Many times we have tendencies to overcomplicate things. I remember a time when I was visiting my sister in Phoenix, and she was making a fancy 3D Scooby-Doo cake for my nephew’s 4th or 5th, and she needed the brown icing. Now when decorating these cakes, the common practice is to make white icing and use food coloring to make all of the other colors you need. She left that morning around 10:00 to look for brown food coloring. Around noon she called to tell us that she could not find brown food coloring at any store on this side of town, and was driving to the far side of the city to look at those stores. I asked her why she couldn’t just use chocolate icing, and she was having no part of it. She was so laser focused on her solution that she couldn’t hear that that chocolate icing is also brown… Fast forward to 6:30 PM, and she comes walking through the door frustrated and exhausted from her day of going store to store all over the large city looking for the elusive brown food coloring. As you can probably guess, she had chocolate icing with her because it finally hit her that the chocolate icing is brown… . The cake turned out amazing, and the lesson was learned.
So, why this story? I feel that in life and in business we sometimes leave our blinders on and become laser focused on one certain way of doing something. We know that the way we se it will work, and think that we know best, and we are going to make it happen exactly how it is playing out in our head. No other way seems possible, and when someone offers up a simpler solution, our immediate thought is “it can’t be that simple”, or “if it’s that simple of a solution, there is no way it could work”. Have you ever said these things? As an application engineer, I take a lot of calls from people that are much smarter than me with grandiose plans. Many times the problem they need to solve, is much simpler than the solution they have in mind. I’ve seen elaborate plans, that probably took hours if not days to develop, come down to simply needing a simple out of the box Blow-Off System.
At EXAIR, we specialize in intelligent compressed air products with a primary focus on blow off, drying, and cooling. When it comes to these things, our product lines (pointedly for this blog, our Air Nozzles and Jets) are head and shoulders above our competition. The vast majority (with the exceptions of the High power or high force nozzles – for obvious reasons) all meet both OSHA standards concerning noise and dead end pressure. Here is a list of all of our Super Air Nozzles showing the SCFM, Force and Decibels:
Our Blow Off Systems (some sample pics below) are a fantastic and smart solution for so many applications. It really doesn’t get much easier than this, a Magnetic base, a Stay-Set Hose, and a Super Air Nozzle, all in one. I feel that these are heavily under utilized. Simply connect your air hose, bend the Stay-Set Hose to the direction of spray that you need, and boom, Bob’s your uncle…
Sometimes things can be as simple as using chocolate icing for brown icing, or using an EXAIR Blow-Off System in your application. Of course if you need more than that, we will help you find the right solution for you. Call today to speak with an experienced application engineer that is eager to help.
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Flow rate is the quantity of material that is moved per unit of time. Generally, the quantity of material can be expressed as a mass or a volume. For example, mass flow rates are in units of pounds per minute or kilograms per hour. Volumetric flow rates are stated in cubic feet per minute, CFM, or liters per hour, LPH. The trick begins when volumetric flow rates are used with compressible gases. In this blog, I will go over the various acronyms and the reasons behind them.
What acronyms will be covered?
CFM – Cubic Feet per Minute
SCFM – Standard Cubic Feet per Minute
ACFM – Actual Cubic Feet per Minute
ICFM – Inlet Cubic Feet per Minute
The volumetric component of the flow rate is CFM or Cubic Feet per Minute. This term is commonly used for rating air compressors. From the history of air compressors, they could calculate the volume of air being drawn into the air compressor by the size of the cylinder. With the volume of the compression chamber and the rotations per minute of the motor, RPM, they could calculate the volumetric air flows. As conditions change like altitude, temperature, and relative humidity, the volumetric value of CFM changes. To better clarify these conditions, compressor manufacturers have decided to add terms with a definition. (For your information, air compressors still use CFM as a unit of air flow, but now this is defined at standard temperature and pressure).
The first letter in front of CFM above now defines the conditions in which volumetric air flow is being measured. This is important for comparing pneumatic components or for properly sizing pneumatic systems. Volume is measured within three areas; temperature, pressure, and relative humidity. We can see this in the Ideal Gas Law, reference Equation 1.
P * V = n * R * T
P – Absolute Pressure
V – Volume
n – Number of molecules of gas
R – Universal Gas Constant
T – Absolute Temperature
The volume of air can change in reference to pressure, temperature, and the number of molecules. You may ask where the relative humidity is? This would be referenced in the “n” term. The more water vapor, or higher RH values, the less molecules of air are in a given volume.
