Right on schedule with the change in temperature as summer turns to fall, I woke up with a scratchy throat, runny nose, and a bit of fatigue this morning. I weighed my options for relief in the medicine cabinet: pain reliever/fever reducers, over-the-counter cold & flu medication that add cough suppressants, expectorants, and decongestants to the mix, homeopathic remedies with zinc, echinacea, all natural immune boosters, and a jar of honey for my tea or bourbon, depending on the time of day…and my mood. If my symptoms worsen, I can get tested for the flu or COVID, and may be prescribed antiviral medication. In any case, rest and hydration will likely be important factors in my recovery.
Much like my medicine cabinet, the Air Knives section of the EXAIR catalog has a selection of remedies for problems that can be addressed by a curtain of air. If the curtain of air needed is 36″ or less, we can consider any of the three styles of Air Knife we make: Super, Standard, or Full Flow. If it has to be more than that, the Full Flow Air Knives are out (36″ is their max length) but Standard Air Knives come in lengths up to 48″. Super Air Knives give us the most range here; they come in lengths up to 108″, and can actually be coupled together to provide uninterrupted curtains of flow in whatever length is needed.
Standard and Full Flow Air Knives come in aluminum or 303SS. Aluminum is lightweight and suitable for general purpose applications where high heat and corrosive elements are not a factor. Aluminum Air Knives are rated to 180°F. Type 303 Stainless Steel is suitable for mildly corrosive environments, and is rated to 800°F ambient temperatures.
Super Air Knives are available in aluminum and 303SS, as well as 316SS and PVDF. Type 316 Stainless Steel is stronger and more corrosion resistant than Type 303, and offers superior resistance to certain pitting, which makes it the best choice for food, pharmaceutical, and surgical product manufacturers. PVDF (polyvinylidene fluoride) Super Air Knives have Hastelloy C276 hardware and PTFE Shims. They provide superior corrosion resistance in more aggressive situations than Stainless Steel can like, like in electroplating, solar cell and lithium ion battery manufacturing, strong acid & caustic chemical handling, etc.
The first Air Knife developed by EXAIR was the Standard Air Knife (formerly known as the EXAIR Knife) and are still quiet and efficient alternatives to drilled pipes, manifolds with open-ended blowing nozzles, and blower-powered air knives. They use a Coanda profile (more on that in a minute) which causes the airflow to turn 90° from where it exits the linear nozzle formed by the shim between the cap & body. This primary air stream entrains surrounding air from the environment, resulting in a total developed airflow that’s 30 time greater than the compressed air consumption of the Air Knife. This entrainment creates a low velocity boundary layer, which reduces the sound level, but there still is some wind shear produced along the Coanda profile.
Because of the end ports in the relatively small profile of the body, there’s 1/2″ on each end where there’s no flow. Since we identify them by the length of the air curtain they generate, Standard Air Knives are physically 1″ longer than their published length (a Model 2012 12″ Aluminum Standard Air Knife has an overall length of 13″, a Model 2018SS 18″ 303SS Standard Air Knife is actually 19″ long, etc.) Full Flow Air Knives use a Coanda profile as well, but they have rear ports, so there’s full flow (as advertised) from end to end. Here’s more on how the Standard and Full Flow Air Knives work:
The latest, and greatest generation of engineered Air Knife in EXAIR’s arsenal is the Super Air Knife. As detailed above, they offer the most choices in length & materials. They’re also the most efficient, and quietest. Because the airflow exits straight from the linear nozzle formed by the shim gap between the body & cap, with no wind shear, the low velocity boundary layer produced by the entrainment of surrounding air means the sound level (with an 80psig inlet pressure) is a remarkably low 69dBA at a distance of three feet. Any style (Standard, Full Flow, or Super) Air Knife will perform just fine in just about any application that requires a curtain of airflow. If noise level, and/or operating cost, are on your mind, though, the Super Air Knife is certainly worth considering. With just a few details about the application, we can calculate the difference in operating cost for all three models of a given length, and provide you with the ROI (return on investment) for the Super Air Knife. If you’d like to find out more, give me a call.
Russ Bowman, CCASS
Application Engineer
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