Where Can’t I Use An EXAIR Super Air Knife?

Considering the material options available, there are very few places you CAN’T use a Super Air Knife. Most often, we find those to be due to extreme elevated temperature, like this one:

A caller from a glass manufacturing company wanted to replace a drilled pipe in a cooling application. Thing is, glass makers deal with their product in molten form, which is HOT…the ambient temperature that this drilled pipe is exposed to reaches 800°C, or 1,472°F.  Because of the temperature, and corrosive atmospheric elements (SO2 is also present, as if the heat wasn’t bad enough,) they have to replace the drilled pipe every so often, and wanted to explore other solutions.

Now, this was a rare case where a Super Air Knife would not have necessarily offered an improvement over a drilled pipe:

  • The air flow from the drilled pipe is primarily straight from their compressed air system.  Since the Super Air Knife entrains air from the surrounding environment at a rate of 40:1, the resultant flow would be very close to the 800°C ambient temperature…and not as effective at cooling as the much cooler compressed air supply temperature.  It wouldn’t have helped to reduce consumption if it simply didn’t work.
The Super Air Knife takes a supply of compressed air (1), discharges it through a gap that runs the length of the Air Knife (2,) and entrains an enormous amount of “free” air from the surrounding environment (3.)
  • Another great thing about the Super Air Knife is that it’s dramatically quieter than any other method of compressed air blowing.  Of course, if you find yourself in a 800°C sulfur dioxide environment, hearing protection is the least of your concerns.

    When supplied at 80psig, the EXAIR Super Air Knife produces a hard hitting, powerful curtain of air, with a sound level of only 69dBA.
  • EXAIR Super Air Knives (and all of our Intelligent Compressed Air Products) are compliant with OSHA Standard 1910.242(b) which limits the outlet pressure of a compressed air blowing device used for cleaning to 30psi…this protects personnel from high velocity debris and air embolisms.  Again, not a concern in an unoccupied (and uninhabitable) space.

Again, that’s a rare case…a very specific exception to a broadly inclusive rule, in light of the options EXAIR offers.  Consider:

  • Aluminum Super Air Knives are durable, lightweight, and suitable for most any installation in a typical industrial/commercial environment.  They’re good to 180°F (82°C) and are fitted with stainless steel fasteners to eliminate corrosion in damp environments.  The polyester shim can be replaced with a custom stainless steel shim, increasing the temperature rating to 400°F (204°C) if needed.
  • Type 303 Stainless Steel Super Air Knives offer higher tensile strength, and are good to 800°F (427°C.)  They are popular in applications with factors like high heat, corrosive environments, frequent spray down cleaning, outdoor installations, etc.
  • Type 316 Stainless Steel Super Air Knives are often specified in food and pharmaceutical applications, due to their even higher resistance to chemical attack and pitting.  They’re also rated to 800°F (427°C) and have the same high tensile strength as the Type 303 Stainless Steel models.
  • Some situations call for better corrosion resistance than these high grades of austenitic stainless steels – and that’s where EXAIR’s PVDF Super Air Knife comes in.  Fitted with PTFE shims and Hastelloy© C-276 hardware, they are especially well suited for processes involving the harshest of corrosive agents, such as electroplating, solar cell manufacturing, and lithium ion battery production, just to mention a few.  They would, in fact, be ideal for the SOenvironment at the glass factory, if it weren’t for the temperature…they’re rated to 275°F (135°C.)

Performance is identical, regardless of construction materials, and all EXAIR Super Air Knives come in lengths from 3″ to 108″ (except PVDF…those go up to 54″ lengths) and ship quickly from our well maintained inventory.  Aluminum and Stainless Steel models can be coupled together for even longer flow lengths.  Plumbing Kits and Universal Air Knife Mounting Systems make for easy and quick installation, and all Super Air Knife Kits come with an Automatic Drain Filter Separator, a Pressure Regulator, and a Shim Set for reliability, clean air flow, and total performance control.

If you need a reliable, cost effective, safe, quiet, and efficient curtain of air, EXAIR’s Super Air Knives are what you’re looking for.  If you’d like to discuss a particular application and/or product selection, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook

A Glass Company Needed a Vortex Tube to Keep Their Pyrometer Reading Accurately

Cooling with the Vortex Tube
Cooling with the Vortex Tube

A glass company was using a pyrometer to measure the temperature of the glass. As with many instruments, it is important to keep the electronics cool for proper operations.  In this case, they were having issues with the accuracy of the measurement.  They contacted EXAIR for a solution.

With their pyrometer, it was designed with a “cooling” device already. This was basically compressed air that would blow around the instrument.  Because of the surrounding area, the compressed air was heating up to 50 deg. C.  This additional heat would not cool the pyrometer properly, and it was causing unreliable readings.  He gave me the design specifications for cooling, and it was 40 liters per minute of compressed air at a maximum of 25 deg. C.  I told him that we had the perfect solution to keep his instrument cool, and it is the EXAIR Vortex Tube. Vortex Tubes are a low cost, reliable, maintenance-free solution that uses compressed air to power the Vortex Tube to produce cold air as low as -46 deg. C. They thrive in remote locations, high temperature environments, and harsh conditions with little to no worry about maintenance (other than providing a source of clean air). With a range of cooling capacities from 135 BTU/hr to 10,200 BTU/hr, I was sure that we could meet the requirements for proper cooling.

To determine the correct size, I had to look at the temperature drop and the flow requirement. The Vortex Tube would have to decrease the incoming temperature from 50 deg. C to at least 25 deg. C.  This would equate to a minimum temperature drop of 25 deg. C.  With the chart below, I see that we are able to get a 29.7 deg. C temperature drop at a 70% Cold Fraction and 3 bar inlet pressure.  EXAIR Vortex Tubes are very adjustable to get different outlet temperatures by adjusting the inlet pressure and the Cold Fraction.  The Cold Fraction (CF) is the volume of cold air flow that will be coming out the cold end.  By adjusting a screw on the hot end of the Vortex Tube, the cold flow can be change to the desired CF.

Vortex Performance Chart
Vortex Performance Chart

The other requirement was the amount of air flow, 40 SLPM (Standard Liters per Minute).  In comparing the above information to the catalog data at 6.9 bar, we have to consider the difference in absolute pressures. With an atmospheric pressure of 1 bar, the equation looks like this:

VTflow = CAF/CF * (Catalog Pressure + 1 bar)/(Supply Pressure + 1 bar)

VTflow – Catalog Vortex Tube flow

CAF – Cold Air Flow

CF – Cold Fraction

Catalog Pressure – 6.9 bar

Supply Pressure – Chart above

From this equation, we can solve for the required Vortex Tube:

VTflow = 40 SLPM/0.7 * (6.9 bar + 1 bar) / (3 bar + 1 bar) = 112.9 SLPM.

In looking at the catalog information, this would equate to our model 3204 Vortex Tube which uses 113 SLPM of compressed air at 6.9 bar. So, after installing, the Vortex Tube was able to supply 20.3 deg. C air at a flow of 40 SLPM; keeping the pyrometer reading correctly and accurately.

Sometimes compressed air by itself is not enough to “cool” your instruments. The EXAIR Vortex Tubes can reduce the temperature of your compressed air to the desired requirement.  If you believe that your measuring equipment is being affected by temperature, please contact an Application Engineer at EXAIR to find the correct product for you.

 

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