## People of Interest: Robert Boyle – 1627 to 1691

Being in the compressed air industry for over 35 years, you come across many interesting people from the past that have created laws that we are still using today.   Robert Boyle is one of those people.  He was born on January 25, 1627 in Lismore Castle in Ireland.  He published the book “The Sceptical Chymist” in 1661, and many considered his work to be the foundation of modern chemistry.  He dabbled in many areas of study, but with a young university student, Robert Hooke, they found Boyle’s Law.

The experiment was performed using a ‘J’ shaped glass tube sealed on the shorter leg, and open to atmosphere on the longer leg.  Mercury was poured into the tube, such that the level was equal on each side. The volume of the trapped air was noted. Additional mercury was poured into the tube, and it was observed that the mercury did not stay level, and measurements of the heights of each tube leg were recorded.  The height difference of the mercury is effectively a measure of the pressure of the trapped air.  Through the experiment and the data, Boyle discovered a relationship between the volume and the pressure of air.  The data as published, is shown below.

Boyle noticed the pressure times the volume of air for the initial condition equaled the pressure times the volume at any other mercury height.  So, the pressure is proportional to the inverse of the volume, Equation 1.

Equation 1: P ∝ 1/V

Or P * V = k (a constant)

For comparing the same substance under two different sets of conditions, Boyle’s law can be expressed as Equation 2.

Equation 2:  P1 * V1 = P2 * V2

Equation 2 looks very familiar.  One of Boyle’s most famous discoveries was to become the first of the gas laws, relating the pressure of a gas to its volume. Combining Boyle’s Law with Charles’s Law, Gay-Lussac’s Law, and Avogadro’s Law; you will have the basis and creation of the ideal gas law;

Equation 3:   P * V = n * R * T

which includes the major factors that affect a gas; temperature, pressure, volume, the amount of the gas, and the ideal gas constant.

Robert Boyle passed away on December 31st, 1691, and from his work, EXAIR uses the pressure and volume of compressed air for our Intelligent Compressed Air® Products to make them efficient, safe, and effective.  If you would like to speak more about how EXAIR can benefit your pneumatic system, one of our Application Engineers can help you determine the best solution.

John Ball
Application Engineer
Email: johnball@exair.com

Robert Boyle image courtesy of Skara KommunCreative Commons License

## ICFM, SCFM, ACFM, CFM What does it all mean!

A common question we get asked is “What does SCFM mean?” Most people are aware of CFM but the “S” in front seems to be less known about! Well strap on your seat belt, we are about to go into a compressed air worm hole all about volumetric flow rates!

Here at EXAIR we rate all of our products air consumption in SCFM at a given supply pressure. CFM stands for Cubic Feet per Minute, but one definition will not satisfy the conditions that will be experienced in many applications by a number of variables  (altitude, temperature, pressure, etc.). Air by nature is a compressible fluid. The properties of this fluid are constantly changing due to the ambient conditions of the surrounding environment.

This makes it difficult to describe the volumetric flow rate of the compressed air. Imagine you have a cubic foot of air, at standard conditions (14.696 psia, 60°F, 0% Relative Humidity), right in front of you. Then, you take that same cubic foot, pressurize it to 100 psig and place it inside of a pipe. You still have one cubic foot, but it is taking up significantly less volume. You have probably heard the terms SCFMACFM, and ICFM when used to define the total capacity of a compressor system. Understanding these terms, and using them correctly, will allow you to properly size your system and understand your total compressed air consumption.

SCFM is used as a reference to the standard conditions for flow rate. This term is used to create an “apples to apples” comparison when discussing compressed air volume as the conditions will change. EXAIR publishes the consumption of all products in SCFM for this reason. You will always notice that an inlet pressure is specified as well. This allows us to say that, at standard conditions and at a given inlet pressure, the product will consume a given amount of compressed air. It would be nearly impossible, not to mention impractical, to publish the ACFM of any product due to the wide range of environmental conditions possible.

ACFM stands for Actual Cubic Feet per Minute. If the conditions in the environment are “standard”, then the ACFM and SCFM will be the same. In most cases, however, that is not the case. The formula for converting SCFM to ACFM is as follows:

ACFM = SCFM [Pstd / (Pact – Psat Φ)](Tact / Tstd)

Where:

ACFM = Actual Cubic Feet per Minute
SCFM = Standard Cubic Feet per Minute
Pstd = standard absolute air pressure (psia)
Pact = absolute pressure at the actual level (psia)
Psat = saturation pressure at the actual temperature (psi)
Φ = Actual relative humidity
Tact = Actual ambient air temperature (oR)
Tstd = Standard temperature (oR)

The last term that you’ll see floating around to describe compressed air flow is ICFM (Inlet Cubic Feet per Minute). This term describes the conditions at the inlet of the compressor, in front of the filter, dryer, blower, etc. Because several definitions for Standard Air exist, some compressor manufacturers have adopted this simpler unit of measure when sizing a compressor system. This volume is used to determine the impeller design, nozzle diameter, and casing size for the most efficient compressor system to be used. Because the ICFM is measured before the air has passed through the filter and other components, you must account for a pressure drop.

