Compressed Air Best Practices - May 2008 - (Page 33)

Compressed Air Industry AUTOMOTIVE ASSEMBLY | 05/08 | The table at left points out: Sizing buffer air for units that have the double labyrinth seals worn to the full estimated 3%, will require 280 to 300 cfm/1000 hp of total air under these conditions including 150 cfm of buffer air. Those that don’t require seal buffer air really only need control air plus any bleeds, leaks, etc. Programmed bleeds can be isolated and the valves and vacuum pumps can be converted to electric and thus requires no start up air. There can be great difference of opinion as to the performance between electric and pneumatic valves. In general, the 100 cfm estimate for starting air requirement without buffer air seems somewhat oversized with a normal well maintained compressor. Not all compressors have a normal, well maintained life. The dryer purge air is directly proportional to the rated air demand with a desiccant regenerative heatless dryer and to the actual flow demand with a membrane dryer. Selecting the appropriate compressed air supply: With the normal operating hours of this start up air system, probably less than 10–15 hours per year (30 minutes once a month), energy efficiency is not a high priority. The driving criteria is reliability — ability to deliver the required quality of air and ease of maintenance and inspection. In our basic sizing model, we have estimated 100 cfm as enough control air to handle a normal, well maintained centrifugal not needing seal buffer air regardless of size or brand. This 100 cfm is needed at a nominal 85 psig to serve the highest rated required pressure (80 psig). This need may vary with compressor brand model and type and make of valve. If the air can be used at a lower regulated pressure, it will extend the effective flow time of the storage. With 15 cfm or purge air included for the dryer purge air, the total becomes 115 cfm at 85 psig. The presence of significant leaks and worn out valves and cylinders can dramatically affect this value. For the low pressure buffer seal air (10 psig regulated to 5 or 7 psig), we have used the highest wear estimate as the double labyrinth seals — 3% of full load flow. This puts the buffer air from 500 hp to 2,000 hp in 50 hp including the appropriate volume of dryer purge air. When discussing the best possible size with several very experienced compressor manufacture personnel, they all agreed a 60 to 75 hp class unit should always work (250–325 cfm) for a 1,000 hp class unit unless it is a truly poor conditioned unit. For more information contact Hank Van Ormer, tel: 740-862-4112, email: hankvanormer@aol.com, www.airpowerusainc.com See the WIX distributor nearest you or visit wixfilters.com. A member of the Affinia family of brands: Aimco • BrakePro • McQuay-Norris • Nakata • Raybestos • Spicer • WIX The super absorbent way to protect your air tools. Why should you use AquaChek? That’s simple. AquaChek Filters extend the life of your air tools and equipment by eliminating rust and corrosion. How? They use an advanced polymer media that absorbs 28 times its weight in water and traps unwanted particulate down to one-half a micron in size. Any other questions? 33 http://www.wixfilters.com http://www.wixfilters.com http://www.wixfilters.com http://www.airpowerusainc.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices - May 2008

Compressed Air Best Practices - May 2008 Contents From the Editor Utility-Air News The Compressed Air Audit of the Month Pneumatics Real World Best Practices Delta Industries: Doing What is Right for Customers Delta Industries: Six Truths You Need to Know about Really Putting the Customer First Power Supply Industries Resources for Energy Engineers Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - May 2008

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