Tag: counterflow

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

Counter-flow – How to Mount Air Knives for Maximum Effect

Published on by Neal RakerLeave a comment

counter flow
Example: Counter-flow arrangement

As with any tool, there can be a right way and a wrong way to use the tool. In this article I will explain 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 (yellow 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. In the photo above, note that the air knife is oriented to blow from right to left and the parts are travelling on the conveyor belt from left to right. This is a simple example of how we set up counter-flow.

Also, with regard to effective Air Knife mounting strategies; the Super Air Knife in the photo is mounted using our Universal Air Knife Mounting System which allows for maximum flexibility for positioning and stability of the Air Knife once set. The Universal Air Knife Mounting System is another great accessory that you can recommend to clients to make the set up very easy. Of course a suitable compressed air filter and pressure regulator should be used for clean air and adjustability of force in the application.

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.

If you find yourself with an Air Knife application and are unsure about how to proceed with mounting it, the idea explained above is one of the core foundations we utilize for solid Air Knife mounting technique.

Neal Raker, International Sales Manager
 nealraker@exair.com
@EXAIR_NR