Consider these Variables When Choosing Compressed Air Pipe Size

Here on the EXAIR blog we discuss pressure drops, correct plumbing, pipe sizing, and friction losses within your piping system from time to time.   We will generally even give recommendations on what size piping to use.  These are the variables that you will want to consider when selecting a piping size that will suit your need and give the ability to expand if needed.

The variables to know for a new piping run are as follows.

  • Flow Rate (SCFM) of demand side (products needing the supplied compressed air)
  • System Pressure (psig) – Safe operating pressure that will account for pressure drops.
  • Minimum Operating Pressure Allowed (psig) – Lowest pressure permitted by any demand side point of use product.
  • Total Length of Piping System (feet)
  • Piping Cost ($)
  • Installation Cost ($)
  • Operational Hours ( hr.)
  • Electical Costs ($/kwh)
  • Project Life (years) – Is there a planned expansion?

An equation can be used to calculate the diameter of pipe required for a known flow rate and allowable pressure drop.   The equation is shown below.

A = (144 x Q x Pa) / (V x 60 x (Pd + Pa)
A = Cross-Sectional are of the pipe bore. (sq. in.).
Q = Flow rate (cubic ft. / min of free air)
Pa = Prevailing atmospheric absolute pressure (psia)
Pd  = Compressor discharge gauge pressure (psig)
V = Design pipe velocity ( ft/sec)

If all of these variables are not known, there are also reference charts which will eliminate the variables needed to total flow rate required for the system, as well as the total length of the piping. The chart shown below was taken from EXAIR’s Knowledge Base.


Airflow Through 1/4″ Shed. 40 Pipe

Once the piping size is selected to meet the needs of the system the future potential of expansion should be taken into account and anticipated for.   If no expansion is planned, simply take your length of pipe and start looking at your cost per foot and installation costs.    If expansions are planned and known, consider supplying the equipment now and accounting for it if the additional capital expenditure is acceptable at this point.

The benefits to having properly sized compressed air lines for the entire facility and for the long term expansion goals makes life easier.   When production is increased, or when new machinery is added there is not a need to re-engineer the entire system in order to get enough capacity to that last machine.   If the main compressed air system is undersized then optimal performance for the facility will never be achieved.   By not taking the above variables into consideration or just using what is cheapest is simply setting the system up for failure and inefficiencies.   All of these considerations lead to an optimized compressed air system which leads to a sustainable utility.

Brian Farno
Application Engineer Manager

Calculating Air Volume for Cooling


Robot motor in need of cooling



Accompanying information about motor in need of cooling

Usually, when discussing application solutions we can make recommendations for proper product based on experience, empirical test data, and application parameters.  Sometimes, though, we need to take things just a little further and aim to dial in the recommended solution before any testing ever occurs.

I recently had an exercise in this, involving the need to cool the robot motor shown in the photo above.  This motor, existing in two forms (one weighing 23kg and the other weighing 25kg) is currently operating, creating heat, and registering a temperature of 90°C.  The desired operating temperature is 60°C, and we can safely assume an ambient temp. no higher than 35-40°C.

The questions posed to me were:  “Which product should be used to cool this motor?  And, how do you know?”  So, I took a certain degree of liberty (though not much) in considering the motor in question is comprised of copper windings, and these windings comprise the total weight of the motor.

Considering this, our knowns for this application were:

Weight:                              23kg and 25kg

Material:                            Copper

Starting temp:                   90°C

Ending temp:                    60°C


What we didn’t know was:

Specific heat of copper:                  (determined to be 0.385 Joules/g°C)

Amount of airflow to cool this motor by 30°C:                     XXX cubic feet per minute


This airflow was determined using the process shown below, and the resulting calculations shown below.

heat load calc process

Process to calculate the required airflow in a cooling application



The calculations used to determine the required airflow in this application


Super Air Amplifier Performance Specs

Performance specifications of our Super Air Amplifiers

The end result was confirmation that EXAIR model 120022, our 2” Super Air Amplifier, can use just 15.5 SCFM of compressed air at 80 PSIG to produce an airflow to cool this motor.  And, thanks to the skills of the team here at EXAIR we have the numbers to back up that claim.

If you have an application with a similar need and think we may be able to help, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer

Calculating Compressed Air Cost & Savings Made Easy

If you have ever looked through our catalog, website, blog, twitter feeds, or even our Facebook page, you will see that we can almost always put a dollar amount behind the amount of compressed air you saved by installing EXAIR’s Intelligent Compressed Air Products.   No matter which platform we use to deliver the message, we use the same value for the cost of compressed air which is $.25 per 1,000 Standard Cubic Feet of compressed air. This value is derived from average commercial and industrial energy costs nationwide, if you are on either coast this value may increase slightly. On the positive side, if your cost for compressed air is a bit more, installing an EXAIR product will increase your savings.

So where does this number come from?   I can tell you this much, we didn’t let the marketing department or anyone in Accounting make it up.   This is a number that the Engineering department has deemed feasible and is accurate.

To calculate the amount we first look to what the cost per kilowatt hour is you pay for energy.  Then we will need to know what the compressor shaft horsepower  of the compressor is, plus the run time percentage, the percentage at full-load, and the motor efficiency.

If you don’t have all of these values, no worries.   We can get fairly close by using the industry accepted standard mentioned above, or use some other general standards if all you know is the cost of your electricity.

The way to calculate the cost of compressed air is not an intense mathematical equation like you might think.  The best part is, you don’t even have to worry about doing any of the math shown below because you can contact us and we can work through it for you.

