Plastics Technology

NOV 2018

Plastics Technology - Dedicated to improving Plastics Processing.

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the bend and remain in suspension, the airflow through shal- lower upward slopes tends to push material to the bottom of the conveying pipe. This forces the system to drag it uphill against not only gravity and but also friction. The relative amount of friction is lower with harder materials (like HDPE or acrylic) that may slide more easily; but friction increases with more rubbery materials, such as TPEs and flexible vinyl. If sloping conveyor pipe runs are sufficiently long—10 ft or more—they can really stress vacuum-pump performance, reducing throughput by up to half, depending on the length and type of material involved. System design flaws like this can have a significant impact on equipment performance. IF ALL ELSE FAILS, UPGRADE If, after a thorough check, you determine that the existing piping and elements are leak-free and functioning properly, but your existing pump and controls are inadequate for the material volume or lengths required, you can substantially "tune up" the power of your existing conveying system quite easily by replacing and upgrading your pump. If your first thought is to rebuild an aging pump, or to replace it with a larger model of the same type, consider the merits of upgrading to a long-distance positive-displacement vacuum pump (LDP) of equal or greater horsepower. Typically, these pumps deliver a significant bump in conveying performance with little or no major changes required to existing conveying hardware. Compared with traditional lobe-style positive-displacement vacuum pumps of the same horsepower, new long-distance pumps can provide up to twice the throughput or twice the conveying distance. How do they do it? More powerful LDP pumps enable processors to increase the level of vacuum within their conveying systems. A higher level of vacuum means that the airstream in the system can suspend and carry more material through the line. Many typical existing conveyor systems run at vacuum levels of 10-11 in. Hg (absolute). However, with an LDP pump of comparable horsepower, it is possible to run at 12-15 in. Hg or perhaps a bit higher. This difference—a greater level of vacuum—enables the same conveying-system plumbing to carry far more material over the same distance or to pull mate- rials over much longer distances. To manage this additional pump capacity within your existing conveying system, it is a good idea to equip your new vacuum pump with a variable-frequency drive (VFD). Using either the VFD or a conveyor control, you can "tune" the performance of the pump to match system require- ments. For example, you can tune the pump speed (rpm) and air volume (cfm) to exactly match the line size and conveying speeds required, while maintaining the operating pressure to match conveying distance and material throughput needs. For even more precise control and system flexibility, you might also consider upgrading to a conveying control that The effective distance involved in moving material across a facility can add up to a lot more than the distance between point A and point B. Regular filter cleaning, followed by careful reconnection and leak-free sealing, is essential to maintaining proper vacuum levels and airflow in all conveying system components, from vacuum pumps to receivers, and more. Upgrading to a long-distance, positive-displacement vacuum pump increases the level of vacuum in a conveying system, enabling its airstream to suspend and carry more material over longer distances. 42 NOVEMBER 2018 Plastics Technology T ips & Technique s

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