Common Malfunction and Analysis on Rolling Bearings

1. Common malfunction phenomena in rolling bearings.
　There are two kinds of phenomena in rolling bearing malfunction, one is temperature where the bearing is installed is too high, the other one is that there is noise when the bearing is in operation.
1.1. Higher temperature in bearing.
　When operating, the part of installation bearing allowed having a definite temperature, When the shell of machine is touched by hand, it is natural that hand isn’t felt very hot, contrarily indicated that there are higher temperature on bearing.
　The causes of higher temperature of bearing are the lubricating oil isn’t subject to requirement or deterioration, the viscosity of lubricating oil is higher; the mounting of machine is tighter; the mounting of bearing is closer; the bearing race runs on the shaft or in housing; the load is bigger or the cage of bearing or scroll bar is fragmental,etc.
1.2. Bearing noise.
　The rolling bearing is allowed having slight running sounds at work, if noise is bigger or unusual noise or clash, it indicates that bearing has malfunction.
　The cause of rising noises on rolling bearing is complicated; one is the abrasion between the fit face of bearing inner ring and outer ring. As the abrasion, the fit relation is broken between the bearing and housing, the bearing and shaft, resulting in axes deviates from the correct position, the shaft rotating produces noises in high speed. When bearing fatigues, the external of metal will flake, also in bearing the radial internal clearance will bigger and produce noises. Besides, the lack of bearing lubrication will produce dry friction and broken bearing etc. will produce noises. After the abrasion of bearing, the cage loose or broken will also produce noises.

2. Malfunction and analysis.
　When bearings are dismantled, malfunctions and reasons can be judged from damages of the bearings.
2.1. Metal flaked away from raceway.
　The bearing rolling elements and the raceway of inner and outer ring all support pulsating load periodicity, so periodical contact stress are produced in them. When circular times reached a certain value, weariness flaking will happen on working face of rolling elements, inner and outer raceways. If bearing load is too large, this weariness flake will be enforced. In addition, if bearings are correctly installed or the shaft is bent, weariness flaking phenomena on raceways will also be seen.
　Weariness flaking on bearing raceways will reduce the rotating precision of shaft, make noise and vibration in devices.
2.2. Bearing burnt.
　Burnt bearing has tempered color on raceways and rolling elements. Usually the reasons are insufficient lubrication, lubricant not qualified or alterative and too tight fitting,
2.3. Shape distortion
　If concavities shown on contact faces of raceways and rolling elements, it indicate bearing has been distorted. The reason is under large static or impactive load, part stress on bearing working face exceed the yielding limitation of material, this instance always happen on bearings which are used for low-speed rotating.
2.4 Bearing housing crack.
　The reasons for crack in bearing housing possibly are too tight fitting, inner ring or outer ring loose, containers in bearing distorted, or face for fitting bearing not be fully machined.
2.5 Retainer smashed.
　The reasons are insufficient lubrication, rolling elements smashed or bearing housing deflective.
2.6 Metal of retainer clinked on rolling elements.
　Possible reason is rolling elements are clipped in retainer or insufficient lubrication.
2.7 Raceway of bearing housing seriously wearied out.
　Possibly something are fallen in bearing housing, lubrication oil is not sufficient or lubricant brand is not suitable.