Importance Of Proper Pneumatic Tube, Pipe, And Fittings

When it comes to engineered compressed products, the number one cause of less-than-optimal performance is improper supply line sizing.  This can mean one of two things:

  • The hose, pipe, or tubing running to the device is too small in diameter.
  • The hose, pipe or tubing is big enough in diameter, but too long.

The problem with either of these is line loss (follow that link if you want to do the math.)  Put simply, the air wants to move faster than it’s physically permitted to.  Any time fluid flows through a conduit of any sort, friction acts on it via contact with the inside surface of said conduit.

With smaller diameters, a larger percentage of the air flow is affected…no matter what diameter the line is, the air closest to the inner wall is affected by the friction generated.  When diameter increases, the thickness of this affected zone doesn’t increase proportionally, so larger diameters mean less of the air is affected by friction.  It also means there’s a lot more room (by a factor of the square of the radius, times pi…thanks, Archimedes!) for the air to flow through.

Likewise, with longer lengths, there’s more contact, which equals more friction.  Length, however, is often a non-negotiable.  You can’t just up and move a 100HP air compressor from one part of the plant to another.  So, when we’re talking about selecting proper supply lines, we’re going to start with the distance from the compressed air header to our device, and pick the diameter that will give us the flow we need through that length.  In fact, that’s exactly how to use the Recommended Infeed Pipe Size table in EXAIR’s Super Air Knife Installation & Maintenance Guide:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.

Once we have the correct line size (diameter,) let’s consider the fittings:

  • Tapered pipe threads (NPT or BSPT) are the best.  They offer no restriction in flow, and are readily commercially available.  If you’re using pipe, these are the standard threads for fittings.  If you want to use hose, a local hydraulic/pneumatic shop can usually make hoses with the fittings you need, at the service counter, while you wait.
  • If you need to frequently break and make the connection (e.g., a Chip Vac System that’s used throughout your facility,) quick connects are convenient and inexpensive.  Push-to-connect types are by far the most common, but a word of warning: they’re notoriously restrictive, as the inside diameter of the male end is markedly smaller than the line size.  If you use them, go up a size or two…a quick connect made for 1/2 NPT connections will work just fine for a 1/4″ line:
  • The nice thing about these quick connects is that you don’t have to depressurize the line to make or break the connection.  If you have the ability to depressurize the line, though, claw-type fittings (like the one shown on the right) provide the convenience of a quick connect, without the restriction in flow.

Proper air supply is key to performance of any compressed air product.  If you want to know, at a glance, if you’re supplying it properly, install a pressure gauge right at (or as close as practical) to the inlet.  Any difference in its reading and your header pressure indicates a restriction.  Here’s a video that clearly shows how this all works:

I want to make sure you get the most out of your compressed air system.  If you want that to, give me a call with any questions you might have.

Russ Bowman
Application Engineer
EXAIR Corporation
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What’s So Great About Air Entrainment?

Air entrainment is the phenomenon that occurs when air (or any gas) under pressure is released from a device in such a way that a low pressure is generated in the immediate area of the air (or gas) discharge.  Air (or gas) from the surrounding environment is then pulled (or entrained) into the discharged air stream, increasing its volumetric flow rate.  EXAIR Corporation has been engineering & manufacturing compressed air products to take maximum advantage of this phenomena since 1983…and we’ve gotten better & better at it over the past 36 years.

Obviously, the first thing that’s so great about air entrainment is…free air flow.  Every cubic foot that’s entrained means that’s a cubic foot that your compressor didn’t have to spend energy compressing.  Considering the EXAIR Super Air Knife’s entrainment ratio of 40:1, that makes for a VERY efficient use of your compressed air.

