Going to extremes to deliver savings

Dry bearing lubrication sounds like a contradiction in terms. Yet in applications that run slowly at high temperatures, where conventional greases deteriorate rapidly, dry lubricated bearings offer a solution. Dry lubricants contain graphite and molybdenum disulphide components, which function to eliminate friction. This specially engineered mixture eliminates the need for grease re-lubrication, delivering reliable, improved performance and allowing significant cost savings to be made in reduced maintenance and downtime. Typical applications that benefits from these bearings are bakeries, food processing, mills and foundries, where parts such as rollers are repeatedly subjected to extremely high temperatures. 

To deal with high temperature applications, greased bearings are typically lubricated with a centralised lubrication system to counteract lubricant loss and prevent bearing failure. However, these systems drive up energy costs, consume excessive amounts of costly, high temperature greases, and are prone to pipe blockages caused by burnt grease. Even when working optimally, centralised lubrication systems must apply large and costly amounts of lubricant to compensate for heat-induced grease degradation.

By moving away from grease lubrication, dry lubrication bearings can help avoid the associated operating costs and productivity limitations that can occur when grease lubricated bearings are exposed to high temperatures. SKF dry lubrication bearings are having a significant impact on reliability, safety and costs in high temperature applications. In some cases, they have enabled the removal of centralised lubrication systems and even cut insurance costs due to the reduced fire hazard.

SKF recently extended meantime between failure (MTBF) for British baking firm Warburtons from six months to three years with SKF extreme temperature deep groove ball bearings, a dry lubrication option that removes the need for using expensive high temperature greases. The new bearings have brought a range of benefits to Warburtons, including reduced maintenance costs, minimised risk of product contamination and the reduction of unscheduled downtime.

Warburtons wanted to increase efficiency in the ovens at its Enfield site, where oven unloaders transport trays of product on rollers repeatedly throughout the day. The efficient daily repetition of this process depends on the use of resilient bearings that can cope with regular temperatures of up to 120°C (and local temperatures in excess of 200°C if unloader trays jam). In addition, the need for re-lubrication placed a heavy burden on maintenance, both in terms of time and expense, since regular re-application with expensive high temperature greases was required. 

Despite the fact that frequent re-lubrication was being carried out, Warburtons had been experiencing a series of bearing failures on their oven unloaders and the maintenance downtime was proving costly. Automatic lubricators had been considered but were not a viable option as, in this application, they would have been prone to frequent failure like the bearings, and so maintenance engineers were required to apply lubrication in hard-to-access points that posed a threat to their safety. With so many problems to address, Warburtons decided to tackle the issue of both the bearing failures and the frequent, expensive re-lubrication.

The answer came in the form of SKF extreme temperature deep groove ball bearings (VA228). These dry lubrication bearings are fitted with a graphite cage that releases minute amounts of graphite powder to lubricate the bearing, offering an excellent dry lubricant option for low-speed, high temperature applications such as ovens. For hygiene-sensitive industries such as food and beverage, these bearings offer the significant additional benefit of eliminating the risk of product contamination from grease. SKF extreme temperature deep groove ball bearings provided a powerful solution, minimising product contamination while withstanding temperatures to 350°C.

The reduced costs of work related to repairs, manual lubrication, product or component consumption, and lubricant consumption achieved by installing SKF extreme temperature deep groove ball bearings totals almost £7k per year, while the total benefits of MTBF against costs are expected to deliver a return on investment of 200%.