Tag: time in contact

Contact Time: How to get the most from your EXAIR products

Published on by John BallLeave a comment
Poor Position vs Good Position

You may have heard us speak about contact time.  I would like to cover what that means in this blog.  Contact time refers to the amount of time that a target part is in the high-velocity airstream produced by an EXAIR blowing product.  The longer the contact time, the more effective the blow-off or cooling effect. Optimizing the mounting position of the EXAIR solution relative to the target makes a huge difference in effectiveness.  When our customers typically purchase EXAIR products, they have a tendency to improperly install them, reducing their performance capabilities.  Let’s look at a Super Air Knife.  In the photo above, you can see the relationship between a perpendicular and a recommended setup angle.  I have some recommendations that can help to increase the contact time and improve the performance. 

Super Air Knife Chamfer
  1. Angle – EXAIR machines a chamfer on the cap of the Super Air Knife as a starting point.  You want to have the chamfer parallel with the target line of movement.  This will create an air flow angle of about 45 degrees relative to the target.  This angle will increase the contact area and contact time, which is very beneficial for removing debris and/or heat.  Depending on the speed and height of the target, this can be altered for further refinement.
  2. Distance – For optimum performance, the Air Knife should be between 3″ (76 mm) to 12″ (305 mm) from the target.  If you are too close, the amplification ratio is sacrificed, and the force is reduced.  If you are too far, the air pattern will start to change, causing the velocity and force to decrease. 
  3. Counter-Flow – The direction of the air flow should be blowing in the direction opposite the target movement.  As an example, if the parts are moving from left to right, you want the Air Knife to blow from right to left.  This will allow the contamination to be blown back away from the cleaned surfaces, and it will increase the impact force to remove contamination, i.e. a head-on collision vs. a rear-end collision.

With these few simple steps, you will begin to maximize the performance and effectiveness of your EXAIR blowing solution.  Some accessories can help with the setup, like Swivel Fittings and Stay Set Hoses for the nozzles and the Universal Mounting Kit for the Air Knives.  You can modify the impact angle to best suit complex parts and systems.  If you need any help to get the most out of our products, you can contact an Application Engineer at EXAIR.  We will be happy to hear from you.     

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

How to Position and Mount your Air Knife

Published on by Jordan T ShouseLeave a comment

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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Mounting Options for EXAIR’s Super Air Knife

Published on by Tyler DanielLeave a comment

 

Super Air Knife installed using the Universal Air Knife Mounting system.

The key towards a successful Super Air Knife  application is making sure it’s installed properly. Using the chart on the installation & maintenance guide to ensure your plumbing is properly sized is the first step. This ensures that an adequate volume of compressed air is able to reach the knife, without causing an unnecessary pressure drop.

super air knife pipe size

Once you’ve planned out the distribution of compressed air to the Super Air Knife you must consider how to mount it in your application. Across the bottom of the knife are ¼-20 tapped holes spaced out evenly every 2” along the knife. A 30” Model 110030 will have (15) holes, a 60” 110060 (30), and so on. These holes are tapped through to allow you to mount the knife to best suit the application.

If you’d rather have a more “out of the box” solution, EXAIR offers our Universal Mounting System. It gives you the ability to mount onto a conveyor rail or machine frame and provide precise positioning for all of EXAIR’s Super Air Knives, Standard Air Knives, Full-Flow Air Knives, as well as the Standard and Super Ion Air Knives. Each system comes with (2) 1/2-13 x 5” long bolts, 2’ long stainless steel rod, mounting hardware, angle bracket, and adjustable swivel clamps. Check out the video below for a demonstration of the adjustability you can achieve with the Model 9060 Universal Mounting System.

Another critical factor to consider is the mounting position of the knife. If the material is moving along a conveyor, the knife should be positioned as closely as possible with the airflow oriented against the direction of travel of the material. By doing so, we increase the amount of time that the material is in contact with the airflow. We call this term counter-flow. Maximizing the time in contact with the laminar airflow from the Super Air Knife gives us the best chance at a successful result. Whether we’re talking about cooling, drying, or cleaning, the longer that the material is in contact with the laminar airflow the better the results will be.

air knife counter flow

In this photo, the Super Air Knife is positioned upside down at an angle above a conveyor belt, against the direction of travel. We recommend installing the Super Air Knife in this orientation as it allows the airflow to get closest to the material being blown off. They’ve used their own brackets to allow the knife to be adjusted when blowing residual dust off of a conveyor for a mining application. The dust on the belt would build up over time and was difficult to remove. By installing a Super Air Knife, they’re able to continuously remove the dust from the conveyor belt before it becomes a problem.

If you have an application that would be better served with one of EXAIR’s Super Air Knives, give us a call. An Application Engineer is ready to assist you in selecting the proper material, length, and mounting method.

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