When a bearing overheats, the grease may melt and leak out at best, or even burn out at worst! The following are the common reasons why bearings overheat:

(1) Friction between the bearing cap and the shaft

Because the inner circle of the bearing cap is eccentric or burrs are knocked out during assembly, it rubs against the shaft locally, causing the shaft to heat up.

The burrs on the bearing cap can be trimmed with a fine seat. If the inner circle of the bearing cap is eccentric, it can be trimmed on a lathe. If both the bearing cap and the shaft are worn, the shaft can be re-polished and the bearing cap generally needs to be replaced with a new one.

(2) Uneven inner and outer circles of the rolling bearing

Due to machining errors, the bearing holes on the two end caps may not be concentric after assembly, causing the inner and outer rings of the bearing to be non-parallel. Ball bearings have a certain degree of adaptability to non-parallelism.

Roller bearings have increased friction loss due to the non-parallel contact between the rollers and the inner and outer rings, causing the bearing to heat up.

If the concentricity error is not large, the heating condition will disappear on its own after the motor runs at no load for a period of time. If the concentricity error is large, the roller bearing will often heat up and burn out. At this time, the concentricity of the housing and the end cover should be carefully checked and corrected. (3) The grease is not clean or the amount is inappropriate If foreign matter such as sand and iron filings are mixed into the grease, it is easy to cause the bearing to heat up and be damaged. The following method can be used to hear a rustling sound in the running bearing: place one end of a screwdriver (a tool used to open bottle caps, unscrew screws, etc.) against the outer cover of the bearing, and put your ear against the screwdriver handle to hear this sound. In this case, the bearing cover should be disassembled and cleaned, and then replaced with clean, compliant grease. If there is too much grease, the motor will heat up when it starts running, and some grease will be squeezed out from the gap of the bearing cover, and the heating phenomenon will disappear quickly. If there is too little grease, a "rubbing" or slight "chuckling" sound can be heard, causing the bearing temperature to rise. At this time, grease of the same specification as the original should be added, and the temperature rise will decrease. Generally, motors used in underground scraper conveyors and belt conveyors should be regularly overhauled to remove coal dust and debris from the motor fan. The bearings should be greased once a month and cleaned and oiled every three months to maintain good lubrication. (4) Bearing clearance is too small or too large If the bearing clearance is too small, the shear friction loss of the oil flow in the clearance will be too large, which will cause the bearing to heat up. At the same time, if the clearance is too small, the oil volume will be reduced, and there will be no time to remove the heat generated by friction, which will further increase the temperature rise of the bearing. However, if the clearance is too large, it will change the dynamic characteristics of the bearing and cause the rotor to run unstably. Therefore, it is necessary to select and verify the bearing clearance according to different equipment and usage conditions. In addition, motor body vibration and poor mechanical alignment can also cause the bearing shell temperature to be too high.