Compressed Air Best Practices - April 2008 - (Page 35)

Focus Industry PLASTICS BLOW-MOLDING | 04/08 | to operate at 15" HgV to overcome the pressure differential. Therefore, this system needs a vacuum pump that is 20% larger than would be necessary if the pressure differential were not present. The 20" HgV system will require the supply vacuum pump to operate at 23" HgV and this vacuum pump has to be 43% larger than necessary. The 24" HgV system requires the vacuum pump to operate at 27" HgV, which means that it must be over 100% larger than necessary. These additional flow requirements translate directly into additional energy requirements making this an easy target for kilowatt reduction programs. It is also important to note that even if the existing vacuum pump is kept in place after distribution system modifications are made there will be an increase in vacuum force at the point-of-use. In many cases this translates into an increase in production machine speed or a pick-up in product quality. There are a tremendous number of production vacuum systems that have this level of opportunity and are experiencing issues related to energy waste or are having vacuum supply issues at production machinery. There are many reasons for the present condition of production vacuum distribution systems. One issue is that many vacuum systems were designed with compressed air principles in mind. In comparison to compressed air piping, vacuum pipe diameters need to be very large. A typical 100 horsepower compressed air system with 300 feet of pipe would require a distribution pipe diameter of about 3". On the other hand, a typical 100 horsepower vacuum pump would require pipe diameters of at least 6" but more likely 8" to keep pressure differentials within a reasonable range. It is not uncommon to see properly sized production vacuum headers in average size facilities that are 12" in diameter and greater, especially in the process industries. There are a number of design principles that can assist in keeping vacuum differential as low as possible. Using smooth walled pipe, installing large radius elbows, keeping debris and particulate out of the distribution system and sizing components such as inlet filters so that pressure differential is low even under heavy particulate conditions are a few ideas. While there will always be some pressure differential in the system, the key is to keep it as low as possible so that its ongoing cost does not significantly hurt the bottom line. If you are unsure of the condition of your vacuum distribution system, get an evaluation done to determine where the opportunities lie and what energy reductions are possible. For more information please contact Dan Bott, Dan Bott Consulting LLC, tel: (251) 609-1429, email: dan@dbott.com, www.danbottconsulting.com “A 3" HgV . pressure differential is very common in real world production vacuum systems.” www.airbestpractices.com 35 http://www.danbottconsulting.com http://www.airbestpractices.com

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Compressed Air Best Practices - April 2008 Contents From the Editor Utility-Air News The Compressed Air Audit of the Month: Minimizing Blow-Molding Pressure Fluctuations AF Compressors: Focused on 40 Bar, Oil-Free Air for the PET Industry Real World Best Practices: PET Plants Using Boosters for High-Pressure Air Guaranteeing Audit ROI for Blow-Molders Managing Vacuum Pressure Differential Are You Taking Full Advantage of Pneumatic Valve Technology? Are You Strategic? Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - April 2008

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