Designing a Compressed Air Distribution System

Compressed air is used to operate pneumatic systems in a facility, and it can be segregated into three sections; the supply side, the demand side, and the distribution system.  The supply side is the air compressor, after-cooler, dryer, and receiver tank that produce and treat the compressed air.  They are generally located in a compressor room somewhere in the corner of the plant.  The demand side are the collection of end-use devices that will use the compressed air to do “work”.  These pneumatic components are generally scattered throughout the facility.  To connect the supply side to the demand side, a compressed air distribution system is required.  Distribution systems are pipes which carry the compressed air from the compressor to the pneumatic devices.  For a sound compressed air system, the three sections have to work together to make an effective and efficient system.

An analogy, I like to compare to the compressed air system, is an electrical system.  The air compressor will be considered the voltage source, and the pneumatic devices will be marked as light bulbs.  To connect the light bulbs to the voltage source, electrical wires are needed.  The distribution system will represent the electrical wires.  If the wire gauge is too small to supply the light bulbs, the wire will heat up and the voltage will drop.  This heat is given off as wasted energy, and the light bulbs will dim.

The same thing happens within a compressed air system.  If the piping size is too small, a pressure drop will occur.  This is also wasted energy.   In both types of systems, wasted energy is wasted money.  One of the largest systematic problems with compressed air systems is pressure drop.  If too large of a pressure loss occurs, the pneumatic equipment will not have enough power to operate effectively.  As shown in the illustration below, you can see how the pressure decreases from the supply side to the demand side.  With a properly designed distribution system, energy can be saved, and in reference to my analogy, it will keep the lights on.

Source: Compressed Air Challenge Organization

To optimize the compressed air system, we need to reduce the amount of wasted energy; pressure drop.   Pressure drop is based on restrictions, obstructions, and piping surface.  If we evaluate each one, a properly designed distribution system can limit the unnecessary problems that can rob the “power” from your pneumatic equipment.

  1. Restriction: This is the most common type of pressure drop. The air flow is forced into small areas, causing high velocities.  The high velocity creates turbulent flow which increases the losses in air pressure.  Flow within the pipe is directly related to the velocity times the square of the diameter.  So, if you cut the I.D. of the pipe by one-half, the flow rating will be reduced to 25% of the original rating; or the velocity will increase by four times.  Restriction can come in different forms like small diameter pipes or tubing; restrictive fittings like quick disconnects and needle valves, and undersized filters and regulators.
  2. Obstruction: This is generally caused by the type of fittings that are used.  To help reduce additional pressure drops use sweeping elbows and 45-degree fittings instead of 90 deg. elbows.  Another option is to use full flow ball valves and butterfly valves instead of seated valves and needle valves.  If a blocking valve or cap is used for future expansion, try and extend the pipe an additional 10 times the diameter of the pipe to help remove any turbulence caused from air flow disruptions.  Removing sharp turns and abrupt stops will keep the velocity in a more laminar state.
  3. Roughness: With long runs of pipe, the piping surface can affect the compressed air stream. As an example, carbon steel piping has a relative rough texture.  But, over time, the surface will start to rust creating even a rougher surface.  This roughness will restrain the flow, creating the pressure to drop.  Aluminum and stainless steel tubing have much smoother surfaces and are not as susceptible to pressure drops caused by roughness or corrosion.

As a rule, air velocities will determine the correct pipe size.  It is beneficial to oversize the pipe to accommodate for any expansions in the future.  For header pipes, the velocities should not be more than 20 feet/min (6 meter/min).  For the distribution lines, the velocities should not exceed 30 feet/min (9 meter/min).  In following these simple rules, the distribution system can effectively supply the necessary compressed air from the supply side to the demand side.

To have a properly designed distribution system, the pressure drop should be less than 10% from the reservoir tank to the point-of-use.  By following the tips above, you can reach that goal and have the supply side, demand side, and distribution system working at peak efficiency.  If you would like to reduce waste even more, EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side.  This would be the pneumatic equivalent of changing those light bulbs at the point-of-use into LEDs.

John Ball
Application Engineer
Twitter: @EXAIR_jb


Photo: Light Bulb by qimonoCreative Commons CC0


Six Steps To Optimizing Your Compressed Air System – Step 1: Measure

“To measure is to know – if you cannot measure it, you cannot improve it.”
-Lord Kelvin, mathematical physicist, engineer,and pioneer in the field of thermodynamics.

This is true of most anything. If you want to lose weight, you’re going to need a good scale. If you want to improve your time in the 100 yard dash, you’re going to need a good stopwatch. And if you want to decrease compressed air consumption, you’ll need a good flowmeter. In fact, this is the first of six steps that we can use to help you optimize your compressed air system.

