Compressed Air Best Practices-August 2008

| 08/08 Focus Industry COMPRESSED AIR AUDITS | KNOW YOUR SYSTEM Use of Flow Meters to Determine Loading Many different types of flow measuring devices existed when Manitoba Hydro first started performing scoping studies and audits. We found, however, many of these devices were very expensive and difficult to install, which put them way beyond the reach of all but the largest scoping projects. Many of our customers are small and were typically not interested in paying $4,000 to $5,000 for the purchase and installation of a flow meter. Fortunately, new low cost flow metering devices are now readily available that are easier to install and priced at an affordable level for initial scoping. The device we have currently chosen for most of our installations is a thermal mass flow meter (An example of which can be seen at CDI Meters www.cdimeters.com). This type of thermal mass flow meter is extremely useful for our flow data logging using the 4 to 20 ma output, and is something our customers can use for ongoing monitoring and troubleshooting of their systems using the readable LED display. For larger jobs with pipes over 6" size, standard insertion flow meters can be used, or if applicable, the customer may have onsite flow metering with an output compatible with data loggers. Our experience with adding thermal mass metering to our instrumentation toolbox has been positive. We are finding the extra information is very useful in analyzing the data for compressed air systems, especially on troublesome modulation and centrifugal systems. This new data also helps us better communicate the scoping test results to our customers in a simpler fashion; rather than trying to make them understand the complex method of data analysis involved in synthesizing flow data from compressor power or amps. Thermal Mass with Wet Air Users of flow meters should be cautious, however, as certain conditions can make the data difficult to read or even completely wrong. This is particularly the case when trying to measure flow in an un-dried air stream with a thermal mass style meter. These meters must not be used with air that contains entrained moisture as under these conditions they will read incorrectly. In a compressed air system there are often times where an air stream, thought to be dry, is in fact wet due to dryer or drain failures and/or cooling/air temperature issues with the air compressors and dryer combination. Storage Tank Location The storage receiver location can also have a big effect on the usability of the flow meter output. For systems with large storage receivers, if the flow meter is placed between the air compressors and the receiver, the meter may not capture peak system flows where the peak is supplied by the air stored in the receiver. If the compressors in the system are load/unload style, or if system characteristics are normally highly variable, the flow meter will quickly jump from one flow level to another as conditions change, often making the meter display unreadable. The issue of constantly changing flows can be solved by averaging the readings over a longer time period. The accompanying Figure 5 shows the thick fuzzy line that was produced in a system with highly variable flow. Overlaid on this chart is a 15 minute average. This average brings the plant flows into better focus and aids in analysis of the data. Gas Mileage Gauge for Your Air System Part of the way through our experience with flow meter logging, we took note of a paper by Babu Joseph, Ph.D., P.E. of Southern California Edison titled “Compressed Air Supply Efficiency.” In the paper, Mr. Joseph coins the measurement unit he calls a “CASE Index” (Standard Cubic Feet per kWh) and proposes ways to monitor in real time the supply efficiency of a compressed air system. At the same time, Manitoba Hydro was developing the use of special energy sub-meters to assist our customers in energy and demand reduction projects. An example of one such project can be seen at Manitoba Hydro’s website at www.hydro.mb.ca/pop/pop_profile_inco.pdf. Armed with the CASE report and our experience with power metering, we arranged to place a number of test installations on various compressed air systems. A Thermal Mass Flow Meter 24 www.airbestpractices.com http://www.cdimeters.com http://www.hydro.mb.ca/pop/pop_profile_inco.pdf http://www.airbestpractices.com

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

Compressed Air Best Practices- August 2008 Contents From the Editor Utility-Air News The August Audit of the Month: A Vacuum System Audit Energized for Savings at Seattle City Light and Tacoma Power Know Your System CASE: Compressed Air Supply Efficiency Ecos Air: Managing Incentive Programs Kaeser Compressors: Loyalty, Energy and Growth Building Relationships at Cummins-Wagner McIntire is Moving Forward The 2008 A.I.C.D. Conference & Exhibition Tuthill Vacuum and Blower Systems Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

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