Compressed Air Best Practices - April 2008 - (Page 16)

| 04/08 Focus Industry PLASTICS BLOW-MOLDING | COMPRESSED AIR AUDIT OF THE MONTH Minimizing Blow-Molding Pressure Fluctuations Controlling Plant Air Pressure A 200 hp VSD and a 250 hp fixed speed rotary screw compressors supply the plant low-pressure air system. The plant air system pressure was operating at 135–145 psig during the audit and was controlled by the fixed speed compressors modulation. By adjusting the variable speed set-point to a lower level, we will be able to allow it to control the header pressure much more accurately and therefore at a lower pressure. With the header controlled at 130 psig, the power in the system will be reduced by >35 hp or a savings of >$15K per year. The second fixed speed compressor should be set to auto-start at 120 psig so that it can provide automatic backup in case of a failure of one of the operating compressors. The two 250 hp compressors can be manually rotated into service on a weekly basis to maintain operating condition. Some Sidel machines experience sensitivity to air pressure at the brake/clutch system. A small dedicated receiver with a check valve will protect the brakes on any molding machine from pressure fluctuations if required. Install the tank with a check valve per the diagram. Conclusion Pressure fluctuates in virtually all PET blowmolding facilities from 3 bar to as much as 6 bar. This forces the operating pressures to maximum levels in order to prevent low-pressure events from impacting the production processes. These fluctuations are caused by: 1. Poor air system controls 2. Inadequate storage 3. Installed pressure differential at the blow-molding machines The technical evaluations confirmed that this is the case at this facility. Implementing the recommended actions at this facility will result in energy savings of $151,000 per year with a 21.8 month simple payback. For more information please contact Dean Smith, iZ Systems LLC, tel: (404) 307-6836, email: dsmith@izsystems.com 16 www.airbestpractices.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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