Another thing that’s so great about air entrainment is…it’s quiet.  As you can see from the graphic at the top of this blog, the Super Air Knife entrains air (the lighter, curved blue arrows) into the primary compressed air stream (the darker, straight blue arrows) from above and below.  The outer layers of the total developed flow are lower in velocity, and serve as a sound-attenuating boundary layer.  The sound level of a Super Air Knife (any length…here’s why) is only 69dBA.  That means if you’re talking with someone and a Super Air Knife is running right next to you, you can still use your “inside voice” and continue your conversation, unaffected by the sound of the air flow.

I always thought it would be helpful to have more than just a graphic with blue arrows to show the effect & magnitude of air entrainment.  A while back, I accidentally stumbled across a stunning visual depiction of just that, using a Super Air Knife.  I had the pleasure of talking with a caller about how effective a Super Air Knife might be in blowing light gauge paperboard pieces.  So I set one up in the EXAIR Demo Room, blowing straight upwards, and tossed paper plates into the air flow.  It worked just as expected, until one of the paper plates got a little closer to the Super Air Knife than I had planned:

As you can see, the tremendous amount of air flow being entrained…from both sides…was sufficient to pull in lightweight objects and ‘stick’ them to the surface that the entrained air was being drawn past.  While it doesn’t empirically prove the 40:1 ratio, it indisputably demonstrates that an awful lot of air is moving there.

If you’re looking for a quiet, efficient, and OSHA compliant solution for cleaning, blow off, drying, cooling…anything you need an even, consistent curtain of air flow for – look no further than the EXAIR Super Air Knife.  If you’d like to discuss a particular application and/or product selection, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Chip Shields, OSHA, And You

Safety is a key part of our culture at EXAIR Corporation.  We have regularly scheduled, all-hands required, safety training on a number of topics.  Our Order Entry team can likely tell you as much about our lockout/tagout procedures as our Machinists can.  Nobody even thinks about entering The Shop without safety glasses, and it’s not just because of the signs.

We pay attention to these…
…so we don’t ever have to use this.

OSHA 1910.242(b) states that “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. (emphasis mine)  All EXAIR Intelligent Compressed Air Products are engineered to meet the requirements of the first part (30psi outlet pressure to prevent dead ending…we’ve written about that numerous times, including here, here, and here) and we can also provide pre-installed devices to satisfy the second part:  the EXAIR Chip Shield.

Any EXAIR VariBlast or Heavy Duty Safety Air Gun can come fitted with a Chip Shield, and any Soft Grip Safety Air Gun, except for those with Stay Set Hoses, can as well.  Safety Air Guns with Back Blow Nozzles automatically come with a Chip Shield. The principle is simple: a clear polycarbonate (so you can still see what you’re doing) round disc slips over a short (or long if you want) pipe extension between the gun & the nozzle.  It’s fitted with a rubber grommet so you can position it to where it’s most effective – sometimes that might be closer to the part being blown off; sometimes it may be back a little closer to the operator.

EXAIR Safety Air Guns are available, from stock, with Chip Shields.

If you already have an air gun that’s doing the job, you can easily add an EXAIR Chip Shield to it.  They’re made to fit a wide range of extension diameters, and can even come with the extension if you need it.  We also stock a number of adapter fittings; if you know what threads your air gun has (or if you can send us some photos) we can quickly & easily spec those out for you.

Convenient and inexpensive “thumb guns” with cross drilled nozzles (left) are compliant with the first part of OSHA 1910.242(b). Fitting one with an EXAIR Chip Shield (center) makes it compliant with the second part. A Model 1102 Mini Super Air Nozzle (right) makes it quiet & efficient.
We can provide a Chip Shield for most any device with a threaded fitting. I couldn’t find a way to re-use the non-OSHA-compliant nozzle that came with this gun (thank goodness.)
Another example of a larger air gun fitted with a more powerful cross drill nozzle (left) that can be made totally OSHA compliant with an EXAIR Chip Shield (center.) An EXAIR High Force Super Air Nozzle (right) keeps the power, while reducing noise level and compressed air consumption (right.)

