How to Position and Mount your Air Knife

Today I wanted to start a series about installing EXAIR products, so I figured starting with our selection of hard hitting air knives was the best place to start!

We talk to users, and potential users all the time about how to install an Air Knives. And the answer is…it depends. But, it’s almost always quick and easy.

The EXAIR Super Air Knife. There are a few ways to hold one in place:
*There are 1/4″-20 tapped holes, every 2″ along the bottom. These can be used to bolt it to just about anything you want to bolt it to.
*The 1/4″-20 cap screws can also be replaced with fasteners of sufficient length to allow use of a bracket. In fact, this is what we use for…
*The Universal Air Knife Mounting System – it’s a quick and convenient way to support an Air Knife. It’s especially beneficial to precisely position the Super Air Knife for optimum performance.
*Last but not least, Super Air Knives 24″ and longer need to be plumbed to both ends for proper performance. If you hard pipe it in, it’ll be as well supported as the piping.

EXAIR Super Air Knives are easy to install, no matter what the length, or application.
EXAIR Super Air Knives are easy to install, no matter what the length, or application.

The best way to mount a Super Air Knife in a blowing application so that you achieve the maximum force, time in contact and of course, effectiveness.

There is a term we use, “counter-flow”, to describe the opposing travel of target material/conveyor (red arrow) and the airflow coming from an Air Knife (blue arrow). By having opposing flows, the Air Knife is able to blow the debris, contamination, water or other fluid back into the direction from which it came. Sometimes a catch pan can be used to collect and re-use the fluid.

Air Knife Aimed in the opposite direction of the belts travel. (Counter Flow)

Finally, in the photo above, note that the Super Air Knife is mounted up-side down. We generally recommend this kind of orientation with the cap of the Super Air Knife being closest to the material being blown off. This allows you to get the air knife a bit lower and closer to the target material. The lower the angle, the better. This allows for a longer time in contact between the Super Air Knife and the target material. When the target material spends more time in the high velocity flow, the more likely you are able to impart the desired effect whether that be drying, cooling, blowoff or static elimination. To find a good mounting angle to start, I recommend customers use the front, angled edge of the Super Air Knife cap as a guide for what part of the Super Air Knife to keep parallel to the moving surface. This is a great reference from which blowing angle can be optimized.

Poor Position Good Position

If you’d like to find out more about how easy it is to install an EXAIR Compressed Air Product, give me a call.

Jordan Shouse
Application Engineer

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Super Air Knife to the Rescue in Machining

Home-made blow-off device

As machined parts require tighter tolerances, the surface has to stay clear during turning operations.  A customer that had a CNC machine needed to make a metal tube with a specific diameter.  The metal tube was 17 ½” (445mm) long.  They made their own blow-off “tree” to keep the surface clean from shavings.  They used five open ports to blow at the part surface (reference photo above).  When they started using their home-made device, they were not getting a consistent cleaning during operation.  They wanted to speak to an expert in this type of area, and they contacted EXAIR to see if we could improve their process.

With a series of open nozzles, it is very difficult to get a consistent force along a linear line.  The air becomes very turbulent, which has changing directions of air flow.  It creates a hazardous noise exposure to the operators, and it also wastes compressed air which costs the company a large amount of money to use.  With laminar air, the path flows in the same direction.  This creates a very consistent force with less noise.  Since air is invisible, I like to use water to show the difference.  The photo below shows turbulent and laminar flows. 

Turbulent to Laminar Water

For linear blow-offs, EXAIR offers a wide range of Super Air Knives.  They give a laminar flow pattern along the entire length.  We have stocked lengths from 3” (76mm) up to 108” (2.74 meters) in different materials.  A benefit of the Super Air Knife is the high amplification ratio of 40:1.  This means that for every 1 part of compressed air, it will entrain 40 parts of ambient air.  So, they are very efficient, safe, and effective.  For the application above, I recommended the model 110218 18” Super Air Knife Kit to cover the length of the metal tube.  It has an 18” (457mm) wide air stream that is very powerful to remove chips during the turning operation.  The kit includes a filter, regulator, and shim set.  The filter will remove contaminants from the compressed air system to keep the surface clean.  The shim set and regulator provide the ability to adjust the air to the ideal force level to remove the debris from the surface of the tube. 

Super Air Knife Kits include a Shim Set, Filter Separator, and Pressure Regulator.

One of the biggest attributes that the EXAIR Super Air Knives can offer is that they use much less compressed air than a series of open nozzles. With the engineered design, it can entrain large amounts of ambient air which means that less compressed air is required.  For the nozzle tree, it was using 105 SCFM of air at 80 PSIG.  The model 110218 only requires 52.2 SCFM at 80 PSIG. That is a difference of 52.8 SCFM; half the amount of compressed air as the home-made nozzles. 

Once they installed the Super Air Knife, the first thing that they noticed was the reduction of noise. The model 110218 Super Air Knife only has a noise level of 69 dBA at 80 PSIG, compared to a noise level of an open port which was over 100 dBA. By replacing the nozzle tree with the Super Air Knife, this company…

1. reduced air consumption

2. saved money

3. reduced noise levels

4. increased the effective blowing force

If you find yourself using a home-made blow-off device, you can be creating a hazardous, costly, ineffective method to “do a job”.  Since precision was needed for the company above, they were delighted to contact an expert in this area.  You can also improve your blow-off device by contacting an Application Engineer at EXAIR for assistance.  We would be glad to help. 

