Chain wear is a major problem in armoured face conveyors. Uncontrolled wear leads to costly and time-consuming maintenance, and unplanned downtime of the entire longwall in the event of chain failure. Bucyrus says its Power Chain addresses this with an innovative design that drastically reduces chain wear and prolongs service life. With installed drive power doubling over the last 15 years, Bucyrus engineers determined that huge productivity gains would result from increasing the service life of conveyor chains. Despite the use of high-strength steel and hardened chain pockets, when using conventional chains some working panels cannot be completed without replacement of both chain and chain sprocket. In the best case, conventional conveyor chains last for a single working panel and are then routinely replaced, as scheduled replacement is preferable to the risk of chain failure due to excessive wear. Such replacement is both costly and time-consuming.

The Bucyrus Power Chain was specifically designed to extend service life far beyond a single panel – and first field trials indicate that the Power Chain may last three to four times longer than a conventional conveyor chain. The Power Chain is designed to increase surface area at critical wear points, thus reducing friction and wear. In contrast to regular chains, the Power Chain has two types of link. For instance, in a Power Chain 42×140 mm, the vertical link has a 42 mm diameter and is rolled to form a semicircular cross-section, thus offering more link surface area. The horizontal links are forged, with a 42 mm link surface area. The leading edge – normally round in a conventional chain – is flat, offering a larger contact surface area for chain drive. The central area for securing the flight bar has a key that engages a slot on the flight bar.

The design almost halves surface pressure at contact points – and reduced pressure means reduced wear. Counter intuitively, greater contact surface results in less friction and wear. This is the result of reduced contact pressure and “lubrication” by coal dust.

Initial trials with the Power Chain have demonstrated a drastic reduction in wear rates. Two high productivity longwall mines in the US both completed their first panels without a single chain break in the stageloader, where the Power Chain was used. After 3.5 Mt and 5.5 Mt respectively, chain and sprocket wear was found to be minimal. Both mines are now using the same Power Chain and chain sprockets for a second panel – so instead of having to undertake the time-consuming and costly replacement of the conveyor chain, they were able to deploy the equipment immediately.