Six Steps To Optimizing Your Compressed Air System

There are various methods of measuring fluid flow, but the most popular for compressed air is thermal mass air flow.  This has the distinct advantage of accurate and instantaneous measurement of MASS flow rate…which is important, because measuring VOLUMETRIC flow rate would need to be corrected for pressure in order to determine the true compressed air consumption.  My colleague John Ball explains this in detail in a most excellent blog on Actual (volume) Vs. Standard (mass) Flows.

So, now we know how to measure the mass flow rate.  Now, what do we do with it?  Well, as in the weight loss and sprint time improvements mentioned earlier, you have to know what kind of shape you’re in right now to know how far you are from where you want to be.  Stepping on a scale, timing your run, or measuring your plant’s air flow right now is your “before” data, which represents Step One.  The next Five Steps are how you get to where you want to be (for compressed air optimization, that is – there may be a different amount of steps towards your fitness/athletic goals.)  So, compressed air-wise, EXAIR offers the following solutions for Step One:

Digital Flowmeter with wireless capability.  This is our latest offering, and it doesn’t get any simpler than this.  Imagine having a flowmeter installed in your compressed air system, and having its readings continually supplied to your computer.  You can record, analyze, manipulate, and share the data with ease.

Monitor your compressed air flow wirelessly over a ZigBee mesh network.

Digital Flowmeter with USB Data Logger.  We’ve been offering these, with great success, for almost seven years now.  The Data Logger plugs into the Digital Flowmeter and, depending on how you set it up, records the flow rate from once a second (for about nine hours of data) up to once every 12 hours (for over two years worth.)  Pull it from your Digital Flowmeter whenever you want to download the data to your computer, where you can view & save it in the software we supply, or export it directly into Microsoft Excel.

From the Digital Flowmeter, to your computer, to your screen, the USB Data Logger shows how much air you’re using…and when you’re using it!

Summing Remote Display.  This connects directly to the Digital Flowmeter and can be installed up to 50 feet away.  At the push of a button, you can change the reading from actual current air consumption to usage for the last 24 hours, or total cumulative usage.  It’s powered directly from the Digital Flowmeter, so you don’t even need an electrical outlet nearby.

Monitor compressed air consumption from a convenient location, as well as last 24 hours usage and cumulative usage.

Digital Flowmeter.  As a stand-alone product, it’ll show you actual current air consumption, and the display can also be manipulated to show daily or cumulative usage. It has milliamp & pulse outputs, as well as a Serial Communication option, if you can work with any of those to get your data where you want it.

With any of the above options, or stand-alone, EXAIR’s Digital Flowmeter is your best option for Step One to optimize your compressed air system.

Stay tuned for more information on the other five steps.  If you just can’t wait, though, you can always give me a call.  I can talk about compressed air efficiency all day long, and sometimes, I do!


Line Loss: What It Means To Your Compressed Air Supply Pipe, Tubing, And Hose

“Leave the gun. Take the canolli.”

“What we’ve got here is failure to communicate.”

“I’ll get you my pretty, and your little dog too!”

“This EXAIR 42 inch Super Air Knife has ¼ NPT ports, but the Installation and Operation Instructions recommend feeding it with, at a minimum, a ¾ inch pipe…”

If you’re a movie buff like me, you probably recognize 75% of those quotes from famous movies. The OTHER one, dear reader, is from a production that strikes at the heart of this blog, and we’ll watch it soon enough. But first…

It is indeed a common question, especially with our Air Knives: if they have 1/4 NPT ports, why is such a large infeed supply pipe needed?  It all comes down to friction, which slows the velocity of the fluid all by itself, and also causes turbulence, which further hampers the flow.  This means you won’t have as much pressure at the end of the line as you do at the start, and the longer the line, the greater this drop will be.

This is from the Installation & Operation Guide that ships with your Super Air Knife. It’s also available from our PDF Library (registration required.)

If you want to do the math, here’s the empirical formula.  Like all good scientific work, it’s in metric units, so you may have to use some unit conversions, which I’ve put below, in blue (you’re welcome):

dp = 7.57 q1.85 L 104 / (d5 p)


dp = pressure drop (kg/cm2) 1 kg/cm2=14.22psi

q = air volume flow at atmospheric conditions (FAD, or ‘free air delivery’) (m3/min) 1 m3/min = 35.31 CFM

L = length of pipe (m) 1m = 3.28ft

d = inside diameter of pipe (mm) 1mm = 0.039”

p = initial pressure – abs (kg/cm2) 1 kg/cm2=14.22psi

Let’s solve a problem:  What’s the pressure drop going to be from a header @80psig, through 10ft of 1″ pipe, feeding a Model 110084 84″ Aluminum Super Air Knife (243.6 SCFM compressed air consumption @80psig)…so…

q = 243.6 SCFM, or 6.9 m3/min

L = 10ft, or 3.0 m

d = 1″, or 25.6 mm

p = 80psig, or 94.7psia, or 6.7 kg/cm2

1.5 psi is a perfectly acceptable drop…but what if the pipe was actually 50 feet long?

