Compressed Air Vs. Blower Air Knife & Other Alternatives

An often debated subject is whether it makes more sense to use a compressed air powered Air Knife or a blower powered Air Knife.  Initially, one might think that the blower option might be a more economical solution due to its slightly lower electrical consumption when compared to an air compressor.  However, a blower powered Air Knife is an expensive capital expenditure that requires frequent downtime, costly maintenance of filters, belts, bearings and electricity!  They also take up a lot of space and can produce sound levels that exceed OSHA noise level requirements.  EXAIR’s Super Air Knife even when operated at 80 PSIG (5.5 BAR), is surprisingly quiet at 69 dBA!

OSHA Chart

Another drawback for the blower powered Air Knives is the air volume and velocity can be difficult to control since these are adjusted mechanically.

Some other important maintenance considerations are:

  • Filters must be replaced every 1 – 3 months.
  • Belts must be replaced every 3 – 6 months.
  • Blower bearings wear out quickly due to the high rpm requirements.
  • The Seals wear and can allow dirt and moisture to enter, couple that with high temperature environments and the bearing life will be reduced.
  • Blowers typically add heat to the air flow, making it unsuitable for cooling applications.

In contrast the award winning and highly efficient EXAIR Super Air Knife represents our latest generation of innovation that dramatically reduces compressed air usage and noise, with no moving parts!

The EXAIR Super Air Knife is a great way to clean, dry or cool parts because they deliver a uniform sheet of laminar air flow across it’s entire length with force that can range from a gentle breeze to extreme hard-fitting force!

EXAIR Super Air Knives highly engineered design entrains ambient air at a ratio of 40:1.  This simply means that for every (1) part of compressed air supplied (40) parts of ambient air are pulled into the compressed air stream exiting the nozzle.

How Air Knife Works

1). Compressed air flows into the plenum of the Super Air Knife.  The flow is directed to a precision slotted orifice.

2). As the air-flow exits the air gap it follows a flat surface that directs the air flow in a perfectly straight line.  This creates a uniform sheet of air across the entire length of the Super Air Knife.

3).  Velocity loss is minimized and force is maximized as the room air is entrained into the primary air-stream at a 40:1 ratio.  This all results in a well defined sheet of laminar air-flow with hard hitting force.

Advantages of the Super Air Knife

  • Very Quiet, typically 69 dBA for most applications
  • Minimal Compressed air consumption
  • 40:1 air amplification
  • Uniform air flow across the entire length
  • Force and flow are variable
  • No moving parts – therefore maintenance free
  • Easy mounting – compressed air inlets are conveniently located on each end and the bottom
  • Compact design, rugged design and very easy to install
  • Recessed hardware
  • Stock lengths up to 108″ in Aluminum (max temperature of 180°F/82°C), 303SS or 316SS (max temperature 800°F/427°C)
  • PVDF is available up to 54″ long for superior corrosion resistance (max temperature 275°F/135°C)

EXAIR’s Super Air Knife is also a great replacement for other commonly used, but highly inefficient and noisy compressed air operated devices.

As an example, two commonly used blow-offs are the drilled pipe and flat air nozzles installed into a pipe.  EXAIR performed a head to head test employing the EXAIR Super Air Knife, Blower Powered Air Knife, Drilled Pipe & Plastic Flat Nozzles mounted in a pipe.

Below are the results of that test from a very common application, blowing water off bottles.  As shown in the First Year Cost Column it becomes clear that the true cost of ownership needs to be considered.  Many plants are surprised at how efficient the EXAIR Super Air Knife is compared to other alternatives.

AirKnifeComparisons

Another important consideration is how effective these other blow-off methods are.  The drilled pipe and flat air nozzles have “dead spots” where the air flow is non existent leaving some of your product wet and/or dirty.

When you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you.

Steve Harrison
Application Engineer
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Mounting Options for EXAIR’s Super Air Knife

 

Super Air Knife installed using the Universal Air Knife Mounting system.

The key towards a successful Super Air Knife  application is making sure it’s installed properly. Using the chart on the installation & maintenance guide to ensure your plumbing is properly sized is the first step. This ensures that an adequate volume of compressed air is able to reach the knife, without causing an unnecessary pressure drop.

super air knife pipe size

Once you’ve planned out the distribution of compressed air to the Super Air Knife you must consider how to mount it in your application. Across the bottom of the knife are ¼-20 tapped holes spaced out evenly every 2” along the knife. A 30” Model 110030 will have (15) holes, a 60” 110060 (30), and so on. These holes are tapped through to allow you to mount the knife to best suit the application.

