The temperature of Angular Contact Bearing (in operation) usually rises gradually and should not exceed 90℃. However, due to the high temperature in summer, bearing overheating phenomenon happens from time to time, mostly caused by poor lubrication or excessive clearance and high speed. Specific measures need to be taken for specific problems.

Temperature of Angular Contact Bearing

The normal temperature of the bearing varies with the heat, heat dissipation, rotational speed and load of the equipment. Generally, the temperature of Angular Contact Bearing increases gradually with the operation of the bearing and reaches a stable state after 1 to 2 hours. If the lubrication or installation is not proper, the bearing temperature will rise sharply and abnormally high temperature will appear. In this case, the operation must be stopped and necessary preventive measures must be taken. Using temperature sensor can monitor the working temperature of Angular Contact Bearing at any time, and automatically alarm or stop when the temperature exceeds the specified value to prevent the occurrence of burning shaft accident.

1）If the fit overload is large, the bearing should be heated in an air heating furnace or oil furnace with automatic temperature control, and the heating temperature should be strictly controlled below 100 ℃.

2）The bearings equipped with nylon cage can work continuously and stably for a long time at -40℃～120℃.

(3) In the temperature of more than 125 ℃ for a long time continuous rotation, will reduce the service life of the bearing.

4）Working at 150℃ for no more than 4 hours, the short-term temperature peak can reach 180℃.

Possible causes of Angular Contact Bearing overheating

The causes of high bearing temperature include: improper bearing selection, insufficient or excessive lubrication, lubricant containing impurities, excessive load, bearing damage, insufficient clearance, high friction of oil seal, poor fit of bearing and shaft/bearing box, unreasonable design of bearing box, unreasonable design of lubricant channel, vibration, etc.

1) Improper bearing selection

Bearings must be carefully accounted for in a variety of possible operating conditions (including start-up and shutdown conditions) under the force, bearings are usually selected by 2 times the maximum load.

2）The applied load

The heating of angular contact ball bearings is related to the applied load and rotational speed. The greater the load, the higher the speed, the more heat generated, the higher the temperature.

3）Centrifugal force

The heat generation of Angular Contact Bearing is related to centrifugal force. When centrifugal force is considered, the temperature of each node of the bearing increases significantly. With the increase of speed, the effect of centrifugal force on temperature becomes more obvious.

4）Spin of ball

The heat generation of Angular Contact Bearing is related to the spin of the ball. When considering the spin of the ball, the temperature of the inner ring, rolling body and shaft of the bearing increases with the increase of speed, so the spin effect of Angular Contact Bearing rotation cannot be ignored.

The solution of Angular Contact Bearing overheating

1）Incorrect bearing installation position will cause a large axial force between the ball end face and the inner ring and outer ring block of the bearing housing, resulting in overheating of the bearing. When installing the bearing, the force should be even, and no direct hammering.

(2) Use the bearings of the specified accuracy level.

(3) in use, bearing spindle bending or bearing box (mounting) hole misalignment caused by the solution is to repair the spindle.

(4) bearing tolerance fit too tight, expansion gap is too small caused by heat. Select the appropriate tolerance fit and appropriate clearance.

(5) Poor lubrication causes heating. Should choose the specified brand of lubricating materials, prohibit different brands, different viscosity of grease mixed use

(6) Low quality of assembly causes heating. Improve the quality of assembly.

(7) The inner and outer ring of the bearing is hot. Replace the bearings and related wear parts.

(8) Excessive axial force generates heat. Check the axial force balance measures and institutions.

(9) The bearing itself is damaged and heated up. Replace the bearing.

Special Notes

1）About the installation of bearings

Angular Contact Bearing in pair configuration is used to bear radial load and axial load at the same time, and can also bear pure radial load and axial load in either direction. This kind of bearing is combined by the manufacturer according to certain preload requirements, and provided to the user. When the bearings are installed in the equipment and fastened, the clearance in the bearings is completely eliminated and the rings and balls are in the preload state, thus improving the rigidity of the combined bearings.

Back-to-Back Mounting

When back-to-back (two bearings with opposite wide end faces) mounting, the contact angle line of the bearing spreads along the direction of the rotation axis, which can increase its radial and axial support angle rigidity and maximum deformation resistance (can withstand overturning moment). Can withstand the axial load acting in two directions, but each direction of the load can only be borne by a bearing.

Face-to-face mounting

Face-to-face (two bearings of the narrow end face opposite) installation, bearing contact angle line towards the direction of the axis of rotation convergence, its support angle rigidity is small, and less suitable for bearing overturning moment. As the inner ring of the bearing sticks out of the outer ring, when the outer ring of the two bearings are pressed together, the original clearance of the outer ring is eliminated, which can increase the preload of the bearing. Can bear the axial load in two directions, but each direction of the load can only be borne by a bearing.

Tandem mounting

Tandem arrangement (two bearing wide end face in one direction) installation, bearing contact angle line in the same direction and parallel, can make two bearings share the same direction of the working load. The radial and bearing loads are evenly shared by the bearings. However, the bearing set can only bear the axial load acting in one direction. If also contains the reverse load, it is necessary to add a back-to-back (or face-to-face) mounting method of the third bearing.

Rolling bearings should be lubricated with the following specified grease.

(a) grease life (repeat lubrication interval) should be used to estimate the bearing manufacturer's recommended method or the buyer agreed to an alternative method.

(b) If the estimated grease life is less than 2000 hours, then grease lubrication should not be used.

c) If the estimated grease life is more than 2000 hours, but less than 25000 hours, measures should be taken to inject grease to the running bearings and effectively drain the old or excess grease, the seller should notify the buyer of the time interval required to re-grease.

d) If the estimated grease life is 25000 hours or more than 25000 hours, the grease fitting or any other system should not be installed.

3）Filling amount of grease

The filling amount of grease inside the bearing housing varies according to the bearing speed, bearing housing structure, space volume, grease grade, and gas of the use environment. nsk bearings are recommended as follows.

First fill the grease inside the bearing, at this time, the cage guiding surface should also be stuffed with grease. Then, the space volume outside the shaft and bearing inside the bearing housing is filled with grease in the following quantity.

When the limiting speed is less than 50% rotation, fill 1/2 to 2/3 volume of grease.

When the limiting speed is higher than 50% rotation, fill 1/3 to 1/2 volume of grease.

Even if the grease is of high quality, after a period of time, its performance will deteriorate resulting in lower lubrication performance. Therefore, grease should be replenished at the right time. The grease replenishment interval is expressed by the running time, which can be referred to the relevant manual of the bearing manufacturer.