How to Calculate SCFM (Volume) When Operating at Any Pressure

If you need to operate at a different pressure because you require less or more force or simply operate at a different line pressure, this formula will allow you to determine the volume of air being consumed by any device.

Volume Formula

Using the EXAIR 1100 Super Air Nozzle as our example:

1100

Lets first consider the volume of the 1100 Super Air Nozzle at a higher than published pressure.  As shown in the formula and calculations it is simply the ratio of gauge pressure + atmospheric divided by the published pressure + atmospheric and then multiply the dividend by the published volume.  So as we do the math we solve for 17.69 SCFM @ 105 PSIG from a device that was  shown consume 14 SCFM @ 80 PSIG.

higher

Now lets consider the volume at a lower than published pressure.  As shown it is simply the ratio of gauge pressure + atmospheric divided by the published pressure + atmospheric and then multiply the dividend by the published volume.  So as we do the math we solve for 11.04 SCFM @ 60 PSIG from a device that was shown to consume 14 SCFM @ 80 PSIG.

lower

When you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.  Experience the EXAIR difference first hand and receive the great customer service, products and attention you deserve!  We would enjoy hearing from you.

Steve Harrison
Application Engineer
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Six Steps To Optimizing Your Compressed Air System – Step 1: Measure

“To measure is to know – if you cannot measure it, you cannot improve it.”
-Lord Kelvin, mathematical physicist, engineer,and pioneer in the field of thermodynamics.

This is true of most anything. If you want to lose weight, you’re going to need a good scale. If you want to improve your time in the 100 yard dash, you’re going to need a good stopwatch. And if you want to decrease compressed air consumption, you’ll need a good flowmeter. In fact, this is the first of six steps that we can use to help you optimize your compressed air system.

Six Steps To Optimizing Your Compressed Air System

There are various methods of measuring fluid flow, but the most popular for compressed air is thermal mass air flow.  This has the distinct advantage of accurate and instantaneous measurement of MASS flow rate…which is important, because measuring VOLUMETRIC flow rate would need to be corrected for pressure in order to determine the true compressed air consumption.  My colleague John Ball explains this in detail in a most excellent blog on Actual (volume) Vs. Standard (mass) Flows.

So, now we know how to measure the mass flow rate.  Now, what do we do with it?  Well, as in the weight loss and sprint time improvements mentioned earlier, you have to know what kind of shape you’re in right now to know how far you are from where you want to be.  Stepping on a scale, timing your run, or measuring your plant’s air flow right now is your “before” data, which represents Step One.  The next Five Steps are how you get to where you want to be (for compressed air optimization, that is – there may be a different amount of steps towards your fitness/athletic goals.)  So, compressed air-wise, EXAIR offers the following solutions for Step One:

Digital Flowmeter with wireless capability.  This is our latest offering, and it doesn’t get any simpler than this.  Imagine having a flowmeter installed in your compressed air system, and having its readings continually supplied to your computer.  You can record, analyze, manipulate, and share the data with ease.

Monitor your compressed air flow wirelessly over a ZigBee mesh network.

Digital Flowmeter with USB Data Logger.  We’ve been offering these, with great success, for almost seven years now.  The Data Logger plugs into the Digital Flowmeter and, depending on how you set it up, records the flow rate from once a second (for about nine hours of data) up to once every 12 hours (for over two years worth.)  Pull it from your Digital Flowmeter whenever you want to download the data to your computer, where you can view & save it in the software we supply, or export it directly into Microsoft Excel.

From the Digital Flowmeter, to your computer, to your screen, the USB Data Logger shows how much air you’re using…and when you’re using it!

Summing Remote Display.  This connects directly to the Digital Flowmeter and can be installed up to 50 feet away.  At the push of a button, you can change the reading from actual current air consumption to usage for the last 24 hours, or total cumulative usage.  It’s powered directly from the Digital Flowmeter, so you don’t even need an electrical outlet nearby.

Monitor compressed air consumption from a convenient location, as well as last 24 hours usage and cumulative usage.