If you’d rather have a more “out of the box” solution, EXAIR offers our Universal Mounting System. It gives you the ability to mount onto a conveyor rail or machine frame and provide precise positioning for all of EXAIR’s Super Air Knives, Standard Air Knives, Full-Flow Air Knives, as well as the Standard and Super Ion Air Knives. Each system comes with (2) 1/2-13 x 5” long bolts, 2’ long stainless steel rod, mounting hardware, angle bracket, and adjustable swivel clamps. Check out the video below for a demonstration of the adjustability you can achieve with the Model 9060 Universal Mounting System.

Another critical factor to consider is the mounting position of the knife. If the material is moving along a conveyor, the knife should be positioned as closely as possible with the airflow oriented against the direction of travel of the material. By doing so, we increase the amount of time that the material is in contact with the airflow. We call this term counter-flow. Maximizing the time in contact with the laminar airflow from the Super Air Knife gives us the best chance at a successful result. Whether we’re talking about cooling, drying, or cleaning, the longer that the material is in contact with the laminar airflow the better the results will be.

air knife counter flow

In this photo, the Super Air Knife is positioned upside down at an angle above a conveyor belt, against the direction of travel. We recommend installing the Super Air Knife in this orientation as it allows the airflow to get closest to the material being blown off. They’ve used their own brackets to allow the knife to be adjusted when blowing residual dust off of a conveyor for a mining application. The dust on the belt would build up over time and was difficult to remove. By installing a Super Air Knife, they’re able to continuously remove the dust from the conveyor belt before it becomes a problem.

If you have an application that would be better served with one of EXAIR’s Super Air Knives, give us a call. An Application Engineer is ready to assist you in selecting the proper material, length, and mounting method.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

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
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What’s In My Air, And Why Is It Important?

Everyone knows there’s oxygen in our air – if there wasn’t oxygen in the air you’re breathing right now, reading this blog would be the least of your concerns. Most people know that oxygen, in fact, makes up about 20% of the earth’s atmosphere at sea level, and that almost all the rest is nitrogen. There’s an impressive list of other gases in the air we breathe, but what’s more impressive (to me, anyway) is the technology behind the instrumentation needed to measure some of these values:

Reference: CRC Handbook of Chemistry and Physics, edited by David R. Lide, 1997.

We can consider, for practical purposes, that air is made up of five gases: nitrogen, oxygen, argon, carbon dioxide, and water vapor (more on that in a minute.)  The other gases are so low in concentration that there is over 10 times as much carbon dioxide as all the others below it, combined.

About the water vapor: because it’s a variable, this table omits it, water vapor generally makes up 1-3% of atmospheric air, by volume, and can be as high as 5%.  Which means that, even on a ‘dry’ day, it pushes argon out of the #3 slot.

There are numerous reasons why the volumetric concentrations of these gases are important.  If oxygen level drops in the air we’re breathing, human activity is impaired.  Exhaustion without physical exertion will occur at 12-15%.  Your lips turn blue at 10%.  Exposure to oxygen levels of 8% or below are fatal within minutes.

Likewise, too much of other gases can be bad.  Carbon monoxide, for example, is a lethal poison.  It’ll kill you at concentrations as low as 0.04%…about the normal amount of carbon dioxide in the atmosphere.

For the purposes of this blog, and how the makeup of our air is important to the function of EXAIR Intelligent Compressed Air Products, we’re going to stick with the top three: nitrogen, oxygen, and water vapor.

Any of our products are capable of discharging a fluid, but they’re specifically designed for use with compressed air – in basic grade school science terms, they convert the potential energy of air under compression into kinetic energy in such a way as to entrain a large amount of air from the surrounding environment.  This is important to consider for a couple of reasons:

  • Anything that’s in your compressed air supply is going to get on the part you’re blowing off with that Super Air Nozzle, the material you’re conveying with that Line Vac, or the electronics you’re cooling with that Cabinet Cooler System.  That includes water…which can condense from the water vapor at several points along the way from your compressor’s intake, through its filtration and drying systems, to the discharge from the product itself.
  • Sometimes, a user is interested in blowing a purge gas (commonly nitrogen or argon) –  but unless it’s in a isolated environment (like a closed chamber) purged with the same gas, most of the developed flow will simply be room air.

