| Cable carriers used in Akron's composting facility operate in a harsh environment along the mixing reactors. |
One is the sheer size of the operation: it handles 70 million gallons of raw material every year. Another is a hot and humid working environment where dust and dirt are the norm.
Composting machinery must traverse four mixing reactors that run the length of one building, and power and control lines must be routed to variable-speed drives, motors, switches, and switch-gearing components. Previous designs let cables drag across the floor behind machinery, which posed a safety hazard for workers and raised reliability concerns as well.
The motion-system designer, Jim Steiner, vice president of Allied Power Transmission, Solon, Ohio, says Akron's facility required a cable-carrier system constructed of reinforced plastic to resist ammonia, moisture, and other contaminants and reliably operate over long travel lengths.
The company turned to a customized version of the VariTrak nylon carrier from KabelSchlepp, Milwaukee. The application required four made-to-order systems that travel nearly 800 ft, making them some of the longest carrier systems in the world.
The VariTrak is constructed of standard reinforced-nylon side bands with locking-bolt link connectors. Bolted aluminum frame stays with ultrahigh molecular weight (UHMW) plastic inserts provide a smooth, low-wear surface. The frame stays were customized for maximum internal cavity area and minimum external volume.
The resulting system rides on itself to provide long travel length. Replaceable glide shoes molded from a proprietary self-lubricating polymer minimize friction and wear at the carrier contact points. Finally, standard guide channels were modified to allow for expansion and contraction without warping and to compensate for an uneven travel path.
According to Steiner, modification of standard parts avoided long lead times and high costs usually associated with purely custom designs.