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.
- 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.
- 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.
- 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