Digital Flowmeter.  As a stand-alone product, it’ll show you actual current air consumption, and the display can also be manipulated to show daily or cumulative usage. It has milliamp & pulse outputs, as well as a Serial Communication option, if you can work with any of those to get your data where you want it.

With any of the above options, or stand-alone, EXAIR’s Digital Flowmeter is your best option for Step One to optimize your compressed air system.

Stay tuned for more information on the other five steps.  If you just can’t wait, though, you can always give me a call.  I can talk about compressed air efficiency all day long, and sometimes, I do!

 

Line Vac Helps Students With Automation Projects

Over the past year I received a contact from a professor and student combination from Madison Area Technical College inquiring about the sizes available for our Line Vac products.  They were using a 2″ Line Vac in one of their automation class labs and wanted to try something a little bigger for a new project.  The 2″ Line Vac was one they had used in the past on different projects and had always worked well.   The new project however increased the bag size and made the conveyance difficult for the 2″ Line Vac.


The Initial e mail received.
The Initial e mail received after a short conversation.

With the picture below of their current setup and a good understanding that they will be placing three items into a heat sealed bag that is roughly 3″ long and 2″ wide we settled on using the 3″ Aluminum Line Vac at a low pressure to convey the baggies to their secondary function.   As you can see in the video below, the Line Vac is activated by a sensor and operates for just seconds in order to convey the bag of parts successfully to the other side of the machine cell where the bag is then picked and placed by a robotic arm.

The existing 2" Line Vac they had in place.
The existing 2″ Line Vac they had in place.

After the project was completed we received a mention through social media, as well as a brief video showcasing the Line Vac in use.  The video showcases how easy it is to install an EXAIR Line Vac into a tight space where adding other conventional mechanical conveying systems would be considerably more elaborate.  The Line Vac is being controlled via a PLC that energizes a solenoid valve on a timer to convey the package in a matter of seconds.

 

Social Media Contact
Social Media Contact

We are very pleased to see the projects these kids turned out, and the leadership shown by Peter, their instructor. Manufacturing programs such as this one at Madison Area Technical College are important for our economy and for the future of these kids. We’d like to congratulate them all on their accomplishment.

If you have a project you are trying to move products from one point to another, contact us.  If you are a professor, student, or even a mentor to an educational program that would benefit from EXAIR products, please contact me directly.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

The Effect of Back Pressure on a Vortex Tube Part 2, Calculating Btu/Hr.

My previous blog post was about how Vortex Tubes react when there is back pressure due to a restriction on either the hot or cold discharge of the Vortex Tube.  In it I mentioned that there is a formula to calculate what the cooling capacity (Btu/Hr) will be if there is no way to avoid operating the Vortex Tube without back pressure on the discharge. That is the calculation focus of this blog – calculating Btu/hr of a Vortex Tube with back pressure.

To continue with the same example, the calculations from the previous blog are shown below.  Last time the example Vortex Tube was operating at 100 psig inlet pressure, 50% cold fraction, and 10 psi of back pressure. We will need some additional information to determine the Btu/Hr capacity. The additional information needed is the temperature of the supplied compressed air as well as the ambient air temperature desired to maintain.  For the example the inlet compressed air will be 70°F and desired ambient air temperature to maintain will be 90°F.

(100 psig + 14.7 psia) / (10 psig + 14.7 psia) = X / 14.7 psia
4.6437 = X / 14.7
X= 14.7 * 4.6437
X = 68.2628
(Values have been rounded for display purposes)

The calculation above gives the compensated operating pressure (X = 68.2628) which will be needed for the BTU/hr calculation. The rated air consumption value of the Vortex Tube will also need to be known.  A 30 SCFM rated generator will be used for this example, the normal BTU capacity of a Vortex Tube with a 30 SCFM generator is 2,000 BTU/hr.

First, determine the new consumption rate by establishing a ratio of the compensated pressure (68.2628 psi) against the rated pressure (100 psi) at absolute conditions (14.7 psia).

