Super Air Knife Shims & How They Affect Performance

To Shim or not to Shim… The Super Air Knife is a fabulous piece of equipment. Between the quiet laminar flow of air, and the intense 40 to 1 ratio of entraining the ambient air around it, this Knife is definitely cutting edge (pun intended). As you look at the front edge of the Super Air Knife, or as we call it “the place where the magic happens“, you will see that there is a very small slit or gap where the air flows. The gap in that metal is caused by the shim that is inside the Super Air Knife. We control the size of this gap with shims. Hark, what light through yonder air gap breaks?… Sorry, I get carried away sometimes.

The shims in the Aluminum Super Air Knives are made of a polyester plastic, the PVDF Super Air Knife Shims are made of PTFE, and I will give you two guesses what the Stainless Steel Super Air Knife Shims are made of, you guessed it… Flubber… Just kidding, they are stainless steel of course.

All of our Super Air Knives, regardless of material, ship standard with a 2 thou shim installed. 2 thou you ask? I did too. That is 2 thousandths of an inch, or 0.002″. This is the height of the gap where the Air Flows out. When you are looking at all of our published numbers in the catalogue or on the website, all of those performance numbers are based on this 2 thou shim. Here is the Super Air Knife performance table:

Pic by Conmongt, licensed by Pixabay

So, what if you need more or less air than what’s on this list? We can adjust the gap. We can add shims up to @ 0.01″ to increase the flow. Or we can go down to 0.001″ (1 thou). This poses the question of, what happens to performance? The good news with the shims is that the Air Consumption is a direct linear proportion to this performance table, and the force is very close to the same. So if you double to a 4 thou shim, you double the air consumption and force. Velocity and sound level will vary, but I do not have data to what degree.

As we size these, generally see people wanting more air, larger gaps (more shims), But conversely, we can decrease the air flow down to a 1 thou shim (1/2 of the published values above). Technically we can go smaller than 1 thou, but there is a limit to where a hole is no longer a hole. Here is a breakdown of our stock shims, with colors and sizes for the Super Air Knives:

The Super Air Knives are in a class of their own. As long as you feed the Super Air Knives enough air (SCFM) you can run them at most any psig to retrieve the desired air flow for you application. As an added means of flexibility, you can change the gap size with shims. I have put in a request to change the name of these to Super Flexible Air Knives, but I’m not holding my breath.

Public Domain Picture Licensed by Pixabay

One more thing about Shims. We can customize your shims!! Now I am not talking about putting your logo on them (but money talks!!), but we can customize your length. Let me give you an example. Let’s say that you need 58″ of airflow, no more no less. Our standard length Super Air Knives are 54″ and 60″. We can make you a custom knife, which is a great option, but for 1 or 2, this is probably not very cost-effective. But we can make you a custom shim. We can have the knife only push 58″ of air with a shim blocking the rest. Furthermore, you can decide if you want 58″ centered on the knife, or all 58″ starting from the left, or right side. It is a very cost-effective way to get a custom flow width.

Please let me know of you have any questions, or would like to discuss any of this further.

Thank you for stopping by,

Brian Wages

Application Engineer

EXAIR Corporation
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Compressed Air Usage in Food & Beverage Industry: Bottle Blowoff with Super Air Knives

When it comes to the usage of compressed air in the food & beverage industry, applications for EXAIR products are abundant. The range of sizes (3″ through 108″) and materials (aluminum, 303SS, 316SS, and PVDF) allow us to handle corrosive, high temperature and chemical environments.

One common process that we’re able to help improve is on bottling or canning lines for a wide variety of different companies in the beverage industry. These processes generally run at a very high speed and need a way to complete the process with as little manual intervention as possible.

