Extended service life in harsh conditions

Downtime is the enemy of quarry/mine operators and construction project managers. Critical plant and equipment must offer reliable performance to meet demanding output targets, project deadlines and budgets. Whether extraction, transportation, preparation, separation or enrichment, these processes are subject to contamination and debris, not to mention heavy loads, shock loads and vibration. Bearing selection is vital to ensure long service life. Getting it right means that mining and construction sites can maximise their uptime and productivity while simultaneously reducing maintenance costs.

Leveraging state-of-the-art design, material, lubricant and seals, NSK Self-Lube^® bearings exceed the life of conventional bearings. Furthermore, by selecting Self-Lube^® bearings with triple lip seal and shaft end protectors, it is possible to reduce the costs associated with downtime and repairs. NSK recommends its specially developed triple-lip seal for applications with a high degree of contamination. Bonded to a protective outer steel pressing (secured in the outer ring), this one-piece moulded nitrile seal with three lips makes for a highly efficient sealing design that protects the bearing in severe operating environments.

NSK Self-Lube^® bearing units comprise a broad portfolio of reliable inserts and housings. Notably, these cost-effective solutions provide a fast and straightforward solution for mounting bearings without the need for complex housings or special shaft arrangements. Standard Self-Lube^® bearing inserts also have a locating groove to allow the easy fitting of an optional end cap protector. The cap helps to protect personnel from rotating components and the bearing from external contamination.

The combination of easy use, self-lubrication and long service life mean that increasing numbers of companies in the quarrying, mining and construction sectors are now reducing their costs for replacement bearings, maintenance and downtime. A case in point involves a company that was experiencing frequent reliability problems with the bearing units assembled in a vibrating drum. These bearings work in severe environments, where they suffer exposure to sand that often wholly covers the units. In addition, due to the nature of the application and its difficult access, the regularity and increasing cost of maintenance was proving an issue.

Following a comprehensive failed bearing analysis as part of its AIP Added Value Programme, NSK proposed Self-Lube^® bearing units with triple lip seals, which increased the operating life by a factor of 10 against the previous solution. In addition, the three high-integrity nitrile seal lips with lubrication traps have provided an effective way of stopping the ingress of contaminants.

In another customer success story, a company supplying ready-mixed concrete and other construction materials invited NSK to perform an application review of its augur screw pump bearings. The augur pumps transfer ash (an abrasive mixture of ash, sand, glass, fibres and metal grit) into waiting containers. Here, the screws lift the ash at an angle of approximately 40 °, where the lower bearing units frequently fail. Upon examination of the failed bearings, NSK was able to identify several issues. For instance, after removing the flinger seal, it was evident that no contact seal was running against the inner ring of the bearing. It had likely worn away, and there was now a direct contamination path into the bearing. Further problems included heavy cage corrosion and the absence of lubrication. The ingress of fine dust and particulates had probably soaked up any grease and created a grinding paste, eroding the rubber seal.

To rectify the situation, NSK again recommended its Self-Lube^® bearing units. In this case, NSK also suggested the inclusion of a small disc plate with an additional seal. This minor redesign would help stop most of the contamination and significantly reduce pressure on the bearing seal as it features a path for the debris to escape. By further improving the sealing, using the triple lip sealing solution on the Self-Lube^® insert bearing, it is likely that reliability will significantly improve. In addition, the use of an end cap protector for the bottom bearing could also benefit the company as it will help reduce any dust ingress.