Why do bearings fail? This is a common manufacturing question, but one that is not always easy to answer. Failure can be a result of many factors; extreme working conditions, maintenance and lubrication schedules, or industry-specific demands. Early indications of bearing failure can include machinery that is running unevenly, or at an exceptionally loud volume, or with reduced accuracy.
Common causes of bearing failure
Lubrication Failure : According to a recent study, up to 80 percent of bearing failures are caused by improper lubrication. This includes insufficient lubrication, use of improper lubricants or excessive temperatures that degrade the lubricant.
Contamination: Contamination is caused by foreign substances getting into bearing lubricants or cleaning solutions. These include dirt, abrasive grit, dust, steel chips from contaminated work areas and dirty hands or tools.
Improper Mounting: In most instances, bearings should be mounted with a press fit on the rotating ring.
Misalignment: Bent shafts, out-of-square shaft shoulders, out-of-square spacers, out-of-square clamping nuts and improper installation due to loose fits can cause misalignment, which may result in overheating and separator failure.
False Brinelling: Rapid movement of the balls in a raceway while equipment is idle wears away at the lubrication. In addition, a lack of rotation in the bearing does not allow fresh lubricant to return to the spot. Both of these conditions result in false brinelling
Corrosion: Moisture, acid, low-quality or broken-down grease, poor wrappings and condensation from excessive temperature reversals can cause corrosion that is abrasive to the finely finished surfaces of ball and roller bearings.
Electrical Damage (Fluting): Constant passage of alternating or direct current, even with low currents, can lead to electrica
Fatigue (Spalling): Spalling is often the result of overloading, an excessive preload, tight inner-ring fits and using the bearing beyond its calculated fatigue life l damage.
Overheating: Overheating is generally the result of excessive operating temperatures and improper lubrication. High temperatures can cause grease to bleed (purge the oil), which reduces the lubricant’s efficiency. In elevated temperature conditions, oxidation can lead to the loss of lubricating oils from the grease, leaving a dry, crusty soap that can seize the bearing. Higher temperatures also reduce the hardness of the metal, causing early failure.
Excessive Loads: Putting too much load on a bearing is another common cause of failure.
Improper Storage and Handling: Improper storage exposes bearings to dampness and dust. Storing bearings in excessively high temperatures can also degrade a grease’s shelf life, so always check with the grease manufacturer for storage specifications. Handling bearings by opening boxes and tearing wrappings prematurely can let in dirt and expose bearings to corrosive elements.
Fit: A tight fit can be caused by excessive loading of the rolling element when interference fits exceed the radial clearance at operating temperatures. Micro-motion between fitted parts where the fits are too loose in relation to the acting forces may result in a loose fit.
Common signs of bearings beginning to fail:
Abrasion – Generally caused by excessive wear and friction against mating hardware.
Creep – Occurs when there is slipping at the surface fitting.
Flaking – Particle flaking is common with rolling element bearings.
Seizure – This often occurs when bearings are overheated from continuous rotation
By becoming aware of the different problems that can cause a bearing failure and the signs to look for, you have already taken a big step toward limiting machine failures. Of course, you don’t have to wait for the symptoms of a bearing failure to take action. Regular preventive measures can keep your bearings at peak performance for as long as possible, saving your business time and money.
Bearing Corporation also offers training workshops, seminars as well as demonstrations with regards to fitment of bearings. We can also assist your company by examining and analysing bearing failures, and thereafter, providing you with an in depth report outlining the cause of the bearing failure. Contact us on 011 451 8500 for more information.