Since 1983, EXAIR Corporation has been manufacturing quiet, safe, and efficient compressed air products for industry (emphasis mine.)  If you have concerns or questions about safety in regard to your compressed air use, call me.

Russ Bowman
Application Engineer
EXAIR Corporation
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EXAIR Standard Air Knife: Engineered For Performance

In 1983, EXAIR Corporation was founded with the goal of engineering & manufacturing quiet, safe, and efficient compressed air products for industry.  By 1988, the EXAIR-Knife (now known as the Standard Air Knife) was quickly becoming the preferred choice for replacing loud and inefficient drilled pipes, long nozzle manifolds…anywhere an even, high velocity curtain of air was required.

The EXAIR Standard Air Knife’s design takes advantage of a fascinating principle of fluidics to achieve quiet and efficient operation: the Coanda Effect, which is the tendency of a fluid jet to stay attached to a convex surface.  If you want to see it for yourself, hold the back of a spoon, handle up, under the kitchen faucet.  Those who haven’t seen it before may assume that gravity will take over and the water will fall from the bottom of the spoon’s ‘bowl’ – but it doesn’t:

Likewise, the air flow (which is just another example of a fluid jet) exiting the Standard Air Knife’s shim gap follows a convex surface (which we call the “Coanda profile”) causing it to entrain large amounts of air from the surrounding environment:

Compressed air flows through the inlet (1) to the Standard Air Knife, into the internal plenum. It then discharges through a thin gap (2), adhering to the Coanda profile (3) which directs it down the face of the Air Knife. The precision engineered & finished surfaces optimize entrainment of air (4) from the surrounding environment.

This entrainment does two things for us:

  • First, because we’ve engineered the design for maximum entrainment, it’s very efficient – creating a high flow rate, while minimizing air consumption.  In the case of the Standard Air Knife, the entrainment ratio is 30:1.
  • Secondly, this entrainment forms an attenuating boundary layer for the air flow, resulting in a high velocity, high volume airflow that is also incredibly quiet.

The EXAIR Standard Air Knife comes in lengths from 3″ to 48″, and in aluminum or 303SS construction.  All sizes, in both materials, are on the shelf and available for immediate shipment.  For most applications, we recommend the Kit, which includes a Shim Set (to make gross changes to flow & force,) an Automatic Drain Filter Separator (keeps the air clean & moisture free,) and a Pressure Regulator (to dial in the performance.)  Deluxe Kits add our Universal Air Knife Mounting System and EFC Electronic Flow Control.

(From left to right) Aluminum Standard Air Knife Kit, SS Standard Air Knife Kit, Deluxe Aluminum Standard Air Knife Kit, Deluxe SS Standard Air Knife Kit.

If you need a hard hitting curtain of air for blow off, drying, cleaning, cooling, environmental separation, etc., the EXAIR Standard Air Knife is an easy and economical solution.  If you’d like to discuss your application and/or product selection, give me a call.

Russ Bowman

Application Engineer
EXAIR Corporation
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Solving Performance Issues of Air Operated Industrial Vacuums

This blog will focus on the EXAIR Chip Vac, but the troubleshooting process and steps for achieving optimal performance are consistent among EXAIR’s entire line of air operated industrial vacuums.

There’s really not that much that CAN go wrong with an EXAIR Chip Vac System. They have no moving parts to wear or electrical components to burn out. As long as they’re supplied with clean air, they’ll run darn near indefinitely, maintenance free.

