When the going gets tough, the tough bearings get going

Quarrying and mining environments - a real-life proving ground for innovation in bearing manufacture

There are no tougher environments for bearings to work in than quarrying and mining. Combining enormously heavy loads and shock loads with a dust- and debris-laden atmosphere, this is a real-life proving ground for innovation in bearing manufacture.

Essentially, there are two approaches to overcoming the problems of the environment. Firstly, there is the development of a bearing of the quality and robustness to resist the wear and tear of the operating conditions, and secondly, there is the development of new and ever more effective methods of protecting the bearing from ‘the outside world’.

Timken, for example, offer standard bearings which are durable in a mining environment, but they also continue to develop still more resistant models, with engineered surfaces, heat-treated processes and surface finishes specifically designed to enhance bearing life and minimise raceway and roller damage. Timken spherical roller bearings (SRBs), for example, are made from high quality steel, with a fully-machined brass cage specifically engineered for tough applications such as shaker screens – providing greater durability and cooler operation than alternative materials.

The latest advance from Timken is the single row EMA series of cylindrical roller bearings, which also feature a brass cage (made in one piece) with a fully milled pocket design. The land-riding cage is unique in the industry and minimises drag on the roller elements, helping to reduce heat generation and enhance lubrication flow. High cage rigidity also allows for more rollers than with other configurations – all helping to achieve longer life, improved uptime and reduced maintenance costs, even in the harsh conditions under which these bearings must operate.

Having started with a high quality bearing, the next step is to ensure it is as well-protected as possible against the dust, dirt and debris that are a fact of life in a quarrying or mining environment. Once these aggressive elements get into the bearing and mix with the lubricating grease, they act as a highly effective grinding paste which will sooner or later take its toll on even the best engineered, highest quality bearing.

Keeping the lubricating grease fresh – continually purging contaminated grease – is one way to prolong bearing life. The simalube single point lubricator has been specially designed for use in gravel pits and quarries, to maintain the correct supply of lubricant to bearings. A fit-and-forget solution, the simalube dispenser reliably dispenses lubricant just where it’s needed, and is itself hermetically sealed to prevent any contamination of the lubricant by dust or debris.

Which grease to use in these harsh environments is a crucial decision. OKS produces high performance greases ideal for these conditions, specifically developed to withstand heavy and shock loading, extend lubrication intervals and prevent corrosion and ingress of contaminants. OKS 410 and OKS 4100 are both molybdenum disulfide based greases able to withstand high and extreme pressures respectively.

Another option is the sealed bearing, such as the SKF explorer sealed spherical roller bearing. As SKF puts it, these bearings offer ‘all the benefits of an open bearing – sealed in’ and help to increase bearing service life as well as increasing uptime and reducing grease consumption and maintenance. For applications with a large grease usage consumption can be reduced by 90% or more over the bearing life.

An effective seal – such as the Simrit Simmering – will also help to keep the dust and dirt out of the bearing. The simmering is designed and manufactured to withstand high temperatures and pressure fluctuations, as well as coping with shaft misalignment. Benchmark testing proves the Simmering leads to lower friction and power loss, less shaft and seal wear, lower change in radial load and interference, and a lower sealing edge temperature. The result is longer seal life, better protected bearings and ultimately, more reliable, more productive machinery.

Going further still, with multiple layers of protection, SKF has developed the ‘three-barrier solution’ for harsh operating environments, which is not only effective but also simple. To avoid the need for continual purging of the bearing with fresh grease, the three barrier solution seals in the grease and protects it from contamination. The first level of protection is the SKF l or s housing seal. This is then backed up by packing the housing itself with grease to act as a contaminating barrier. And finally, the third layer of protection is the integral bearing seal, which keeps the bearing lubricant in, and contaminants out of, the bearing cavity.

As you would expect, all these solutions are available from ERIKS, and ERIKS engineers can help you to make the best choice for your particular application. So even if conditions are tough, the decision won’t be.