Split roller bearings cut downtime from eight hours to one

The ability of Revolvo's range of SRB split roller bearings to provide safeguards against the crippling costs of downtime in continuous production environments was demonstrated recently at the Anglo Platinum Mine in South Africa. 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 downtime costs estimated at between R10,000 and R500,000 per hour, the ability of the SRB split roller bearing to be installed in about one hour, compared to eight for a solid bearing, meant that these costs were minimised.

Anglo Platinum took the decision to change many of its solid bearing applications to split roller bearings due to the potential for extended downtime in the event of a bearing failure. This decision was made easier by the fact that many of the spherical roller bearings assemblies on their fans were coming to the end of their design life.

Replacing oil-fed spherical roller bearings

OE Bearings, Revolvo's sole distributor in South Africa, supplied the SRB units. Warwick Steinhobel, a director of the company, says: "Shaft ventilation at the Anglo Platinum Mines has made great advances, in terms of bearing application, thanks to the decision to make use of grease-lubricated SRB split roller bearing assemblies, instead of continuing with the circulating oil-fed spherical roller bearing assemblies that were installed originally.

"From the technical, economic and pure design point of views, split roller bearings offer a host of advantages and cut downtime significantly. Basically, the simplicity of fitting a split roller bearing compared to a spherical roller bearing is a major factor in its longevity. Split bearings have a longer life span because they cannot be cross-located. They also provide superior sealing arrangements, which means longer bearing life with greatly reduced levels of maintenance.

"The fact that the SRB split bearings only take about one hour to fit, as opposed to solid bearings that take eight hours, is also a major factor when you are dealing with downtime 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 up-time."

Benefits of grease

Mr Steinhobel also points out the benefits of using grease lubrication rather than oil, and the problems, in terms of bearing life, that could be overcome using 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. The friction that must be overcome between the outside diameter of the bearing and the inner surface of the housing can be excessive. Among the problems encountered can be fretting corrosion, incorrect fits or ovality of the housing bore. All of these reduce bearing life. In fact, if a spherical roller bearing on a 100mm, one-metre shaft can no longer move in its housing, a temperature increase of only 10 degrees Celsius will be sufficient to reduce bearing life substantially: to below 50 per cent."

The number of follow-up orders that OE Bearings has received for these bearings illustrates the success of Anglo Platinum's conversion to SRB 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 & South Shaft, RPM Amandalbult shaft 1, 2 and 13 shafts, 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.