Maintenance, Repair, Lubrication and Mounting of Industrial Bearing

To keep the bearing in good repair as long as possible, and to maintain inherent property of the bearing, the bearing should be maintained, examined and repaired. So accidents can be prevented beforehand, the operating reliability is ensured, and productivity and economical efficiency can be enhanced. Maintain performance standard of corresponding machine operating condition in the best state regularly. The maintaining coverage includes monitoring operating state, making up or changing lubricant and inspection by regular demounting. Items in operation comprise rotation sound, vibration and temperature of bearing, and lubricant state etc.

Bearing cleaning: when demounting the bearing to examine and repair, record bearing appearance at first, affirm the lubricant remains, and wash the bearing after sampling lubricant for examination. Gasoline and kerosene are usually used as cleaning agent. For bearing cleaning after demounting, there are coarse cleaning and fine cleaning. Put the bearings in container respectively. Then put wire netting as pad at the bottom, so the bearings can not contact dirt in the container. In coarse cleaning, if the bearing rotates with dirt, the rolling surface will be damaged. So it must be paid attention to the problem. Use brush to remove lubricating grease and adhesion on bearings in the coarse cleaning oil. Turn to fine cleaning after the bearings are almost clean.

In fine cleaning, bearing is rotated and carefully cleaned in cleaning oil. In addition, cleaning oil should be keep clean.

Bearing repair and estimation: the demounted bearing should be examined and cleaned whether it can be used or not after it is cleaned. The raceway surface, the rolling surface, the matching surface state, the wearing situation of the holder, the bearing windage increase and whether there is damage and abnormity of relevant and irrelevant dimensional precision should be examined. For non-separate small-sized ball bearing, use one hand to make the inner race horizontal, rotate the outer race and affirm whether it rotates smoothly.

For separate bearings like tapered roller bearing, raceway surfaces of the rolling element and the outer race can be respectively examined.

Because large-sized bearings can not be rotated by hand, pay attention to and examine the appearance of rolling element, raceway surface, holder and rib surface. The mort important the bearing, the more attention we should paid when examining.

Objective of bearing lubricating:

The objective of rolling bearing lubrication is to reduce internal friction and wearing, and prevent sintering. Lubrication effects are as follow:

(1) Reduce friction and wearing

Prevent metal contact and reduce friction and wearing on contact positions of ferrule, rolling element and holder.

(2) Prolong fatigue life

If the rolling contact faces are well lubricated when rotating, bearing rolling fatigue life can be prolonged. Otherwise, if the oil viscosity is low, the lubricating oil film thickness is not good, and the fatigue life will be shortened.

(3) Discharge frictional heat and cool

Heat generated by friction or transferred from outside can be discharged and cooled by circulating type oil supply. So bearing overheating and lubricating oil aging are prevented.

(4) Others

Bearing lubrication are also provided with other effects, such as preventing foreign body intruding bearing bowel, or preventing rust and corrosion. Lubricating methods:

Bearing lubricating methods are divided into grease lubrication and oil lubrication. To make bearings function well, lubricating methods suitable for use condition and use objective should be chose at first. If lubrication is the only objective being considered, lubricity of oil lubrication dominates. But grease lubrication is provided with advantage of simplifying bearing ambient structure. So the advantages and disadvantages of grease lubrication and oil lubrication should be compared.

Bearing mounting:

Correct bearing mounting affects the accuracy, life and performance of the bearing. Therefore, design and assembly apartment should do sufficient research on bearing mounting. The mounting should be done according to performance standard. Items of performance standard are usually as follow:

(1) Clean bearing and components related to bearing

(2) Examine dimension of related components and their machining situation.

(3) Mount

(4) Examine the mounted bearing

(5) Supply lubricant

It is hoped to open bearing package before mounting. For common lubrication by lubricating grease, cleaning is not required, and lubricating grease is directly filled. Cleaning is also not required in common lubrication by lubricating oil. But bearings for instrument and high speed should be cleaned by clean oil to remove antirust on bearing. The bearing whose antirust is removed is vulnerable to rust, so it should not be deposited and neglected. Moreover, bearings enclosed in lubricating grease can be directly used without cleaning.

Bearing mounting methods are different because of the bearing structure, matching and condition. As most of the bearings are rotation of axes, the inner race should be interference fit. Cylindrical bore bearing is usually pressed in by press machine, or thermal inserting is applied. In occasion with taper bore, bearing is mounted on tapered bore, or being mounted by sleeve. When bearing is mounted to casing, windage fit is usually adopted, and there is magnitude of interference on the outer race. The bearing is commonly pressed in by press machine, or mounted by shrink fit method after cooling. Dry ice is used as coolant in shrink fit occasion, water in the air coagulates on the shaft, so proper rust prevention method is required.