A leading Midwestern supplier of high-quality limestone to U.S. markets is reducing costs and improving safety by using a series of innovative conveyor belt cleaners to help eliminate carryback and the problems it causes. North American Limestone Corporation (NALC) reports the cleaners from Martin Engineering (Neponset, IL/USA) – engineered specifically for rock/aggregate applications – have been so effective that the facility no longer has service crews spend up to two hours per day shoveling and washing down accumulation from beneath the conveyors. By minimizing the need for staff to work in close proximity to fast-moving belts, the cleaners help diminish any chance of accidents or injury. Instead, by returning fines to the material flow, the company is able to reduce risk and improve overall process efficiency, saving the complex thousands of dollars in lost material and unproductive maintenance time.
NALC supplies a range of limestone products from its 243 Complex in Cloverdale, IN to a number of industries in the Midwest, including fine-grind materials and high-calcium crushed limestone. The company serves customers in such diverse applications as cement production, electric power generation, coal mining, industrial manufacturing and various construction segments. In order to efficiently produce a consistent volume and quality level, the facility employs an expansive series of crushers, mills, screens and other equipment, with material transported primarily by conveyor.
Over time, material handling system operators began noticing that a growing amount of material was being carried back from the unloading points, which would accumulate and eventually create mounds of spillage that piled up beneath the structure. In keeping with its long-range plans to employ industry best practices for bulk handling and fugitive material control in its operations, company officials conducted an assessment and contacted Martin Engineering for advice.
According to NALC Vice President of Operations Dana Boyd, “Carryback is a common problem within our industry. 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.”
To rectify the issue, Martin Engineering recommended the PV Primary Cleaner with Twist™ Tensioner for key locations along the conveyor network throughout the facility. The Martin® PV Cleaner is a durable, one-piece blade that contains approximately 20 % more urethane than comparable primary cleaners, yielding a longer life in challenging service conditions. The aggressive blade angle is able to remove even wet, sticky sand from belts 18-72 inches (450-1800 mm) wide.
The PV Cleaner blades feature Martin Engineering’s patented Constant Angle Radial Pressure (CARP) design for consistent cleaning throughout all stages of blade life. The specially-engineered curved blade maintains the same contact angle, even as the belt wears, helping to retain cleaning efficiency and allow for residual material fines on the belt to be deposited back into the material flow and not underneath the conveyor.
The belt cleaner and tensioner combination also helped eliminate material buildup on the return side of the belt, which could cause additional problems with the belt or return rollers. When foreign material is trapped between the belt and the pulley, it can allow the belt to 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/or the conveyor structure.
Belts at NALC include 2-, 3- and 4-ply construction, according to the load each one is designed to carry, and they run at 100-400 feet per minute (30.48-121.92 meters per minute). Mechanical splices are used on all of them, which can be a concern with some belt cleaner designs. But the unique Twist Tensioner on the Martin design allows the spliced sections to pass smoothly, without damage to the belt or blade.
Initially installed in March of 2012, NALC has found that the PV cleaner has all but eliminated the carryback and spillage. The tensioner supplies consistent pressure to keep the blade against the belt for effective cleaning, regardless of the state of blade wear, with minimal re-tensioning required.
Engineered to simplify maintenance and reduce costs, the mounting system delivers “no-tool” replacement, as it’s simply dropped into place and secured with a wire lock pin. Thus, one never has to deal with corroded bolts or other fasteners during blade changes.