Industry News Display
2017-02-21 Plant Engineering
Healthy ball bearings are one of the most important details for preventing potential disaster in a manufacturing facility and knowing what to look for during routine maintenance is key.
By: David Manney, L&S Electric
Healthy ball bearings are one of the most important details for preventing potential disaster in a manufacturing facility. With proper maintenance and care, ball bearings last for a long time. It is important to ensure correct installation and application of the bearings to extend their lifespan because they are fragile. Certain issues can occur, however, if bearings are not lubricated or installed the correct way. There are some easy steps in dealing with five common bearing problems and how to address them.
False brinelling refers to the condition where elliptical wear marks form in an axial direction at different positions of the ball bearing. It is also common to find a sharp demarcation along with a bright finish often surrounded by brown debris forming a ring. The usual culprit for this type of failure is external vibration. Vibration impacts the motion between the raceway and balls in non-rotating bearings. In case the bearing is not turning, it is impossible to form an oil film preventing the wear of the raceway. As a result, the wear debris tends to oxidize, and this speeds up the wear process.
One effective technique to address this issue is to isolate the bearings from the source of external vibration. One way to isolate the bearings is to use grease containing molybdenum disulfide. These components prevent wear when applied to the bearings when they oscillate. True brinelling also occurs, and this happens when there is an excessive load that goes beyond the ring material's elastic limit. Using hammers during bearing installation and removal, or forcing a bearing onto a shaft can cause brinelling.
Indentations in the raceways suggests bearing failure. The problem gets worse with greater bearing vibration and premature fatigue. This is why it is important to avoid pushing the outer ring just to secure the inner ring onto the shaft. Never use too much force when installing bearings.
Premature fatigue and failure in bearings occur due to excessive loads, along with improper preloading and tight fits. At first, the issue appears as a normal fatigue, except for the presence of overheating and spalling in the affected area. Minimizing the load addresses this problem. Redesigning the unit is another possible solution by using a bearing that handles a greater load or weight capacity.
In a typical situation, angular contact bearings receive an axial load in a single direction. When loading these components in another direction, this leads to the most stress on the bearings. This stress creates friction and increasing temperatures, which increases vibration and leads to premature failure. Correct installation of the bearing is an effective course of action to take when reverse loading happens. It is also essential that when angular contact bearing is installed, the resultant thrust needs to be put on the wide face of the outer ring, which is the inner ring's opposite face.
Fatigue failure or spalling
Spalling is a type of problem with bearings is typical with the balls, outer, or inner ring. It appears as a fracture or damages of the running surfaces. This leads to the removal of small particles of the material affected. When ignored, the continued operation of the damaged components increases spalling. Replace the part if fatigue failure affects the bearing. Another practical solution is redesigning the system using a more robust bearing with greater resistance to fatigue failure.
The typical signs of contamination include dents in the balls and raceways that lead to wear and excessive vibration. There are also several types of airborne contaminants; including dirt and dust that get into the tight spaces of the bearing. Dirty work areas and foreign elements mixed in the lubricants increase the risk of contamination.
To cut down on contamination failures, ensure that all work areas, fixtures, and tools are clean. If there are grinding operations taking place nearby, move all bearing assembly sites farther away. Be sure to keep seals in check since any damaged ones no longer serve their purpose of protecting the bearings from contamination.
Being aware of these issues and the corresponding solutions will prolong the lifespan and condition of the bearings. Healthy bearings enhance productivity and reduce the chances of unplanned downtime.