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Detecting Bearing Faults -  Part 4

If you asked most people whether vibration analysis improved reliability, they would answer, "Yes." But I would disagree.

What is your definition of reliability?

If your definition of "reliability" is whether or not bearings are failing catastrophically and unexpectedly, then it would be true to say that vibration analysis does improve reliability. But let's draw a parallel with your car for a moment.

How would you feel if your car failed as often as most rotating machines?

If you found that every three months your car engine failed and thus you often found yourself stranded on the side of the road, then you would correctly say that your car is unreliable. But if the mechanics added a red light to your car's dashboard that warned of imminent failure so you could avoid being stranded on the side of the road, you would feel like that was a step in the right direction. But if the red light comes on every three months, you would still feel as if your car is unreliable. You would be within your rights to ask the mechanics to make a change so that your car would run six years - or much longer - without the red light coming on.

We need red lights on our motors and pumps

The same is true with your rotating machinery. In most plants, the vibration analysts are the "red light" on the dashboard. They take readings, see that there is a problem, then wave their hands to say, "you need to take action because the bearing is about to fail." If the vibration analyst does a good job, then there will be more time between the red light coming on and the machine failing. As a result, the maintenance department will have more time to deal with the repair: order the parts, find the most convenient time to shut the machine down, operate the machine through a critical period, operate the machine more safely, etc.

But there is much more that the vibration analyst and the maintenance and operations departments can do. The goal has to be to increase the life of the bearing - that's what makes a machine more reliable.

How can you improve reliability?

There are four key components to improving the reliability of rotating machinery.

Purchase and design

Rotating machinery and its support structures should be designed and purchased with reliability in mind. The lifetime costs should be prioritized over the up-front purchase price. Vibration analysts can contribute to the design and selection process by referencing the experience gained from similar machines - that is, if a certain design has proven to have problems, do not use it again. Vibration analysts can also contribute by performing "acceptance testing" (incoming inspections) of new and overhauled machines to ensure that they are fit for your company's use.


If a machine is operated correctly, there are less stresses on the components (bearings, shaft, seals, etc.). It is primarily up to the operators to ensure a machine is operating correctly, but the vibration analyst and other condition monitoring technicians can perform tests to verify that it is operating properly.


Similarly, if a machine runs more smoothly, there will be less stress on the components and it will be more reliable. The maintenance department has an important role to play. The bearings and gears should be lubricated correctly. In addition, the shafts should be precision aligned; there should be no soft foot; the rotating elements should be correctly balanced; there should be minimal resonance; the bearings should be installed correctly; and so on. If the maintenance department gets all of the fundamental maintenance issues right, then the machine will be far more reliable. As a result, the vibration analyst should see very few fault conditions develop.

So what is the role of the vibration analyst? The vibration analyst may be involved in precision alignment and should be involved with field balancing. The vibration analyst can certainly take the required readings to check for misalignment, soft foot, lubrication problems, bearing installation problems, unbalance, looseness, resonance, flow problems, and so on. If these tests are performed correctly and the conditions are corrected quickly, the machine will provide many years of reliable operation.

Yes, it will take cooperation between maintenance and the condition monitoring group, and it will require the vibration analyst to master all the necessary skills, but it is definitely worth it.

Continuous improvement

Even with the best intentions, there will still be failures. The important factor is to learn from failure. Root cause failure analysis can be used to determine why a machine failed - but it is important to go back and make changes so that the failure does not occur again. A vibration analyst can play a very important role. The vibration data can hold the clue as to why a machine failed. It may be that a bearing failed, for example, but careful examination of the data may identify a condition (unbalance, misalignment, resonance, etc.) that led to the failure. When the bearing is removed from the machine, it should be examined to determine why the failure occurred. In the example in Figure 1, the pump was in standby mode for long periods and experiencing vibration from a second unit, thus "false brinelling" occurred.

Figure 1 - This bearing has failed due to false brinelling. Image adapted from FAG Publ. No. WL 82 102/2 ED

How do you make all this happen?

The answer is training and communication. Unless you have buy-in at all levels in the organization, reliability will always be a seemingly impossible dream. Everyone must believe that reliability is a very high priority (safety may be a higher priority, but reliable plants are safer plants). Reliability adds to the bottom line of the balance sheet. While there will be an initial investment (training, instrumentation, design modifications, etc.), the improvements in production, quality and energy efficiency, and the reduction in maintenance costs (parts and labor) and safety incidences will result in a very fast return on investment.

What type of training is required?

In this author's opinion, you need three types of training: awareness, management and practitioner.

Awareness: Operators, millwrights and everyone up through to management need to have basic training on the concept of reliability, condition- based maintenance and the condition monitoring technologies. People should not feel threatened by the technology; and everyone should be pulling in the same direction. And they should all believe in the philosophy so that when recommendations for repairs and changes to procedure are made, they are followed without question.

Management: Managers, engineers and purchasing personnel need a deeper understanding of the same three areas (reliability, condition-based maintenance and the condition monitoring technologies) so the program can be run correctly and all design and repair decisions are made with reliability in mind.

Practitioner: It may seem obvious that the vibration analysts, aligners, balancers, lubricators, bearing installers and other people need training to do their job properly, but you would be surprised at how few actually have adequate training. Assumptions are made about a person's knowledge; sadly each person learns the same mistakes from their fellow workers. Companies may buy modern vibration analyzers, state-of-the-art laser alignment systems and other high-tech equipment, but without adequate training, the money is wasted (and the opportunity is lost). See Figure 2.

Figure 2 - Laser alignment systems are great, but without adequate training, they will be misused


A good vibration analyst will detect a bearing defect before it fails. A better analyst will detect the defect earlier and communicate the status so action can be taken to minimize the cost of repair. But the best vibration analysts do everything possible to reduce the likelihood that the bearing will ever develop a defect in the first place.

Jason Tranter is the founder of Mobius Institute and author of iLearnVibration and other training materials and products. Jason has been involved in vibration analysis in the USA and his native Australia since 1984. Before starting Mobius Institute, Jason was involved in vibration consulting and the development of vibration monitoring systems.

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