About Rotary Screw Air Compressors

Recently, EXAIR Application Engineers have written blogs about reciprocating type air compressors: Single Acting (by Lee Evans) and Dual Acting (by John Ball.) Today, I would like to introduce you, dear EXAIR blog reader, to another type: the Rotary Screw Air Compressor.

Like a reciprocating compressor, a rotary screw design uses a motor to turn a drive shaft. Where the reciprocating models use cams to move pistons back & forth to draw in air, compress it, and push it out under pressure, a rotary screw compressor’s drive shaft turns a screw (that looks an awful lot like a great big drill bit) whose threads are intermeshed with another counter-rotating screw. It draws air in at one end of the screw, and as it is forced through the decreasing spaces formed by the meshing threads, it’s compressed until it exits into the compressed air system.

Rotary Screw Air Compressor…how it works.

So…what are the pros & cons of rotary screw compressors?

Pros:

*Efficiency.  With no “down-stroke,” all the energy of the shaft rotation is used to compress air.

*Quiet operation.  Obviously, a simple shaft rotating makes a lot less noise than pistons going up & down inside cylinders.

*Higher volume, lower energy cost.  Again, with no “down-stroke,” the moving parts are always compressing air instead of spending half their time returning to the position where they’re ready to compress more air

*Suitable for continuous operation.  The process of compression is one smooth, continuous motion.

*Availability of most efficient control of output via a variable frequency drive motor.

*They operate on the exact same principle as a supercharger on a high performance sports car (not a “pro” strictly speaking from an operation sense, but pretty cool nonetheless.)

Cons:

*Purchase cost.  They tend to run a little more expensive than a similarly rated reciprocating compressor.  Or more than a little, depending on options that can lower operating costs.  Actually, this is only a “con” if you ignore the fact that, if you shop right, you do indeed get what you pay for.

*Not ideal for intermittent loads.  Stopping & starting a rotary screw compressor might be about the worst thing you can do to it.  Except for slacking on maintenance.  And speaking of which:

*Degree of maintenance.  Most maintenance on a reciprocating compressor is fairly straightforward (think “put the new part in the same way the old one came out.”)  Working on a rotary screw compressor often involves reassembly & alignment of internal parts to precision tolerances…something better suited to the professionals, and they don’t work cheap.

Like anything else, there are important factors to take under consideration when deciding which type of air compressor is most suitable for your needs.  At EXAIR, we always recommend consulting a reputable air compressor dealer in your area, helping them fully understand your needs, and selecting the one that fits your operation and budget.

Russ Bowman
Application Engineer
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Adjustable Spot Cooler: How Cold Can You Go?

I had the pleasure of discussing a spot cooling application with a customer this morning. He wanted to get more flow from his Adjustable Spot Cooler, but still keep the temperature very low.  He machines small plastic parts, and he’s got enough cold flow to properly cool the tooling (preventing melting of the plastic & shape deformation) but he wasn’t getting every last little chip or piece of debris off the part or the tool.

After determining that he had sufficient compressed air capacity, we found that he was using the 15 SCFM Generator. The Adjustable Spot Cooler comes with three Generators…any of the three will produce cold air at a specific temperature drop; this is determined only by the supply pressure (the higher your pressure, the colder your air) and the Cold Fraction (the percentage of the air supply that’s directed to the cold end…the lower the Cold Fraction, the colder the air.)

Anyway, the 15 SCFM Generator is the lowest capacity of the three, producing 1,000 Btu/hr of cooling. The other two are rated for 25 and 30 SCFM (1,700 and 2,000 Btu/hr, respectively.)

He decided to try and replace the 15 SCFM Generator with the 30 SCFM one…his thought was “go big or go home” – and found that he could get twice the flow, with the same temperature drop, as long as he maintained 100psig compressed air pressure at the inlet port.  This was more than enough to blow the part & tool clean, while keeping the cutting tool cool, and preventing the plastic part from melting.

Model 3925 Adjustable Spot Cooler System comes with a Dual Outlet Hose Kit, and three Generators for a wide range of cooling performance.

If you’d like to find out how to get the most from a Vortex Tube Spot Cooling Product, give me a call.

Russ Bowman
Application Engineer
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Real Heroes Of Science: James Clerk Maxwell

People who watch way too much TV (like me) will certainly remember the “Real Men of Genius” commercials.  Here’s one of my personal favorites:

Local radio stations all over the country made parodies of these, as did sketch comics.  While trying to come up with something for my weekly blog, I saw that today was the anniversary of the passing of 19th century physicist James Clerk Maxwell.  So, if you’ll try to keep the background music from the video above playing in your head while you read this, let’s see if I can pay proper tribute:

James Clerk Maxwell…even though Albert Einstein is famous for the Special Theory of Relativity, he credited YOU for laying the groundwork.  You not only theorized the relationship between electricity, magnetism, and light, but you also proved it mathematically…so Albert didn’t have to.  He said your work was “the most profound and the most fruitful that physics has experienced since the time of Newton.”

