(May 4, 2011)

Newark, UK – A European cement plant, which was experiencing regular bearing failures on a high temperature fan operating at 150 degrees C. Typically, during an 18-month period, the original split bearings used on the fan would fail at least three times: a failure rate that was considered unacceptable.

An examination of the application and of the split bearings, revealed that a combination of high temperature and heavy load was causing the premature failures.

As a solution, NSK recommended the use of Hi-TF spherical roller bearings mounted in plummer blocks fitted with labyrinth seals. This combination is capable of continuous operation at 200 degrees C under heavy load. This has resulted in a cost savings at the plant of Euro9,130 a year on the operation of the fan.

The Hi-TF microstructure – a material with a high volume of retained austenite and a high hardness – is said to relax the stress concentrations on the edges of indentations on the bearing surfaces. This extends life even under conditions where there is an insufficient oil film and surface damage, such as peeling, easily occurs.

The bearings also offer increased resistance to wear and seizure, as a result of the dispersion of large number of fine carbides and nitrides in the bearing material, according to NSK.

In comparative tests with bearings made of conventional materials, such as SUJ2 steel, the Hi- TF material structure has shown less than one third the rate of wear and a 20% increase in seizure resistance, the supplier said.

Hi-TF, noted NSK, had previously proven its worth on a screw pump for conveying slurry at a cement plant in the US. In this application a large angular contact bearing was experiencing dust contamination.

Hygroscopic dust was wearing the raceways and increasing clearance to the point that, to avoid catastrophic failures, the bearings had to be changed prematurely, and on a regular basis.

Hi-TF Steel managed the problem by offering resistance to the contamination, with the new bearings also running quieter and smoother and offer shocking load protection, the company said.

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