We received a call about an application to remove water from the surface of rubber sheets. The reason for the call was because they were using a drilled pipe. It was loud and not removing an adequate amount of water. (Reference the photo below). EXAIR comes across this quite a bit. A drilled pipe has turbulent flow which causes loud noises, ineffective blowing, and wastes compressed air. With our Super Air Knives, we can create a stronger force as the airstream is laminar. With the laminar flow, they are also quiet. For example, our Super Air Knives have a noise level of only 71 dBA at 80 PSIG. Also, since all of the air volume is traveling in the same direction, the liquid water will flow away from the airstream.
The rubber sheet was 1200 mm wide, and I recommended a model 110248 48” (1,219 mm) Aluminum Super Air Knife Kit. The kit includes the Super Air Knife, a filter, a regulator, and a shim set. The filter removes the debris and water from the compressed air line to optimize the performance of the air knife as well as keep your product clean. The regulator is used to make the “fine” adjustment to the blowing force while the shim set is used as the “coarse” adjustment. Now they could reduce the inlet pressure to not overuse the compressed air and to get the proper removal of water from the sheet. And with the 40:1 amplification ratio, the Super Air Knife will bring in 40 parts of ambient air to every part of compressed air, saving them a lot of money.
After installation, the customer contacted me again and mentioned that they thought the performance would be better. They sent me a photo of the setup. (Reference below). I noticed that they mounted the Super Air Knife as they did with the drilled pipe. They had the Super Air Knife blowing perpendicular to the surface, which is not optimal. I sent them the following setup points to help.
Contact time is effectively the space in which the target is located within the airstream. The longer the contact time, the more effective the Air Knife is at removing contamination (water in this case). When customers install EXAIR Super Air Knives, they can have a tendency to install them incorrectly, reducing their performance capability. In the photo above, you can see that the Super Air Knife is at 90 degrees to the surface of target travel, reducing contact time to a minimal value. The following suggestions are how we would advise customers to mount our equipment to get the most effectiveness within their operation.
- 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. This will create an air flow angle at about 45 degrees. This angle will increase the contact area and contact time, which is very beneficial for removing debris and/or heat. (Note: this would indicate that the cap is mounted nearest to the surface being treated.
- Distance — For optimum performance, the Air Knife should be between 3” (76mm) to 12” (305mm) from the target. If the Super Air Knife is too close, the amplification ratio cannot propagate and the force is reduced. If you are too far from the target surface, the air pattern will start to change, causing the velocity and force to decrease, resulting in less effective blowing action.
- Counter-Flow — The direction of the air flow should be blowing against the target surface movement, in what we term a counter-flow direction. Example: if the target parts are moving from left to right on a conveyor, 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 into the direction it came from, 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, this customer was able to maximize the performance of their EXAIR Super Air Knife. The sheets were dried through improved technology, efficiency, and correct positioning. If you are still using antiquated products for blow-off, and you wish to improve your process with quiet, safe, and efficient products, an Application Engineer at EXAIR can assist you.
John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb