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We were discussing bearing removal and cleaning procedure and also we have seen the bearing installation procedure. Today we will see here the basic importance of lubrication for smooth operation of a bearing and also types of lubrication usually preferred in industries.

Let us see first the various important functions of lubricant for a better performance of a bearing.
  1. Reduction of wear tear and friction
  2. Dissipation of heat
  3. Providing protective layer against dust and corrosion

Reduction of wear tear and friction

As we know that bearing will have inner ring, outer ring and rolling elements i.e. balls or rollers. During operation of bearings, there will be continuous rubbing action or wear-tear between moving parts of bearings. Due to these rubbing actions, there will be produced friction between moving parts.

If bearings are used under heavy load with high speed applications, in that case lots of friction will be created and hence it will lead the wear of surfaces of bearing parts. Therefore internal clearance of bearings will be increased and further premature failure of bearing will be there. 

If we run the equipment under damage bearing, it will also damage the bearing seat on shaft and bearing seat in the housing bore.

Healthy lubrication practices of respective bearings will eliminate the creation of friction by providing the smooth relative motion between bearing parts and therefore it will also save the bearing housing and shaft and we will secure the better service life of respective bearings.

For more information about the importance of lubrication in bearing operation, please refer the post “8 ways to prevent bearing failures”.

Dissipation of heat

Friction will be created, if lubricants are not provided, due to continuous rubbing actions between moving parts of bearings. Friction between moving parts of bearings will develop the heat and therefore it will lead the premature failure of moving parts of bearings and further shaft and housing also.

Healthy lubrication practices of respective bearings will avoid the temperature to reach at a point at which bearing parts might be affected. 

Providing protective layer against dust and corrosion

Bearings will not work properly if moisture, dust or any other foreign particle got inserted inside the bearings as dust, moisture or foreign particle will corrode the bearing parts and further will restrict the bearing to work properly and therefore premature failure of bearing will be there.

There is no use of bearings those are affected due to corrosion and therefore bearings will be protected by layer of lubricant just since it is manufactured. Before packaging the bearings, layer of suitable lubricants will be applied over the surface of bearing parts by the manufacturer for avoiding the effect of corrosion.

We must note it here that during installation of bearings, we should never remove the layer of lubricant from the surface of bearing parts as these layers are provided for avoiding the damaging of bearings.

Type of lubricants

Selection of suitable lubricants depend on various factors such as type of bearing, operating temperature , operating speed, type of bearing housing, load and working nature of bearings. We must follow the lubricants as per recommendation of manufacturer of equipments.

However, there are two basic types of lubricants those are usually used in industries i.e. oil and grease.

Grease will be used as lubricant in most of engineering applications. But there are some critical applications where load and speed, both will be high and we need to dissipate the heat generated continuously for securing the smooth performance of our equipments. Oil lubrication systems are usually preferred for such applications.

We can see the application of bearings those are oil lubricated in steel shredder equipment. There will be a rotor in shredder machine and it will run at higher speed for example 600 to 800 rpm. Rotor will be supported by two bearings at both ends and these bearings will be oil lubricated. 

A separate lubrication system will be provided to these bearings, where oil will be circulated continuously through the bearings. Heated oil will pass through the cross flow type of heat exchanger, where it will be cooled and again will pass through the bearings for dissipating the generated heat.

We will discuss "How to understand bearing numbers" in our next post.

Do you have suggestions? Please provide your suggestions.

Reference: SKF Bearing Maintenance manuals
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