NSK has revealed how it has reduced bearing-replacement costs on oven fans for a domestic appliance manufacturer through its Cost-Saving Programme.

The manufacturer was experiencing problems with housed bearing units on a fan application.



The bearings were running hot due to their location above an oven, and this was causing failures resulting in bearing replacements once a month, at a combined cost of GBP12,000 per year.

The nature of the bearing problem was compounded by the fact that the temperature at which the failures were occurring was well within the operating range (-40C to +180C) of the fan bearings.

This fact was revealed when an NSK engineer visited the manufacturer's site in an attempt to reduce the high costs resulting from the failures.

This discovery moved the focus of the inspection procedure from the bearings onto the maintenance procedures adopted by the fan users, and in particular, the type of lubricant used.

Self-lube bearings with high-temperature HLT s are initially filled with the Kluber Asonic HQ72-102 grease during manufacture.

This is a high-performance grease developed to ensure long-term, reliable operation in high-temperature applications.

However, NSK's investigation revealed that the failed bearings were filled with another type of grease that had inferior operating performance to the Asonic HQ72-102; this was the cause of the failures.

The role of grease ion in ensuring reliable bearing life is much misunderstood, according to NSK, and is one reason why the company runs regular Maintenance Seminars as part of its Cost-Saving Programme.

The seminars also address another major issue with grease - that of incompatibility.

Some greases cannot be mixed with others, even when both types meet specifications.

Unless this incompatibility is understood and accounted for, switching to different grease can have serious consequences for bearing life.

Having identified the nature of the problem on the oven-fan bearings, NSK recommended a maintenance programme to overcome it, and prevent it happening again.

This involved, among other activities, regular regreasing of the HLT s on a weekly basis.

The programme has proved a success - the bearings have now been operating satisfactorily for 12 months without problems.

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