Split roller bearings reduce installation and down time

22nd June 2007

Platinum Major, Anglo Plati-num has used UK bearing manufacturer Revolvo’s range of SRB split roller bearings to reduce installation and down time from eight hours to just one hour.

The ability of these split roller bearings to provide safeguards against the costs of down time in continuous production environments was demonstrated recently at Angloplat mines.

The SRB split roller bearings are replacing solid bearings on vent fans at a number of mines owned by Anglo platinum. The fans are crucial to production, and with down time costs estimated at between R10 000 and R500 000 an hour, the ability of the SRB split roller bearing to be installed in about one hour, compared with eight for a solid bearing, means that these costs are reduced.

Anglo platinum took the decision to change many of its solid bearing applications to split roller bearings owing to the potential for extended down time in the event of a bearing failure.

This decision was made easier by the fact that many of the spherical roller bearing assemblies on their fans were coming to the end of their design life.

Revolvo’s sole distributor in South Africa, OE Bearings, supplied the split roller bearing units.

“Shaft ventilation at the Anglo Platinum mines has made great advances, in terms of bearing application, thanks to the decision to make use of SRB grease-lubric-ated split roller assemblies, instead of continuing with the circulating oil-fed spherical roller-bearing assemblies that were installed originally,” says OE Bearings director Warwick Steinhobel.

“From a technical, economic and pure design point of view, split roller bearings offer a host of advantages and cut down time significantly,” comments Steinhobel.

The simplicity of fitting a split roller bearing compared with a spherical roller bearing is a major factor in its longevity. Split bearings have a longer lifespan because they cannot be cross-located.

It also provides superior sealing arrangements, which means longer bearing life with greatly reduced levels of maintenance.

“The fact that the SRB split bearings take only about one hour to fit, as opposed to solid bearings which require eight hours, is also a major factor when you are dealing with down-time costs that can reach R500 000. Fast change-out is essential and the SRB split bearings are much more efficient in this area in ensuring maximised plant uptime,” explains Steinhobel.

Commenting further on the technical advantages of Revolvo’s SRB split roller bearings, Steinhobel points out the benefits of using grease lubrication rather than oil and the problems, in terms of bearing life, that could be overcome using the SRB split bearings instead of spherical roller bearings in plummer blocks.

“Axial displacement within the plummer block housings incorporating spherical roller bearings is handled by allowing the entire bearing to slide within the housing,” says Steinhobel.

The friction between the outside diameter of the bearing and the inner surface of the housingthat must be overcome can be excessive. Among the problems encountered can be fretting corrosion, incorrect fits or ovalness of the housing bore.

“All these reduce bearing life. In fact, if a spherical roller bearing on a 100-mm, one-metre shaft can no longer move in its housing, a temperature increase of only 10 �C will be sufficient to reduce bearing life substantially to below 50 %,” says Steinhobel.

Steinhobel says the number of follow-up orders that OE Bearings has received for these bearings is evidence of the success of Anglo Platinum’s conversion to split roller bearing units.

To date, OE Bearings has received orders worth in excess of R900 000, providing split bearings for a total of 18 fans at mines that include Modikwa Platinum North and South shaft, Rustenburg Platinum mine, Amandelbult shaft 1, 2 and 13, Brakspruit, Bleskop and Rustenburg Waterval East fan.

These bearing installations are by no means exclusive to the platinum sector. OE Bearings also supplies SRB bearings for service on fans within the iron-ore, chrome, gold, paper and food sectors.