Six Steps to Compressed Air Optimization: Step 3 – Use Efficient and Quiet Engineered Products

Compressed air is expensive, and you should treat it that way.  Frequent readers of the EXAIR Blog are familiar with our Six Steps to Compressed Air Optimization, and you may have seen these recent installments on Steps 1 and 2:

Six Steps to Optimization: Step 1 – Measure the Air Consumption

Six Steps to Compressed Air Optimization: Step 2 – Find and Fix Leaks

Now, there isn’t a strict order in which you MUST perform these steps, and they’re not all applicable in every air system (looking at you, Step 5: Use Intermediate Storage,) but these are likely the steps that a certified auditor will take, and the order in which they’ll take them.  If you’re looking for immediate, quantifiable results, though, Step 3 is a great place to start.  Consider:

  • A 1/4″ copper tube blow off can consume as much as 33 SCFM when supplied with compressed air at 80psig.  It’ll give you a good, strong blow off, for sure.  You can crimp the end and get that down to, say, 20 SCFM or so.  Or, you can install a Model 1100 Super Air Nozzle with a compression fitting, and drop that to just 14 SCFM.
    • If you’re tracking your compressed air usage, you’ll see that replacing just one of them saves you 45,600 Standard Cubic Feet worth of compressed in one 5 day (8 hour a day) work week.  That’s $11.40 in air generation cost savings, for a $42 (2020 List Price) investment.
    • If you spend time in the space where it’s installed, you’ll notice a dramatic improvement in the noise situation.  That sound level from the copper tube is likely over 100 dBA; the Super Air Nozzle’s is only 74 dBA.
This user was only a handful of compression fittings & nozzles away from over $800 in annual compressed air savings.
  • Drilled pipes are another common method to create a blow off.  They’re easy & cheap, but loud & expensive to operate.
    • A pipe drilled with 1/8″ holes and supplied @80psig will consume 13 SCFM per hole, and the holes are typically drilled on 1/2″ centers.
    • An EXAIR Super Air Knife consumes only 2.9 SCFM per inch of length, and because it’s an engineered product, it’s a LOT quieter as well.  Drilled pipes are, essentially, open ended blow offs just like the copper tube mentioned above.  When you let compressed air out of a hole like that, all the potential energy of the pressure is converted to force…and noise.
    • Drilled pipes are among the worst offenders; almost always well in excess of 100 dBA.  Super Air Knives generate a sound level of only 69 dBA with 80psig compressed air supply.  They are, in fact, the quietest compressed air blowing product on the market today.
This Model 110048 48″ Aluminum Super Air Knife replaced a drilled pipe for over $5,000 annual compressed air savings.

These aren’t just theoretical “for instances” either – the data, and the photos above, come from actual Case Studies we’ve performed with real live users of our products.  You can find them here, and here (registration required.)

These are two examples of EXAIR product users who only used Step 3 of our Six Steps, although BOTH of them were already practicing Step 4 (Turn off the compressed air when it isn’t in use)…they had their blow offs supplied through solenoid valves that were wired into the respective machine controls, and the Air Knife user HAD to do Step 6 (Control the air pressure at the point of use) to keep their product from being blown clear off the conveyor..

But we’ll be happy to help you with optimizing your compressed air system using any or all of the Six Steps. Give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Piping and Instrumentation diagrams (P&ID)

When it comes to drawings and diagrams to map out a process system, the piping and instrumentation diagrams (P&ID) are a great way to situate and find components.  They use different symbols to represent the type of products, the layout in the system, installation, and process flow.  These standard symbols are created by ANSI or ISO.  They are used in electrical, hydraulic, and pneumatic processes.  Since EXAIR has been manufacturing Intelligent Compressed Air Products since 1983, I will cover some pneumatic symbols and the process flow in this blog.

A colleague, Russ Bowman, wrote an article about “Knowing Your Symbols Is Key To Understanding Your Drawings”.  As a reference, air compressors are the start of your pneumatic system, and there are different types as represented by the symbols below.

