Spill no more

Limestone producer reduces costs, improves safety with innovative belt cleaner design.

A Midwestern limestone supplier is reducing costs and improving safety by using a series of conveyor belt cleaners to help eliminate carryback and the problems it causes.

North American Limestone Corp. (NALC) reports that its cleaners – designed by Martin Engineering specifically for aggregate applications – are effective to the point that the facility no longer has service crews spend up to two hours per day shoveling and washing down accumulation from beneath the conveyors.

According to NALC, the cleaners also help diminish any chance of accidents or injury by minimizing the need for staff to work in close proximity to fast-moving belts. Instead, by returning fines to the material flow, the company is able to reduce risk and improve overall process efficiency, saving the operation thousands of dollars in lost material and unproductive maintenance time.

Problem solving

NALC supplies a range of limestone products from its 243 Complex in Cloverdale, Ind., including fine-grind materials and high-calcium crushed limestone, to a number of industries in the Midwest. The company serves customers in diverse applications such as animal feed production, electric power generation, coal mining, industrial manufacturing and construction.

In order to efficiently produce and maintain a consistent volume and quality level, the facility employs a series of crushers, mills, screens and other equipment, with material transported primarily by conveyor.

Over time, material-handling system operators began to notice that a growing amount of material was being carried back from unloading points, which would accumulate and eventually create mounds of spillage that piled up beneath the structure. Company officials conducted an assessment and reached out for advice on potential solutions.

“Carryback is a common problem within our industry,” says Dana Boyd, NALC vice president of operations. “If not addressed, not only does spillage create safety hazards, but it also adds unnecessary work for the maintenance team when they could be focusing on other priorities.”

NALC worked to solve the issue with Martin Engineering, which recommended its PV primary cleaner with a Twist tensioner for key locations along the conveyor network. The PV cleaner is a one-piece blade that contains about 20 percent more urethane than comparable primary cleaners, Martin Engineering says, yielding a longer life in challenging service conditions. The blade angle is capable of even removing wet, sticky sand from belts 18 in. to 72 in. wide.

The belt cleaner and tensioner combination also helped to eliminate material buildup on the return side of the belt, as well. The buildup could cause additional problems with the belt or return rollers. For example, when foreign material is trapped between the belt and the pulley, it can make the belt slip, causing the non-carrying underside of the belt to wear prematurely.

Even small particles and fines can grind away on the less durable, more easily damaged inside surface of the belt. Further, material that builds up on tail pulleys often causes the belt to wander, which, in turn, can damage the belt edge and the conveyor structure.

The results

Belts at NALC include two-, three- and four-ply construction and are based on the load each one is designed to carry. They run at 100 to 400 ft. per minute. Mechanical splices are used on all of them, and that can be a concern with some belt cleaner designs. But the Twist tensioner’s design allows spliced sections to pass smoothly without damage to the belt or blade.

NALC’s PV cleaner was installed in March 2012. Now, the operation says the cleaner has eliminated carryback and spillage. The tensioner, meanwhile, supplies consistent pressure to keep the blade against the belt for effective cleaning, regardless of the state of blade wear and with minimal re-tensioning required.

The mounting system is engineered to simplify maintenance and reduce costs, as it’s simply dropped into place and secured with a wire lock pin.
“This cleaner uses an aggressive angle of attack to the belt for improved cleaning efficiency,” says Dave Mueller, Martin Engineering senior product specialist. “And the quick-replacement feature means never having to deal with corroded bolts or other fasteners during blade changes.”

According to NALC’s belt maintenance crews, the time and cost savings experienced were felt immediately. And now that the maintenance crew spends less time cleaning up, it’s spending more time on core business tasks.

“Our maintenance crews have crucial functions they need to address to keep the plant running,” Boyd says. “Not having to worry about carryback and spillage during these times is important.”

Take note

North American Limestone Corp.’s PV cleaner was installed at its Cloverdale, Ind., operation in March 2012. The operation says the cleaner has since helped it eliminate carryback and spillage.