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pensates, pushing the belt in the opposite direction where it often over-travels and the process repeats itself. The result is a belt that continually walks from side to side." Addressing the Problem CEMA (specifically, the 7 th edition) has outlined several conditions that need to be met for belts to remain in-path; these include a conveyor structure frame that is aligned and leveled; conveyor tail and head pulleys that are square and aligned on the conveyor frame; straight belt with s q u a r e s p l i c e s ; b e l t i n g t h a t i s i n g o o d contact with troughing rolls; troughing and return idlers that are square with the conveyor frame; properly tensioned belt- ing; and centrally loaded material on the belt itself. There are times, Maloy said, when all requirements can be checked off from that list, and even be realistically accom- plished, but still the operator is left with an issue. It is that time that thinking outside the box may become the next step. Richwood has had great success doing just that, as it outlines in two field case studies. Their solution: the ON-Track Tracking Idler. Case Study No. 1: 60-in. belt width, ROM coal, 2,800 tons per hour (tph), 770 feet per minute (fpm), 16ยบ incline, 475-ft centers head to tail One of the largest coal preparation plants in northern West Virginia was fac- ing constant problems with belt tracking and misalignment. Side travel of the return belt was extreme. System inspec- tion confirmed that the belt tracked as far as 12 in. off-center in either direction entering the mid-positioned conveyor drive. Even though the conveyor was being correctly loaded in the center, belt track- ing varied depending on percentage of load on the conveyor. Approximately 75 ft ahead of the drive area, there was evidence that the belt had been rubbing the struc- ture on both sides of the conveyor (see adjacent photo). Costly belt edge damage was a major concern due to the frequent contact with the vertical I-beam structure supporting the drive. "This was not only a threat to the con- veyor belt, but also created safety hazards to personnel due to damage to conveyor structure and the need for constant atten- tion, with maintenance crew members routinely trying to train the belt by adjust- ing return idlers on the running convey- or," Maloy said. "This conventional method to attempt to train belting to cen- ter of structure was not providing a work- able solution on this system." As a result, multiple conventional training idlers were replaced with a single ON-Track unit entering the conveyor drive, eliminating belt misalignment and the consistent problems on this conveyor. Case Study No. 2: 72-in. belt width, coal, 4,600 tph, 800 fpm, 2,506-ft centers head to tail In consideration of this new method of controlling belt tracking, a large coal pro- ducer in southwestern Pennsylvania elected to install the ON-Track Tracking Idler on a large overland conveyor system where they were experiencing persistent problems. The unit was installed about 30 ft prior to the conveyor's mid-drive. Once in place, the belt immediately centered itself in the track- ing unit, reducing side travel from 10 in. to no more than 2 in., even with a misaligned vulcanized splice in the system. Under vari- able loading conditions, testing confirmed the path of the return belt was positively controlled at all times. There have been no c o n v e y o r e q u i p m e n t c o n t i n u e d 30 www.coalage.com November 2015 There are no edge guides required for Richwood's ON-Track system. Richwood's design is proactive, avoiding scenarios such as this one, where the structure was damaged by a walking belt.