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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Long Super Air Knives Help Dry Oil Pans

Last week I was contacted by a local machining company who was stamping oil pans for a large automotive manufacturer. Stamping, also referred to as pressing, is an industrial machining process where a flat material, like sheet metal, is placed into the stamping press and a press die stamps down to form a specific shape or mold.

metal stamping
Example of Metal Stamping Machines

As the oil pan exits the stamping press the parts are sent through a water rinse to remove any particulate and then hung from a drying rack. After the parts are dry they are sent to a paint booth then an oven for the paint to cure. They were beginning to see reject parts after the curing process due to residual water droplets being present which caused the paint to bubble or streak in this particular area. As a quick fix, on each side of the drying rack they ran compressed air to long lengths of 1″ PVC pipe with approximately (21) 1/8″ drilled holes spaced about every 4 inches to try and dry the parts more efficiently. While this did improve the dry cycle time, they were still seeing the rejects due to gaps in the airflow continuing to leave water drops. Another concern was their compressed air usage as they have a large number of rotary presses requiring compressed air so this particular application was, as the customer stated – “getting whatever air is left”, and potentially starving other processes of required air.

Once again EXAIR had the perfect solution, the Super Air Knife. The Super Air Knife produces an even, high velocity curtain of air across the entire length of the knife. Extremely efficient, the unit uses only 1 part of compressed air while entraining 40 parts of surrounding, ambient air. In this particular application, I recommended the customer mount one 84″ knife on the front and another 84″ unit on the back of the rack, allowing the parts to pass through the laminar airflow removing the excess water from both sides of the part.

SAK
Lengths up to 108″ in single piece construction.

Addressing the compressed air usage – each 1/8″ drilled hole is going to consume roughly 21.4 SCFM @ 80 PSIG, so for a quantity of (21) drilled holes, the total would be 449 SCFM per PVC pipe. In contrast, an 84″ Super Air Knife is going to consume only 243.6 SCFM @ 80 PSIG, or just a little over half of what they are currently using!

Justin Nicholl
EXAIR Corporation
justinnicholl@exair.com
@EXAIR_JN

 

Metal Stamping Machines image courtesy of Sam Beebe Creative Commons License