(68.2628 PSIG + 14.7 (atmospheric pressure)) / (100 PSIG (rated pressure) + 14.7) = .7233
.7233 x 30 SCFM  = 21.7 SCFM Input 

Second, the volumetric flow of cold air at the previously mentioned cold fraction (50%) will be calculated.  To do this multiply the cold fraction setting (50%) of the Vortex Tube by the compensated input consumption (21.7 SCFM) of the Vortex Tube.

50% cold fraction x 21.7 SCFM input = 10.85 SCFM of cold air flow

Third, the temperature of air that will be produced by the Vortex Tube will need to be calculated.  For this consult the Vortex Tube performance chart which is shown below. To simplify the example the compensated operating pressure (68.2628 psi) will be rounded to 70 psig and to obtain the 70 psig value the mean between 80 psig and 60 psig performance from the chart will be used.

Cold Fraction
EXAIR Vortex Tube Performance Chart

For the example: A 70 psig inlet pressure at 50% cold fraction will produce approximately an 88°F drop.
Fourth, subtract the temperature drop (88°F) from the temperature of the supplied compressed air temperature (70°F).

70°F Supply air – 88°F drop = -18°F Output Air Temperature

Fifth,  determine the difference between the temperature of the air being produced by the Vortex Tube (-18°F) and the ambient air temperature that is desired (90°F).

90°F ambient – -18°F air generated = 108°F difference.

The sixth and final step in the calculation is to apply the answers obtained above into a refrigeration formula to calculate BTU/hr.

1.0746 (BTU/hr. constant for air) x 10.85 SCFM of cold air flow x 108°F ΔT = 1,259 BTU/hr.

In summary, if a 2,000 BTU/hr. Vortex tube is operated at 100 psig inlet pressure, 50% cold fraction, 70°F inlet air to maintain a 90°F ambient condition with 10 psi of back pressure on the outlets of the Vortex Tube the cooling capacity will be de-rated to 1,259 BTU/hr.  That is a 37% reduction in performance.  If a back pressure cannot be avoided and the cooling capacity needed is known then it is possible to compensate and ensure the cooling capacity can still be achieved.  The ideal scenario for a Vortex Tube to remain at optimal performance is to operate with no back pressure on the cold or hot outlet.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Who You Gonna Call?

This week the world lost a great writer, actor, and comedian with the death of Harold Ramis. Ramis is famous on screen for playing Dr. Egon Spengler in the movie Ghostbusters. What he wrote surprises me even more. Looking through Ramis’s IMDB page, I find most movies that I loved as a kid or that my dad quoted to me on a regular basis had Ramis’s name as a writer. Just to recap for the uninitiated in the cult of Ramis, his writing credits include Animal House, Meatballs, Caddyshack, Stripes, Ghostbusters, Groundhog Day, and Analyze This. He also directed Caddyshack, National Lampoon’s Vacation, Multipilicity, Bedazzled, and Year One. He also has a severely overlooked scene in Knocked Up as the grandfather to be. Talking to my wife I discovered, that she may or may not have seen the entire Ghostbusters movie, so now we have our big weekend plans.  I tried to get her to watch already, but she seemed distracted. I will just try again this weekend.  I’m thinking a Ramis marathon is in order.  I’m thinking CaddyShack, Ghostbusters, Ghostbuster 2 and Groundhog Day.

ghostbusters

The closest thing to a family rated movie in the list is Ghostbusters, though as I was reminded by my colleagues there are some off color jokes. Maybe it is best to find it on TV, if you are going to watch with the kids. One of my favorite scenes is when the hotel manager, played by Michael Ensign, has to call the Ghostbusters as a last resort. The hotel is a very ritzy joint, where problems like physics, logistics and ghosts should obviously be no problem for the immense amount of money it costs to rent out their grand ballroom. It is not in the movie, but you could imagine the Michael Ensign character has already called an exterminator, a priest, and the police.  None of these people have had any luck removing the green slimy ghost from the hotel. Therefore, on the night of a great party for an important guest, he has to stoop to calling the Ghostbusters.  Hilarity ensues.