Singer: Albert Einstein pretty much called you an “Einstein” the way we call geniuses “Einsteins.”

Professor Maxwell…you devoted your life to learning.  About EVERYTHING.  As if solving Einstein’s problem with the Theory of Relativity (40 years before he knew he had a problem with it) wasn’t enough, you decided to find out what the rings of Saturn were made of.  Over 100 years before we could send the Voyager spacecraft to find out for sure.  And you were right.

Then you discovered how to take color photographs by experimenting with light filters.

Singer: Not only did you tell us what Saturn’s rings were made of, we have color photographs of them thanks to you….

James Clerk Maxwell…your theory that a “friendly little demon” could somehow separate gases into hot and cold flows, while unproven in your lifetime, did actually come to fruition by the development of the Vortex Tube.  Which does just that.

Singer: That’s right, I just drew a straight line from Maxwell’s Demon to EXAIR’s Vortex Tube & Spot Cooling Products!

So here’s to you, James Clerk Maxwell…may we continue to recognize your brilliance, and be inspired by your drive to push forward in scientific developments.

Singer (building to final crescendo): James Clerk Maxwell, a Real Hero Of Sci-i-i-i-i-ence!

If you’d like to hear the musical parts of this actually get sung, or if you’d like to find out more about Vortex Tube products and their uses (it might be best to stick with that second part actually,) give me a call.

Russ Bowman
Application Engineer
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The Case For The Cold Gun

Albert Einstein famously said, “Nothing happens until something moves.” And unless it’s in a perfect vacuum when it moves, there’s gonna be friction. Especially if it’s in contact with something else besides air.  And where there’s friction, there’s heat. This pretty much applies to almost every single evolution in the manufacture of…well, just about everything.

I’m probably not telling you anything you don’t already know, but heat can be a BIG problem.  It can:

  • Shorten tool life. Not only do worn tools take longer to cut, they can also present safety issues.  You can get hurt WAY worse by a dull blade than a sharp one.
  • Cause thermal expansion. If you’re machining something to a precise tolerance, and friction heat causes it to grow, it won’t be the same size when it cools down.
  • Melt plastics. And even softer metals.  This isn’t good for the part…or the tool, either.

Those are just a few of the problems heat causes in manufacturing operations, and they’ve been traditionally addressed with mist (liquid) coolants.  And they work just fine…most of them are water-based, and if you want to get heat out of a solid piece of something, water will do the job VERY quickly.  Other additives in the coolant provide a measure of lubricity, corrosion control, emulsion prevention, etc.  It’s easy, well-known, and time-tested.  There are some drawbacks, however:

  • It can be messy.  When a part (or a tool) in motion gets sprayed down with liquid, it tends to fling that liquid all over the place.  That’s why most machines fitted with mist coolant have spray shields.
  • Not only is it a hassle to clean up, if you don’t stay on top of the clean-up, it can lead to slip hazards.
  • Speaking of hazards, if you can smell that mist (and you know you can,) that means you’re breathing it in too.  Remember the lubricants, corrosion inhibitors, emulsion preventers, etc., I mentioned above?  Yeah…they’re not all what you might call “good for you.”
  • Recirculation systems are common, which means the coolant sump is gathering solids, so the lines and/or spray nozzles can clog and be rendered useless.

EXAIR Cold Gun Aircoolant Systems not only address all of the above problems with heat, but eliminate all the problems associated with liquid coolant:

  • They incorporate EXAIR’s Vortex Tube technology to produce a stream of cold air.
  • They’re reliable.  There are no moving parts; if you supply them with clean, dry air, they’ll run darn near indefinitely, maintenance free.
  • They’re quick & easy.  With a built-in magnet for mounting and a flexible cold air hose, you can be be blowing cold air right where you want it as quickly as you can attach an air hose and open the valve.
  • Speaking of opening the valve, that’s all it takes to run a Cold Gun.  They’re producing cold air at rated flow and temperature, right away.  No “ramp up” time to get into operation.
  • They’re clean.  That cold air stream just becomes…well, air.  No mess.  No slip.  No clean up.  No smell.  No problem.

We’ve got four Models to choose from, depending on the nature of the application:

Both the standard and the High Power come with a Filter Separator, and are available with a one, or two, outlet cold air hose.

If you need to cool parts or tools down, and want it to be effective and clean, give me a call.

Russ Bowman
Application Engineer
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Super Air Knife Makes EVERYTHING Better

When we compare the EXAIR Super Air Knife to other methods of providing a curtain or sheet of air flow in terms of operating cost, efficiency, safety, and sound levels, the Super Air Knife is ALWAYS the clear choice.

The EXAIR Super Air Knife is the most efficient and quietest compressed air blow off product on the market today.

The Super Air Knives successfully replace these, and many other methods of providing a curtain or sheet of air flow all the time, while saving compressed air and decreasing noise.  The word “replace” oftentimes means “do the same job as.”

What you’re about to read is NOT one of those times.

