Deep Impact

Therese Dunphy

December 1, 2009

Using the right impact bed helped Hilltop Stone keep its conveyor belts running smoothly.

by Chip Winiarski

On most days, Hilltop Stone, located about 20 miles south of Cincinnati in Butler, Ky., produces 14,000 tons of crushed limestone in a 16-hour period. At this rate, Hilltop Stone easily generates nearly $100,000 in daily revenue when production is at full operating capacity.

Hilltop Stone realizes the value of equipment it uses to move limestone and the role it plays in keeping production running at full speed, so when its conveyor system continued to interrupt production by breaking down due to the harsh working environment, it turned to Flexco DRX impact beds for more reliable service and improved efficiency.

Founded in 1941, Hilltop Basic Resources, Inc. produces a variety of aggregates for commercial, industrial, and government projects from its seven plants in Ohio, Kentucky, and Indiana.

Identifying problems

Producing aggregates is a demanding job and can take a toll on equipment. This was the problem with Hilltop Stone’s previous conveyor system — it was simply unable to withstand rigorous quarry conditions. Depending on discharge point, limestone rocks as large as 18-inches in diameter fall onto the impact beds from a height of between 7 and 10 feet.

“The issue we were dealing with is that the impact beds would break right down the middle and, in some cases, the conveyor would break with them,” says Terry Figgins, quarry manager of Hilltop Stone’s Butler facility. “When they would break, we would have to fishplate the sides of the conveyor to keep them going. It was a very time-consuming repair.”

An average of five times a year, Figgins says the conveyor system could be down for maintenance for time periods ranging from just a few hours to an entire day or more. “When we’re producing 14,000 tons a day and the system is down completely, you can do the math on how much that’s costing us,” he adds.

Company officials ran the math and determined it was time to make a change, replacing its previous impact beds with three Flexco DRX3000 impact beds. Designed to meet the needs of impact areas requiring extreme energy absorption from large-size material or severe height, the impact beds can handle up to 3,000 pound-foot applications of impact energy.

The first unit was installed at Hilltop Stone in 2006. The belt it is installed on measures about 580 feet in length, with a width of 42 inches. A second impact bed, with a 300-foot-long by 48-inch-wide belt, was put into service nearly two years ago. Both impact beds are moving rock up to 18-inches in diameter on three-ply, 800 PIW-rated belts.    

Figgins says his crew installed both impact beds in about 6 hours. “The installation was pretty simple,” he notes. “We just slid them in and put on the two side pieces and that was it — a very painless process.”

The new impact beds are engineered not only to be strong, but also to deaden impact energy, reduce vibration, and extend belt life. To further protect the belt, impact energy absorbers along the base of the impact bed can compress up to 3 inches to minimize impact and vibrations on the bed and belt.  

“With our old impact beds, there wasn’t any give or release to them, which often damaged the belt,” Figgins says, adding that belts on his previous conveyor system generally lasted less than a year. “But these new impact beds do have give to them — and it saves the belts.”

Avoiding downtime

The material transfer system defines the process wherein material flows down through a chute onto a waiting conveyor, while the transfer point is the area of the conveyor where material impacts the belt. Since this part of the belt is taking the brute force of falling material, the transfer point is probably the biggest ongoing source of problems in a conveyor system.

Three common types of conveyor belt problems at the transfer point include top cover damage, tensile failure, and crushing of the belt carcass. Top cover damage is caused by the sharp, jagged edges of aggregate and the manner in which they land on the belt. Tensile failure of the carcass is usually indicated by a tear or hole in the belt which cuts the belt’s cord fibers and weakens the belt as a whole. Finally, crushing of the belt carcass can cause tracking problems, delamination of the top cover, or premature comb through — a condition where the mechanical fasteners spread apart due to added stress on the belt.

A slide-out feature allows the impact bed to separate in the middle and slide out for direct access to the bars. Figgins says he is able to quickly and easily inspect the beds, adding that he hasn’t had to perform any major service on the two impact beds. “The only thing we do is make sure they’re clean so they move up and down,” he says. 

Expanding solutions

Based on the performance of the first two impact beds, Hilltop Stone has added a third unit at its Butler, Ky., quarry. The new impact bed has been installed on a belt that stretches 260 feet in length and 42 inches in width. Much like the first two impact beds, Figgins says it only took 4 to 8 hours to install. It began moving rock up to 18-inches in diameter when the line became operational this past March.

“It’s the only type of impact bed that truly is an impact bed,” Figgins explains. “An impact bed to me is something that has some give to it. All the other ones are just flat beds, and the rock comes down and pierces the belt.”

In evaluating their overall effectiveness, Figgins says the company is pleased with the impact beds’ performance and return on investment. “They don’t break down and the belts last longer,” he adds. “We don’t have any more worries. It’s just a win-win situation for us.”

Chip Winiarski is Flexco’s market manager for heavy-duty applications. He serves customers, distributors, OEMs, design firms, and belting companies engaged in surface mining, quarry, aggregates, cement, and related industries.

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