## How to Size a Receiver Tank and Improve your Compressed Air System

My colleague, Lee Evans, wrote a blog about calculating the size of primary receiver tanks within a compressed air system.  (You can read it here: Receiver Tank Principle and Calculations).  I would like to expand a bit more about secondary receiver tanks.  They can be strategically placed throughout the plant to improve your compressed air system.  The primary receiver tanks help to protect the supply side when demands are high, and the secondary receiver tanks help systems on the demand side to optimize performance.

I like to compare the pneumatic system to an electrical system.  The receiver tanks are like capacitors.  They store energy produced by an air compressor like a capacitor stores energy from an electrical source.  If you have ever seen an electrical circuit board, you notice many capacitors with different sizes throughout the circuit board (reference photo above).  The reason is to have a ready source of energy to increase efficiency and speed for the ebbs and flows of electrical signals.  The same can be said for the secondary receiver tanks in a pneumatic system.

To tie this to a compressed air system, if you have an area that requires a high volume of compressed air intermittently, a secondary receiver tank would benefit this system.  There are valves, cylinders, actuators, and pneumatic controls which turn on and off.  And in most situations, very quickly.  To maximize speed and efficiency, it is important to have a ready source of air nearby to supply the necessary amount quickly.

For calculating a minimum volume size for your secondary receiver tank, we can use Equation 1 below.  It is the same as sizing a primary receiver tank, but the scalars are slightly different.  The secondary receivers are located to run a certain machine or area.  The supply line to this tank will typically come from a header pipe that supplies the entire facility.  Generally, it is smaller in diameter; so, we have to look at the air supply that it can feed into the tank.  For example, a 1” NPT Schedule 40 Pipe at 100 PSIG can supply a maximum of 150 SCFM of air flow.  This value is used for Cap below.  C is the largest air demand for the machine or targeted area that will be using the tank.  If the C value is less than the Cap value, then a secondary tank is not needed.  If the Cap is below the C value, then we can calculate the smallest volume that would be needed.  The other value is the minimum tank pressure.  In most cases, a regulator is used to set the air pressure for the machine or area.  If the specification is 80 PSIG, then you would use this value as P2.  P1 is the header pressure that will be coming into the secondary tank.  With this collection of information, you can use Equation 1 to calculate the minimum tank volume.  So, any larger volume would fit the requirement as a secondary receiver tank.

Secondary Receiver tank capacity formula (Equation 1)

V = T * (C – Cap) * (Pa) / (P1-P2)

Where:

V – Volume of receiver tank (cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P2 – Regulated Pressure (PSIG)

If you find that your pneumatic devices are lacking in performance because the air pressure seems to drop during operation, you may need to add a secondary receiver to that system.  For any intermittent design, the tank can store that energy like a capacitor to optimize the performance.  EXAIR stocks 60 Gallon tanks, model 9500-60 to add to those specific locations, If you have any questions about using a receiver tank in your application, primary or secondary, you can contact an EXAIR Application Engineer.  We can restore that efficiency and speed back into your application.

John Ball
Application Engineer
Email: johnball@exair.com

Photo: Circuit Board courtesy from T_Tide under Pixabay License

## Opportunities To Save On Compressed Air

If you’re a regular reader of the EXAIR blog, you’re likely familiar with our:

This guideline is as comprehensive as you want it to be.  It’s been applied, in small & large facilities, as the framework for a formal set of procedures, followed in order, with the goal of large scale reductions in the costs associated with the operation of compressed air systems…and it works like a charm.  Others have “stepped” in and out, knowing already where some of their larger problems were – if you can actually hear or see evidence of leaks, your first step doesn’t necessarily have to be the installation of a Digital Flowmeter.

Here are some ways you may be able to “step” in and out to realize opportunities for savings on your use of compressed air:

• Power:  I’m not saying you need to run out & buy a new compressor, but if yours is

aging, requires more frequent maintenance, doesn’t have any particular energy efficiency ratings, etc…you might need to run out & buy a new compressor.  Or at least consult with a reputable air compressor dealer about power consumption.  You might not need to replace the whole compressor system if it can be retrofitted with more efficient controls.

