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Canada's “Rock to Road”
Magazine
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Pavers Combat Material & Thermal Segregation The anti-segregation system employed by Cedarapids Inc. in its 400 and 500 series of Grayhound Remix pavers differs from conventional paver models in that the slat conveyor assembly has been replaced with twin, counter-rotating auger assemblies. This specially designed auger system uniformly pulls material from the varying locations of the paver hopper and continuously reblends the hot mix just before it is transported to the screed. The Remix paver distributes segregated material over an area five times larger that slat conveyor delivery systems. The result is a homogenous mat behind the screed. In addition, the paver has been proven in tests to reblend material with over 90ÁF thermal segregation in the truck to less than 10ÁF difference after existing the paver. The Remix concept was originally developed by John Trygg, president of Konza Construction, a paving contractor located in Kansas. He saw an opportunity to cost-efficiently reduce the amount of segregation in the final mix placed by a conventional asphalt paver. Cedarapids, Konza Construction, the Kansas Asphalt Pavement Association and the Kansas Department of Transportation partnered to further develop his idea. The Grayhound Remix paver is the result of their combined efforts. According to Cedarapids, a number of improvements have been incorporated into the latest generation of Remix pavers to boost machine productivity and reblending capabilities.
Cedarapids CR551RX remix paver with a Cedarapids MS-3 material transfer device. Inset: Schematic shows twin counter-rotating auger system. These improvements include a new control system and newly redesigned feed augers. With the new controls, the operator sets the ratio between feed augers and screed spreading augers, from 0-100 per cent, and the system’s speed sensors automatically control the flow of asphalt to the screed, based on the actual spread auger speed. The speed sensors ensure uniform flow of asphalt to the screed, allowing the paving screw to focus on mat quality rather than the machine. Along with the speed sensors, the system employs new load sensing transducers to constantly monitor the feed augers. As auger load increases, the system automatically proportions material flow to the screed to regulate the load on the engine and the machine components. This in turn, states Cedarapids, optimizes paver productivity and increases the service life of the paver’s components. The redesigned feed augers are now constructed with a chromium carbide overlay to deliver longer service life. A constant 254 mm diameter offers more face surface area along the entire shaft length for increase asphalt throughput. The auger flights feature a variable pitch design (distance between each flight), ranging from full pitch 254 mm towards the rear to half pitch (127 mm) towards the front of the hopper for more efficient mixing. According the manufacturer, this new auger design allows a consistent draw of material from all areas of the hopper and facilitates a thorough reblending of hot mix. A single hydraulic motor with a pant-leg gearbox now drives each set of counter-rotating augers. The hydraulic gearbox eliminates the need for flow dividers and chain drive. The gearboxes ensure that the two augers are working in sync for more uniform material flow to the spread augers. Material rate can be varied between the two sets of augers, allowing the operator to control the feed rate to either side of the screed. Contractors can also use a hopper insert in conjunction with a material transfer unit to channel material directly into the auger blending zones for more efficient material utilization. By Robert L. Consedine, Editor
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