Page 45 - Hub-4 Magazine Issue 73

Quarrying
Are your bearings tough enough?
By Alan Stewart, Brammer Buck & Hickman Bearing Product Manager – SKF Products
Bearings keep machinery moving. Wherever there is a machine or vehicle that has rotating parts, you will find bearing units. Across all industries, bearings are one of the most often replaced components, but in construction
and aggregates all the more so due to the exceptionally harsh operating conditions. Here, bearings face multiple challenges, from ingress of dirt and dust, through to very heavy loads and frequently working in extreme temperatures.
As with any component, you want your bearings to provide long, trouble free performance. To maximise lifetime expectancy, the bearing must be correctly installed, lubricated and maintained. However, regular lubrication and maintenance is problematic when it comes to construction and aggregates sites as these are often remote, downtime for maintenance is very expensive, and safety is a running concern with such heavy equipment at hand.
Selecting the correct bearing is therefore essential to ensure reliable, long life. Here we look at the top three challenges faced in this sector and suitable bearing options to meet those challenges.
Operating Conditions
Construction and aggregates sites are notoriously wet and dusty and are often impacted by extreme temperatures. Furthermore, the machinery and vehicles in operation are heavy duty, placing substantial loads on to the bearing units.
In this environment, open bearings quickly become damaged from ingress of dirt. Using proper sealing solutions such as sealed bearings and shaft seals is therefore essential. Sealed bearing units are initially lubricated and then sealed, preventing dirt for entering and mixing with the lubricant. Specialist sealing solutions have been developed for this sector, including SKF’s Three-Barrier Solution which consists of a sealed spherical roller bearing, bearing housing with labyrinth S seals and a specially formulated lubricant to act as a contamination barrier.
These three barriers protect the bearing from contaminants, leading to extended bearing service life on average three times longer than standard open bearings. It is particularly well suited to conveyor systems.
To function in applications where heavy loads are the norm, you want a bearing that is both hard and tough. In the past,
hardened steel did not have all of the necessary properties to make it suitable for use, but new heat treatment processes have been developed to remedy this. Also, consider both axial and radial loads when choosing your bearings. Double row tapered roller bearings are a good option they accommodate combined loads and can locate a shaft axially in both directions with a precise axial clearance or preload.
Remote Locations
Remote Locations, especially when it comes to aggregates, are common in this sector, making next day part delivery doubtful.
Businesses therefore need to ensure maximum bearing life to minimise costly downtime. This means using product that is fit for purpose: a bearing that has been designed to cope with the strain of this specific environment and its heavy loads. This applies to the bearing itself, plus sleeves, housings, seals and transmission products. SKF’s Slewing bearings, for example, have been designed with a high carrying capacity and high resistance to overturning moments in excavators, bucket wheel excavators and stocker / reclaimers. There are countless more examples of bearings that have been specifically designed for this demanding sector, but the point here is not to compromise on the choice of bearing based purely on price as this is a false economy, leading to early bearing failure. Of course, the bearings must also be correctly mounted using the right tools and maintained.
When you are miles from anywhere, relubrication can also present a number of challenges. You need to have the appropriate lubrication on site at all times and people who can reapply it
regularly and correctly. Ineffective lubrication represents over half of all bearing failures. That’s why we recommend having a lubrication strategy in place.
As part of that strategy, it may
seem obvious, but check that you have the right
lubrication for each application. One lubricant will not work for all! If in doubt, refer back to the machine manufacturer to identify the correct lubricant. Keep lubricants clearly labelled so mistakes are avoided. Ensure your staff are trained in lubrication application and therefore apply the right amount of lubricant when it is needed. Alternatively, consider the use of single point or multi-point automatic lubrication systems which will safely apply the correct amount of lubricant, regardless of where the site is located.
A further option is to simply avoid relubrication issues altogether by opting for sealed bearing units.
www.hub-4.com March-April 22 - Issue 73
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