The Importance Of Properly Sized Compressed Air Supply Lines

EXAIR Corporation manufactures a variety of engineered compressed air products that have been solving myriad applications in industry for almost 37 years now.  In order for them to function properly, though, they have to be supplied with enough compressed air flow, which means the compressed air supply lines have to be adequately sized.

A 20 foot length of 1/4″ pipe can handle a maximum flow capacity of 18 SCFM, so it’s good for a Model 1100 Super Air Nozzle (uses 14 SCFM @80psig) or a Model 110006 6″ Super Air Knife (uses 17.4 SCFM @80psig,) but it’s going to starve anything requiring much more air than those products.  Since compressed air consumption of devices like EXAIR Intelligent Compressed Air Products is directly proportional to inlet pressure, we can use the flow capacity of the pipe, the upstream air pressure, and the known consumption of the EXAIR product to calculate the inlet pressure of a starved product.  This will give us an idea of its performance as well.

Let’s use a 12″ Super Air Knife, with the 20 foot length of 1/4″ pipe as an example.  The ratio formula is:

(P2 ÷ P1) C1 = C2, where:

P2 – absolute pressure we’re solving for*

P1 – absolute pressure for our published compressed air consumption, or C1*

C1 – known value of compressed air consumption at supply pressure P1

C2 – compressed air consumption at supply pressure P2

*gauge pressure plus 14.7psi atmospheric pressure

This is the typical formula we use, since we’re normally solving for compressed air consumption at a certain supply pressure, but, rearranged to solve for inlet pressure assuming the consumption will be the capacity of the supply line in question:

(C2 P1) ÷ C1 = P2

[18 SCFM X (80psig + 14.7psia)] ÷ 34.8 SCFM = 49psia – 14.7psia = 34.3psig inlet pressure to the 12″ Super Air Knife.

From the Super Air Knife performance chart…

This table is found on page 22 of EXAIR Catalog #32.

…we can extrapolate that the performance of a 12″ Super Air Knife, supplied with a 20 foot length of 1/4″ pipe, will perform just under the parameters of one supplied at 40psig:

  • Air velocity less than 7,000 fpm, as compared to 11,800 fpm*
  • Force @6″ from target of 13.2oz total, instead of 30oz*
  • *Performance values for a 12″ length supplied with an adequately sized supply line, allowing for 80psig at the inlet to the Air Knife.

Qualitatively speaking, if you hold your hand in front of an adequately supplied Super Air Knife, it’ll feel an awful lot like sticking your hand out the window of a moving car at 50 miles an hour.  If it’s being supplied with the 20 foot length of 1/4″ pipe, though, it’s going to feel more like a desk fan on high speed.

The type of supply line is important too.  A 1/4″ pipe has an ID of about 3/8″ (0.363″, to be exact) but a 1/4″ hose has an ID of only…you guessed it…1/4″.  Let’s say you have 20 feet of 1/4″ hose instead, which will handle only 7 SCFM of compressed air flow capacity:

[7 SCFM X (80psig + 14.7psia)] ÷ 34.8 SCFM = 19psia – 14.7psia = 4.3psig inlet pressure to the 12″ Super Air Knife.

Our Super Air Knife performance chart doesn’t go that low, but, qualitatively, that’s going to generate a light breeze coming out of the Super Air Knife.  This is why, for good performance, it’s important to follow the recommendations in the Installation Guide:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.
All Installation Guides for EXAIR Intelligent Compressed Air Products contain recommended air supply line sizes for this very reason.  If you have any questions, though, about proper compressed air supply, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Process Improvement, ROI and Safety from One Air Nozzle

Process improvement projects can be detailed, complex, expensive, and take a long time to prove their worth.  Today, I want to tell you about one that WAS NOT ANYTHING like that.

A metal stamping company used compressed air to blow their products from their dies.  They did what many do – they ran some copper tubing, and aimed it at the platen so it would properly eject the parts as they were stamped.  They KNEW it was loud, and they suspected it was inefficient as well.

After discussing the setup and seeing a picture of it (the one on the left, below,) I recommended installing a few engineered Super Air Nozzles to lower the noise levels considerably.  Boy, was I wrong.  About “a few” nozzles, that is…turns out, they only needed one Model 1122-9212 2″ Flat Super Air Nozzle with 12″ Stay Set Hose.  The copper tubes come from a manifold that already had 1/4 NPT ports – installation took a matter of minutes.  Nothing detailed, complex, or expensive about it:

This loud & inefficient copper tubing blowoff was just a compression fitting (and a Model 1122 2″ Flat Super Air Nozzle) away from being quiet and efficient.

It didn’t take much longer than that to prove its worth either: as soon as they noticed how much the noise level went down on THIS press, they ordered them for the other eighteen presses in their facility as well.