SCFM is the most commonly used term, and it can be the most confusing. The idea behind this volumetric air flow is to set a reference point for comparisons. So, no matter the pressure, temperature, or relative humidity; the volumetric air flows can be compared to each other at that reference point. There have been many debates about an appropriate standard temperature and pressure, or STP. But as long as you use the same reference point, then you can still compare the results. In this blog, I will be using the Compressed Air and Gas Institute, CAGI, reference where the “Standard” condition is at 14.5 PSIA, 68 o F, and 0% RH. Since we have a reference point, we still need to know the actual conditions for comparison. It is like having the location of a restaurant as a reference, but if you do not know your current location, you cannot move toward it. Similarly, we are “moving” the air from its actual condition to a reference or “Standard” condition. If we do not know the actual state where the air began, then we cannot “move” toward that reference point. We will talk more about this later in this blog.
ACFM is the volumetric air flow under actual conditions. This is actually the “true” flow rate. Even though this term is hardly used, there are reasons why we will need to know this value. We can size an air compressor that is not at “Standard” conditions, and we can use this value to calculate velocity and pressure drop in a pneumatic system. We can correlate between SCFM and ACFM with Equation 2.
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)
ICFM is one of the newest terms in the history of air compressors. This is where devices are added to the inlet of an air compressor, affecting flow conditions. If you have a blower on the inlet of an air compressor, the volumetric flow rate changes as the pressure and temperature rises at the “Inlet”. If a filter is used, then the pressure drop will decrease the incoming pressure at the “Inlet”. These devices that affect the volumetric flow rate for an air compressor should be considered. The equation to relate ACFM to ICFM is Equation 3.
ICFM = ACFM * (Pact / Pf) * (Tf / Tact)
ICFM – Inlet Cubic Feet Per Minute
ACFM – Actual Cubic Feet per Minute
Pact – absolute pressure at the actual level (PSIA)
Pf – Pressure after filter or inlet equipment (PSIA)
Tact – Actual ambient air temperature (oR)
Tf – Temperature after filter or inlet equipment (°R)
To expand on my explanation above about SCFM and ACFM, a technical question is asked often about the pressure when using SCFM. The reference point of 14.5 PSIA is in the definition of the term for SCFM. Remember, this is only a reference point. The starting location is also needed as it gives us the ACFM value where the air values are true and actual. Then we can make a comparison of actual air usage.
As an example, let’s look at two air nozzles that are rated at the same air flow; 60 SCFM. The EXAIR Super Air Nozzle, model 1106, is cataloged at 60 SCFM at 80 PSIG, and a competitor is cataloged at 60 SCFM at 72 PSIG. By comparison, they look like they use the same amount of compressed air, but actually they do not. To simplify Equation 2, we can compare the two nozzles at the same temperature and RH at 68 oF and 0% RH respectively. This equation can be reduced to form Equation 4.
ACFM = SCFM * 14.5 / (P + 14.5)
@72 PSIG Competitor:
ACFM = 60 SCFM * 14.5 PSIA/ (72 PSIG + 14.5 PSIA)
= 10.1 ACFM
@80 PSIG EXAIR Super Air Nozzle:
ACFM = 60 SCFM * 14.5 PSIA / (80 PSIG + 14.5PSIA)
= 9.2 ACFM
Even though the SCFM is the same amount, you are actually using 10% more air with the competitive nozzle that was reported at 60 PSIG. So, when it comes to rating pneumatic products, improving efficiency, and saving money; always determine the pressure that you are at. The more you know about volumetric flow rates, the better decision that you can make. If you need more information, you can always contact our Application Engineers at EXAIR. We will be happy to assist.
Producing compressed air can be expensive, but it is necessary for pneumatic systems. And a large part of that expense is wasted energy, in the form of heat. Waste will add to your overhead and affect your bottom line. EXAIR has a line of products to help reduce air consumption at the point-of-use to save you money. This would include replacing open-pipes and tubes with EXAIR Super Air Nozzles and Super Air Knives. But, let’s look at the supply side inside your compressor room. The air compressor operates at about 10% efficiency where most of that loss is in a form of heat.
Wouldn’t it be nice to recover some of that expense? You can. By equipping your air compressor with a heat recovery system. These systems are designed to recover the loss of heat for other uses. Today, they can recover somewhere between 50% for liquid-cooled compressors to 80% for air-cooled compressors. The heat can come from the after-coolers, the electric motor, the “heat of compression”, and the oil cooler. This reclaimed heat can be used to heat water, warm rooms, pre-heat steam systems, and dry parts.
