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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Many Air Knife Materials and Shim Options to Suit Your Application

The EXAIR Super Air Knives are used in many applications ranging from part drying, to web cleaning, to conveyor blowoff, and many other uses. For most processes, the aluminum models provide the performance required and withstand the environmental conditions present.

Ambient temperature limits for the aluminum models is 180°F (82°C). EXAIR also offers the air knives in types 303 and 316 Stainless Steel, which increase the temperature limit to 800°F (427°C) and provides a great degree of corrosion resistance. For the harshest, most corrosive environments, an air knife constructed of Polyvinylidene Fluoride (PVDF) with a temperature limit to 275°F (135°C) is available.

Super Air Knives
Aluminum, Stainless Steel and PVDF Super Air Knives

But what can we do about those applications where the increased corrosion resistance isn’t needed and the temperatures do not approach anywhere near to 800°F (427°C)?

The solution to this situation is an aluminum air knife with a custom stainless steel shim. The aluminum material is rated to 400°F (204°C) and the shim is good to 800°F (427°C) so this knife can be used in those hotter environments up to 400°F (204°C). This option helps to keep the cost of the knife low, by utilizing the lower cost aluminum for the body and cap.

The table below details the materials of construction options for the Super Air Knife – a wide array of material offerings to suit even the hottest, harshest conditions.

Air Knife Temperature Table

We recommend consulting with an Application Engineer to review the application, process, and environmental conditions, and we can present best options.

And don’t forget, the shims can be further customized for special blowoff requirements. See the blog that my colleague, Russ Bowman, posted here.

If you have questions about Super Air Knives or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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Video Blog : Changing Shims In An Air Wipe

EXAIR’s Air Wipes provide a 360° uniform, high velocity airflow that adheres to the outside surface of a round part, such as pipe, hose, cable, etc., as it passes through the throat or center of the device.

In this short video, we show how to change the shim inside of an Air Wipe, letting you achieve an increase or decrease in outlet flow and force while maintaining the same operating pressure.

If you have any questions, please contact an Application Engineer at 800-903-9247.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

 

1″ And 2″ Flat Super Air Nozzles Overview

In most “general” blowoff applications, the conical airflow pattern from a standard round shaped nozzle is ideal when trying to remove dust or light debris from the surface of a part or material. However in certain applications, a focused, laminar flow of air is required to produce the desired result, such as cleaning peanut butter from a fill nozzle or ejecting parts in a stamping operation.

EXAIR manufactures our 1″ Flat and 2″ Flat Super Air Nozzles, which provide a 1″ and 2″ (respectively) wide, forceful stream of high velocity, laminar airflow while consuming only a small amount of compressed air. Both the 1″ and the 2″ are available in Zinc Aluminum alloy, rated up to 250°F (121°C), or 316 Stainless Steel construction, rated up to 1,000°F (538°C)

1″ Flat Super Air Nozzle

2″ Flat Super Air Nozzle

Their unique design incorporates a specially designed, replaceable shim, to maintain a critical gap between the cap and body, resulting in the focused airflow. They are shipped from stock with a .015″ shim installed.

Using the optional shim kit, the shims can be changed out to .005”, .010” or .020”, which allow you to increase or decrease the force and flow by either opening or closing the gap, providing more or less force and flow to meet the demand of the application.

(Here’s a short video showing how easy it is to change out the shims)

We also offer our High Power versions of these nozzles which feature a thicker shim installed (0.025″) for applications requiring higher thrust and velocity.

If you have an application you would like to discuss or to see how the Flat Super Air Nozzles might improve your process, give me a call, I’d be happy to help.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN