Double the Life, Half the Trouble - SKF Bearings

There are 250km of conveyors on the site, operating, much like the mine, round the clock – 365 days a year.

The longest section is 5.6km, with each section incorporating around 40 bearings, in the heads and tails of the pulleys, as well as the bend rolls.

The conveyors transfer approximately 240,000m³ per day of mined coal, and move approximately 500 million tonnes each year of other material that’s been extracted and in turn used to rebuild the mine.

Grease was the word       

By nature, the coal mine was highly contaminated by dirt, grit and other foreign bodies, all of which frequently found their way into the bearings. Spherical roller bearings were in operation, and thanks to the aggressive environment of the site, they were continually failing, causing repeated and costly downtime, which in any process has a negative effect on productivity.

In a non-stop operation, down time is catastrophic, so as a stop-gap measure, the maintenance engineers frequently applied large amounts of grease to the bearings. However, this not only created additional problems and expense in terms of disposal, but also raised concerns relating to Germany’ strict environmental regulations.

Doubling the Duty

One significant aspect of conveyor maintenance is lagging rework on the pulleys, and with the aim of minimising downtime – to achieve a benchmark reduction of 3% in operating costs – the coal mine operator called in SKF.

SKF application specialists suggested a test of sealed spherical roller bearings on the bend rolls, replacing the existing open versions. In addition to installing the SKF 23228-2CS5/VT143 sealed spherical rolling bearings, the housings were filled with grease (for life) and a labyrinth seal was added at the end of the roller.

This longer life cycle enabled the coal mine to achieve its goals of performing bearing maintenance at the same time as lagging rework.

This provided a reduction in downtime, enabling maintenance engineers to spend time across other critical plant tasks, as well as seeing considerable cost savings on used grease disposal and a reduction from four hours to two in bearing mounting time.

The previous open bearings typically lasted an average of 730 days (2 years), but the SKF solution lasted more than four full years – an impressive 100% increase in service life.