Let’s create an example. A company has a 100 HP air-cooled compressor that is running 8 hours per day for 250 days per year. The heat recovery system will be able to reclaim 60% of the heat to warm city water in the plant. If the electrical cost is $0.10 per KWh, we can calculate the savings.
In practice, reclaiming the maximum percentage may not be cost effective. Your company can determine the best percentage for heat recovery by calculating the Return on Investment (ROI). I wrote a blog post that can help you estimate (ClickHere).
As mentioned above, EXAIR saves you money and increase efficiency on the demand side. EXAIR has engineered nozzles to help reduce compressed air usage. The following is a quick calculation by replacing an open-end blow-off with an EXAIR Super Air Nozzle. If you have a ¼” (6mm) copper tube, it will use 33 SCFM (935 SLPM) of compressed air at 80 PSIG (5.5 bar). As a common replacement, EXAIR uses a model 1100 Super Air Nozzle which will use 14 SCFM (396 SLPM) at 80 PSIG (5.5 bar). With a simple tube fitting, you can mount the ¼” NPT Super Air Nozzle to the end of the ¼” copper tube. If we use the same pretext as above, we can find the annual cost savings. With an air compressor that produces 5 SCFM/hp, we can get a cost savings with the Super Air Nozzle. The difference in air flow at 80 PSIG (5.5 bar) is:
19 SCFM * 1 HP/ 5 SCFM * 0.746 KW/HP * 8 hr/day * 250 days/yr * $0.10/KWh = $566.96 savings per year per nozzle.
Whether it is on the supply side or the demand side, companies are looking to reduce or reuse the wasted energy to have a more efficient compressed air system. The heat recovery system is a bit more complex, but should be considered. The EXAIR engineered nozzles are more simplistic, and they can give you a return on your investment in a short period of time. If you would like to discuss how to improve your compressed air system from the supply side to the demand side, an Application Engineer at EXAIR will be happy to assist you.
You may have asked…why should I switch over to an engineered compressed air product if my system already works? Or…How can your products be much different?
Manufacturing has always been an advocate for cost savings, where they even have job positions solely focused on cost savings. Return on Investment (ROI) is a metric they look toward to help make good decisions for cost savings. The term is used to determine the financial benefits associated with the use of more efficient products or processes compared to what you are currently using. This is like looking at your homes heating costs and then changing out to energy efficient windows and better insulation. The upfront cost might be high but the amount of money you will save over time is worth it.
How is ROI calculated? It is very simple to calculate out the potential savings of using an EXAIR Intelligent Compressed Air® Product. We have easy to use calculators on our websites Resources where filling in a few blanks will result in an ROI when switching to a EXAIR product! Here they Are, Calculators.
I’ll go ahead and break down the simple ROI calculations for replacing open blow offs with an EXAIR Super Air Nozzle:
¼” Copper Pipe consumes 33 SCFM at 80 psig (denoted below as CP)
A Model 1100 ¼” Super Air Nozzle can be used to replace and only uses 14 SCFM at 80 psig (denoted below as EP)
(CP air consumption) * (60 min/hr) * (8 hr/day) * (5 days/week) * (52 weeks/year) = SCF used per year for Copper Pipe
(33) * (60) * (8) * (5) * (52) = 4,118,400 SCF
(EP air consumption) * (60 min/hr) * (8 hr/day) * (5 days/week) * (52 weeks/year) = SCF used per year for EXAIR Product
(14) * (60) * (8) * (5) * (52) = 1,747,200 SCF
SCF used per year for Copper Pipe – SCF used per year for EXAIR Product = SCF Savings
4,118,400 SCF – 1,747,200 SCF = 2,371,200 SCF in savings
If you know the facilities cost to generate 1,000 SCF of compressed air you can calculate out how much this will save. If not, you can use $0.25 to generate 1,000 SCF which is the value used by the U.S. Department of Energy to estimate costs.
($592.80/year) / (5 days/week * 52 weeks/year) = $2.28 per day
(Cost of EXAIR Unit) / (Daily Savings) = Days until product has been paid off
($42) / ($2.28/day) = 17.9 days
As you can see it doesn’t have to take long for the nozzle to pay for itself, and then continue to contribute toward your bottom line.
If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.