The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

Air compressors are considered the fourth utility in industries because they use so much electricity; and they are inefficient.  So, you need to use the compressed air as efficiently as possible.  As a typical pneumatic system, the air compressors, receiver tanks and compressed air dryers would be on the supply side.  The distribution system, or piping, connects the supply side to the demand side.  This symbol is represented by a simple line.  The demand side will have many different types of pneumatic devices.  Since there are so many, ANSI or ISO has created some common types of equipment.  But if there isn’t a symbol created to represent that part, the idea is to draw a basic shape and mark it.

From top left, and then down: Automatic Drain Filter Separator, Pressure Regulator, and Super Air Knife

As an example, if I were to do a P&ID diagram of the EXAIR Super Air Knife Kit; it would look like the above diagram.  The kit will include the Super Air Knife with an Automatic Drain Filter Separator and a Pressure Regulator.  The Filter Separator is a diamond shape and since it has an Automatic Drain, a triangle is placed at the bottom.  Filter Separators are used to clean the compressed air and keep the Super Air Knife clean.  The Automatic Drain will discard water and oil from the filter bowl when it accumulates over a float.  The next item is the pressure regulator which is represented by a rectangle with an adjustment knob to “dial in” the desired blowing force.  And at the end, we drew a rectangle, which does represent a Super Air Knife, as marked.

Using the P&ID diagram for the process flow is also important.  You noticed that the Filter Separator will come before the Pressure Regulator.  This is significant when installing this system.  Remember the statement above about “using your compressed air as efficiently as possible”?  Inefficiencies come from two basic areas; pressure drop and overusing your compressed air.  Pressure drop is based on velocity.  The lower the velocity, the lower the pressure drop.  If the Filter Separator is placed after the Pressure Regulator, the lower pressure will increase the velocity.  Since air expands at lower pressure, the volume of air will increase.  And since the area of the compressed air pipe is the same, the velocity will have to increase.   For the second part with overusing compressed air, the Pressure Regulator will help.  You want to use the lowest amount of air pressure as possible for the Super Air Knife to “do the job”.  The lower air pressure will use less compressed air in your operation.

EXAIR products are engineered to be safe, efficient, and effective in your compressed air system.  If you need help to place them in your P&ID diagrams, an Application Engineer can help you.  It is important to have the pneumatic devices in the proper place, and if you want to efficiently use your compressed air, you can use EXAIR products for your blow-off devices.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Cooling With Compressed Air: Air Knife vs. Vortex Tube Products

One of the popular applications for the EXAIR Super Air Knife is cooling. When mounted so that the air flow sweeps across the surface of a product, the laminar nature of the air flow works to maximize the contact time with the surface, which also maximizes the heat transfer…which means better product cooling than, say the turbulent air flow from a fan or blower.

Still, it’s common for us to get questions about how to provide even faster cooling.  Well, the two main variables in heat transfer are the time the air is in contact with the product, and the difference in temperature between the product surface and the air.

We’ve already touched on “time in contact”…sweeping the laminar flow across the surface at as low of an angle as you can, against the direction of travel, is ideal.  Combine that with the extraordinarily high air flow due to the entrainment level of the Super Air Knife, and you get an awful lot of air in contact with the surface, for a (relatively) long time.

Super Air Knives cool steel casting from 1,725°F (940°C) to 200°F (93°C) in under 20 minutes.

The difference in temperature, though, is a little trickier to deal with.  Because the developed flow from the Super Air Knife is mostly entrained ambient temperature air from the surrounding environment, you’re at the mercy of that ambient temperature.  One of the most common question – of the common questions about faster cooling – is, can you feed a Super Air Knife with cold air from a Vortex Tube?  The answer is no, for two big reasons:

  • The Vortex Tube’s cold flow can’t be back pressured, which would happen if you fed it through the plenum of a Super Air Knife and tried to make it come out the 0.002″ gap.
  • Even if it did work, the entrained air which, remember, makes up most of the flow, is still room temperature…meaning the total developed flow is a lot closer to room temperature than however cold the air you fed the Super Air Knife would be.

If the surface area to be blown on, to effect the desired cooling, is suitably sized, a Vortex Tube can be installed at a low angle to sweep its flow across.  The cold air flow from a Vortex Tube can also be distributed to more than one point, to cover more surface area.  That’s exactly what we do with our Dual Point Hose Kits for our Adjustable Spot Coolers, Mini Coolers, and Cold Gun Aircoolant Systems:

Dual Point Hose Kits can distribute air to both sides of a part, or onto a wider surface, than a single point discharge.

