Bearing failures can be caused by a number of factors, including:
- Fatigue, which can occur naturally over time, but also occurs prematurely if the incorrect bearing is chosen for the task.
- Incorrect installation or mounting, which can lead to significantly higher wear and tear and ultimately premature failure. Examples include misalignment, incorrect fits - too loose or too tight - out-of-roundness in shafts or housings. About 25% of bearing failures occur because of incorrect mounting.
- Lubrication problems, which can occur if too little, too much or incorrect lubrication is applied to the bearing. Incorrect or insufficient lubrication is the single biggest cause of bearing failure, accounting for more than 45% of problems.
- Poor maintenance or monitoring, because even the best precision bearings are not ‘set-and-forget' technologies. Their maintenance needs change with service and local conditions, so good monitoring and suitable maintenance is vital. (See conclusion for further details.)
- Contamination, which can occur when foreign substances enter the bearing. It is often considered to be the major component of lubrication problems. Contamination is particularly prevalent in aggressive process and manufacturing environments, such as mining, primary production and bulk handling.
Bearing contamination challenges
"Despite it being an eminently preventable problem, a staggering 25% of all bearing failures are caused by contamination," says Martin Grosvenor, industrial sector manager, Schaeffler Australia.
"Contaminants can include airborne dust, dirt or any abrasive substance that finds its way into the bearing. The main sources of these contaminants are dirty tools, contaminated work areas, dirty hands and foreign matter in lubricants or cleaning solutions."
Symptoms of a contaminated bearing include excessive vibration and wear, which is best detected before it becomes expensively obvious in the form of unscheduled maintenance, or worse, production breakdown.
The Schaeffler solution
In challenging environments or operations where the risk of contamination is high, such as continuous casting plant and conveyor belts, Schaeffler's FAG Sealed Spherical Roller Bearing (SRB) is ideally suited to the task.
FAG SRBs are a special rolling bearing design where the inner ring runs inside the outer ring on two rows of rollers. The bearings have an angular adjustment of up to 2° and are not only designed for high load carrying capacity but can also compensate misalignments, due to the fact that the symmetrical barrel rollers orient themselves freely on the concave outer ring raceway.
FAG Sealed SRBs offer the same benefits as open SRBs, but with seals typically consisting of nitrile rubber or, high performance fluoro rubber depending on the application and operating conditions.
Seals made from fluoro rubber comprise particularly high-performance materials that may release vapour when heated to approx. +300 °C. This may occur if, for example, a gas torch is used in the dismounting of a bearing. In such cases, the appropriate safety data sheet must be observed and this is available from Schaeffler upon request.
"The seals effectively close off the bearings, giving them an increased operating life compared with open bearings, because they are protected from contaminants. Additionally, they require significantly lower quantities of grease to keep them lubricated (up to 80% less in some applications), which means they can assist in reducing environmental impacts too," said Grosvenor.
Other features of Sealed SRBs include:
- Very high basic dynamic and static load ratings
- Environmentally friendly characteristics
- Lower grease consumption and disposal costs
- No requirement for expensive relubrication systems
- Reduced maintenance outlay
- Simple reconditioning
X-life Sealed SRBs
Schaeffler's FAG Sealed SRBs are also available in X-life ranges, which have improved kinematics, optimised surfaces, are made from higher performance materials and do not have a rigid central rib.
These enhanced characteristics of the premium X-life range mean that under identical operating conditions, basic dynamic and static load ratings as well as the basic rating life of the bearing is significantly improved. In certain applications, this means that a smaller bearing arrangement can be designed.
Conclusion - the importance of maintenance and monitoring
High quality bearings are a worthwhile investment because they will operate reliably for longer. In order to optimise the performance and operating life of such a valuable investment, proper maintenance and monitoring is essential. In some cases, it can as much as double the operating life of the bearing.
One method is to install monitoring technology such as Schaeffler's FAG SmartQB (incorporating SmartCheck technology) ready-to-use monitoring solution for electric motors, pumps, and fans. It is easy to install and does not require any specific knowledge about vibration diagnosis, including for common installations such as vibratory, grinding and rolling processes.
Another innovative new method is to use the bearing as the monitoring device. Schaeffler has recently introduced to Australasia it's new and radically advanced VarioSense roller bearings that report on their own condition and load through built-in sensor clusters.
Schaeffler's new FAG VarioSense bearings are configurable sensor bearings for monitoring machines, processes, bearing condition and load across diverse industries where downtime is costly and maintenance is expensive.
To complement advanced bearing technologies and monitoring solutions, a maintenance programme tailored to each individual application is ideal. In addition to checking that the bearing is operating properly and without contaminants, this should include re-lubrication to ensure the bearing does not suffer any premature damage.