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

Laminar Flow vs Turbulent Flow for Compressed Air Blowoff

You’ll often hear us refer to laminar vs turbulent flow when discussing our blowoff products. In any blowoff process or application, laminar airflow is going to be much more effective at cooling or drying than the turbulent airflow delivered by commonly found homemade blowoff devices or cheap knockoffs. To read more about the math behind it, check out my colleague John Ball’s previous post here.

Allow me to use the Super Air Knife to help illustrate the benefit of laminar vs turbulent flow. When a wide, even, laminar flow is necessary there isn’t a better option available on the market than EXAIR’s Super Air Knife. What really sets EXAIR’s Super Air Knife above the competition is the ability to maintain a consistent laminar flow across the full length of the knife compared to similar compressed air operated knives. This is even more evident when compared against blower operated knives or fans. A fan “slaps” the air, resulting in a turbulent airflow where the airflow particles are irregular and will interfere with each other. A laminar airflow, by contrast, will maintain smooth paths that will never interfere with one another.

visual representation of a turbulent flow on top and laminar flow on bottom

The effectiveness of a laminar airflow vs turbulent airflow is particularly evident in the case of a cooling application for automotive computers coming out of a wave soldering machine. The chart below shows the time to cool computers to ambient temperatures for an automotive electronics manufacturer. They used a total of (32) 6” axial fans, (16) across the top and (16) across the bottom as the computers traveled along a conveyor. The computers needed to be cooled down before they could begin the testing process. By replacing the fans with just (3) Model 110012 Super Air Knives at a pressure of just 40 psig, the computers were cooled from 194°F down to 81° in just 90 seconds. The fans, even after 300 seconds still couldn’t remove enough heat to allow them to test.

While the fans no doubt made for large volume air movement, the laminar flow of the Super Air Knife resulted in a much faster heat transfer rate.

Utilizing a laminar airflow is also critical when the airflow is being used to carry static eliminating ions further to the surface. Static charges can be both positive or negative. In order to eliminate them, we need to deliver an ion of the opposite charge to neutralize it. Since opposite charges attract, having a product that produces a laminar airflow to carry the ions makes the net effect much more effective. As you can see from the graphic above showing a turbulent airflow pattern vs a laminar one, a turbulent airflow is going to cause these ions to come into contact with one another. This neutralizes them before they’re even delivered to the surface needing to be treated. With a product such as the Super Ion Air Knife, we’re using a laminar airflow pattern to deliver the positive and negative ions. Since the flow is laminar, the total quantity of ions that we’re able to deliver to the surface of the material is greater. This allows the charge to be neutralized quickly, rather than having to sit and “dwell” under the ionized airflow.

With lengths from 3”-108” and (4) four different materials all available from stock, EXAIR has the right Super Air Knife for your application. In addition to shipping from stock, it’ll also come backed up by our unconditional 30-day guarantee. Test one out for yourself to see just how effective the Super Air Knife is on a wide variety of cooling, cleaning, or drying applications.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

Understanding Air Entrainment or Amplification Ratios and Air Knives

Super Air Knife has 40:1 Amplification Ratio, entrainment is illustrated as the curved blue arrows.

EXAIR’s Super Air Knife is the top performer among our engineered air knives and it dramatically reduces compressed air usage and noise when compared to other blow-off systems. The Super Air Knife delivers a uniform sheet of laminar airflow across the entire length of the air knife. Even at high pressure of 80 PSIG (5.5 BAR), the sound level is surprisingly quiet at 69 dBA for most applications.

One feature of the Super Air Knife is its Amplification Ratio, or the ratio of ambient air to compressed air within the forceful blast of air from the Super Air Knife. The design of the Super Air Knife entrains ambient air at an amplification ratio of 40:1 (ambient air to compressed air). Entrainment is defined in the simplest of terms as: to draw in and transport (something, such as solid particles or gas) by the flow of a fluid. The Super Air Knife design produces two low pressure areas where surrounding air is pulled into the primary compressed air stream and is delivered to your target. EXAIR’s Intelligent Compressed Air® products use the principle of entrainment to give you more air volume than just the compressed air being introduced from your air compressor.  This will maximize the force value for your application with the minimum amount of compressed air. Any pipe, manifold, or fitting can be modified to blow compressed air, however, these homemade blow offs will be very noisy and perform poorly when it comes to air entrainment, or amplification ratios. In contrast EXAIR’s intelligent compressed air solutions are engineered to be very quiet and use conservative amount’s of compressed air while maximizing the output volume through entrainment. 

Furthermore, the table below demonstrates the differences between blow-off systems and the efficiency of EXAIR’s Super Air Knife. You can see that the Super Air Knife outperforms all or most other options when comparing purchase price, sound level, maintenance, horsepower required and electrical costs.

The use of EXAIR’s Super Air knife not only save air consumption but you can notice the lower decibel rating which meets or exceeds OSHA Standard 29 CFR-1910.95(a) for maximum allowable noise exposure. If you have questions or need help with EXAIR’s Super Air Knife or any of our Intelligent Compressed Air Products please contact us and let us help you.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: Twitter: @EXAIR_EK