• Pressure: Not every use of your compressed air requires full header pressure.  In fact, sometimes it’s downright detrimental for the pressure to be too high.  Depending on the layout of your compressed air supply lines, your header pressure may be set a little higher than the load with the highest required pressure, and that’s OK.  If it’s significantly higher, intermediate storage (like EXAIR’s Model 9500-60 Receiver Tank, shown on the right) may be worth looking into.  Keep in mind, every 2psi increase in your header pressure means a 1% increase (approximately) in electric cost for your compressor operation.  Higher than needed pressures also increase wear and tear on pneumatic tools, and increase the chances of leaks developing.
• Consumption:  Much like newer technologies in compressor design contribute to higher efficiency & lower electric power consumption, engineered compressed air products will use much less air than other methods.  A 1/4″ copper tube is more than capable of blowing chips & debris away from a machine tool chuck, but it’s going to use as much as 33 SCFM.  A Model 1100 Super Air Nozzle (shown on the right) can do the same job and use only 14 SCFM.  This one was installed directly on to the end of the copper tube, quickly and easily, with a compression fitting.
• Leaks: These are part of your consumption, whether you like it or not.  And you shouldn’t like it, because they’re not doing anything for you, AND they’re costing you money.  Fix all the leaks you can…and you can fix them all.  Our Model 9061 Ultrasonic Leak Detector (right) can be critical to your efforts in finding these leaks, wherever they may be.
• Pressure, part 2: Not every use of your compressed air requires full header pressure (seems I’ve heard that before?)  Controlling the pressure required for individual applications, at the point of use, keeps your header pressure where it needs to be.  All EXAIR Intelligent Compressed Air Product Kits come with a Pressure Regulator (like the one shown on the right) for this exact purpose.
• Air Quality: Dirty air isn’t good for anything.  It’ll clog (and eventually foul) the inner workings of pneumatic valves, motors, and cylinders.  It’s particularly detrimental to the operation of engineered compressed air products…it can obstruct the flow of Air Knives & Air Nozzles, hamper the cooling capacity of Vortex Tubes & Spot Cooling Products, and limit the vacuum (& vacuum flow) capacity of Vacuum Generators, Line Vacs, and Air Amplifiers.

Everyone here at EXAIR Corporation wants you to get the most out of your compressed air use.  If you’d like to find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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## EXAIR Air Nozzles – Here’s Their Simple ROI

Return on Investment, or ROI, is the ratio of profit over total investment.  Many people use it to check stocks, financial markets, capital equipment, etc.  It is a quantitative way in determining the validity for an investment or project.   You can use the ROI value to give a measurable rate in looking at your investment.

For a positive ROI value, the project will pay for itself in less than one year.  Any negative values would represent a high-risk investment.  In this blog, I will compare the ROI when replacing a ¼” NPT open pipe with a model 1122 2” Flat Super Air Nozzle.  Let’s start by looking at Equation 1 to calculate the Return on Investment:

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

The second part of the equation, Total Project Cost, is the cost of the nozzles plus the labor to install them onto the machine.  The model 1122, 2” Flat Super Air Nozzle, has a price of \$70.00 each.  The cost of a ¼” NPT Pipe that is roughly 2” long is around \$1.50 each.  What a difference!  How could EXAIR been in business for over 35 years?  Let’s continue on with the Return on Investment…

The amount of time required to install the nozzles to the end of a pipe is 1/2 hour (generously).  The labor rate that I will use in this example is \$75.00 per hour (you can change this to your current labor rate).  The labor cost to install a nozzle is \$35.00.   The Total Project Cost can be calculated as follows: (\$70 – \$1.50) + \$35.00 = \$103.50.  The next part of the equation, Total annual savings, has more complexity in the calculation, as shown below.

As a reference, EXAIR Super Air Nozzles for compressed air would be considered like LED light bulbs for electricity.  The open pipes and tubes would represent the incandescent light bulbs.  The reason for this parity is because of the amount of energy that the EXAIR Super Air Nozzles can save.  While LED light bulbs are a bit more expensive than the incandescent light bulbs, the Return on Investment has a high percentage, or in other words, a short payback period.  On the other hand, the open pipe is less expensive to purchase, but the overall cost to use in your compressed air system is much much higher.  I will explain why.

To calculate the Total Annual Savings, we need to generate a blow-off scenario (You can use your actual values to calculate the ROI for your project).  In this example, I will compare the ¼” NPT open pipe to the 2” Flat Super Air Nozzle.  (The reason behind this comparison is that the model 1122 can screw directly onto the end of the 1/4” NPT pipe.)   The amount of compressed air used by a 1/4” NPT open pipe is around 140 SCFM (3,962 SLPM) at 80 PSIG (5.5 Bar).  The model 1122 has an air consumption of 21.8 SCFM (622 SLPM) at 80 PSIG (5.5 Bar).  At an electrical rate of \$0.08 per Kilowatt-hour, we see that the cost to make compressed air is \$0.25 per 1000 standard cubic feet, or \$0.25/1000SCF.  (Based on 4 SCFM per horsepower of air compressor).

