What You Can Do With A Vortex Tube…And What You Can’t

Vortex Tubes are near the top of the list of the most interesting uses of compressed air: Cold (and hot) air, generated instantly, from a device with no moving parts. Why don’t we use them for EVERYTHING? It’s not that it CAN’T be done, but it can be impractical to do so. Consider:

While researching our Cabinet Cooler Systems, some callers will ask about using this technology to cool a space larger than an electrical panel, like a server room. I spoke with just such a caller once, who had 7.5kW worth of heat estimated in a server room that was under construction, and had been asked to research cooling solutions…so we did:

  • Since 1 watt equals 3.41 Btu/hr, 7.5 kilowatts equals 25,575 Btu/hr worth of cooling required.
  • Our highest capacity single Cabinet Cooler generates a cooling capacity of 2,800 Btu/hr, so we talked about ten of them, for ~10% safety factor, which was reasonable for the purposes of our discussion.
  • Each 2,800 Btu/hr Cabinet Cooler uses 40 SCFM @100psig, for a total of 28,000 SCFM. Using a common thumbrule that says a typical industrial air compressor generates 4 SCFM per horsepower, that means they’d need a 100HP compressor (or that much capacity from their whole system) just to run these Cabinet Coolers. Adding that cooling capacity to their HVAC requirements made more sense.

Of course, with every rule, there’s an exception: an independent crane operator carries a Model 3250 Large Vortex Tube with him for cab cooling in the tower cranes he’s contracted to operate. While the US Department of Energy considers “personnel cooling” to be an inappropriate use of compressed air, the small fans typically found in these cranes’ cabs offer little comfort to an operator spending all day, 50 feet off the ground, in the summer heat of the Deep South!

EXAIR offers 24 distinct Vortex Tube models with cooling capacities from 135 Btu/hr to 10,200 Btu/hr.

Another common question regards the use of a Vortex Tube with another EXAIR product…the most common being an Air Knife. These callers want to blow cold air onto something, but instead of the conical and relatively small flow pattern the Vortex Tube discharges, they want to blow a curtain of cold air. The design & function of both the Vortex Tube, and the Air Knife, work against this idea:

  • The cold air has to exit the Vortex Tube at, or very near, atmospheric pressure. If it encounters much back pressure at all, performance (as measured by the temperature and flow rate of the cold air) will deteriorate.
  • An Air Knife, by design, is pressurized all the way to the point where the compressed air flow exits the 0.002″ thick gap. That’s far too much back pressure for a Vortex Tube to operate under.
  • Even if the Vortex Tube DID supply cold air, under pressure, to the Air Knife, the tremendous amount of environmental air entrained by the Air Knife would still result in a total developed flow temperature that was much closer to ambient temperature for the area.
Since the Super Air Knife entrains air from the surrounding environment at a rate of 40:1, the resultant air temperature, regardless of the temperature of the air supply, is always going to be pretty close to ambient.

One “workaround” for this is what we informally call a “cold air knife” – that’s when you plumb the cold air from a Vortex Tube into a length of pipe with a series of holes drilled along its length. Let’s say a building products manufacturer wanted to blow cold air across a 10ft wide continuous sheet of roofing material…because they did:

  • I recommended that they take a PVC (because it’s non-conductive and wouldn’t transfer heat from ambient as fast) pipe a little longer than 10ft, cap the ends, drill 1/8″ holes every inch (total of 120 holes).
  • From the table below, we see that a 1/8″ diameter hole can flow as much as 1.1 cubic feet per minute @1psig*, so 120 of those holes will pass ~132 cubic feet per minute worth of air flow.
  • Four Model 3240 Vortex Tubes were specified: when set to an 80% Cold Fraction, 80% of the 40 SCFM that each will consume, or 32 SCFM, is directed to the cold end. 32 SCFM X 4 3240’s = 128 SCFM. Close enough. They plumbed those 4 Vortex Tubes at approximate equal distances along the length.
*I picked 2psig because that’s the maximum back pressure before it starts to change performance. I also assumed we’re not going to round the entrance of the holes, so I applied the 0.61 multiplier from the table notes.

