Premature failure of rolling bearing causes due to improper bearing selection. Bearing is a delicate machine element, however, it can withstand the tough service condition of the machine. The rolling bearing has a definite bearing life. The rated life of a rolling bearing is the number of revolutions attained by a bearing in normal operating conditions before its first sign of premature failure. Premature failure of rolling bearing, gives an indication such as noise in the bearing, bearing temperature rise, increased power consumption. Premature failure of rolling bearing can occur due to the following reasons:
(1) Improper Bearing Storage.
(2) Improper Bearing Installation.
(3) Improper Bearing Lubrication.
(4) Severe Atmospheric Conditions.
Bearing storage to be done in dust-free and dry premises. Ingression of dust and moisture in the bearing may cause damage to internal components of the bearing and induce premature fatigue failure of the bearing. During inspection and repacking of bearing care to be taken to handle the bearing in such a way that no foreign matter can contaminate the bearing. Proper handling and storage of bearing can prolong its life. Steps to be taken to avoid damage to the bearing due to improper storage:
(1) Avoid storing in high humidity areas.
(2) Store bearing in a cool and dry place.
(3) Store bearings on the shelf.
(4) Do not remove cardboard packing of bearing.
(5) Do not remove the wrapping of the bearing before its installation.
(6) Do not store the bearing for a long time because the anti-rust compounds applied in the bearing may get degraded.
Improper bearing installation reduces the bearing life and increases the premature fatigue failure of bearings. For proper installation of bearing all necessary precautions recommended by the bearing manufacturer to be followed strictly. Before installation of bearing following preparation to be made:
(1) Check the shaft and housing Clarence, check for shaft diameter, roundness, and chamfer radius.
(2) The shaft on which the bearing is to be mounted must be checked for shaft thoroughness and shaft deflection.
(3) Ensure the radial internal clearance in the bearing. It is critical to maintaining the proper radial internal Clarence available in the original design. The standard Clarence scale in ascending order is C2, C0, C3, C4, and C5.
Deficient Clarence in the bearings may cause the bearing problems as follows:
(1) A proper film of lubricant must be maintained between the rolling element. Reduced internal clearance hampers the lubricant flow in the bearing and leads to premature bearing failure.
(2) Reduction in radial clearance obvious when bearing is press fit.
(3) In normal bearing operation heat is generated, which creates a thermal expansion of inner and outer rings. This reduces the internal clearance and hence reduces the optimum bearing life.
(4) Proper and clean tools to be used for bearing installation. Tools must be free from cracks, sharp edges, breakages, chipping, and deformation, which may cause damage to the bearing during the mounting process.
(5) If excessive force is applied when pressing a bearing on the shaft, stop installation. Check the cause and rectify them.
(6) When mounting a bearing on the shaft, force should not be applied to the outer ring. This may cause damage to the rolling element, retainer, and outer ring.
(7) Oil bath or induction heating devices are to be used when heating of bearing is required during installation. The bearing temperature should never exceed 120 degrees centigrade. Heating more than 120 degrees may reduce the hardness of the bearing material and reduces the optimum life of the bearing.
(8) The heated bearing must not be handled with a bare hand. This can cause serious burn injuries.
Improper lubrication means the lubricant is not provided in appropriate quantity and quality. The purpose of lubrication is to maintain a thin film of lubricant between the rolling element. Lubricant plays the following functions in the bearing:
(1) Reduces friction due to the rubbing of mating parts.
(2) Dissipate the heat generated during the movement of bearing.
(3) Reduces premature fatigue failure and prolongs the bearing life.
(4) Prevents rust and corrosion due to moisture and weather conditions.
(5) Do not allow foreign matter like dust and water to enter into the rolling element of bearing.
To achieve the proper lubrication in bearing an appropriate lubricant to be used. Cleanliness of lubricant to be taken care of. Proper lubricant storage to be done to avoid dust and water contamination in the bearings. Oil and grease are used for lubrication. Oil lubrication is suitable for high-speed and high-temperature applications. Grease lubrication is used because of its easy handling due to viscosity.
Bearing lubrication failure reasons:
(1) Wrong lubricant application.
(2) Insufficient quantity of oil or grease.
(3) An excessive quantity of oil or grease.
(4) Oil and grease mixed together.
(5) Contamination of metallic particles.