The 1/4″ copper tubes blew continuously from a pressure regulator set @60psig…the three of them theoretically consumed a total of ~80 SCFM.  The Model 1122, at 60psig supply, consumes only 17.2 SCFM.  Simple return on investment was as follows:

  • 80 SCFM was costing them $48.00 a week
    • 80 SCFM X 60 min/hr X 8 hr/day X 5 days/week X $0.25/1,000 CFM = $48.00
  • 17.2 SCFM, using the same formula, only costs $10.32 a week (I’ll let you do the math; it’s good practice.)
  • They saved $37.68 a week.  The Model 1122-9212 costs $116.00 (2020 pricing) – that means that each of them paid for themselves in just a hair over three weeks.
  • $37.68 x 50 work weeks per year = $1884.00 saved annually per nozzle
  • $1884 x 18 (the number of presses) = $33,912 saved annually 

Considering they also didn’t have to listen to those very loud open ended copper tube blowoffs, I think you’ll have to agree it made for a very good investment.  They did. The new nozzle runs at 77 decibels, a comfortable level and well below the OSHA standard [29 CFR – 1910.95(a)] for allowable noise exposure.

If you’d like to find out how EXAIR Intelligent Compressed Air Products can save you money on compressed air – and save everyone’s hearing – give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Why Use EXAIR Super Air Knives: Return on Investment

Return on Investment, or ROI, is the ratio of profit over total investment.  Many people use it to check stocks, financial markets, capital equipment, etc.  It is a quantitative way in determining the validity for an investment or project.   You can use the ROI value to give a measurable rate in looking at your investment.  For a positive ROI value, the project will pay for itself in less than one year.  Any negative values would represent a high-risk investment.  In this blog, I will compare the ROI between an EXAIR Super Air Knife to a common drilled pipe.  Let’s start by looking at Equation 1 to calculate the Return on Investment:

Equation 1:  ROI = (Total annual savings – Total Project Cost) / Total Project Cost * 100

The Total Project Cost is the cost of the product with the labor to install.  In our example, we will use a 24” (610mm) wide blow-off device.  One device will be an inexpensive drilled pipe and the other will be a high-efficiency EXAIR Super Air Knife.  The drilled pipe had (48) 1/16” (1.6mm) diameter holes spaced ½” (13mm) apart.  EXAIR manufactures the model 110024 Super Air Knife with a .002” (.05mm) slot along the entire length.  Both have a blowing width of 24” to cover the conveyor.  The model 110024 has a retail price of $491.00 each.  The cost of the drilled pipe was around $50.00.  What a difference in price!  But, how could EXAIR remain a leader in this industry for over 35 years?

Let’s continue on with the Return on Investment.  The amount of time required to install the Super Air Knife across the conveyor only took a maintenance staff about one hour to mount.  The labor rate that I will use in this example is $75.00 per hour (you can change this to your current labor rate).  The labor cost to install the knife is $75.00.   The Total Project Cost can be calculated as follows: ($491 – $50) + $75.00 = $516.00.  The next part of the equation, Total annual savings, is a bit more in-depth, but the calculation is shown below.

Super Air Knife

EXAIR manufactures engineered products to be efficient and safe.  The Super Air Knife has a 40:1 amplification ratio which means that 40 parts of “free” ambient air is entrained for every 1 part of compressed air.  For comparison, the Super Air Knives are to compressed air systems as LED lightbulbs are to electricity.  In that same way, the drilled pipe would represent an incandescent lightbulb.  The reason for this analogy is because of the amount of energy that the EXAIR Super Air Knives can save.  While LED lightbulbs are a bit more expensive than the incandescent lightbulbs, the value for the Return on Investment is at a higher percentage, or in other words, a short payback period.  On the other hand, the drilled pipe is less expensive to make, but the overall cost for using it in your compressed air system is much higher.  I will explain how below.

To calculate the Total Annual Savings, we will use the same blow-off scenario as above.  The amount of compressed air used by the drilled pipe is around 174 SCFM (4,924 SLPM) at 60 PSIG (4.1 Bar).  The model 110024 Super Air Knife has an air consumption of 55.2 SCFM (1,563 SLPM) at 60 PSIG (4.1 Bar).  At an electrical rate of $0.08 per Kilowatt-hour, we can figure the cost to make compressed air.   Based on 4 SCFM per horsepower of air compressor, the electrical cost is $0.25 per 1000 standard cubic feet, or $0.25/1000SCF.  To calculate an annual savings, let’s use a blow-off operation of 8 hours/day for 250 days a year.   Replacing the drilled pipe with the model 110024 Super Air Knife, it will save you (174 SCFM – 55.2 SCFM) = 121.8 SCFM of compressed air.  To put this into a monetary value, the annual savings will be 121.8 SCFM *$0.25/1000SCF * 60 Min/hr * 8hr/day * 250 day/yr = $3,654 per year.