To calculate an annual savings, let’s use a blow-off operation of 8 hours/day for 250 days a year.   Replacing the ¼” NPT open pipe with a model 1122, it will save you (140 SCFM – 21.8 SCFM) = 118.2 SCFM of compressed air.  To put this into a monetary value, the annual savings will be 118.2 SCFM *\$0.25/1000SCF * 60 Min/hr * 8hr/day * 250 day/yr = \$3,546/year.  Now if you have more than one blow-off spot in your facility like this, imagine the total amount of money that you would save.

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 = (\$3,546 – \$103.50) / \$103.50 * 100

ROI = 3326%

With a percentage value that high, we are looking at a payback period of only 9 days.  You may look at the initial cost and be discouraged.  But in a little over a week, the model 1122 will have paid for itself.  And after using it for just 1 year, it will save your company \$3,546.00.  Like with any great idea, the LED light bulb clicked on in my mind.  What could be the total savings if you looked at all the blow-off applications in your facility?

In my experience, a loud blowing noise from your equipment is generally coming from an open pipe or tube.  With these “cheap” ways to blow compressed air, it will cost your company a lot of money to use as shown in the example above.  If you would like to team up with EXAIR to set up ways to increase savings, improve productivity, and increase safety, you can contact an Application Engineer to get started.  It can be as simple as screwing on a Super Air Nozzle.

John Ball
Application Engineer
Email: johnball@exair.com

## Compressed Air System Maintenance

When I was seventeen my grandfather took me to a used are dealership and helped me buy my first car. It wasn’t anything special, as it was a 1996  Chevrolet Lumina. It had its fair share of bumps and bruises, but the bones were solid. We took it home and he taught me how to do all the basics, we changed the oil, oil filter, air filter, brakes, pretty much every fluid we could, we changed.

You see my grandfather retired from Ford Motor Company after 50+ years of service. And he always said, “If you treat it right, it will treat you right.”; and I’ve lived by that ever since.

Just like a car, air compressors require regular maintenance to run at peak performance and minimize unscheduled downtime. Inadequate maintenance can have a significant impact on energy consumption via lower compression efficiency, air leakage, or pressure variability. It can also lead to high operating temperatures, poor moisture control, and excessive contamination.

Most problems are minor and can be corrected by simple adjustments, cleaning, part replacement, or the elimination of adverse conditions. This maintenance is very similar to the car maintenance mentioned above, replace filters, fluids, checking cooling systems, check belts and identify any leaks and address.

All equipment in the compressed air system should be maintained in accordance with the manufacturers specifications. Manufacturers provide inspection, maintenance, and service schedules that should be followed strictly. In many cases, it makes sense from efficiency and economic stand-points to maintain equipment more frequently than the intervals recommended by the manufactures, which are primarily designed to protect equipment.

One way to tell if your system is being maintained well and is operating properly is to periodically baseline the system by tracking power, pressure, flow (EXAIR Digital Flowmeter), and temperature. If power use at a given pressure and flow rate goes up, the systems efficiency is degrading.

## Types Of Maintenance

Maintaining a compressed air system requires caring for the equipment, paying attention to changes and trends, and responding promptly to maintain operating reliability and efficiency. Types of maintenance include;

1. Poor Maintenance – Sadly, some plants still operate on the philosophy, “If it isn’t broke, don’t fix it.” Due to the lack of routine preventative maintenance, this practice may result in complete replacement of an expensive air compressor as well as unscheduled and costly production interruptions.
2. Preventive  Maintenance – This type of maintenance can be done by plant personnel or by an outside service provider. Usually, it includes regularly scheduled monitoring of operating conditions. Replacement of air and lubricant filters, lubricant sampling and replacement, minor repairs and adjustments, and an overview of compressor and accessory equipment operation.
3. Predictive  Maintenance – Predictive maintenance involves monitoring compressor conditions and trends , including operating parameters such as power use, pressure drops, operating temperatures, and vibration levels. The Right combination of preventive and predictive maintenance generally will minimize repair and maintenance costs.
4. Proactive Maintenance – If a defect is detected, proactive maintenance involves looking for the cause and determining how to prevent a recurrence.

Unfortunately, even the best maintenance procedures cannot eliminate the possibility of an unexpected breakdown. Provisions should be made for standby equipment to allow maintenance with out interrupting production.

