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March 2020 / 33 This clean air condition is normally present when pneumatic conveying systems are starting, stopping, or pausing. The system will idle, and the blower will run at its directed speed with no material feed present. Whenever a process is halted, the decision must be made whether to stop the blower. The blower will be turned off after a period of time if it's determined that there will be an extended amount of downtime. For a rapid-cycling process, the blower will be left on to save the stop-and-start wear on the motor. The amount of time a dilute-phase system spends in idle varies by application, but it should be noted that major power reductions are possible using the dynamically con- trolled system. Savings of 70 to 80 percent are typical for these idling periods, and since no work is actually accomplished, it's really a waste-reduction strategy. The results of these experiments establish that several performance factors related to dilute-phase pneumatic conveying can be directly tied to the sys- tem's effective air velocity. The level of control over the effective air velocity can have a positive or negative impact on abrasion, degradation, buildup, and power consumption. Lastly, static velocity controls are an improvement over standard dilute-phase operation, but dynamic controls have been shown to provide more benefit across a wider range of process variables. PBE Reference 1. Jonathan O. Thorn, et al., "Algorithm to Enhance Perfor- mance of Dilute Phase Pneumatic Conveying Systems," 8th World Congress on Particle Technology, April 2018. For further reading Find more information on this topic in articles listed under "Pneumatic conveying" in Powder and Bulk Engi- neering's article index in the December 2019 issue or the article archive at PBE's website, www.powderbulk.com. Jonathan O. Thorn (j.thorn@schenckprocess.com, 800-821-2476) is the executive director, process technol- ogy at Schenck Process in Kansas City, MO. He earned a master's degree in chemical engineering from Penn- sylvania-based University of Pittsburgh, focusing on pneumatic conveying-related studies. He has more than 20 years of industry experience and works in many fac- ets of application, design, and R&D as it relates to dry materials handling and processing. Schenck Process Kansas City, MO 816-891-9300 www.schenckprocess.com