Air Knives & What You Don’t Normally See

In the day-to-day life of an Application Engineer here at EXAIR, you get to speak about every single one of our engineered solutions, and sometimes you find yourself getting into discussions about items we don’t make and even some new ways to use products that we haven’t showcased. The run-of-the-mill applications for Super Air Knives are cleaning, cooling, or drying materials off, whether it be stationary and the knife moves or if the product is moving and proceeding through the sheet of air produced by the Super Air Knife. No matter which of these applications, the one thing in common is that they are all supplying the Super Air Knife with compressed air. Okay, some use compressed nitrogen, and they are few and far between. There is another motive material that can be used that isn’t a gas and that doesn’t get discussed too much; water!

Just last week, I was speaking with a customer who was struggling with a point of their application where they needed a waterfall of liquid and didn’t want to use liquid atomizing spray nozzles because they were required to have a continuous “sheet” of liquid in order to have optimal performance. They knew the Super Air Knives worked great on their drying section, so they called and asked how they do with water?

Well, the answer is they do pretty well considering they were designed for compressed air, which is compressed and expands rapidly to atmospheric conditions and helps with our performance, while water cannot be compressed, only pressurized. The good news is we do have some data and pictures from tests on something like this. So I pulled out the information I had and shared it with the customer.

As you can see, increasing the gap a little bit and keeping a good supply lends to a nice stream at lower operating pressures, not even full city line water pressure. While we tested numerous gaps and inlet pressures, some of the best flows were from 17 psig inlet pressure and with a .004″ and up to a .012″ gap. The customer in this case was happy enough that they decided to get a knife and shim sets in to test under our 30-day guarantee, and it turns out they were getting the performance they needed with the .004″ thick gap and about 15 psig inlet pressure.

While the point of this was to showcase how well a product works with something other than compressed air that it wasn’t designed around, I hope to also emphasize that we truly have tested a vast number of variables with most of our products. If we don’t have test data on what you are thinking, as long as it is safe, and we have the ability, we will conduct a test. If we think the best thing to do is for you to get it in and test it, then we will back up our stock product offering with a 30-day guarantee. If we know it isn’t going to be a good fit, we will also tell you that.

If you want to discuss anything revolving around the point of use using compressed air or pressurized liquid being used in a process within your facility, please contact an Application Engineer today!

Brian Farno
Application Engineer

Will Water Move Through EXAIR Air Knives and Air Wipes? (Images included)

Today, I would like to discuss a question that comes up time and time again over the years.  “What happens when I put water through a Super Air Knife?” That raised another question from myself of what about a Super Air Wipe?

The answer is quite simple, it will come out, just not as good as compressed air does.   The engineering and design for Super Air Knives were all based around compressed air use.  With any good product of course comes the question in time, how else can we use this?   A number of applications for the Super Air Knife is blowing moisture off a part that has been applied through a series of wash/rinse nozzles.  What if the knife could apply the liquid and then a second knife could remove the liquid.  Below are some images from testing that was done on a Stainless Steel Super Air Knife at various gap sizes and various pressures.    The “best” performance visually was from operating the air knife with .004″ gap and approximately  a 17 PSIG inlet pressure (this is for a 12″ Super Air Knife).

Water flowing through a 12" Stainless Steel Super Air Knife
Water flowing through a 12″ Stainless Steel Super Air Knife

As you can see in the photos, the water does flow fairly well immediately out of the knife, and becomes more turbulent as it gets further away from the knife.   The stream actually begins to break up and thus the effective distance of the knife may be reduced when using it to flow liquids.   This is not going to perform like a pressure washer, the maximum distance for the stream of liquid before it completely fell off was around 10′ from the discharge point.   If this were to be used to remove loose debris or to cover a part in water to help cool the part the stream would be more than enough to perform.

As noted above the operating pressure was fairly low, and the gap was at a .004″ thickness.  I recently tested a 1″ Stainless Steel Super Air Wipe as well.  The shim gap was once again set to .004″ thick to permit a better flow and a low pressure, approximately 10-12 psig inlet pressure.  As you can see the flow of water is not as smooth as the air flow out of a Super Air Wipe but if a light rinsing process was needed, or a water cooling process, this would work well.

1" Stainless Steel Super Air Wipe w/ Water
1″ Stainless Steel Super Air Wipe w/ Water


So the answer to the main question at hand is yes, a Super Air Knife and Super Air Wipe will both operate with a pressurized liquid source under the correct circumstances.   While they do not operate exactly like they do with compressed air, the results still prove useful in certain applications.

Brian Farno
Application Engineer Manager