After almost 30 years of utilization, a North-American Silver- and Gold-Mine took action together with specialists of Martin Engineering to update its conveyor system with improvements regarding safety, spillage reduction, endurance and efficiency.
Robert Stepper, Richard Shields
(ed. wgeisler - 27/2/2017)
“There’s a long fall going to the secondary crusher, and that creates a huge disturbance in the material flow,” explained crusher Operations / fixed plant maintenance superintendent Wayne Maita. “We were seeing a lot of dust and spillage in that area. It not only affected the air quality and presented a potential safety risk from accumulated material on floors and structures, but it also meant putting operational personnel in close proximity to the moving conveyor for cleanup.” (see opener image)
Maita estimated that dealing with the spillage required 5-10 man-hours per day, seven days a week. So in addition to the safety aspect of the fugitive material, there was a significant cost in wasted labor.
Coeur also noticed belt damage occurring as a result of fugitive material. “As material escapes, it accumulates on idlers and other components, often creating friction points that contribute to excessive wear and premature failure,” commented Martin Engineering Product Engineer Daniel Marshall. “That can have immediate costs such as belt replacement and seized bearings. And once an idler freezes, the constant belt movement can wear through the shell with surprising speed.”
The proposal for Conveyor B included a number of upgrades to eliminate belt sag, provide effective edge sealing and remove dust from the material stream, while withstanding the heavy loads and near-constant usage. Specific components were recommended for durability under the heavy load and impact at the transfer point.
A team of eight technicians from Hardrok and two Martin supervisors began work during a scheduled outage, starting by leveling out the conveyor structure and adding 4x4” (10.2 x 10.2 cm) angle iron reinforcement as needed to straighten out the belt path. They removed existing clamps, skirt seal, skirt boards, belt support components and belt cleaner assemblies, and modified the inlet chute to accommodate a new containment system and provide a clean, flat surface at a CEMA standard width.
Five Martin EVO combination cradles were then installed to absorb the impact of the falling load, while minimizing friction and belt wear. The design features steel-reinforced impact bars and adjustable wing supports to match standard trough angles of 20º, 35º or 45º. Instead of the full layer of support bars that appear on a true impact cradle, the combination cradle replaces the center bars with an impact idler roll, a design that delivers a flat surface for an effective edge seal, but minimizes the friction of having sliding bars all the way across. Eccentrics built into the supports also deliver five degrees of wear adjustment, so the alignment between wings and idlers can be optimized for effective transfer point sealing.
The cradles employ Martin Engineering’s Trac-Mount technology, allowing the units to slide in and out easily for maintenance or replacement. The modular components are light enough to be removed by one person, without using heavy lifting equipment. “Conveyor downtime is extremely expensive, especially for high-speed operations,” Marshall added. “The longer components last and the easier they are to replace, the lower the cost of ownership.”
Impact cradles absorb the force of the falling load, yet slide in and out for easy service.
Technicians also installed five EVO slider cradles with low-friction bars to support the belt edges and stabilize the belt line, eliminating belt sag and bounce. The slider cradles are also track mounted for ease of installation and maintenance. Located in the chute box after the impact cradles, the units feature “double-life” slider bars, which offer a superior seal with low friction. The proprietary box design allows each bar to be flipped over at the end of its useful life to provide a second wear surface. The result is a flat and stable belt surface throughout the settling zone, reducing fugitive material and extending belt health.
Tackling the Spillage
Forty feet (12.2 m) of modular chute wall was used to replace the old structure, with a tail box and integrated dust curtains. A chromium carbide overlay on the inside protects the new containment system from intermittent high-burden depths on the conveyor.
The modular chute wall allows easy installation of skirt boards and stilling zone components to manage dust.