Another consideration of air make up involves EXAIR Gen4 Static Eliminators.  They work on the Corona discharge principle: a high voltage is applied to a sharp point, and any gas in the vicinity of that point is subject to ionization – loss or gain of electrons in their molecules’ outer valences, resulting in a charged particle.  The charge is positive if they lose an electron, and negative if they gain one.  Of the two gases that make up almost all of our air, oxygen has the lowest ionization energy in its outer valence, making it the easier of the two to ionize.  You can certainly supply a Gen4 Static Eliminator with pure nitrogen if you wish, but the static dissipation rate may be hampered to a finite (although probably very small) degree.

At EXAIR Corporation, we want to be the ones you think of when you think of compressed air.  If you’ve got questions about it, give us a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Air photo courtesy of Bruno Creative Commons License

The Super Air Knife Vs. a Homemade Drilled Pipe Solution

A drilled pipe has been used for many years to blow compressed air across a span for cleaning, cooling, and drying.  They are a simple tool that was created from spare parts and many holes.  The cost to make this type of product is not expensive, but to use this product in your application is very expensive.  Similarly, an incandescent lightbulb is inexpensive to purchase, but it will cost you much more in electricity than a LED light bulb.  Since 1983, EXAIR has been innovating safe and efficient products to be used in compressed air systems.  In this blog, I will compare the drilled pipe with the Super Air Knife.

Even though you can find the components relatively easily to design your own drilled pipe, this blow-off design is very costly and stressful to your compressed air system.  Typically, the holes along the pipe are in a row next to each other.  As the airstream leaves from each hole, it will hit the airstream from the one next to it.  This will cause turbulent air flows which has inconsistent forces and loud noises.  Also, with turbulent air flows, the ability to entrain the surrounding ambient air is very small.  We call this the amplification ratio.  The higher the amplification ratio, the more efficient the blow-off device is.  For a drilled pipe, the amplification ratio is near 3:1 (3 parts ambient air to 1 part compressed air).

A colleague, Brian Bergmann, wrote a blog about the amplification ratio of the EXAIR Super Air Knife.  (Read it HERE.)  This blog demonstrates how EXAIR was able to engineer an efficient way to blow air across a span.  The unique design of the Super Air Knife creates an amplification ratio of 40:1 which is the highest in the market.   Unlike the drilled pipe, the gap opening runs along the entire knife for precise blowing.  This engineered gap allows for laminar air flow which has a low noise level, a consistent blowing force, and maximum amplification ratio.  With these benefits, the Super Air Knife can reduce the amount of compressed air required, which will save you money and save your compressed air system.

In comparing the drilled pipe to the Super Air Knife, I will relate both products in a simple cooling application.   Thermodynamics expresses the basics of cooling with an air temperature and an air mass.  Since both products are represented in the same application, the air temperature will be the same.   Thus, the comparison will be with the amount of air mass.  In this example, the customer did some calculations, and they needed 450 Lbs. of air to cool the product to the desired temperature.  At standard conditions, air has a density of 0.0749 lbs/ft3.  To convert to a volume of air, we will divide the weight by the density:

450 lbs. / (0.0749 lbs./ft3) = 6,008 ft3 of air

To meet this requirement, reference Table 1 below.  It shows the volume of air required by your compressed air system to meet this demand.  As you can see, your compressor has to work 13X harder to cool the same product when using a drilled pipe.  Just like the LED light bulbs, the Super Air Knife has more efficiency, more innovation, and uses less compressed air.  In turn, the Super Air Knife will save you a lot of money in electrical costs.  If you would like to see how much the Super Air Knife can save compared to the drilled pipe, we have that information in this blog.  (Read it HERE.)  For my reference, it will reduce the stress of your compressed air system.

if you would like to compare any of your current blow-off devices with an innovative EXAIR product, you can contact an Application Engineer.  We can do an Efficiency Lab to shine an LED light on saving energy and money with your compressed air.

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

Great Stuff About Jets

There are a number of fascinating facts about jets…both the aircraft engines and the EXAIR Intelligent Compressed Air Products:

  • Because they don’t require dense air to engage spinning blades (like their propeller driven counterparts,) they can operate at much higher altitudes. (Jet aircraft engines only)
  • They provide a high thrust, directed airstream, which makes them great for part ejection, chip removal, and part drying. (EXAIR Air Jets only)
  • With few or no moving parts, they are extremely reliable, durable, and safe. (Both jet aircraft engines and EXAIR Air Jets)
  • They use the Coanda effect (a principle of fluidics whereby a fluid flow tends to attach itself to a nearby surface, and follow that surface regardless of the flow’s initial direction) to do what they do.
    • EXAIR Air Jets use this principle to generate a vacuum in their throat, pulling in a large amount of “free” air from the surround environment, making their use of compressed air very, very efficient.
    • Jet (and propeller driven) aircraft wings employ the Coanda effect to create aerodynamic lift, enabling the plane to fly.

