An essential guide to compressed air system analysis, plus how to cut costs

Learn how to measure and analyze a compressed air system to help save energy and cut costs

By Plant Engineering January 3, 2024
Courtesy: CFE Media

Compressed air system cost insights

  • Eric Bessey emphasizes the importance of understanding and analyzing compressed air systems by measuring airflow, air consumption and pressure profiles to identify opportunities for cost-saving and energy efficiency improvements.
  • Tom Taranto adds that assessing the supply and usage sides of the system is crucial, as a significant portion of compressed air is often lost to leakage or used inappropriately, prompting the need to identify areas where alternative energy sources could be more efficient.

There are many factors affecting the bottom line of a facility. A leak or inefficiency in a compressed air system may spell higher costs. Watch the educational webcast “Energy efficiency: Focus on compressed air systems” and then read this transcript for additional details. This has been edited for length and clarity.

Compressed air system experts:

  • Tom Taranto, Principal Engineer and Owner, Data Power Services LLC, Baldwinsville, New York
  • Eric Bessey, President, TTed Solutions, Beaverton, Oregon

Eric Bessey: Perhaps one of the key things that people struggle with is just basic understanding of what information they need to gather to analyze their compressed air system. Just like any big system, you might consider your house heating, for instance. It starts with an analysis of what it is that’s being used and how it’s being supplied. Then with that knowledge, you can look at how improvements may be made.

For compressed air, the key things are:

  • What the airflow is.
  • How much air are we using?

How much air are we using and at what pressure? Then how much is this costing us? Air is expensive and there are ways to reduce the air consumption, power consumption and save energy. With the measurements that we take, we can develop profiles called baseline profiles to determine what average airflow profiles are being supplied and being used by the plant.

We will also understand what various pressure profiles there are through the plant, get an idea of how the pressure is being used throughout the plant, how it might vary through time and so forth. Eventually, getting down to the ultimate operating costs is the answer. There are several measurement tools that we use.

We start off by basic measurements of pressure. In Figure 1, the upper left of a pressure transducer or sensor is shown. In the middle, we have a power meter and you may recognize some of the what we call Rogowski coils. Those blue, splitable coils that you wrap around the three phases of a 480-volt, three-phase motor. Down the lower left, we have a flow meter and flow metering is a complicated subject.

Courtesy: CFE Media

Courtesy: CFE Media

There are different types of flow metering and they range all the way from very simple and inexpensive, to more complicated, very expensive and they can be suitable for all kinds of conditions. Some are suitable for outdoors, indoors, chemicals and whatnot.

Bottom right, we have a data logger. This is a device that collects data and they’re nice.

Data loggers sit there in the core and they collect data. Then a week or two or a month later, you can download the data to your computer for analysis. Lastly, there’s a dewpoint sensor in the upper right. Some people are very interested and very concerned about how much moisture they might have in the system. Dewpoint sensors can be installed and data logged.

Tom Taranto: If you stop and think for a minute, it doesn’t really cost you money to put air into the system. What costs you money is when the air comes out of the system. In addition to analyzing how the supply side of the system is functioning, we also want to try to figure out where is that air going to and how is it getting out of the system?

There is a consensus of a lot of people that were involved in the Compressed Air Challenge. Only about half of t he air that goes into most systems does something productive. That rest of the air is lost to leakage, or to inappropriate use or artificial demand.

What’s inappropriate use? Inappropriate use is somewhere where you’re using compressed air as the power source, the energy source, where there are other ways to do the job with different energy sources that can get the job done equally as well or better and with much less energy intensity.

This is the next step in the analysis. After you measure what’s going in, you should look at what are your big air users. Get an idea of what the leakage rate is and look at things with a critical eye and say, “Is compressed air really the best thing to do this?” Now, you’ll begin to develop the whole picture of how your system is consuming the compressed air energy.