Again, 1.5 psi isn’t bad at all.  8.2 psi, however, is going to be noticeable.  That’s why we’re going to recommend a 1-1/4″ pipe for this length (d=1.25″, or 32.1 mm):

I’m feeling much better now!  Oh, I said we were going to watch a movie earlier…here it is:

If you have questions about compressed air, we’re eager to hear them.   Call us.

Russ Bowman
Application Engineer
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More Efficient Compressed Air Use Could Lead To Energy Rebates

The use of compressed air can be found in almost any industry and is often referred to as a “fourth utility” next to water, gas and electric. The generation of compressed air accounts for approximately 1/3 of all energy costs in an industrial facility, in many cases, it’s the largest energy user in an industrial plant. With an average cost of $ 0.25 per every 1,000 SCF used, compressed air can be expensive to produce so it is very important to use this utility as efficiently as possible.

Utility companies recognize the benefit of using engineered products to reduce compressed air usage, like the ones manufactured by EXAIR, and offers rebate incentives for making a switch. Our local utility provider here in Cincinnati, Duke Energy, offers a $ 20 incentive for each replacement engineered nozzle.


Our Model # 1100SS 1/4″ FNPT and Model # 1101SS 1/4″ MNPT Super Air Nozzles

In their specification, the nozzle must meet a certain volumetric flow rate (SCFM) at 80 PSIG operating pressure for a given pipe size. For example, when looking at a 1/4″ nozzle, the flow rate must be less than or equal to 17 SCFM when operated at 80 PSIG. Our most popular nozzles for “general” blowoff applications would be our Model # 1100 (1/4″ FNPT) or our Model # 1101 (1/4″ MNPT) Super Air Nozzles. These nozzles require 14 SCFM @ 80 PSIG so this would be the ideal solution to reduce the air demand and take advantage of the rebate.

Here at EXAIR, much of our focus is to improve the overall efficiency of industrial compressed air operating processes and point of use compressed air operated products. If you’d like to contact one of our application engineers, we can help recommend the proper engineered solution to not only save on your compressed air usage but also assist with possible energy rebates available in your area.

Justin Nicholl
Application Engineer



Video Blog: EXAIR’s New Wireless Digital Flowmeter Installation

Model 9093ZG

This year EXAIR has introduced the new Wireless Digital Flowmeter. This meter is capable of monitoring compressed air consumption and transmitting the usage data to your PC wirelessly using ZigBee mesh networking protocol.

Each meter has a range of 100′ and allows for multiple meters to be installed on the same network, “piggybacking” off of one another. As long as the next meter is installed within 100′ of the first, you will only require one ZigBee gateway.

Take a look at my short video below that will walk you through the steps of installing the EXAIR Logger Software and the Device Discovery Software found on the website. Then, start logging your data!


Tyler Daniel

Application Engineer


Twitter: @EXAIR_TD


Return on Investment: A Calculation to Support Using EXAIR Products

EXAIR Products

Return on Investment, or ROI, is the ratio of profit over total investment.  Many people use it to evaluate stocks, financial markets, capital equipment, etc.  It is a quantitative way in determining the validity of an investment or project.   Recently, there has been a big push by power companies for energy efficiency within the manufacturing sectors.  EXAIR, in partnership with Energy Star, has been manufacturing safe and efficient products since 1983.  An ROI will give a measurable value to communicate more thoroughly with your financial decision-makers.

Equation 1:  ROI = (Total annual savings – Total Project Cost) / Project Cost * 100

In an earlier blog, I wrote about a project with a company in calculating compressed air savings; “EXAIR Super Air Nozzles: 38 Day ROI Saves Money”.  In this blog, I determined the total compressed air savings and the payback period by switching to EXAIR Super Air Nozzles.  The payback period is the amount of time it will take for the project to pay for itself; and for the above manufacturer, it was calculated at 38 days.  To associate this to a Return on Investment, I will use that information from the blog to calculate the ROI.  Equation 1 shows that for any positive ROI value means that the payback period is less than one year.  The larger the ROI value, the quicker the investment that you made will start earning money for your company.

The first part of the equation, Total Annual Savings, is calculated by amount of compressed air savings when using EXAIR Super Air Nozzles in a blow-off application.  When this customer switched from copper tubes, which uses an excessive amount of compressed air, to the model 1110SS Super Air Nozzles, the compressed air consumption dropped by 80%.  Compressed air is considered a fourth utility in manufacturing plants because the amount of electricity to make compressed air is very large.  At a rate of $0.08/KWh, each Super Air Nozzle saved this company $306.00 per year.  As described in the blog, the facility used four nozzles per machine, and they had 25 machines in their facility.  The total annual savings is calculated as follows:

Equation 2: Total Annual Savings = $306 * 4 * 25 = $30,600 per year.