Murphy’s Law, of course, is still in full force, so if something CAN go wrong, it WILL go wrong.  The Chip Vac is, alas, no exception.  Good news is, because of the Chip Vac‘s simplicity, troubleshooting is simple as well.  The most common problems we see with ANY of our engineered compressed air products (not just the Industrial Vacuums) are related to compressed air supply:

  • New users might not consider the air demand required by a new product, and may provide an inadequate supply line.  The Chip Vac, for example, will consume 40 SCFM @80psig for rated operation, and will need a 1/2″ (inside diameter) hose to supply that, assuming a length of no more than 20ft.  Hooking one up to a common 3/8″ hose on a 50ft reel, for example, will “starve” the Chip Vac, resulting in degraded performance.
  • Also, the preferred method of connection is a hose with threaded fittings on the ends.  A local hydraulics/pneumatics shop can likely make these, while you wait.  Push-to-connect quick connect fittings are restrictive by nature, and should be avoided.  Quarter turn claw-type fittings are great…the main drawback (which can be solved with an upstream shutoff valve) is the line has to be depressurized to make or break the connection.
  • If you absolutely want to use a push-to-connect type, you can oversize it (use one made for larger hose with, say, 3/4 NPT fittings) and use bushing/adapters to get to your actual hose size.

    If you must use quick connects, the 1/4 turn claw type (left) is the least restrictive. Push-to-connects (center) are likely to starve your product, unless you oversize them (right) like we do in our Efficiency Lab.
  • Speaking of supply issues, make sure nobody’s bumped into a valve handle & partially closed it (I have,) ignored the maintenance schedule & didn’t change a clogged filter element (I have,) or ran something into a copper line hard enough to crimp it, but not rupture it (I haven’t…that was Tim, who, aside from this incident, was really pretty good with a forklift.)

The issues above apply to not only any compressed air system, but most fluid power/fluid handling systems.  Since this blog is about Chip Vac troubleshooting, let’s move on to some specifics.  If you’re sure you’re getting proper air supply to the Chip Vac (by the way, a pressure gauge right at the inlet – like the one that comes with our Premium Chip Vac System’s air hose – will eliminate any doubt,) then let’s look at some potential issues downstream:

  • Dirt & debris can collect inside the Chip Vac itself, obstructing the outlet holes, and lowering your vacuum flow.  You can disassemble and clean it pretty easily, though.
  • The Filter Bag can get clogged, especially if you’re vacuuming up a lot of dust or powdery materials.  If this happens, turn the Chip Vac off and shake the Filter Bag to dislodge the material, allowing it to fall back into the drum where it belongs.
  • Speaking of which, if you find that, all of a sudden, the Filter Bag is clogging, remove the drum lid and check for the Silencing Hose.  This serves two functions…the first is in the name (just a little discharge hose mitigates the sound level of the Chip Vac‘s exhaust flow.)  Secondly, it directs the vacuumed material positively into the drum, limiting the amount that is “dust-storms” in the upper area of the drum, where it’s more prone to make it into the Filter Bag.
Pro tip: check for the Silencing Hose when you remove the lid to empty the drum. DON’T throw the Silencing Hose in the trash.

I’m not going to unequivocally state that this is an all-inclusive list (see “Murphy’s Law,” above,) but these are the Usual Suspects if you’re just not getting the most out of your Chip Vac.  If you ever have any questions, though, give us a call.  We’re here to help.

Russ Bowman
Application Engineer
EXAIR Corporation
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Vortex Tube Cold Fractions Explained

Simply put, a Vortex Tube’s Cold Fraction is the percentage of its supply air that gets directed to the cold end. The rest of the supply air goes out the hot end. Here’s how it works:

The Control Valve is operated by a flat head screwdriver.

No matter what the Cold Fraction is set to, the air coming out the cold end will be lower in temperature, and the air exiting the hot end will be higher in temperature, than the compressed air supply.  The Cold Fraction is set by the position of the Control Valve.    Opening the Control Valve (turning counterclockwise, see blue arrow on photo to right) lowers the Cold Fraction, resulting in lower flow – and a large temperature drop – in the cold air discharge.  Closing the Control Valve (turning clockwise, see red arrow) increases the cold air flow, but results in a smaller temperature drop.  This adjustability is key to the Vortex Tube’s versatility.  Some applications call for higher flows; others call for very low temperatures…more on that in a minute, though.