If you would like to discuss improving your compressed air efficiency or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer
Send me an email
Find us on the Web

Images Courtesy of Tampere Hacklab

## Refrigerant Compressed Air Dryer Systems

No matter what your use of compressed air entails, moisture is very likely an issue.  Air compressors pressurize air that they pull in straight from the environment and most of the time, there’s at least a little humidity involved.  Now, if you have an industrial air compressor, it’s also very likely that it was supplied with a dryer, for this very reason.

For practical purposes, “dryness” of compressed air is really its dew point.  That’s the temperature at which water vapor in the air will condense into liquid water…which is when it becomes the aforementioned issue in your compressed air applications.  This can cause rust in air cylinders, motors, tools, etc.  It can be detrimental to blow offs – anything in your compressed air flow is going to get on the surface of whatever you’re blowing onto.  It can lead to freezing in Vortex Tube applications when a low enough cold air temperature is produced.

Some very stringent applications (food & pharma folks, I’m looking at you) call for VERY low dew points…ISO 8673.1 (food and pharma folks, you know what I’m talking about) calls for a dew point of -40°F (-40°C) as well as very fine particulate filtration specs.  As a consumer who likes high levels of sanitary practice for the foods and medicines I put in my body, I’m EXTREMELY appreciative of this.  The dryer systems that are capable of low dew points like this operate as physical filtration (membrane types) or effect a chemical reaction to absorb or adsorb water (desiccant or deliquescent types.)  These are all on the higher ends of purchase price, operating costs, and maintenance levels.

For many industrial and commercial applications, though, you really just need a dew point that’s below the lowest expected ambient temperature in which you’ll be operating your compressed air products & devices.  Refrigerant type air dryers are ideal for this.  They tend to be on the less expensive side for purchase, operating, and maintenance costs.  They typically produce air with a dew point of 35-40°F (~2-5°C) but if that’s all you need, they let you avoid the expense of the ones that produce those much lower dew points.  Here’s how they work:

• Red-to-orange arrows: hot air straight from the compressor gets cooled by some really cold air (more on that in a moment.)
• Orange-to-blue arrows: the air is now cooled further by refrigerant…this causes a good amount of the water vapor in it to condense, where it leaves the system through the trap & drain (black arrow.)
• Blue-to-purple arrows: Remember when the hot air straight from the compressor got cooled by really cold air? This is it. Now it flows into the compressed air header, with a sufficiently low dew point, for use in the plant.

Non-cycling refrigerant dryers are good for systems that operate with a continuous air demand.  They have minimal dew point swings, but, because they run all the time, they’re not always ideal when your compressed air is not in continuous use.  For those situations, cycling refrigerant dryers will conserve energy…also called mass thermal dryers, they use the refrigerant to cool a solution (usually glycol) to cool the incoming air.  Once the glycol reaches a certain temperature, the system turns on and runs until the solution (thermal mass) is cooled, then it turns off.  Because of this, a cycling system’s operating time (and cost) closely follows the compressor’s load – so if your compressor runs 70% of the time, a cycling dryer will cost 30% less to operate than a non-cycling one.

EXAIR Corporation wants you to get the most out of your compressed air system.  If you have questions, I’d love to hear from you.

Russ Bowman
Application Engineer
EXAIR Corporation
Visit us on the Web

## 6 Steps to Optimizing Your Compressed Air System

If you’re a follower of the EXAIR Blog, you’re probably well aware that compressed air is the most expensive utility in an industrial environment. The average cost to generate 1000 Standard Cubic Feet of compressed air is \$0.25. If you’re familiar with how much air you use on a daily basis, you’ll understand just how quickly that adds up.

To make matters worse, many compressed air systems waste significant amounts of compressed air just through leaks. According to the Compressed Air Challenge, a typical plant that has not been well maintained will likely have a leak rate of approximately 20%!! Good luck explaining to your finance department that you’re carelessly wasting 20% of the most expensive utility.

The best way to save energy associated with the costs of generating compressed air is pretty straightforward and simple: TURN IT OFF! Placing valves throughout your distribution system allows you to isolate areas of the facility that may not need a supply of compressed air continuously.

Even a well-maintained system is going to have a leakage rate around 10%, it’s darn near impossible to absolutely eliminate ALL leaks. By having a valve that allows you to shut off the compressed air supply to isolated areas, you’re able to cut down on the potential places for leaks to occur.

