Generally sitting between a belt and a drive system, most typical conveyor pullies, two open spherical roller bearings support the pulley system using their radial and axial load carrying attributes. These open bearings and the sealing systems they contain should be robust as well as able to fortify the system against operational and environmental challenges common to mines.
Down with downtime!
Not only should bearings be protected against debris, dust, and other unwanted abrasive contaminants (water, grime etc.), they must contend with heavy loads and wide variances of speed, too. The bearing also needs to remain adequately aligned for long periods, as unplanned maintenance stoppages are a mine operator’s biggest foe. Loss of production and the procurement of spare parts for mining equipment can amount up to 10,000 and 14,000 USD.
Insufficient lubrication caused by high-pressure washdowns at the end of a busy day is another cause of premature bearing failure in the mining industry. One way of keeping on top of this is to relubricate more often. But, again, this is a time-consuming process that also limits machine availability. Our research has shown that in 8 of out 10 mining plants, availability is less than 87 percent. This is a number which SKF looks to improve with innovative bearing and sealing solutions for the critical mining industry.
Three is the magic number
Good news for mine operators: SKF’s dedicated R&D experts are heavily invested in improving the understanding of all the potential failure modes of conveyor pulleys. This is to ensure an ever-more valuable and industry-specific product portfolio.
One upgraded bearing solution is able to ensure 92 percent availability of conveyors and has a service life which can be up to four times longer than traditional open bearings.
The SKF solution (as shown in the image below) comprises a cutting-edge, mining-specific housing with a strong flexible SKF Taconite seal①. But this is just “barrier one” of three different barriers for defense that the solution comprises. The bearing-sealing arrangement is fortified even further with a housing cavity where a specially formulated grease② (SKF recommends the biodegradable, low-toxicity ester oil-based LGGB 2) is stored – and withheld for much longer than standard conveyor roller bearings are able to.
The upgraded SKF bearing solutions with three barriers of defense mean re-greasing twice a year instead of once a week, saving up to 90 percent of the time and cost of greasing (up to 99.9 percent if not purged) and increasing safety for maintenance workers.
These two defensive characteristics protect the sealed spherical roller bearing③ which sits at the heart of the arrangement. High load-bearing capabilities of the bearing itself, as well as the contact seals’ ability to prevent contamination ingress support mine operators by extending bearing service life and mean time between failures.
A contact shaft sealing for heavy-duty machinery
The solution pictured below is an improved alternative for larger, heavy-duty machinery. Given the increased likelihood of radial misalignment, a SKF Taconite (labyrinth) would not provide a solution here. As you see from the left-hand side of the diagram below, this solution (lip seals) has a single radial shaft seal with a cover plate①. Specially formulated grease② and the integrated bearing seal③ complete the three-barrier solution to protect the spherical roller bearing. If we take into account the optional axial shaft seal (or V-ring) as shown by the red arrows, it could even be considered a four-barrier solution to provide maximum bearing protection.
For more on the basics of contact seals, watch this short video.
Reduced maintenance
Improved safety
Indonesian mine strikes gold
And the SKF solution is already at work improving productivity, safety, and reliability of conveyor pullies in many mines – all over the world. One gold mine in Indonesia was recently boosted with the unique SKF bearing-sealing component.
Its pulley system was suffering frequent breakdowns and unplanned production losses. The culprits were substandard bearings which would only last for about eight months on average. Given that the bearings would take around four hours to replace, the company was unnecessarily leaking money. The gold mine owners found their solution in the contamination-resistant solution from SKF with its three barriers of defense.
You can read more about this particular success story – and many more regarding the upgraded solution – right here. The product guide is also available. But as always, feel free to contact your local SKF representative for more information or specifications of this unique solution.
For more on the basics of contact seals, watch this short video.