Correct mounting of bearings

14-05-2020

The correct installation of bearings is very important, but in the actual operation is always easy to run off, problems emerge endlessly.The reason is that some details were not noticed, resulting in bearing damage during the installation. This article shares several examples of bearing installation errors, as well as the correct installation methods and tips.

1) friction and heating between the end face of the inner ring and the shaft shoulder produce cracks

Loose coordination between shaft and bearing inner hole
Thermal crack is generated on the end face of the inner ring. The continuous extension of the thermal crack will make the bearing inner ring fracture in use.

Due to the loose matching between the shaft and the inner hole, the shaft and the inner hole surface slide.Sliding friction will cause heat and cause the bearing to be damaged due to heat.

Housing aperture is too loose with bearing outside diameter (commonly known as "outer ring")

Because of the loose match between the aperture of the housing and the choice of the outside diameter of the bearing, sliding occurs between their surfaces.Sliding friction will cause heating and damage to the bearing.

1) the hammer directly hits the bearing

Install the bearing with inner ring (or outer ring) interference fit, it is forbidden to hit the end face of the bearing inner ring (or outer ring) directly with a hammer, so that it is easy to knock out the retaining edge.The sleeve shall be mounted on the end face of the inner ring (or outer ring) by hammering the sleeve.

2) transfer the mounting force through the rolling body

When installing the interference fit bearing of the inner ring, the force cannot be transmitted to the inner ring through the outer ring and the rolling body.This will knock out the bearing raceway and the surface of the rolling body, causing noise and premature damage to the bearing during operation.The correct method is to apply the force directly to the inner ring face with the sleeve.

Overheating temperature

Some users use acetylene spray gun to heat the bore of the bearing. When the heating temperature exceeds 727℃ (the phase transition temperature of the bearing steel), the metallographic structure inside the bearing steel will change.When the bearing is cooled, the bearing bore does not return to its original size and is usually larger than it was before heating.

Correct bearing mounting method

Bearings should be mounted in dry, dust-free areas and away from equipment that produces metal debris and dust.When it is necessary to install in a complex environment, pollution should be kept to a minimum.

When installing bearings, mechanical, heating or hydraulic methods should be selected according to the type and size.

Cylindrical bearing mounting

1) cold installation

When installing a small bearing that is not too tightly fitted, the bearing can be fitted to the proper position by tapping gently on the sleeve through a sleeve and hammering.Knock should be as even as possible on the bearing ring, in order to prevent the bearing tilt or skew.

Most bearings are mounted by pressing in.If the inner and outer rings of the bearing are to be mounted on the shaft and in the bearing seat at the same time, it must be ensured that the same pressure is applied to the inner and outer rings at the same level as the contact surface of the mounting tool.

2) hot installation

In general, it is not possible for larger bearings to be mounted without heating the bearing or bearing seat, as the larger the size, the greater the force required for mounting.The difference in temperature between the bearing ring and the shaft or bearing seat required for thermal installation depends mainly on the interference and the diameter of the bearing fit.The heating temperature of the open bearing shall not exceed 120℃.Heating bearings with seals and dust caps above 80 ° c is not recommended (make sure the temperature does not exceed the allowed temperature of seals and grease).

When heating the bearing, it should be heated uniformly, and there must not be local overheating.

Cone bearing mounting

Bearing with tapered hole, its inner ring is mostly installed by interference fit.The amount of interference is determined by the axial push distance of the inner ring on the conical shaft diameter, the set sleeve or the return sleeve.The larger the advance distance on the conical mating surface, the smaller the radial internal clearance of the bearing. The interference can be determined by measuring the clearance reduction or the axial advance distance.

Small and medium bearings may be propelled to a suitable position on the conical shaft diameter by means of a bearing mounting tool or, preferably, by a locking nut.In the case of a set sleeve, use a sleeve nut that can be locked with a hook or impact wrench.The backing sleeve can be pushed into the bearing bore by bearing mounting tools or end plates.

Larger bearings require more force to mount, so hydraulic nuts should be used.The hydraulic nut can be used to mount the tapered bore bearing on the tapered shaft diameter

Oil injection method

The working principle of oil injection method is: hydraulic oil is injected into the matching surface between bearing and shaft diameter through oil hole and oil groove under high pressure to form a layer of oil film.The oil film separates the mating surfaces, which greatly reduces the friction between the mating surfaces.This method is usually used when the bearing is mounted directly on the conical shaft diameter.

The necessary oil holes and grooves shall be part of the overall shaft design.This method can also be used to install the bearing on the set sleeve or the return sleeve if the set sleeve and the return sleeve have been processed with oil holes and oil grooves




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