Compressed Air Best Practices - April 2008 - (Page 26)

| 04/08 Compressed Air Industry PLASTICS BLOW-MOLDING | REAL WORLD BEST PRACTICES PET PLANTS USING BOOSTERS FOR HIGH-PRESSURE AIR Specification For Final Specificatio inlet There should be an inl and discharge regulator installed in the booster system. there The inlet regulator is th to provide a consistent pressure to the booster. If the pressure is too low it will create too many compression ratios and potentially cause damage. If the inlet pressure is too high it may cause internal damage to the unit and excessive heat. This also allows the piping and receivers to create effective storage to handle random spike demands caused by the many pulses per minute in both directions. The discharge regulator is there to provide a constant pressure to the process. The constant pressure will allow the process to operate more effectively. With the regulator in place, operation personnel can effectively “dial in” the best pressure in which to operate without changing the settings on the compressor. This regulator may also be installed at or near the process or blow-molder rather than near the discharge of the receiver or check valve. The inlet regulator should be pilot operated. This gives a much finer response time over other types. It may be a rotary vee notch valve with pilot operated actuator. Inlet air to the booster should be dry and clean. With centrifugal or oil-free rotary screws, we usually recommend heat of compression from descent twin tower dryers which will dry the incoming air enough to not require any further drying or cooling of the air delivered to the high-pressure systems. The schematics below show two different high-pressure booster installations. The heat of compression dryer will deliver very dry air (to -40 ˚F PDP) with little or no significant electrical energy use. For more information contact Hank Van Ormer, tel: 740-862-4112, email: hankvanormer@aol.com, www.airpowerusainc.com NOTE: These schematics are taken from actual compressed air audits we have performed. They are not to be construed as recommending particular pipe sizing, receiver sizing and location etc. Pulsation Tanks (Receiver Tanks) The receiver tanks will slow down the air and dampen the pulses of the Booster Compressor. On a Reciprocating compressor there is about a 10% change in pressure on the inlet and discharge of the unit. This is caused by the inlet air filling the cylinder and by the discharge air leaving the compressor. The receivers allow the pressure changes to occur in them instead of the piping. This is critical on the inlet to the booster to not allow the pulses to possibly back pressure the centrifugal and cause it to surge. The discharge receiver will allow the regulator to receive a relatively stable flow of air with minimal fluctuations in pressure. Typical High-Pressure System with Dedicated Primary High-Pressure Compressor. Separate Compressor for Low-Pressure System. Air Receivers Example Inlet (low-pressure) — 400-gallon vertical receiver with a 200 psi MWP with a 200 psig rated safety valve — gauge and automatic condensate drain Note: 200 psig is standard in the 400-gallons class and is recommended in case of back pressure problem. Discharge (high-pressure) — 400-gallon vertical receiver with an 800 psi MWP, with a 800 psi rated safety valve, gauge and appropriate automatic condensate drain (high-pressure) 26 www.airbestpractices.com http://www.airpowerusainc.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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