Now, since I’m not a pilot, nor do I particularly like to fly, but I AM a fluid dynamics nerd, the rest of this blog will be about the Air Jets that EXAIR makes.

All of our Air Jet products operate on the same principle…using the Coanda effect (as described above) to generate a high volume air flow while minimizing compressed air consumption:

(1) Compressed air enters and is distributed through an annular ring, and directed towards the discharge via the Coanda effect.
(2) This causes entrainment of surrounding air, both through the throat, and at the discharge.
(3) The total developed flow has tremendous force and velocity, for a minimal consumption of valuable compressed air.(1) Compressed air enters and is distributed through an annular ring, and directed towards the discharge via the Coanda effect.
(2) This causes entrainment of surrounding air, both through the throat, and at the discharge.
(3) The total developed flow has tremendous force and velocity, for a minimal consumption of valuable compressed air.

There are four distinct models of the EXAIR Air Jet:

  • Model 6013 High Velocity Air Jet is made of brass for economy and durability.  The annular ring gap (see 1, above) is fixed by a 0.015″ thick shim.  Performance can be modified by changing to a 0.006″ or 0.009″ thick shim, which come in the Model 6313 Shim Set.
  • Model 6013SS is a Type 303 Stainless Steel version, for higher temperatures – good to 400°F (204°C) – and superior corrosion resistance.
  • Model 6019 Adjustable Air Jet is brass construction, and dimensionally identical to the Model 6103.  Instead of a shim that sets the annular ring gap, though, it has a threaded plug, with a micrometer-style indicator, to “fine tune” the gap.
  • Model 6019SS is the Type 303 Stainless Steel version…fine tuning adjustability, good for high heat and/or corrosive elements.
Four distinct models to meet the needs of your air blowing application.

If you’d like to find out more about EXAIR’s quiet, efficient, and safe Air Jets, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Vac-u-Gun: Low Cost Vacuum, Blowoff and Transfer

What is the Vac-u-Gun?  It is a low cost solution to many types of cleaning operations within an industrial setting.  The Vac-u-Gun is a vacuum gun, a blow gun, and a transfer tool, all-in-one! It is lightweight, easy to use, has durable die cast construction, and best of all, no moving parts to wear out. Simply hook up to a compressed air hose, and get to work.

Vac u Gun Hose

The Vac-u-Gun contains a nozzle insert that dictates the direction of air flow and operation. By simply unscrewing the the cap, reversing the orientation of the nozzle insert, and re-installing the cap, the gun is changed from a vacuum device to a blowoff device, and vice-versa.

vac u gun orientation
Reverse the direction of the nozzle insert to change from vacuum to blowoff

The Vac-u-Gun can be used in three modes- Vacuum, Transfer and Blowoff-

Vacuum Mode – Vacuum shavings, absorbents, sawdust, or spills into a reusable bag, or into a receptacle via the vacuum hose. Why blow it off and the have to sweep it up later?

Transfer Mode – Transfer small parts, pellets, or trim over long distances, using the smooth bore vacuum hose.

Blowoff Mode – Blow chips, water, coolant, or scrap away from the work area. The large 1-1/4″ diameter outlet directs the air over a larger area in less time. The Vac-u-Gun uses less compressed air than an ordinary blow gun.

Vac-U-Gun Specifications

There are many advantages to a Vac-u-Gun, and some are:

Low cost, no moving parts/maintenance free, durable die cast construction, easy to switch form vacuum to blow mode, safe – no electricity, meets OSHA pressure requirements, lightweight and portable, versatile, and quiet.

Versatile!  In just seconds, the Vac-u-Gun can transform from a powerful, handheld vacuum tool into an efficient blow gun or transfer tool for lightweight materials. Each Vac-u-Gun System comes with the attachments needed to suit numerous industrial applications.

Three (3) Vac-u-Gun System options are available and shown below-

Vac-u-Gun System Options

All of the Systems include the Vac-u-Gun, brush, crevice tool, skimmer tool and (2) extension wands.

The Model 6192 Collection System also includes the reusable bag with clamp for debris collection.

The Model 6292 Transfer System also includes the vacuum hose, for transferring the debris to a collection point.

The Model 6392 All Purpose System also includes both the reusable bag and clamp and the transfer hose, providing the most versatility of all.

To view a video that shows the Model 6392 All Purpose System, and demonstrates how it works, please view the video below-

 

If you have questions about the Vac-u-Gun or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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