After this scene, we are reintroduced to the great Ray Parker Jr.’s great Ghostbusters theme song known in my house as ““Who You Gonna Call?” Well if you have an industrial compressed air problem or general manufacturing question, EXAIR is a great place to start. With over 100 years of industrial experience available and 45 years with the company, the Application Engineers who answer technical questions here at EXAIR should be able to help you. Even if we don’t have the product/process for you, we have a wealth of contacts that provide cooling, blow off, coating, cleaning and painting options to help you solve your problem. Just don’t call us about ghost, we’ve got nothin’. We could help you create a ghost effect for your April Fools joke.  Air Amplifiers and some neon streamers under a black light can scare anyone, but I will use that in some other blog.

Harold R

Bye Mr. Ramis you will be missed!

Dave Woerner
Application Engineer
Davewoerner@EXAIR.com
@EXAIR_DW

Algebra!

algebra

I know a great many people that this meme applies to. My co-workers and I, however, are not among them. As Application Engineers, we use algebra all the time, and we all (as far as I know) like it. For instance:

-We publish the compressed air consumption of most of our products assuming a supply pressure of 80psig. If you want to know what it is at a different pressure, you can go get a flow meter*, install it in your supply line, regulate your pressure to the desired point, and hope your flow meter is calibrated. Or, you can call us…and we’ll use algebra.  While you wait.

*Some flow meters are rated for a certain pressure, so to recalculate the flow at another pressure, you have to use algebra anyway. Ain’t that a kick in the teeth?

-We take great pride in our ability to quickly and accurately specify the appropriate Cabinet Cooler System for your electrical enclosure, if you can give us just a few key pieces of information. We do this using algebra.

Math doesn’t give us the answers to all the questions we get…and that’s not always a bad thing:

Super Air Knife selection often simply comes down to the length of the air “curtain” that you need. We stock them in lengths from 3”-96”, and they can be coupled together for any greater length you want.

Our selection of Super Air Nozzles offer a wide range of air flow patterns and force. Whether you want to blow 2 ounces of force in a 2” pattern, 23 pounds of force in a 15” pattern, or anywhere in between, we’ve got a wide variety to choose from.

If you’d like to know which EXAIR product is right for your application, we’ll be happy to help. Even (or should I say “especially”) if it requires the use of algebra.

Russ Bowman
Application Engineer
EXAIR Corporation
(513)671-3322 local
(800)923-9247 toll free
(513)671-3363 fax
Web: http://www.exair.com
Blog: https://blog.exair.com/
Twitter: twitter.com/exair_rb
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Connections – We’re All in This Together

Lately I’ve been interested in the How The Universe Works series on The Discovery Channel.  The premise of the show is to explain some of the often confusing areas of theoretical physics or astronomy as they relate to the formation of our universe.  I find this fascinating.

As the endless questions and possibilities are raised by devoted scientists and dreamers alike, I frequently notice the onset of my own, more philosophical thoughts that depart a bit from the focus of the show.  One of the tangent thoughts I regularly have as I enjoy the program is about the connection of matter, energy, and people.  I enjoy the idea that no matter a person’s location, predicament, or direction they are connected to everything in existence on a fundamental level.

Anyone with children will stress to you the importance of solid fundamentals, as will an engineer.  I spent some time this morning doing calculations for convective heat transfer with respect to time.  I started by refreshing myself on the principles by referencing a blog by Russ Bowman – always a good read.

I quickly realized when working through the problem that although this wasn’t the typical application I’m accustomed to analyzing, the solution was found using the same foundational disciplines I apply to compressed air.  The equations were different, but the connection to the solution was the same.

Maybe this is proof of the connection I find myself pondering.  Or maybe its proof that the engineering department at EXAIR has got you covered.

Lee Evans
Application Engineer
leeevans@exair.com
@EXAIR_LE