A paper products manufacturer has a machine that treats a specialty product, and the process generates ozone (O3) at levels that would exceed personnel exposure limits, so they need to be contained.  They installed a long piece of drilled pipe to blow an air barrier, but they could only run the machine at about 65% of their desired capacity before the ozone level in the operators’ area exceeded their limits.

This company was familiar with several of our product lines already…they had several Cabinet Cooler Systems, a Reversible Drum Vac, and Super Air Knives in a variety of applications, so they knew how they worked.  Since the barrier needed to be 120″ long, though, this was going to be a much larger scale than they were used to.

Not only was the drilled pipe loud and inefficient, it was not particularly effective either.

Still, the installation of two Model 110060 60″ Aluminum Super Air Knives, coupled with our Model 110900 Air Knife Coupling Kit, was quick and easy.  Then came the good part: they found they were able to operate the machine at 100% capacity, while keeping the ozone at a safe level in the operators’ area.

EXAIR Super Air Knives provided a total solution: quiet, efficient, and most of all, EFFECTIVE.

Then came the better part:  The machine was pretty loud (we couldn’t do anything about that,) at 93dBA when it was running.  With the drilled pipe in operation, it was 94.5dBA.  When they took that out and installed the Super Air Knives, there was no net increase in noise level…it remained at 93dBA.

THEN came the even better part: Compressed air consumption was reduced to about 30% of what the drilled pipe was using.  Right in line with our table above.  Just another validation of the trustworthiness of our published data.  As EXAIR’s President is fond of saying, “Claims are easy, proof is hard.”

If you’re looking for a quiet, efficient – and effective – solution for a compressed air product application, give me a call.

Russ Bowman
Application Engineer
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Back Blow Air Nozzles Clean Inside Diameters

They say time flies when you’re having fun. Maybe that’s why I found it a little hard to believe it’s been almost two years since we introduced the Back Blow Air Nozzles. They’ve become yet another “textbook” solution to a great many applications:

*Model 1004SS M4 Back Blow Air Nozzles are used to dry the inside of a closed cylinder after a zinc bonding process.  They’re also fitted to Model 1204SS-12-CS M4 Back Blow Safety Air Gun to remove chips & cutting fluid from freshly cut pipe ends.

*Our Model 1006SS 1/4 NPT Back Blow Air Nozzle won Plant Engineering Magazine’s “Product Of The Year” Bronze Award in 2015, and are successfully employed in a wide range of uses:

  • Blowing out splined bores by a gear manufacturer
  • Quickly cleaning out spindles between tool changes by a CNC machinery operator
  • Removing the last bits of powder from spent toner cartridges by a printing equipment recycler

*The Model 1008SS 1 NPT Back Blow Air Nozzle is becoming famous in hydraulic cylinder repair shops…after a cylinder bore is honed, one quick pass of the powerful blast it produces cleans bores from 2″ to 16″.  We can even put it on the Model 1219SS Super Blast Back Blow Safety Air Gun, with a 1ft, 3ft, or 6ft extension.

EXAIR Back Blow Air Nozzles come in three sizes, for bores from 1/4″ to 16″ in diameter!

If you want to see how they work, check out this video:

I could have sworn Lee Evans just made that video, but apparently, it’s over a year old now.  Time does indeed fly, and I promise we’re having fun!  If you’d like to find out more about how a Back Blow Air Nozzle – or any of our engineered compressed air products (old or new) – can make your operations quieter, more efficient (and hence, probably, more fun,) give me a call.

Russ Bowman
Application Engineer
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Super Air Knife Plumbing Kit Allows Installation In Tight Quarters

I recently had the pleasure of helping a long-time user of our Super Air Knives with a challenging application. They already use quite a few of our Model 110012SS 12″ Stainless Steel Super Air Knives to clean & dry their nonwoven material as it’s being rolled for packaging. They like them because they’re quiet and efficient, but also because they’re durable…this particular product off-gasses a mildly corrosive vapor, which used to corrode other equipment in the area. Not only does the Stainless Steel Super Air Knife resist corrosion itself, the air flow keeps these vapors contained. Two birds, one stone.

They have a new product…same kind of material, but much wider…that needed to be blown off, and the identified the Model 110060SS 60″ Stainless Steel Super Air Knife as a “no-brainer” solution. Thing is, it had to be a pretty even air flow across the length, and a 60″ Super Air Knife has to get air to four ports across its length for optimal performance. And, they wanted to install it at a point where it would serve not only as a blow off, but as a vapor barrier, just like the 12″ Super Air Knives they’re already so fond of. The space was a little limited, though, so they opted for the Model 110060SSPKI 60″ Stainless Steel Super Air Knife with Plumbing Kit Installed, which allowed them to simply run an air supply line to both ends.

EXAIR SS Super Air Knives can be ordered with a Plumbing Kit installed, or you can easily install a Plumbing Kit on your existing Super Air Knife.

If you want to find out more about an engineered solution for your compressed air application – cleaning, drying, vapor barrier, or all of the above – give me a call.

Russ Bowman
Application Engineer
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