Compressed Air Best Practices - March 2008 - (Page 44)

| 03/08 Focus Industry FOOD PROCESSING | REAL WORLD BEST PRACTICES MEASURING PRESSURE DEWPOINT IN A COMPRESSED AIR SYSTEM p Stainless steel should be used on all air-sampling lines, from the main air line to the sample system. Plastic and rubber lines should not be used because they will absorb moisture through the material. This will cause false high dewpoint readings There should be no low points in the sample system line from the main pipeline to the sample unit. If saturation occurs, the condensed water will collect in the low spots and give false readings until it dries out or is drained from the system Keep all fittings as simple as possible. These fittings should also be made of stainless steel and used wherever possible Note: If high dewpoint readings are present, check all fittings to the sample unit and in the sample unit itself for leaks. Moisture will travel against the flow of air through “wicking” at any “leak” and will give false high dewpoint readings. p p Direct Insertion Probes Some probes are designed to be installed directly into the main distribution line. They are installed through a ball valve into the pipeline. This can be done while the system is still pressurized. The perceived benefits to these types of probes are the simplicity of installation and lower material cost associated with the initial installation. There seems to be no accuracy benefit to this type of installation. There are several issues for concern, such as: p p p What does the laminar effect do to the reading? How do rust, scale, debris and other contaminants affect the probe itself? Maintenance issues: will plant personnel remove the probe for regular maintenance while the system is still pressurized? Many feel that if the probe is installed in an off-line sample system where it is accessible to maintenance personnel, then it will be easier to maintain and will be maintained in a professional manner. The three types of probes generally recommended for installation into air systems are the thin film polymer, aluminum oxide and the ceramic oxide. All three have very high accuracy ratings and all are capable of a fast recovery from saturation, after the wetted probe is exposed to dry air. In the case of a refrigerated dryer application versus a desiccant dryer, the drying time is directly related to the humidity differential between the wet probe and the dry air. The desiccant dryer application will “dry out” faster then the refrigerated dryer because of the higher humidity differential. All three probes are reasonable selections for either desiccant or refrigerated systems. However, the thin film polymer is somewhat less accurate at the lower pressure dewpoints of desiccant systems. For more information please contact Don Van Ormer, tel: (740) 862-4112, email: DonaldvanOrmer@aol.com, www.airpowerusainc.com Data and illustrations provided by: COSA Instruments www.cosa-instrument.com Vaisala Inc. www.vaisala.com GE Panametrics www.gesensing.com/panametricsproducts General Eastern www.gesensing.com/generaleasternproducts 44 www.airbestpractices.com http://www.cosa-instrument.com http://www.vaisala.com http://www.gesensing.com/panametricsproducts http://www.gesensing.com/generaleasternproducts http://www.airpowerusainc.com http://www.airbestpractices.com

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

Compressed Air Best Practices - March 2008 Contents From the Editor Utility-Air News The Compressed Air Audit of the Month: Saving Energy with Blowers in Canada Do You Provide World-Class Service? Managing Rotary Screw Air Compressors at Midwest Bakery The Difference Between Acfm and Scfm for Proper Vacuum Sizing Best Practices — Multi-Module Process Air Dryers The Vacuum Formation Process in Building Compressed Air Filter Elements Solberg Manufacturing Real World Best Practices: Measuring Pressure Dewpoint in a Compressed Air System Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - March 2008

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