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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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

EXAIR’s Super Air Knife Performs Well at Low Cost for Blowoff

There are many ways to blowoff, cool, and/or dry materials.  A few of these methods are the drilled pipe, an array of flat nozzles, using a blower driven air knife and the EXAIR Super Air Knife.  We’ll examine each in further detail, for blowoff of water after a bottling cleaning operation.  Testing was done at 60 PSIG of supply pressure.  The blower utilized a 10 hp motor and was a centrifugal type spinning at 18,000 RPM.  Sound levels were taken with product not present to test the sound of each of the blowoff types.

SAK black1 (2)

pipe-black (2)Drilled pipe is a common blowoff because it is very inexpensive and easy to make.  But drilled pipe performs poorly.  The low cost to make the drilled pipe is quickly outpaced by the inefficiency and high compressed air costs.  The holes are easily blocked and the noise level is excessive, both of which violate OSHA requirements.  Also, the air pattern across the length can be very inconsistent, with areas of low flow and areas of turbulent flow.

flatnozzle (2)Flat air nozzles installed along a length of pipe is another inexpensive option, but it can be a poor performer.  The flat nozzles are available in many materials, from many manufacturers.  The flat nozzles do offer some efficiencies, but similar to drilled pipe, the operating costs and noise levels are high. Air pattern across the length can be inconsistent with areas of high and low flows, leading to incomplete drying or cooling. Also, many of these nozzles are made from plastic material which breaks or cracks when it it hit which causes additional expense and maintenance to replace broken nozzles.

blower (2)A blower air knife can prove to be an expensive and noisy option.  Typically, the initial purchase price is high.  Operating costs are lower than the drilled pipe and flat nozzles and in line with the Super Air Knives.  The blowers can be very large and space for two 3″ diameter hoses requires extra mounting space compared to low profile other options. Noise levels are high, at 90 dBA.  Annual costs for bearing and filter maintenance can be significant.

gh_SAK_750x696EXAIR Super Air Knives performed exceptionally well in removing the water in one pass due to the strong, laminar flow of air.  Sound level was low at just 69 dBA, well within OSHA requirements for an hour 8 hour exposure time. Safe operation is assured, as the Super Air Knife design cannot be dead-ended.  Maintenance costs are low, as the Super Air Knife has no moving parts to breakdown or wear out.

Air-Knife-Blowoff-Comparison
** A pair of 12″ Super Air Knives was used for this comparison

Ultimately, the Super Air Knife is a low cost way to blowoff, dry, clean and cool.

If you have questions about Super Air Knives, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Professor Penurious, Mystery Solver!

ZOINKS! What have Professor Penurious and the gang gotten into this time? Enjoy viewing this video – we sure do enjoy making them…And recognizing that some day the Oscar committee will be calling.

Russ Bowman
Application Engineer
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Chain-Chain-Change, Change Out That Drilled Pipe…

Life is full of change.  It might sound trite, but truer words were never spoken.  I used to get up around 6:30 on work days.  Now, thanks to my son’s middle school schedule, I’m usually seeing him out the door at that time.  Getting up earlier was certainly a difficult change at first, but it’s had its benefits.  Not the least of which is spending a little extra time with the boy in the morning.

One of our favorite things to do while eating breakfast is to watch the ‘How things are made’ types of shows. Of course, watching these types of shows with an engineer has its downside.  While we can usually explain exactly what’s happening in the process of whatever is being made, the problem is that we often do.  Meaning we wind up talking over the program, which, ironically, is one of my greatest pet peeves.  Speaking of change, guess that’s something I need to work on…

20141002_062454

At any rate, this morning we saw a show on making saltines.  At the sight of the copper pipe positioned near where the cracker dough comes off the die-cut wheel, I knew exactly what was up. ‘They’re using drilled pipe! That’s not safe and a HUGE waste of compressed air!  That’s the perfect application for a Super Air Knife!”  Guess watching these programs with an EXAIR engineer has an additional risk: We can get a little over-excited when we see OSHA violations and wastes of compressed air! I think I about made my son jump out of his gym shorts, but he’s watched these sorts of shows with me before.  He knew the risks…

Life is full of change, and while perhaps I can get better at not talking while the TV show is on, I doubt I’ll ever stop cringing at safety violations and wasting compressed air.  Do you have drilled pipe in your plant?  If so, you could be in violation of multiple safety standards and are definitely wasting money on compressed air.  EXAIR can help you minimize harmful noise levels and keep you in compliance with OSHA’s dead-end pressure standard. Please give EXAIR a call to begin saving air and increasing safety!

Dan Preston
Engineer-at-large
DanPreston@exair.com
1-800-903-9247