March 22, 2005

New roof support offers boost to mining industry

by K.C. Jaehnig


Caption follows story

(Pronouncer: “Kroeger” is “CRAY-gur”) CARBONDALE, Ill. -- A safe, simple roof support developed at Southern Illinois University Carbondale for the mining industry should be on the market within the next few months.

Excel Mining Systems Inc. will manufacture the K Prop, named for its inventor, Assistant Professor of Mining and Mineral Resources Engineering E. Bane Kroeger. The 14-year-old company, headquartered in Bowerston, Ohio, sells roof systems to coal and hard rock mining companies throughout the country.

“We have a full product line but don’t presently have a roof prop,” said Excel President and CEO Bruce A. Cassidy Sr.

“We liked the design — being able to put some active load on the roof at installation. It’s one of the few props that has that capability.”

The K Prop consists of two steel pipes, each with a flat plate at one end. The pipes telescope together, allowing the prop to adjust to fit roofs of varying heights. There’s also a steel collar, which clamps down at the point where the two pipes join.

It’s that collar and some machine work around the pipes’ connecting edges that account for the prop’s near-instant ability to support a roof as it’s being jacked into place.

“Having the outer pipe clamped in compression makes the prop four to five times stronger

than it would be if it were in tension,” said Kroeger, whose first designs for his roof support relied on tension.

“Steel is very strong in compression but weaker in tension, and the taller the prop, the more susceptible it becomes to buckling.”

The K prop can support loads from 10,000 to 100,000 pounds. A miner working alone can install one in less than two minutes.

“That should reduce the total cost of supplemental support installation by a significant amount because up to 60 percent of the costs in a mine are from labor,” Kroeger said.

Excel’s Cassidy also expects to see savings up front.

“This prop replaces wooden props, and as hardwoods are becoming more scarce, the price is going up,” he said.

In addition, when miners build timber cribbing (heavy wooden support posts stacked to the mine roof like Lincoln Logs) in certain areas of the mine, they can suffer lower back injuries.

“From a safety standpoint, there’s much less chance of injury (with the K prop),” Cassidy said.

Safety is also a concern with other steel props on the market, Kroeger said, because most use bolts that require a specific amount of tightening to support the roof. “If these things aren’t installed to the manufacturers’ specifications, the roof could come down,” he said.

Kroeger said the idea for his K prop came during a class lecture on an existing support system that couldn’t bear the weight of a roof until workers had finished tightening the bolts.

“I was thinking there had to be a better design,” he recalled.

“When you’re installing something against the roof and the floor and applying pressure, you don’t want to be under it because if a layer of that roof is loose, it could fracture and fall on you. It’s a safety issue.”

Working on his own after hours in an SIUC machine shop with scrap pipe that he bought at a junkyard, Kroeger designed, tested and refined scores of roof supports in developing the K prop.

“It’s been fun,” he said. “Of all the things I do at SIU this is what I enjoy most — coming up with new ideas, building them and actually doing the testing.”

Leading in research, scholarly and creative activities is among the goals of Southern at 150: Building Excellence Through Commitment, the blueprint for the development of the University by the time it celebrates its 150th anniversary in 2019.

(Caption: Prop-er respect — Using a hydraulic lift, E. Bane Kroeger tests his mine roof prop at Southern Illinois University Carbondale’s Coal Research Center. Kroeger, an assistant professor of mining and mineral resources engineering, says his invention begins supporting the roof while it’s still being installed.)