R-PRO Conveying System
Variable-Speed Capability gives Users New Options
The patent-pending R-PRO dense-phase vacuum-conveying system developed by Conair to minimize pellet fracturing, "angel hair" and equipment wear caused by conventional dilute-phase conveying, made its first European appearance at this year's K trade fair in Düsseldorf, Germany.
When the Conair R-PRO [Resin-PROtection] conveying system was first introduced a year ago, the focus was on slow-speed dense-phase conveying, which eliminates pellet fracturing, dust, "angel hair," equipment wear and other problems caused by conventional high-speed vacuum conveying. However, Doug Brewster, Conveying Product Manager, and the inventor of the system, says R-PRO is not only capable of running at low speeds. It can also operate in the more conventional dilute phase, with individual pellets fully suspended in the high-speed air… or at any speed in between. He reports that, as material speed increases, there is a gradual transition from dense phase to dilute phase, and “we have found we can control that transition very effectively and run right on the edge in a sort of mixed pulse phase. We think we can use this for higher-volume unloading where more airflow may be desirable but truly high-speed operation is not necessary or desirable.”
In slow-speed, dense-phase conveying, pellets move in compact slugs of material at speeds between 300 ft/min (91.5 m/min) up to 1200 ft/min (366 m/min). In conventional high-speed conveying, 4500 ft/min (1372 m/min) is a typical low speed and air speeds up to 6000 ft/minute (829 m/min) are not uncommon. Response to this innovation has been very positive, especially since conveying throughput and distances are comparable to high-speed systems. In addition, since R-PRO uses standard deep-vacuum pumps, conveying tubes and material receivers, the system costs only a little more than conventional systems and can be easily retrofitted to existing systems.
The variable-speed capabilities of R-PRO now give processors the flexibility to tune the system to their exact needs. For highly abrasive glass- and mineral-filled materials, Brewster says, the slowest material speeds are “absolutely the best.” However, he continues, “we are finding that we can run at higher speeds with some materials and still avoid a lot of the usual problems. This can be a big advantage for unloading bulk trucks and railcars where more airflow is helpful.” He suggests this mid-range speed would be good with materials like PET and acrylic, which are only mildly abrasive, or with light-bulk-density materials (e.g.: 15 lb/cu ft), like PE sheet flake. “It’s really easy to raise or lower material speed and airflow,” Brewster says, “and we can do it with great precision and control. The great news is the flexibility that the R-Pro system provides. The customer can set up and store programs (up to ten per receiver station) and convey different materials at different speeds.”
Conair Corporate Office
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