The inlet pressure is determined by taking the barometric pressure and subtracting a reasonable loss for the inlet air filter and piping. According to the Compressed Air Handbook by the Compressed Air and Gas Institute, a typical value for filter and piping loss is 0.3 psig. The need to determine inlet pressure becomes especially critical when considering applications in high-altitudes. A change in altitude of more than a few hundred feet can greatly reduce the overall capacity of the compressor. Because of this pressure loss, it is important to assess the consumption of your compressor system in ACFM. To convert ICFM to ACFM use the following formula:

ICFM = ACFM (Pact / Pf) (Tf / Tact)

Where:

ICFM = Inlet Cubic Feet Per Minute

P = Pressure after filter or inlet equipment (psia)

Tf = Temperature after filter or inlet equipment (°R)

If you’re looking into a new project utilizing EXAIR equipment and need help determining how much compressed air you’ll need, give us a call. An Application Engineer will be able to assess the application, determine the overall consumption, and help recommend a suitably sized air compressor.

Jordan Shouse
Application Engineer

Send me an email
Find us on the Web

## How Can You Benefit from EXAIR’s Efficiency Lab?

How many times have you purchased a new product and worried if it was the right choice? Well EXAIR can provide that confidence using our calibrated testing equipment to compare your current product to an EXAIR product, in our Efficiency Lab. Whenever I needed a new process or product I would spend countless hours researching how will this benefit me, my employer or my customer? Research is not only time consuming but also very costly.

EXAIR believes in their product so much that we offer an Efficiency Lab where we will test your production product and help show that our products will not only work for you, but also show that they can save money, as well as make your work environment a safer place.

EXAIR has provided performance values (force, noise, air consumption, ROI) for many of our products. We make purchasing from EXAIR fun because you know in advance that our products will meet or exceed your expectations. Further backing up our commitment with the Efficiency Lab we offer an 30 Day Unconditional Guarantee. EXAIR believes in our products and want to make your purchase a risk free process.

We can test the performance of your current product to EXAIRs Intelligent Compressed Air products for air consumption, force, noise levels… and provide a comprehensive report of our analysis, including simple ROI.

What does our Efficiency Lab cost? EXAIR believes in our products so much, that this is a free service to our customers. Simply call and talk to one of our Application Engineers at 800.903.9247 or you can send an email to lab@exair.com or visit www.exair.com and talk on our live help. If you feel we can help with a comparison them simply send your product(s) freight prepaid to EXAIR Corporation attention to our Efficiency Lab. All trials will be on a confidential basis unless you provide permission to share.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com

## Super Air Knife’s Adjustability and Flexibility = Success

The EXAIR Super Air Knife is the most efficient compressed air knife on the market. We know this because we’ve tested them, and our competitors’ offerings, for performance, using the same instruments, controls, and procedures. We’re not going to publish data that we can’t back up, and that’s a fact.

They’re also ideally suited to a wide variety of applications – they come in lengths from 3 inches to 9 feet long (and can actually be coupled together for uninterrupted air flows of even longer lengths,) a variety of materials for just about any environment. But the best thing about our Super Air Knives is how you can adjust the air pressure and flow to complete a wide variety of tasks. You can adjust them in two different ways, Replacing or adding Shims, or regulating the incoming air pressure.

A larger shim gap will give you higher flow and force from your Air Knife. Honestly, the 0.002″ shim that comes pre-installed in all of our Air Knives is perfectly suitable for most blow off applications, and appropriate air supply conditions are the first thing you should check for before going with thicker shims, but if you do indeed need a boost, a thicker shim will indeed give you one…here’s a blog with the video to show you how it’s done:

Another advantage to having a Pressure Regulator at every point of use is the flexibility of making pressure adjustments to quickly change to varying production requirements.  Not every application will require a strong blast sometimes a gentle breeze will accomplish the task.  As an example one user of the EXAIR Super Air Knife employs it as an air curtain to prevent product contamination (strong blast) and another to dry different size parts (gentle breeze) coming down their conveyor. For Performance at different supply pressures see the chart below.

EXAIR products are highly engineered and are so efficient that they can be operated at lower pressures and still provide exceptional performance!  This save’s you money considering compressed air on the average cost’s .25 cents per 1000 SCFM.

If you’d like to discuss altering the performance of your Super Air Knife, give us a call.

Jordan Shouse
Application Engineer
Find us on the Web http://www.exair.com/28/home.htm