The second part of the equation, Total Project Cost, is the cost of the nozzles plus the labor to install them onto the machines.  The model 1110SS Super Air Nozzle has a price of $46.00 each.  These engineered nozzles are designed to use less compressed air by entraining the “free” ambient air, making them very efficient for blow-off applications.  The amount of time required to install four nozzles to each machine was 1 hour.  This time included tapping, fixturing, and testing each setup.  The labor rate that I will use in this example is $75.00 per hour (you can modify this to your current labor rate).  The labor cost to install four nozzles is $75.00 per machine.   The Total Project Cost can be calculated as follows:

Equation 3: Total Project Cost = ($46 * 100 nozzles) + ($75 * 25 machines) = $6,475

With the Total Annual Cost and the Project Cost known, we can insert these values into Equation 1 to calculate the ROI:

ROI = (Total annual savings – Total Project Cost) / Project Cost * 100

ROI = ($30,600 – $6,475)/$6,475 * 100

ROI = 373%

When a decision maker sees this large of a value for a Return on Investment, it makes it very easy to proceed with an energy-saving project to install EXAIR Super Air Nozzles on their machines.

Besides cost savings, there are some additional things that EXAIR products can provide.  It may be difficult to put a value on the savings, but these products can improve your process and save your company money.  First, they can reduce repair or replacement costs on maintenance items for the air compressors.  If you use less compressed air, then the running hours of the compressor is reduced.  Second, some things that can be easily overlooked is safety.  The Intelligent Compressed Air® products have a much lower sound level where expensive PPEs may not be required.  Another safety feature is dead-end pressure in which the operator could risk health in using open pipe or substandard nozzles.  Some other enhancements in using EXAIR products are improved system reliability, increased productivity, and reduced unscheduled downtimes (typically seen with broken plastic nozzles).  These added benefits plus the short ROI can validate a energy-savings project in your facility.

Power companies see the great value in using efficient engineered products in compressed air systems as they currently offer rebates.  If you need help to see if your local power company does offer rebates, EXAIR can research the programs for you.  The rebates will reduce the cost of each nozzle as well as cut the overall project cost.  EXAIR also offers an Efficiency Lab.  We will compare your current blowing device with an EXAIR product to find any compressed air savings.  It is simple to do.  Just fill out the form, Efficiency Lab, and ship your product to us.  We will test each product with calibrated equipment and report the results.  The comprehensive report will include compressed air savings which can be used for the ROI calculations above.  For the company above, they were able to save $30,600 a year with a ROI at 373%.  If you would like to team up with EXAIR to establish annual savings, project improvements, and rebates, you can contact an Application Engineer to get started.  We will be happy to work with you.

John Ball
Application Engineer
Twitter: @EXAIR_jb

Removing Condensation Is Key To Maintaining Performance

When air is compressed, it is heated to a point that causes the water or moisture  to turn to vapor. As the air begins to cool, the vapors turn to condensation, which can cause performance issues in a compressed air system. Many times this condensation forms in the basic components in the system like a receiver tank, dryer or filter.

Condensation is formed from water vapor in the air

It’s important to remove this condensation from the system before it causes any issues. There are four basic types of condensate drains that can be used to limit or prevent loss of air in the system.

The first method would be to have an operator manually drain the condensation through a drain port or valve. This is the least reliable method though as now it’s the operator’s responsibility to make sure they close the valve so the system doesn’t allow any air to escape which can lead to pressure drops and poor end-use device performance.

Example of a float drain

Secondly, a float or inverted bucket trap system can be used in plants with regular monitoring and maintenance programs in place to ensure proper performance.. These types of drain traps typically require a higher level of maintenance and have the potential to lose air if not operating properly.

An electrically actuated drain valve can be used to automatically drain the condensate at a preset time or interval. Typically these incorporate a solenoid valve  or motorized ball valve with some type of timing control.  These types of systems can be unreliable though as the valve may open without any moisture being present in the line, which can result in air loss or it may not be actuated open long enough for acceptable drain off. With these types of drains, it’s best to use some type of strainer to remove any particulate that could cause adverse performance.

Lastly,  zero air-loss traps utilize a reservoir and a float or level sensor to drain the condensate and maintain a satisfactory level. This type of setup is very reliable but does require the reservoir be drained frequently to keep the system clean and free of debris or contaminants.

If you have any questions or would like to discuss a particular process, contact an application engineer for assistance.

Justin Nicholl
Application Engineer


Condensation image courtesy of Anders Sandberg via creative commons license

Float drain image courtesy of the Compressed Air Challenge