With the Total Annual Cost and the Project Cost known, we can insert these values into Equation 1 to calculate the ROI:

ROI = (Total annual savings – Total Project Cost) / Project Cost * 100

ROI = ($3,654 – $516.00) / $516.00 * 100

ROI = 608%

With a percentage value that high, we are looking at a payback period of only 52 days.  You may look at the initial cost and be discouraged; but in a little over a month, the model 110024 will have paid for itself.  And after using it for one year, it will save your company $3,654.00.  Some things that may be overlooked are safety issues.  With some inexpensive blow-off devices, the noise levels are over the OSHA limits.  The drilled pipe had a noise level of 91 dBA while the Super Air Knife only had a noise level of 65 dBA.

In my experience, a loud blowing noise from your equipment is generally coming from an inefficient and safety-concerned product.  With these “cheap” ways to blow compressed air, it will cost your company a lot of money to use as shown in the example above.  If you would like to team up with EXAIR to set up ways to increase savings, improve productivity, and promote safety, an Application Engineer can help you to get started.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Which Air Nozzle Is Right For Me?

Well, the obvious answer is, of course, an engineered air nozzle…you’re likely aware of this, or you wouldn’t be reading posts on the EXAIR Corporation blog.  We have no issue with narrowing that down a bit, and saying that the answer is an EXAIR air nozzle.  I bet you knew that was coming as well.  So let’s assume that, because of the cost of compressed air, the potential hazards of its unregulated discharge, and the flat-out racket it can make (unless you do something about it,) you’re looking for something efficient, safe, and quiet.

Now that we’re on the same page, let’s unpack that question.  The nature of the application will let us know the airflow pattern & characteristics (mainly flow & force) that we need.

For example, if you need just a pinpoint of airflow, our Atto Super Air Nozzle blows a 1/2″ diameter pattern at a distance of 3″.  Get a little closer than that, and it’s as tight as you want it to be.  Now, it’s only generating a force of 2oz (at 12″ away) but keep in mind that’s all concentrated in a small fraction of an inch diameter.  Which is plenty for most applications that need that precise of an airflow.

Atto Super Air Nozzle

If you DO need a little more flow & force, our Pico and Nano Super Air Nozzles offer incremental increases in performance.  The pattern starts to widen out, but that’s a function of the increased flow expanding in to atmospheric pressure…it has to go somewhere, you know.  But, again, the closer you get, the more focused the flow is to the centerline of the nozzle.

On the other end of the spectrum are EXAIR’s High Force Air Nozzles.  These are particularly useful for stubborn blowoff applications – a foundry blowing slag off hot strip as it cools, for example.  Our largest of these, a 1-1/4 NPT model, generates 23 lbs of force…that’s over 25 times the power of our standard Super Air Nozzle.

 

With 23 lbs of hard hitting force, this 1-1/4 NPT Super Air Nozzle is perfect for the most extreme blow off and cleaning jobs.

Speaking of the standard Super Air Nozzle, it’s the most popular answer to the Big Question.  It’s suitable for a wide range of blowoff, drying, and cooling applications, like the kinds of jobs an awful lot of folks use open end blowoff devices on.  Open ended tubes blow out a great amount of air, but they’re wasteful and noisy, and OSHA says you can’t use them unless you regulate the pressure to 30psig…where they’re not even going to be all that effective.

Choose from (top left to bottom right) 316SS, Zinc Aluminum, or PEEK Thermoplastic…whatever you need to stand up to the rigors of your environment.

If you’ve got a 1/4″ copper tube, for example, it’ll use 33 SCFM when supplied with compressed air at 80psig.  It’ll for sure get the job done (albeit expensively, when you think of all that compressed air consumption,) but it’ll be loud (likely well over 100 dBA) and again, OSHA says you can’t use it at that pressure.  So, you can dial it down to 30psig, where it’ll be marginally effective, but it’s still going to use more air than the Model 1100 1/4 NPT Super Air Nozzle does at 80psig supply pressure.  The hard hitting force of the Model 1100, under those conditions, will make all the difference in the world.  As will its sound level of only 74 dBA.  Not to mention, it’s fully compliant with OSHA 1910.242(b).  Oh…and you can even install it directly on the end of your existing tube with a simple compression fitting.

One of our customers installed Model 1100 Super Air Nozzles on all their lathe blowoff copper tubes, and saved almost $900 a year in compressed air costs.

We’ve also got engineered Air Nozzles smaller than the 1100 (all the way down to the aforementioned Atto Super Air Nozzle) and a good selection of larger ones, including Cluster Air Nozzles that hold tighter airflow patterns than similar performing single Super Air Nozzles.  They’re available in materials ranging from Zinc-Aluminum alloy, bare aluminum, brass, 303SS, 316SS, or PEEK thermoplastic polymer to meet the requirements of most any area of installation, no matter how typical or aggressive.

If you have an loud, wasteful, and likely unsafe blowoff, you owe it to yourself and everyone else who has to put up with it to consider a better solution.  Call me; let’s talk.

Russ Bowman
Application Engineer
EXAIR Corporation
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