I recently helped a customer that was looking for a better solution for their bottle processing line. The company produces bottled water in South America and was dealing with a series of quality issues. After the bottles are filled and sealed, they go through a washing operation to remove any contaminants from the outside of the bottle. Afterwards, they make their way along a conveyor where a label is applied around the outside of the bottle. The bottles aren’t always completely dry by the time they get to the labeling step. Any residual moisture on the outside of the bottle can present a problem where the label doesn’t fully adhere to the bottle.

After complaints from their customer about product being received with labels that were peeling off, they implemented a quality check to ensure that the bottles that weren’t properly labeled were fixed before they were shipped out. While this resolved the problem for their customer, it required an extra step. Not only does this add an entire step to the process, but it requires several additional operators to perform the manual task of removing and replacing faulty labels.

After searching and discovering EXAIR’s Super Air Knife they reached out for assistance. Due to the variability of the bottle sizes, they needed a solution that was easily adjusted based on what product was being run that day. Fortunately, EXAIR offers a Universal Mounting System for our Super Air Knives that’ll allow them to easily position their blowoff as they need.

The solution was to install (2) 110036 36” Super Air Knives with (2) Universal Mounting Systems for each. Any knife 24”-54” will necessitate (2) Universal Mounting Systems, 55”-71” will require (3), 72”-95”, and 96” and over will require (5) to sufficiently support the weight of the knife.

The knives provided a strong blast of air that was able to remove any residual moisture from the exterior of the bottles. This eliminated the need to have a post labeling inspection and the bottles were labeled properly on the first go! Adjustments in between different bottle sizes were made simple with the help of the Universal Mounting System.

SAK pre label blowoff
(2) 110036 Super Air Knives positioned with Universal Mounting System

At EXAIR, we’re all about providing safe, efficient, and reliable solutions to a host of industry related problems. With same day shipment for stock items with an order received by 2:00 ET and a team of highly trained Application Engineers, we’re ready to take your call and get a solution out to you today. Don’t just take my word for it, find out for yourself!

Tyler Daniel, CCASS

Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

So… You went and got yourself a Super Air Knife. Now what?

So you went and got yourself a Super Air Knife and now you need to mount it, and start “cutting”. There are a few things we need to review in order to get these installed and functioning correctly. First, let’s take a moment and make sure that your compressed air system has enough air to run this Super Air Knife at its optimal level. Number 1-9 of the top 10 reasons these do not work are linked to the customers lack of air to the Super Air Knife. Step one of this process is to make sure that you have a pressure gauge at the point of use of your Super Air Knife. Knowing that your plant runs 120 psig throughout the system is not a measurement, there are many things that can inhibit this performance from point A to the point of use… Engineering best practices are to have a pressure gauge at each point of use.

Next, we need to make sure your compressor is large enough. At 80 psig, you will need 2.9 SCFM per INCH of Super Air Knife (see table below). 3rd grade math tells us that a 36″ Super Air Knife will need 104.4 SCFM to run efficiently at 80 psig. When given the correct amount of air, this should feel as if you are driving down the road at 50 MPH and you put your hand out the window. This 50 MPH example is true for any length of air knife, at 80 psig, as long as there is enough SCFM. If your Super Air Knife does not feel this way, it is not getting the air it needs…

Back to the 104.4 SCFM. A general rule of thumb is that 1 HP give us @4 SCFM. So in this example, you will need at least a 27 HP compressor to run this 36″ Super Air Knife, and ONLY this Super Air Knife. When sizing EXAIR products, we have to look at the air pressure, and the air volume. One will not work without the other.

Now as we look at this 27 HP (108 SCFM) of compressed air coming to this 36″ Super Air Knife, we need to address how it is getting to the Super Air Knife. How far away from the air compressor is it? Even though the inlet size on the Super Air Knife is 1/4″ NPT, the line from the compressor needs to be big enough to bring the right amount of air to the Super Air Knife. Right off the bat, I can see that any line smaller than a 3/4″ will not work, regardless of how close it is to the compressor. I can also see that this 3/4″ line will only work if the Super Air Knife is 20′ or less away from the compressor. When you bump the line size to 1″, this will allow you to be up to 100′ away. If you have questions on your line sizes, please feel free to ask us to help.

