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.”
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.
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.
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