If you prefer to have us compare your current compressed air blow off or application method to one of our engineered products, we can do that AND provide you a report which includes side by side performance comparisons (volume of flow, noise, force) and dollar savings. This refers to our free Efficiency Lab service.

EXAIR's Efficiency Lab is a free service to all US customers.

EXAIR’s Efficiency Lab is a free service to all US customers.

If you already know how much air you are using, you can use the Air Savings Calculators (USD or Euro) within our website’s knowledge base. Just plug in the numbers (EXAIR product data is found on our website or just contact us) and receive air savings per minute, hour, day and year. We also present a simple ROI payback time in days.

Now, back to the math behind our calculation.
Cost ($) =
(bhp) x (0.746) x (#of operating hours) x ($/kWh) x (% time) x ( % full load bhp)
Motor Efficiency

— Compressor shaft horsepower (generally higher than motor nameplate Hp)
0.746 – conversion between hp and KW
Percent Time — percentage of time running at this operating level
Percent full-load bhp — bhp as percentage of full load bhp at this operating level
Motor Efficiency — motor efficiency at this operating level

For an average facility here in the Midwest $0.25/1,000 SCF of compressed air is accurate.   If you would like to attempt the calculation and or share with us your findings, please reach out to us.   If you need help, we are happy to assist.

Brian Farno
Application Engineer Manager


Where Does 25 Cents For 1,000 Standard Cubic Feet Of Air Come From?

Wasting compressed air 2

Being an Application Engineer at EXAIR you tend to do a good amount of return on investment (ROI) calculations.   This is mainly to tell customers just how fast installing an EXAIR product on their system is going to pay its purchase price back and start saving them money.

In order to do these calculations there are several variables we must know.   The list is below.

  • Cost of EXAIR Product (This is an easy one for us to know.)
  • EXAIR Product Consumption (Another easy one!)
  • Current Product Consumption (If this is an unknown, we will test it for free!)
  • Cost of Compressed Air / 1,000 SCF (This is the most common unknown.)

With these four variables we can calculate the amount of air and the amount of money the EXAIR product will save over an existing non-engineered blowoff.   Let me address the two variables which have to come from you, the customer.

Current Product Consumption – If this value is not known please don’t guess at it.  We offer a free service which we refer to as our Efficiency Lab where you send us in your existing blowoff device and we will test it for force flow and noise level.   If you don’t know what pressure you are operating the piece at we will help you find out how to get that and then we will test our products at the same pressures.   This way you get a true apple to apples comparison.   Then, once we are done testing, you will get a recommendation from us in a formal report as to what EXAIR product will best replace your existing product.  Then we will pay for return shipping of your blowoff device back to you. So, if you don’t know how much air you are currently using then give us a call.  We will figure it out for you.

Efficiency Lab

The EXAIR Efficiency Lab is FREE!

Cost of Compressed Air/ 1,000 SCF – This is more often than not, the unknown variable in the equation.  The good news is there is a general standard assumption of twenty-five cents per 1,000 Standard Cubic Feet of compressed air.   This works out to be around 8 cents per kW/hr.  So even if you don’t know what you pay to compress the air, if you know what you are paying per kilowatt hour for your energy then we can calculate within reason what it costs for you to generate your compressed air. For reference, 8 cents per kilowatt-hour falls between the average US cost per kilowatt hour for commercial end-users (10.7/kWh) and industrial end-users (6.9/kWh).*

The best part of all is…EXAIR has a calculator available right on our website which provides air and dollar savings per minute, hour day and year as well as a payback in days for the EXAIR product purchase. On top of that, any step along the way that you aren’t sure of, we will help you out for free, even testing your product!

In case you would like to see the math, the formula used is below.

Basic Equation To Go From Cost Per kiloWatt Hour to Cost Per 1,000 Standard Cubic Feet of Compressed Air

Basic equation to go from Cost Per kiloWatt Hour to Cost Per 1,000 Standard Cubic Feet of Compressed Air

Brian Farno
Application Engineer Manager

*latest U.S. EIA report here




How Much Force Does It Take?

In case you weren’t aware, the answer to “How much force does it take?” is always going to be, ALL OF IT.   At least that is what we generally think when trying to blow product off a conveyor belt or diverting parts into bin, etc. Speed and efficiency play a direct role in to what nozzle or blow off device you should use in order to get the job done and be able to repeat the process.

The question we are often asked by customers is, “How much force to I need to move this?”  That is a question that we cannot often answer without asking more questions.  The good part of this is, there is a formula to calculate just how much force you need to move an object.   A good video explaining friction is shown below.

In order to answer the question of how much force do I need, we really need to know all of the following:

Weight of the object
Distance from target
Is it on an incline or level
Distance needed to move
Then, the usually unknown variable, the coefficient of friction between the target and what it is sitting on.

Often times it is the thought process of, my target weighs 5 pounds, I need 5 pounds of force in order to move it from the center of this conveyor belt to the edge, this is not the case.   If you wanted to lift the object over a break between two conveyors then you would need slightly more than 5 pounds in order to ensure you are lifting the front edge of the unit high enough to meet the other conveyor.

Whether you know all of the variables or only a few, if you need to get an object moved and you want to try using compressed air to do so, give us a call and we will help you find the best engineered solution for your application.  Then, we’ll back all stock products with a 30 day guarantee if you don’t like how the system performs – but rest assured, we get it right almost every time.

30 Day Guarantee

The EXAIR 30 Day Guarantee

Brian Farno
Application Engineer Manager

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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