Compressed Air Best Practices - February 2009 - (Page 21)

Focus Industry POWER PLANTS | 02/09 | of a compressed air system while it is operating, and hence, under pressure. Pressure dew point is a useful method of describing the humidity in compressed air because it tells us that we must keep the ambient temperature that surrounds the compressed air distribution system above the pressure dew point in order to prevent liquid water from condensing inside the piping. Pressure dew point measurements are described in Part 3 of ISO8573. Classes 7 through 9 are used to describe compressed air that contains liquid water. As mentioned, liquid water appears in the distribution piping and storage when the pressure dew point of the compressed air is higher than the temperature of the ambient air, and it means that the compressed air contains as much water vapor as is possible for it to contain. This condition is usually called “saturated” air. When liquid water is present in the compressed air line, we use the methods described in ISO8573, Part 9 to measure the amount. “How successfully compressed air stream cleanliness requirements are met can have a dramatic impact on overall plant operating costs.” Oil There are only five classes for oil in the standard, but they describe a wide range of concentrations. Again, Class 0 is the most pure, and according to the standard, it describes compressed air that must be more pure than Class 1. Classes 1 through 4 cover the range from less than 0.01 mg of oil content per cubic meter of compressed air to less than 5 mg per cubic meter. It is very important to understand that the oil classes can only be determined by adding the contribution from a.) any liquid oil in the compressed air, b.) the oil aerosols in the compressed air (typically generated by the reciprocal or rotary motion in lubricated compressors) and c.) oil vapors that can come from the oil in the compressor crankcase or sump or from ingestion at the inlet of the compressor. Liquid oil and oil aerosols are measured using the techniques in ISO8573, Part 2, and the oil vapors are measured using the methods in Part 5. Reporting the Purity Classes According to the standard, the purity classes of compressed air shall be expressed by stating the standard reference number and part, the date of issue and the three class designations in a specific order: Particulate Water Oil. For example, if the compressed air purity of an audited air system was expressed as ISO8573.1 : 2001 1 2 1, the Particulate Class would be 1, the Water Class would be 2 and the Oil Class would be 1. If the class for a particular category is omitted, then a hyphen is used in its place. Many manufacturers of equipment powered by compressed air are now using this standard to express the purity level of the compressed air supply required in order to keep their tool or process running smoothly and in control. Air tool manufacturers and paint and powder coating suppliers are just two examples of entities that are using ISO8573 to improve their customer’s satisfaction with their products. For more information, please contact Dan Ryan, Engineering Manager — Filtration, Parker Hannifin Corporation, Filtration & Separation Division: tel: 248-236-8234, email: DRyan@Parker.com, www.Parker.com www.airbestpractices.com 21 http://www.Parker.com http://www.airbestpractices.com

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Compressed Air Best Practices - February 2009 Contents From the Editor Utility-Air News Compressed Air Audit of the Month Air Standards Instrument Air in Nuclear Power Plants Seven Sustainability Projects for Industrial Energy Savings The Pneumatic Advantage Personal Productivity Resources for Energy Engineers Wall Street Watch Advertiser Index Classifieds

Compressed Air Best Practices - February 2009

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