Bearings Equipment Reliability & Maintenance Center

Check Idle Bearings Before Startup

EP Editorial Staff | September 9, 2020

If your plant has been idle for a period of time, bearings in your rotating assets warrant a second look before ramping up production.

By Chris Johnson, SMB Bearings

Your factory equipment may have been idle for a few weeks and now you’re getting ready to restart or step up the level of operations. Here are some factors to consider when caring for rotational elements that have been sitting idle.

Corrosion is always something to watch for when maintaining bearings.

When machinery was operational, it’s likely that the factory was well heated/cooled and ventilated. If your plant has been shut down for a few weeks, perhaps the environmental conditions were not as ideal as they are during normal operation. If normal operating conditions were not maintained during a shutdown, particularly if the shutdown air was humid, confirm that corrosion is not present.

Contamination is an issue of concern.

Particulate contaminants, such as dust, can have a negative impact on a bearing’s performance, thus shortening its life span. For this reason, it’s good to keep the factory environment clean and dust free to maximize the performance and longevity of rotational elements. During a shutdown, normal cleaning schedules are not usually maintained, thus increasing the risk of bearing contamination, particularly in high-precision systems.

In machinery that’s idle for a sustained period, there is potential for grease to stiffen.

Remember, grease is simply oil with a thickener added. If the oil begins to leach out of the grease, then the grease will stiffen, resulting in greater rotational torque for your bearings. Note that this unlikely if the shutdown was just a few weeks.

What checks should engineers and operators make as they restart machinery? If you have the benefit of digital technology, such as predictive maintenance and vibration analysis systems, you’ll be alerted to issues before they emerge. If predictive systems are not in place, extra time performing manual inspections will provide an indication that something is amiss. Ultimately, if you have an ongoing program that consistently maintains your rotating assets, you should have little to fear when restarting your machinery after a brief idle period. EP

Chris Johnson is Managing Director at specialist bearings supplier SMB Bearings, Oxfordshire, UK. For more information, visit


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