How to Calculate Compressed Air Consumption at a Different Inlet Pressure OR Math Doesn’t Lie and Neither Will Your Results

EXAIR Application Engineers field a wide variety of technical assistance questions. Many are quantifiable, and we just need to do a little math.  For instance:

Q. You publish the compressed air consumption of your products assuming a supply pressure of 80psig. What if my supply pressure is different?

A. Compressed air consumption is going to be directly proportional to ABSOLUTE pressure supply. That means you have to add atmospheric pressure of 14.7psia (a=absolute) to your gauge pressure, measured in psig (g=gauged, and zero on the gauge is atmospheric pressure,) and calculate the ratio. For example:

Our catalog publishes most products' performance and specification data for a compressed air supply pressure of 80psig.

Our catalog publishes most products’ performance and specification data for a compressed air supply pressure of 80psig.

Model 1100 Super Air Nozzle consumes 14 SCFM @80psig. How much will it consume @95psig?

1100 recalc

This is good news…if you need that extra amount of flow and force from a little higher pressure supply, you’re still FAR below the air consumption of an open-ended 1/4″ copper tube (33 SCFM @80psig or 38 SCFM @95psig)* or SCH40 pipe (140 SCFM @80psig or 162 SCFM @95psig.)*

*Using the same formula above.  Check my math if you like.  I’m right, but it’ll be good practice.  Those values come from this chart in our catalog, by the way:

open blow air consumption

You can get your own personal copy of our current catalog here.

Of course, if your application doesn’t need all that flow and force, this formula works the other way too…it, in fact, works in your favor, air consumption-wise.  Consider the savings associated with dialing back your supply pressure.  Let’s say, for instance, you replace a open ended 1/4″ SCH40 pipe with a Model 1100 Super Air Nozzle, regulate the supply down to 55psig, and find that it still does what you need it to:

1100 recalc-1

(Remember, the value you’re solving for is ALWAYS the numerator of the fraction, because…Algebra! )

Now, let’s do just a little more math.  Don’t worry; I’m almost finished.  Plus, this is the part you can show your boss and be the hero.  So, we find out that you’re saving 151.7 SCFM by replacing that open pipe blow off with a Super Air Nozzle, and regulating its supply pressure down from your full line pressure of 95psig to 55psig:

162 SCFM – 10.3 SCFM = 151.7 SCFM saved

You may know your facility’s cost of compressed air generation.  If not, $0.25 per 1,000 Standard Cubic Feet (SCF) is a reasonable estimate:

151.7 SCFM X 60 minutes/hour X 8 hours/day X 5 days/week X 52 weeks/year =

18,932,160 SCF/year X $0.25/1,000 SCF = $4,733.04 annual savings

Now, this is just an example…one in which a $34.00 (Model 1100 Super Air Nozzle’s current 2014 List Price) product pays for itself before the end of the second day (again, feel free to check my math and see how right I am.)  Keep in mind that your mileage, as they say, may vary, but the math…and our products’ performance…will hold true according to whatever your conditions are.

How much can you save by using engineered, Intelligent Compressed Air Products from EXAIR?  Call me, and we’ll start the process of finding out.

Russ Bowman
Application Engineer
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4 Responses to “How to Calculate Compressed Air Consumption at a Different Inlet Pressure OR Math Doesn’t Lie and Neither Will Your Results”

  1. Kevin Swayze Says:

    Your formula makes sense but I think you typo’d when you carried your results down and ended up with a misleading annual savings.
    For the calculation of 14 SCFM @80psig increased to 95psig, you got 16.2 SCFM. When you calculated reducing the air to 55psig, you got 10.3 SCFM. When you calculated the difference of the SCFM saved, you left out the decimal in the 16.2 SCFM and typed 162 SCFM ( I don’t see where you got the x 10 multiplier). So in reality your SCFM saved is only 5.9 considering 16.2-10.3 is 5.9.
    With this in mind, 5.9 SCFM x 60 minutes/hour x 8 hours/day x 5 days/week x 52 weeks/year is only 736,320 SCFM. If you multiply it by the .25 average facility air generation cost and divide it by 1000 SCF, your annual savings is only $184.08 not $4,733.04. (Please feel free to check MY math as well)

    • Kirk Edwards Says:

      Hi Kevin. Thank you for your comment and for looking at the blog closely. The 162 SCFM referenced is not a multiplier of the nozzle flow – it is the flow from a 1/4″ Schedule 40 pipe at 95 PSIG. Ultimately the solution in this example is a model 1100 air nozzle at 55 PSIG (10.3 SCFM) and compared to the previously mentioned open line. With that in mind, the math is correct.

      This blog is a clear example of the “quick fix” open air line which uses exceptionally large volumes of air for an application that can be solved with an efficient, well thought out solution. The savings benefits of an engineered air nozzle are significant.

  2. Kevin Swayze Says:

    Hi Kirk. You are correct. I didn’t catch the 162 for the 1/4″ tube. Thanks for straightening me out.

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