The Cold Fraction can be set as low as 20% – meaning a small amount (20% to be exact) of the supply air is directed to the cold end, with a large temperature drop.  Conversely, you can set it as high as 80% – meaning most of the supply air goes to the cold end, but the temperature drop isn’t as high.  Our 3400 Series Vortex Tubes are for 20-50% Cold Fractions, and the 3200 Series are for 50-80% Cold Fractions.  Both extremes, and all points in between, are used, depending on the nature of the applications.  Here are some examples:

EXAIR 3400 Series Vortex Tubes, for air as low as -50°F.

A candy maker needed to cool chocolate that had been poured into small molds to make bite-sized, fun-shaped, confections.  Keeping the air flow low was critical…they wanted a nice, smooth surface, not rippled by a blast of air.  A pair of Model 3408 Small Vortex Tubes set to a 40% Cold Fraction produce a 3.2 SCFM cold flow (feels a lot like when you blow on a spoonful of hot soup to cool it down) that’s 110°F colder than the compressed air supply…or about -30°F.  It doesn’t disturb the surface, but cools & sets it in a hurry.  They could turn the Cold Fraction down all the way to 20%, for a cold flow of only 1.6 SCFM (just a whisper, really,) but with a 123°F temperature drop.

Welding and brazing are examples of applications where higher flows are advantageous.  The lower temperature drop doesn’t make all that much difference…turns out, when you’re blowing air onto metal that’s been recently melted, it doesn’t seem to matter much if the air is 20°F or -20°F, as long as there’s a LOT of it.  Our Medium Vortex Tubes are especially popular for this.  An ultrasonic weld that seals the end of a toothpaste tube, for example, is done with a Model 3215 set to an 80% Cold Fraction (12 SCFM of cold flow with a 54°F drop,) while brazing copper pipe fittings needs the higher flow of a Model 3230: the same 80% cold fraction makes 24 SCFM cold flow, with the same 54°F temperature drop.

Regardless of which model you choose, the temperature drop of the cold air flow is determined by only two factors: Cold Fraction setting, and compressed air supply pressure.  If you were wondering where I got all the figures above, they’re all from the Specification & Performance charts published in our catalog:

3200 Series are for max cooling (50-80% Cold Fractions;) 3400’s are for max cold temperature (20-50% Cold Fractions.)
Chocolate cooling in brown; welding/brazing in blue.

EXAIR Vortex Tubes & Spot Cooling Products are a quick & easy way to supply a reliable, controllable flow of cold air, on demand.  If you’d like to find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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EXAIR Line Vac Replaces Yet Another Injury-Prone Bucket & Ladder Operation

I recently had the pleasure of talking with a caller from a consulting firm that specializes in improved ergonomics.  They work with clients on everything from preventing carpal tunnel syndrome through the use of things like gel-filled mouse pads for office personnel, to preventing injuries in the workplace due to repetitive strain, heavy lifting, and other physically demanding tasks.  They called about an operation where workers used buckets to move 150 pounds of dense pellets from a large container into a smaller vessel for weight load testing.  After the test, they move the pellets back into the container, where they stay until the next test is to be run.  Then they do it again.

This, of course, was a great fit for a 2″ Heavy Duty Line Vac and a 10ft length of Conveyance Hose. They simply move the suction & discharge hoses from, and to, the storage container & test vessel.  Risk of injury is greatly reduced, as the whole Line Vac conveyance system is less than half the weight of one bucket of the material.

Line Vac + Hose + Compressed air supply = complete conveyance system solution.

This is just the latest success story in the long history of EXAIR Air Operated Conveyors.  They’re on the shelf in a range of sizes and materials of construction to meet most any need.  If you don’t see what you’re looking for, though, call me and we can discuss your needs.

Russ Bowman
Application Engineer
EXAIR Corporation
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