Bearing study pinpoints lubricant problems

26 May 2009

When a manufacturer of domestic appliances experienced problems with housed bearing units on a fan application it turned to a bearing specialist in the hope of finding a solution. The bearings were running hot due to their location above an oven and this was thought to be the cause of failures that resulted in bearing replacements once a month.

The temperature at which the failures were occurring was well within the operating range (-40C to +180°C) of the fan bearings. This fact was revealed when an engineer, from motion and control specialist, NSK, 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 themselves onto the maintenance procedures adopted by the fan users, and in particular, the type of lubricant used. Self-Lube bearings with high temperature HLT inserts 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, which had inferior operating performance to the Asonic HQ72-102; this was the cause of the failures.

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 inserts on a weekly basis. The bearings have now been operating satisfactorily for 12 months and NSK says the solution has saved the manufacturer £12,000 (€13,700) in replacement, lost production and maintenance costs.