor bearing assembly process; bearing box clearance adjustment does not meet the requirements.

4) The vibration is large, such as the correct process difference of the coupling does not meet the requirements; the rotor exists dynamic/static unbalance; the foundation rigidity is poor; the ground foot is deficient , the rotation stalls and surges.

    Measures to solve it

     When bearing temperature is high, the problem should be solved from the following aspects:

1) The amount of oil is inappropriate, and the grease is too little or too much.

The bearing housing should be periodically refueled in accordance with the requirements of the work. When the bearing is refueled , sometimes its temperature is too high. It is caused by refueling too much oil. After reaching a certain point ( usually around 10 ℃ to 15 ℃ higher than the normal operating temperature ), it will maintain the same , and then decrease gradually.

2) Bearing grease does not meet requirements or is contaminated.

     If the lubricating grease does not fit, it is hard to form a uniform lubricating oil film, which can not reduce the bearing internal friction and wear and also result in insufficient lubrication and bearing temperature rise. When different types of grease mix, it may occur the chemical reaction which will cause grease metamorphism, blocking and reduce lubricating effect. If the dust falls into when adding grease, it will cause grease pollution, which will lead to grease deterioration inside the bearing box to destroy the bearing lubrication and the bearing temperature rises.

     So we should choose suitable grease, clean the bearing box and bearing in the inspection and repair, check and dredge the oil pipeline. Do not mix the grease of different type. If we replace the different type of grease, the original grease should be cleaned up first. Add the grease regularly during operation and maintenance. Grease should be properly kept with dust prevention measures.

3) Cooling is not enough.

    Check if the pipe is blocked, the inlet and backwater temperature is over standard. If the cooler is not suitable, the cooling effect will be poor and can not meet the requirements. Then we need to change or parallel install the new coolers. For axial flow induced fans, we should also check the heat preservation and sealing of the core tube.

4Check the alignment of the coupling and the bearing after confirming that the above problems do not exist

   Coupling alignment should comply with the technical standards. Coupling alignment of axial flow fan and hydraulic coupler should also consider heat expansion. Fan impeller side thermal expansion will cause bearing box to increase; the temperature of hydraulic coupler in operation rises, which leads to bearing box expansion and bearing increases. The motor needs to be higher when alignment, and reserved amount depends on the machine characteristics and temperature set in operation.