SKF bearings are solid as a rock for Tarmac

SKF has helped the team at Tarmac’s asphalt site in Rochford to increase machine uptime and reliability after specifying more efficient, robust and cost effective bearings for a particularly demanding bucket elevator application.

The latest sealed spherical roller bearings and innovative three-barrier solution from SKF, the world’s leading knowledge engineering company, are being used in extremely demanding bucket elevators at Tarmac’s Rochford plant, the UK’s leading supplier of heavy building materials. The innovative bearings are proving essential to the efficient working of the bucket elevators, eliminating the need for routine maintenance and providing unparalleled service life by exceeding the lifetime of the previous solution two fold.

Perhaps most importantly, the new SKF solution is delivering real cost savings of nearly £2,000 for each bearing system, while allowing Tarmac to realise annual savings of over £1,000 in increased production availability through the prevention of downtime. The new bearings are also over £300 cheaper than the previous bearings and are expected to increase mean time between repairs (MTBR) by 16 months.

Since inventing asphalt, Tarmac is now the UK’s leading supplier of heavy building materials including aggregates and concrete. Indeed, the company maintains most of Britain’s highways. However, the aggressive environment of the Rochford plant, where particularly high levels of heat, dust, debris and other abrasive contaminants are rife, means that all machinery has to be capable of withstanding extremely demanding operating conditions.

Unfortunately, the split bearings previously used in the bucket elevator had an inadequate maximum service life of only eight months, which was proving costly. As a result, the plant fitting team at Tarmac Rochford decided that an alternative solution must be sought to increase Mean Time Between Failures (MTBF). Accordingly, Brammer, an SKF Authorised Distributor, advised that in this specialist type of application it would be particularly helpful for SKF as the leading bearing manufacturer to look at the specific requirements of the plant and specify a suitable solution.

A spokesperson for the team at the Tarmac Rochford asphalt site said: “SKF offered exceptional customer service. It was the only company where someone came to our site to help us solve our problems despite the fact that we weren’t already using SKF bearings. They were working for the industry not just for a sale.”

After identifying the needs for this application, engineers at SKF concluded that sealed spherical roller bearings along with the proven three-barrier solution would meet all of the necessary criteria. For example, they were ready to install units that are lubricated for life, thanks to their efficient contact seals and factory filled high quality grease, while the seals offered excellent protection against solid contaminants and moisture.

Despite the fact that they are meant to be easy to fit, the split bearings that were previously being used required a complex and time consuming installation by comparison with the larger SKF sealed bearings, which are straightforward to install taking only a quarter of the time. The new SKF bearings can be fitted quickly and simply using a unique sleeve and locknut, which eliminates the need for a lock washer; this has a machined side face to keep the bearing straight on the shaft and reduce vibrations. Incremental markings every 15° on the locknut also allow users to measure easily the tightening angle and ensures correct internal bearing clearance during installation.

Furthermore, the previous bearings were hard to access making the job of changing them all the more challenging. When the previous bearings failed, Tarmac suffered a considerable amount of machine downtime, sometimes up to four hours. Add to this a combined eight hours of lost labour from the two operatives, plus up to 250 tonnes in lost asphalt production, and there was a significant amount of wasted resources.

The spokesperson at Tarmac continued, “The SKF solution offered us a cost effective way for us to build additional value into our conveyor without the need to make expensive modifications. Furthermore, we received exceptional technical support from SKF, enabling us to increase efficiencies and productivity, while cutting maintenance requirements and costs still further. As a result, we were confident in SKF’s ability to provide us with high performance, reliable technologies and have also decided to use SKF’s LGHB 2 grease on our vibrating screen for hot materials.”

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