So now that we are confident you have the right amount of air at the point of use, we are ready to mount this bad boy. Obviously we want to look at the angles and positioning, and something we call counter flow. We generally want the air from the Super Air Knife stay in contact with the surface it is cleaning (blowing, cooling, warming, coating, covering etc…) for the maximum amount of time possible. To accomplish this, we need counter flow as seen in the picture to the right. Basically the air is blowing in the opposite direction that the belt is moving.

The last part to discuss here is the physical practicalities of mounting the Super Air Knife. One option is our handy dandy Universal Air Knife Mounting kit seen here to the left. These are a perfect solution for easy and quick installation. You can simply adjust the angles and tighten. You can eventually add thread lock, or something similar for permanent installation. You may need more than one. We recommend one for Air Knives up to 23″, for those 24″-54″ Air Knives we recommend two, 55″-71″ = three, 72″-95″ = four and 96″-108″ = five of these.

This is not the only way to mount these. There are size 1/4″-20 screws every 2 inches in the Super Air Knives. You can simply remove these screws, and attach any type of brace, or mounting bracket to these holes. If our screws are not long enough to fit your bracket, these are pretty easily found locally.

The Super Air Knives is an amazing tool. It can assist in many ways. If you would like to discuss more about these, or any other EXAIR product, please reach out.

Thank you for stopping by,

Brian Wages

Application Engineer

EXAIR Corporation
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Cover picture by PIRO4D and licensed by Pixabay

Plumb it Right for Full Performance!

Many times when we provide the air consumption of an EXAIR product, we get a response like…. “I’ve got plenty of pressure, we run at around 100 PSIG”. While having the correct pressure available is important, it doesn’t make up for the volume requirement or SCFM (Standard Cubic Feet per Minute) needed to maintain that pressure. We commonly reference trying to supply water to a fire hose with a garden hose, it is the same principle, in regards to compressed air.

When looking to maintain an efficient compressed air system, it’s important that you use properly sized supply lines and fittings to  support the air demand (SCFM) of the point-of-use device. The smaller the ID and the longer the length of air supply line, it becomes more difficult for the air to travel through the system. Undersized supply lines or piping can sometimes be the biggest culprit in a compressed air system as they can lead to severe pressure drops or the loss of pressure from the compressor to the end use product.

Take for example our 18″ Super Air Knife. An 18″ Super Air Knife will consume 52.2 SCFM at 80 PSIG. We recommend using 1/2″ Schedule 40 pipe up to 10′ or 3/4″ pipe up to 50′. The reason you need to increase the pipe size after 10′ of run is that 1/2″ pipe can flow close to 100 SCFM up to 10′ but for a 50′ length it can only flow 42 SCFM. On the other hand, 3/4″ pipe is able to flow 100 SCFM up to 50′ so this will allow you to carry the volume needed to the inlet of the knife, without losing pressure through the line.

Pipe size chart for the Super Air Knife

Another problem area is using restrictive fittings, like quick disconnects. While this may be useful with common everyday pneumatic tools, like an impact wrench or nail gun, they can severely limit the volumetric flow to a device requiring more air , like a longer length air knife.

1/4″ Quick Connect

For example, looking at the above 1/4″ quick disconnect, the ID of the fitting is much smaller than the NPT connection size. In this case, it is measuring close to .192″. If you were using a device like our Super Air Knife that features 1/4″ FNPT inlets, even though you are providing the correct thread size, the small inside diameter of the quick disconnect causes too much of a restriction for the volume (SCFM) required to properly support the knife, resulting in a pressure drop through the line, reducing the overall performance.

If you have any questions about compressed air applications or supply lines, please contact one of our application engineers for assistance.

Jordan Shouse
Application Engineer

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