SKF is launching SKF DryLube Bearings, which the company says contains a specially engineered graphite mixture that eliminates the need for relubrication with grease. This is claimed to deliver reliable, improved performance and enables significant cost savings to be made through reduced maintenance and downtime. SKF Drylube Bearings will benefit machines that are repeatedly subjected to extremely high temperatures in applications such as bakeries, food processing, mills, foundries or other heavy industries.
Keeping the bearings properly lubricated in high-temperature environments is quite a challenge, where product surface temperatures can reach 900degC. Operating speeds of equipment such as continuous caster foot rolls used in heavy milling industry can be as low as 5rpm. The effects of cooling water, scale, and chemicals all contribute to an extremely tough operating environment. Ultimately, the consequence of bearing failures can be downtime, often damaging both equipment components and the end product.
To deal with high-temperature applications, 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 amounts of lubricant to compensate for heat-induced grease degradation. This can pose significant fire and safety risks, as excess grease can accumulate outside the bearing housings to create dangerous working conditions - such as slippery floors - and a higher risk of fire. Water cooling systems are also sometimes used, adding to installation and operating costs.
Oil-air lubrication is sometimes used as an alternative to grease lubrication, but this is also not ideal due to the difficulty in forming a good lubricating film, especially at low speeds. This technology also requires a significant capital investment and leads to increased costs for both energy and maintenance.
By moving away from grease lubrication, SKF DryLube Bearings can help to avoid the associated operating costs and productivity limitations that can occur when grease-lubricated bearings are exposed to high temperatures. Heat causes grease to deteriorate quickly, leaving bearings without adequate lubrication.
By filling the empty space inside a bearing with an engineered graphite mixture, SKF provides an efficient and cost-effective alternative to the use of grease in hostile environments. Almost any type of SKF rolling element bearing can be supplied as an SKF DryLube Bearing, providing very low and constant friction, and an extremely high temperature limit of 350degC. SKF DryLube Bearings do not require relubrication, which eliminates the cost and environmental consequences of conventional greasing programmes.
Hugo Carlen, SKF Product Manager, states: "The SKF DryLube Bearing solution is already helping manufacturing industries worldwide to become safer and more competitive. In one installation, by switching to SKF DryLube Bearings, bearings that had been failing every month are now lasting more than two years."
SKF DryLube Bearings are having a significant impact on reliability, safety and costs in high-temperature applications. In some cases, it has enabled centralised lubrication systems to be removed, and has even cut insurance costs due to the reduced fire hazard.
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