Compressed Air Best Practices - April 2008 - (Page 24)

| 04/08 Compressed Air Industry PLASTICS BLOW-MOLDING | REAL WORLD BEST PRACTICES PET PLANTS USING BOOSTERS FOR HIGH-PRESSURE AIR Comparison of Primary with Booster and High Pressure Ratings PRIMARY TO BOOSTER THREE-STAGE CENTRIFUGAL Model Unit Type Inlet Pressure (psig) Full Load Horsepower (bhp) Full Load Motor Efficiency (.me) (est) Full Load Pressure (psig) Full Load (input) kW @ 600 psig: Calculated Full Load Specific Power (scfm/kW) Flow Each @ Rated psig Total Input kW Combined Specific Power (scfm/kW) Combined Annual Electric Cost ($/scfm) @ 600 psig TWO-STAGE DOUBLE ACTING BOOSTER ATMOSPHERIC TO HIGH-PRESSURE FOUR-STAGE CENTRIFUGAL FOUR-STAGE DOUBLE ACTING RECIP. Typical Centrifugal Three-stage 14.5 psig 421 .95 115 330.5 kW 5.7 scfm/kW 1,884 scfm 560.2 3.36 scfm/kW $176.92 scfm/yr 9" & 6" x 9" TS Double-acting 115 psig 291 .945 600 229.7 kW 8.202 scfm/kW 1,884 scfm Typical Centrifugal four-stage 14.5 psig 855.8 .93 600 686.5 kW 2.48 scfm/kW 1,704 scfm 686.5 2.48 scfm/kW 239.71 scfm/yr Typical Balanced opposed 14.5 psig 624.7 .93 600 465.6 kW 3.31 scfm/kW 1,543 scfm 465.6 3.31 scfm/kW 179.54 scfm/yr Based on $0.07/kWh operating for 8,500 hours per year Summary Well-applied primary compressors and boosters deliver about the same operational efficiencies ($176.92 scfm/yr) as the four-stage double acting reciprocating high-pressure unit ($179.54 scfm/yr). The four-stage reciprocating units use 2.55 ratios per stage compared to the 2.09 CR per stage of the booster. Properly applied, both are well within limits. Either of theses units are about 25% more power efficient than a typical four-stage high-pressure centrifugal under the same conditions. The centrifugal offers some other significant benefits in initial cost, projected maintenance cost and installation cost. Qualifying this part of the application requires significant investigation. However, a properly selected and applied booster can be an excellent choice, as would any of the other options depending on the installation and maintenance situation. Installation Guidelines for Booster Applications Installation Guidelines For Booster Applications Check Valves A high-quality check valve should be installed on the inlet to and the discharge from the Booster compressor. The inlet check valve would be installed up stream of a pulsation tank or receiver tank on the inlet line to the booster. This will stop the pulses from entering the main distribution line from the centrifugals and having a negative effect on the controls. It will also protect the main air system from any high-pressure “back feed” if there are inlet valve problems with the Booster. 24 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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