Compressed Air Best Practices - February 2008 - (Page 19)

Focus Industry BULK HANDLING | 02/08 | Dilute Phase Systems The chart at left graphically shows the magnitude of opportunity that exists in electrical energy savings with compressed air produced at the appropriate lower operating pressure instead of using high-pressure air volume (scfm) reduced to a significantly lower pressure (psig). The two most distinct categories of pneumatic conveying are low-pressure or high-pressure systems (there are other names “in between” such as medium phase, lean phase, positive pressure, etc.). The first category is lowpressure systems, also referred to as dilute phase pneumatic conveying systems. These systems utilize entry air pressure under 15 psig and use either positive or negative pressure to push or pull materials through the conveying line at relatively high velocities and volume. They are described as low pressure/high velocity systems and have a high air-tomaterial ratio. A typical low-pressure system using a rotary air lock feeder will use a high pick-up velocity of around 2,500 fpm at the beginning of the system, and about 6,000 fpm at the end. The conveying line pressure is under 15 psig at the beginning and near atmospheric pressure at the end. Low-pressure systems should use a lowpressure positive displacement blower as the primary compressed air source. Often, the abrasive nature of product being transported precludes the use of dilute phase and the associated very high velocities, which will create significant system piping and valve erosion. Dense Phase Systems The second category, high pressure systems, are known as dense phase systems. These systems utilize air pressure above 15 psig (up to 50 psig) in the pipe and use positive pressure to push materials through the conveying line at relatively low velocities (from 100 fpm to a maximum of 1000 fpm) much like extruding. They are described as high pressure/low velocity systems and have a low air-to-material ratio. Dense phase conveying uses smaller amounts of air to move large amounts of bulk solid material in slugs through the conveying line. Generally, the product being transported is often abrasive in nature. The Dense Phase system is selected to eliminate or minimize transfer pipe erosion, by maintaining the design’s moderate velocities and still deliver the appropriate pounds per hour of production. Generally, this type of system requires an air compressor of the appropriate size and pressure (35–100 psig). Dense phase conveying systems, if not already utilizing a dedicated lower pressure air supply, may be able to be taken off the high pressure systems and an appropriate singlestage reciprocating rotary screw or centrifugal (single or two-stage) compressor can be dedicated to this scenario. The electrical energy cost per scfm of this air will be much lower than the high pressure and the unit can easily be shut off when not in use. ULTRASOUND ADVICE SaveThousands in Compressed Air Waste. Go Green. Now is the perfect time to protect the environment while saving signiﬁcant production dollars annually. Poorly maintained compressed air systems cost companies thousands annually in energy waste. With Ultrasound Condition Monitoring, learn how you can immediately begin to cut energy waste while gaining buyers respect and support. Join UE Systems at Ultrasound World IV! January 27-30, 2008 Clearwater Beach, Florida Learn how ultrasound condition monitoring can help reduce energy waste. Log onto UESOUNDADVICE.COM for more info and recieve a FREE sample pack of compressed air leak tags! ADVANCED ULTRASONIC TECHNOLOGY ° CERTIFIED TRAINING COURSES ° WORLD-CLASS SERVICE & SUPPORT www.airbestpractices.com 19 http://UESOUNDADVICE.COM http://UESOUNDADVICE.COM http://www.airbestpractices.com

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Compressed Air Best Practices - February 2008 Contents From the Editor Utility-Air News February Audit of the Month: Dense-Phase Transport System Wreaks Havoc on Compressed Air System Real World Best Practices: Material Conveying with Pneumatic and Vacuum Systems Industrial Vacuum Cleaners Use Compressed Air in Portland Cement Manufacturing Processes The Numatics Air Preparation Group The Ins and Outs of Vacuum Generators Dekker Vacuum Technologies Do Your Meetings Sabotage Your Profits? Resources for Energy Engineers Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - February 2008

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