In fact, both the Single and Dual Point Hose Kits have a variety of tips they can be fitted with for tighter, or broader, flow patterns:

In some cases, multiple Vortex Tube products can be used, and, in other situations, the cold air can be directed through a manifold of some sort:

There are numerous methods to distribute the cold air flow from a lone, or a series of, Vortex Tubes.

Applications like the two on the right above (setting molten chocolate in molds, and keeping those white plastic parts during ultrasonic welding, respectively,) commonly start out as Air Knife inquiries, but the need for refrigerated air leads to creative Vortex Tube solutions.

If you’d like to discuss whether your application is best served by a Super Air Knife or a Vortex Tube Spot Cooling Product, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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The Importance Of Properly Sized Compressed Air Supply Lines

EXAIR Corporation manufactures a variety of engineered compressed air products that have been solving myriad applications in industry for almost 37 years now.  In order for them to function properly, though, they have to be supplied with enough compressed air flow, which means the compressed air supply lines have to be adequately sized.

A 20 foot length of 1/4″ pipe can handle a maximum flow capacity of 18 SCFM, so it’s good for a Model 1100 Super Air Nozzle (uses 14 SCFM @80psig) or a Model 110006 6″ Super Air Knife (uses 17.4 SCFM @80psig,) but it’s going to starve anything requiring much more air than those products.  Since compressed air consumption of devices like EXAIR Intelligent Compressed Air Products is directly proportional to inlet pressure, we can use the flow capacity of the pipe, the upstream air pressure, and the known consumption of the EXAIR product to calculate the inlet pressure of a starved product.  This will give us an idea of its performance as well.

Let’s use a 12″ Super Air Knife, with the 20 foot length of 1/4″ pipe as an example.  The ratio formula is:

(P2 ÷ P1) C1 = C2, where:

P2 – absolute pressure we’re solving for*

P1 – absolute pressure for our published compressed air consumption, or C1*

C1 – known value of compressed air consumption at supply pressure P1

C2 – compressed air consumption at supply pressure P2

*gauge pressure plus 14.7psi atmospheric pressure

This is the typical formula we use, since we’re normally solving for compressed air consumption at a certain supply pressure, but, rearranged to solve for inlet pressure assuming the consumption will be the capacity of the supply line in question:

(C2 P1) ÷ C1 = P2

[18 SCFM X (80psig + 14.7psia)] ÷ 34.8 SCFM = 49psia – 14.7psia = 34.3psig inlet pressure to the 12″ Super Air Knife.

From the Super Air Knife performance chart…

This table is found on page 22 of EXAIR Catalog #32.

…we can extrapolate that the performance of a 12″ Super Air Knife, supplied with a 20 foot length of 1/4″ pipe, will perform just under the parameters of one supplied at 40psig:

  • Air velocity less than 7,000 fpm, as compared to 11,800 fpm*
  • Force @6″ from target of 13.2oz total, instead of 30oz*
  • *Performance values for a 12″ length supplied with an adequately sized supply line, allowing for 80psig at the inlet to the Air Knife.

Qualitatively speaking, if you hold your hand in front of an adequately supplied Super Air Knife, it’ll feel an awful lot like sticking your hand out the window of a moving car at 50 miles an hour.  If it’s being supplied with the 20 foot length of 1/4″ pipe, though, it’s going to feel more like a desk fan on high speed.

The type of supply line is important too.  A 1/4″ pipe has an ID of about 3/8″ (0.363″, to be exact) but a 1/4″ hose has an ID of only…you guessed it…1/4″.  Let’s say you have 20 feet of 1/4″ hose instead, which will handle only 7 SCFM of compressed air flow capacity:

[7 SCFM X (80psig + 14.7psia)] ÷ 34.8 SCFM = 19psia – 14.7psia = 4.3psig inlet pressure to the 12″ Super Air Knife.

Our Super Air Knife performance chart doesn’t go that low, but, qualitatively, that’s going to generate a light breeze coming out of the Super Air Knife.  This is why, for good performance, it’s important to follow the recommendations in the Installation Guide:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.
All Installation Guides for EXAIR Intelligent Compressed Air Products contain recommended air supply line sizes for this very reason.  If you have any questions, though, about proper compressed air supply, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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