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

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Why Dryers Are Needed in Compressed Air Systems

Air compressors are extremely proficient at compressing anything in the air they are intaking. With that air that is taken in, moisture is going to be present. The amount of moisture will all depend on where you are located geographically and the ambient conditions in the area. Here in Ohio, we experience all 4 seasons so the moisture content is higher in the air during the summer months, rather than the winter months. When this air is saturated with water vapor and the conditions are right, the air reaches a point it cannot hold any additional water vapor. This point is known as the dew point of the air and water vapor will begin to condense to form droplets.

When ambient air is compressed, heat is generated and the air increases in temperature. In most industrial compressed air systems, the air is then processed to an aftercooler, and that is where condensation begins to form. To remove the condensation, the air then goes into a separator which traps the liquid water. The air leaving the aftercooler is typically saturated at the temperature of the discharge, and any additional cooling that occurs as the air is transferred will cause more liquid to condense out of the air. To address this moisture, compressed air dryers are used.

It is critical to the quality of the system and components downstream that actions are taken to prevent this condensation in the air. Condensation is generally detrimental to any point of use application and or the piping that conveys the air. Rust and/or corrosion can occur anywhere in the piping, leading to scale and contamination of the compressed air and processes. When trying to dry products off using compressed air or using the air to atomize a liquid such as paint, adding in these contaminants and moisture will cost production losses.

There are several options when it comes to the type of dryer that one may consider installing on their compressed air supply side.

• Refrigerant Dryer – the most commonly used type, the air is cooled in an air-to-refrigerant heat exchanger.
• Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process).
• Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up and needs to be replaced periodically.
• Heat of Compression Type – are regenerative desiccant dryers that use the heat generated during compression to accomplish the desiccant regeneration.
• Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount of water vapor in the air stream.
The air should not be dried any more than is needed for the most stringent application, to reduce the costs associated with the drying process. A pressure dew point of 35°F to 38°F (1.7°C to 3.3°C) often is adequate for many industrial applications. Lower dew points result in higher operating costs.
If you have questions about compressed air systems and dryers or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR, and I or any of our Application Engineers can help you determine the best solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

EXAIR has a new product: The EasySwitch™ Wet-Dry Vac

We have joined our wet vacuum with our dry vacuum to make the EasySwitch Wet-Dry Vac System.  This new addition to our Industrial Housekeeping Products allows your customers to replace their electric wet-dry vacuums that fail prematurely, have potential safety issues, and are very loud.  Below, I will share the features and benefits of the EasySwitch Wet-Dry Vac System as expected from a leader in this industry.  You can watch a video HERE.

A wet-dry vacuum is a contained system that can vacuum up liquid or dirt.  The specific design that separates the liquid application from the dry application is a filter element.  The filter will stop the dirt and debris from re-entering the surrounding air during vacuuming.  The EXAIR EasySwitch Wet-Dry Vac uses this same function for dry materials.  But we offer two different types of filters; a standard filter and a HEPA filter.  The standard filter is a 3-micron pleated element with a large surface area for long life.  The HEPA filter is a 0.3-micron pleated element for finer filtration.  But what is unique about our design is the patent pending lid to easily remove or replace the filter elements.  It makes an easy transition to go from liquid to dry materials and vice versa.   The lid is designed to fit on a common 55 gallon open-top drum.  They are ideal for any applications that is wet, dry, light or heavy.

EasySwitch Wet-Dry Vac Mode Change Instructions

Like with our other Industrial Housekeeping Products, the EasySwitch does not have any motors to wear or electricity to run which makes it safe for liquid applications.  It only needs filtered compressed air.  They are maintenance free, and the sound level is quiet, only 79 dBA.  The applications include coolant, chips, floor cleanup, drains, shavings, sawdust, absorbents, and mold and allergen removal.  For liquid applications, it has a spill free – auto safety shutoff.  This industrial all-purpose pneumatic vacuum can move 36 GPM (136 LPM) of water, 68 Lbs./min (31 Kg/min) of plastic media, and 54 lbs./min (24 Kg/min) of steel shot at 80 PSIG (5.5 bar).  The specifications at 80 PSIG (5.5 bar) for the EasySwitch is that it will only use 53 SCFM (1,500 SLPM) of compressed air to generate -168” H2O (-314 mmHg) of vacuum and 90 CFM (2,548 LPM) of vacuum flow.

EXAIR offers three types of systems with the standard filter or the HEPA filter.  We have the basic system, the Deluxe system, and the Premium system.  The basic system will come with the selected filter, 10-foot (3m) vacuum hose, 20-foot (6.1m) compressed air hose, plastic tools, shutoff valve and gage.  The HEPA filter models will include a Pre-filter to help protect the HEPA media from premature clogging.  The Deluxe system will include the items in the basic system with an upgraded antistatic vacuum hose, heavy-duty tools, a spill recovery kit, a tool holder, and a drum dolly.  The Premium system will include the items in the Deluxe system and it will include a 55 Gallon drum.  A quick guide is below.EXAIR continues to add new products to expand solutions for our customers.  If you have an application where you need an all-around vacuum system that is long lasting, reliable, and quiet; the EasySwitch Wet-Dry Vac is that product for you.  If you need more information, EXAIR has Application Engineers that can help you. Also take advantage of our Industrial Housekeeping Promotion currently running, and receive a free Vac-U-Gun with the purchase of our EasySwitch or any other industrial Vacuum.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Custom 6″ Super Air Wipe Solves Moisture Problem for Food Packaging Manufacturer

At EXAIR, we will never shy away from an application just because we don’t have something on the shelf ready to go from stock. We pride ourselves in the ability to provide a custom solution for an application that requires it. Just because you don’t see something in the catalog doesn’t mean we can’t make it happen! This was the case recently with a customer that manufactures food vacuum packaging machines.

A piece of the bag material is extruded, washed, and then filled with product. After the material is extruded it enters a water-cooling bath just before being inflated. The customer needed a solution for blowing off this excess water before opening the bag and packaging the finished products.

They designed a series of nozzles in a ring to provide a flow of compressed air to remove the residual water after the cooling bath. This worked for the most part, but was not effective at completely removing all of the moisture. After searching online, they came across the EXAIR Super Air Wipe. The Super Air Wipe was the exact tool they were looking for, providing a 360° laminar airflow around the full exterior of the bag. The only problem was that space was severely limited. To allow it to fit in their machine, we manufactured a special 6” Super Air Wipe with a reduced overall footprint and countersunk bolts to fit perfectly. Since air consumption was a concern, we installed a .001” shim to cut the total volume of compressed air needed in half!

EXAIR offers a line of Super Air Wipes available to ship same day from stock as well. The Super Air Wipe is available in aluminum construction in sizes ranging from 3/8” – 11” in diameters. All Super Air Wipes come with stainless steel hardware and stainless steel shims. Sizes up to 4” include a brass tee that supplies one half of the Super Air Wipe while a stainless steel wire braided hose supplies the other side. Sizes over 4” should be piped directly to each ¼ NPT compressed air inlet. In addition to aluminum construction, the Super Air Wipe is also available in 303 stainless steel for corrosive or high temperature applications. The Stainless Steel Super Air Wipe can withstand temperatures up to 800°F and is available in sizes from ½”-4” from stock.

If you’re processing any type of hose, wire, or extruded shapes that could benefit from installing a Super Air Wipe give us a call. With all sizes shipping from stock on an order received by 2:00 pm EDT we can have one to you as early as tomorrow!

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