A Model 3215 Medium Vortex Tube supplied @100psig will flow 10 SCFM worth of cold air when set to a 67% Cold Fraction**, which will give us a curtain of cold air that’s a little more than 71°F colder than the compressed air supply:

**When set to a 70% Cold Fraction (that means 70% of the compressed air supply flow is directed to the cold end), the cold flow from a Vortex Tube supplied @100psig will be 71°F colder than the compressed air supply. At a 67% Cold Fraction, it’ll be a little colder than that.

If you’ve got an application involving the need for cold air, on demand, EXAIR has a variety of products that’ll do just that. Give me a call to find out more.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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What OSHA 1910.242(b) Means For Compressed Air Product Users

Medically speaking, our skin is an organ…and an amazing one at that. It protects our internals from an incredibly harsh environment as we’re bombarded by radiation (sunlight), subjected to summer’s heat & the cold of winter, attacked by fierce invaders (from viruses & bacteria to insects & spiders), all while we carry on at the bottom of a 60 mile-deep ocean (of air!)

Our skin requires some protection too: Sunscreen mitigates some of the harmful effects of solar radiation, shoes protect our feet from the ground, gloves & coats prevent frostbite, and compliance with OSHA Standard 1910.242(b) protects operators who use compressed air devices for cleaning purposes from air embolisms. That’s when air, under pressure, has enough energy to break the skin (tough as it is) and reach the tissue underneath. It’s painful, and serious enough that the victim should absolutely seek emergency medical treatment. If the air breaks a blood vessel and enters the pulmonary system, it can be deadly, in a hurry.

In 1971, the U.S. Occupational Health and Safety Administration (OSHA) determined that air under pressure higher than 30 pounds per square inch is capable of causing such injuries, if the pressurized source is dead-ended into the skin. Based on this determination, they included the following verbiage in Standard 1910.242, regulating the safe operation of hand and portable powered tools & equipment:


1910.242(b) Compressed air used for cleaning. Compressed air shall not be used for cleaning purposes except where reduced to less than 30 p.s.i. and then only with effective chip guarding and personal protective equipment.


In February 1972, OSHA issued Instruction STD 01-13-001 to clarify the meaning of 1910.242(b), with two illustrations of acceptable methods to meet compliance. The first is the use of a pressure reducer (or regulator):

While this method is compliant with the OSHA Standard, it’s kind of impractical, since you’re not going to get a whole lot of cleaning done with such a low energy air flow. If that’s not bad enough, it’s STILL going to be loud, and wasteful as far as the cost of compressed air goes.

The other method illustrated in the Instruction’s enclosures involves the nozzles themselves:

Compressed air product manufacturers use this method to make OSHA compliant Nozzles.

One design that complies with OSHA 1910.242(b) using this method is the cross drilled nozzle:

Unless it’s blocked off, practically all of the air flow goes straight out the end, but if you block off the end, it all goes out the cross drilled hole. As long that hole is properly sized, you won’t build up 30 psi at the main outlet.

If you’re not concerned about high operating cost or deafening noise, you can stop reading now; these are all you need for OSHA compliance with Standard 1910.242(b). If you DO care about spending less money on compressed air or complying with OSHA Standard 1910.95(a) (which you read all about here), let’s spend a minute on engineered compressed air nozzles:

EXAIR Super Air Nozzles discharge compressed air through an annular array of holes, recessed between a series of fins. This causes the primary (compressed air) stream to entrain an enormous amount of air from the surrounding environment.

In addition to making them cost less to operate (since most of the total developed air flow is entrained), they’re also VERY quiet (since the entrained air forms a boundary layer on the outside of the air stream), AND they can’t be dead ended:

Since the fins won’t allow for a complete blockage of the compressed air discharging from the Super Air Nozzle, this design is a prime example of a built-in “relief device” as defined by Instruction STD 01-13-001, above.

All EXAIR Intelligent Compressed Air Products, in fact, incorporate a form of built-in “relief device”:

The overhang of the cap on the Flat Super Air Nozzles and the Super Air Knives prevent them from being dead ended.