You’re likely not running each and every machine continuously all day long, if that’s the case why not shut off the air supply to those that aren’t running? When operators go to lunch or take a break, have them turn off the valves to prevent any wasted air. The fact of the matter is that taking this one simple step can truly represent significant savings when done diligently.

You wouldn’t leave your house with all the lights and TV on, so why leave your compressed air system running when it’s not in use? Even if everyone’s left for the day, leaks in the system will cause the compressor to keep running to maintain system pressure.

Taking things one step further, EXAIR’s Electronic Flow Control (EFC) utilizes a solenoid controlled by photoelectric sensor that has the ability to shut off the compressed air when no part is present. If you’re blowing off parts that are traveling along a conveyor with space in between them, there’s no need to continuously blow air in between those parts. The EFC is able to be programmed to truly maximize your compressed air savings. The EFC is available in a wide range of different capacities, with models from 40-350 SCFM available from stock and systems controlling two solenoid valves for larger flowrates available as well.

It’s no different than turning off your house lights when you leave for work each day. Don’t get caught thinking compressed air is inexpensive “because air is free”. The costs to generate compressed air are no joke. Let’s all do our part to reduce energy consumption by shutting off compressed air when it isn’t necessary!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com

## The Bernoulli Principle

What do baseball, airplanes, and your favorite singer have in common? If you guessed that it has something to do with the title of this blog, dear reader, you are correct.  We’ll unpack all that, but first, let’s talk about this Bernoulli guy:

Jacob Bernoulli was a prominent mathematician in the late 17th century.  We can blame calculus on him to some degree; he worked closely with Gottfried Wilhelm Leibniz who (despite vicious accusations of plagiarism from Isaac Newton) appears to have developed the same mathematical methods independently from the more famous Newton.  He also developed the mathematical constant e (base of the natural logarithm) and a law of large numbers which was foundational to the field of statistics, especially probability theory.  But he’s not the Bernoulli we’re talking about.

Johann Bernoulli was Jacob’s younger brother.  He shared his brother’s passion for the advancement of calculus, and was among the first to demonstrate practical applications in various fields.  So for engineers especially, he can share the blame for calculus with his brother.  But he’s not the Bernoulli we’re talking about either.

Johann’s son, Daniel, clearly got his father’s math smarts as well as his enthusiasm for practical applications, especially in the field of fluid mechanics.  His kinetic theory of gases is widely known as the textbook (literally) explanation of Boyle’s law.  And the principle that bears his name (yes, THIS is the Bernoulli we’re talking about) is central to our understanding of curveballs, airplane wings, and vocal range.

Bernoulli’s Principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure (e.g., the fluid’s potential energy.)

• In baseball, pitchers love it, and batters hate it.  When the ball is thrown, friction (mainly from the particular stitched pattern of a baseball) causes a thin layer of air to surround the ball, and the spin that a skilled pitcher puts on it creates higher air pressure on one side and lower air pressure on the other.  According to Bernoulli, that increases the air speed on the lower pressure side, and the baseball moves in that direction.  Since a well-thrown curveball’s axis of rotation is parallel to the ground, that means the ball drops as it approaches the plate, leaving the batter swinging above it, or awkwardly trying to “dig it out” of the plate.
• The particular shape of an airplane wing (flat on the bottom, curved on the top) means that when the wing (along with the rest of the plane) is in motion, the air travelling over the curved top has to move faster than the air moving under the flat bottom.  This means the air pressure is lower on top, allowing the wing (again, along with the rest of the plane) to rise.
• The anatomy inside your neck that facilitates speech is often called a voice box or vocal chords.  It’s actually a set of folds of tissue that vibrate and make sound when air (being expelled by the lungs when your diaphragm contracts) passes through.  When you sing different notes, you’re actually manipulating the area of air passage.  If you narrow that area, the air speed increases, making the pressure drop, skewing the shape of those folds so that they vibrate at a higher frequency, creating the high notes.  Opening up that area lowers the air speed, and the resultant increase in pressure lowers the vocal folds’ vibration frequency, making the low notes.
• Bonus (because I work for EXAIR) Bernoulli’s Principle application: many EXAIR Intelligent Compressed Air Products are engineered to take advantage of this phenomenon to optimize efficiency:

If you’d like to discuss Bernoulli, baseball, singing, or a potential compressed air application, give me a call.  If you want to talk airplane stuff, perhaps one of the other Application Engineers can help…I don’t really like to fly, but that’s a subject for another blog.

Russ Bowman
Application Engineer
EXAIR Corporation
Visit us on the Web