If you’d like to discuss safe use of compressed air, it’s one of our primary goals here at EXAIR – give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR LLC
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Powerful, Efficient, and OSHA Compliant: EXAIR Super Blast Safety Air Guns

Earlier this year, EXAIR introduced the TurboBlast® Safety Air Gun. They offer the same performance as a number of our Super Blast Safety Air Guns, with some noteable features:

  • Nozzle Guard protects the Super Air Nozzle from damage that could be caused by incidental contact during use.
  • Gate Valve option for easy flow adjustment by the operator, with a simple twist of the ring!
  • Rugged AND comfortable elastomer grip with pushbutton trigger for optimal ergonomics.

These, combined with the features they share with our four most powerful Super Blast Safety Air Guns (high force, automatic shutoff, 3 and 6 foot extensions) make it one of the most innovative blow off products on the market today. With all that going for the TurboBlasts, we still want to emphasize that they’re offered as an enhancement to – and not a replacement for – the Super Blast line. Consider:

Super Air Nozzle Clusters. Because of the Nozzle Guard, Clusters aren’t offered with the TurboBlast products. Clusters concentrate their high force, powerful airflow on a smaller target area than comparable single Super Air Nozzles:

*Force measured at 12″ (305mm) from target. Sound level measured at 3ft (914mm). All measurements taken at 80psig (5.5 BAR).

Back Blow Nozzles. Also because of the Nozzle Guard, the Model 1008SS 1 NPT Back Blow Nozzle is offered on the Super Blast, but not the TurboBlast. It’s made for blowing out pipe with inside diameters from 2″ to 16″ (51-406mm):

EXAIR Super Blast Safety Air Guns fitted with our 1 NPT Back Blow Nozzles are available with 1ft (top left), 3ft (top right) or 6ft (bottom) extensions.

Spring-To-Close Ball Valve. While the ergonomic, pilot actuated pushbutton trigger on the TurboBlast Safety Air Guns is likely to be preferred in a number of situations, the full hand grip of the Super Blast Safety Air Gun’s ball valve proves to be more suitable for certain positions, like when the device is to be operated above shoulder height:

The ball valve handle essentially becomes part of the operator’s grip when using this Model 1215-3 Super Blast Safety Air Gun in an overhead space blow off application.

EXAIR is in the business of helping you get the most out of our products – and your compressed air system. If you have questions, I welcome the opportunity to help…give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR
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Super Ion Air Knives Remove Static, Improve Bottle Cap Production

The leaves have all fallen. The sky, more often than not, is dreary. My winter coat is officially part of the “uniform of the day”. And I got shocked by the laundry room doorknob yesterday. All this means that winter is upon us (here in the Northern Hemisphere anyway), and as far as EXAIR is concerned, it’s “static season”. We’re seeing a definite uptick in the numbers of conversations we’re having about static charge-related issues…and solutions that we can provide.

I had the pleasure of speaking to a caller, last month, who works for the US division of a global manufacturer of bottle caps. A machine that sorts & orients plastic caps was particularly prone to static charge problems last winter, causing a marked decrease in their production, and they wanted to get out in front of the problem this year:

As the caps travel horizontally (white arrows), they pass under a static bar (supplied by the machine manufacturer) which provided some reduction in static charge, but was unable to keep up with the higher magnitudes of static charge experienced during the lower humidity winter months. Bottle caps (right) would pile up, slowing production.
A Model 112230 30″ Gen4 Super Ion Air Knife Kit replaced the OEM static bar, resulting in dramatic improvement…no more piling up of bottle caps.

The increased static charge (beyond the OEM static bar’s ability to handle) reduced production by 1/3. The Super Ion Air Knife restored operation to full capacity for this machine…and three others, once they saw the results of the first one.

If static charge is causing you problems with dust clinging to your product, your product clinging to itself, sheets mis-feeding, materials jamming, tearing, or curling, or nuisance shocks to operators, EXAIR has a variety of safe and efficient Static Eliminator solutions. To find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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