When operating any of your Intelligent Compressed Air Products, something that often gets overlooked is the importance of delivering clean, dry air to those point-of-use products. Many of our products have very tight orifices to help reduce the volume of compressed air they consume. In addition, most have no moving parts to wear out and require no maintenance. That is, unless you’re using unfiltered compressed air.
Rust and scale are commonly found within the distribution system inside your facility. Old iron pipe and receiver tanks are the common culprits. A common misconception is that the air is already filtered as it exits the compressor. While this may be true, there’s still places in the distribution system that can cause issues downstream.
To eliminate the hassle of taking things apart to periodically clean, EXAIR recommends installing a point-of-use filter for all of our Intelligent Compressed Air Products. Kits are available for purchase that come with a properly sized filter to ensure your air is sufficiently clean. To see how quickly debris can clog your products, check out my video below demonstrating the difference between dirty and clean air with a Model 110006 6″ Super Air Knife.
If you’ve already purchased and installed products without filters, it’s never to late to go back and install one. Contact an EXAIR Application Engineer today and we’ll be happy to help you determine the proper size for the volume of air you’re products need.
How did a past inventor help generate efficient compressed air products for EXAIR? In the early 20th century, Henri Coanda who was a Romanian aeronautical engineer that built an experimental Coanda-1910 airplane. There are some debates if the airplane actually flew, but he invented a curved surface for a wing to generate a Coanda effect. The Coanda effect is the “tendency of a fluid jet to stay attached to a convex surface”1. Thus, a moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line. The Wright Brothers who flew the first airplane in the state where EXAIR is located, Ohio, used the Coanda effect to create lift. With a curved profile, the air will adhere to the surface, causing a low pressure which makes the airplane fly.
EXAIR uses this Coanda profile to make some of our Intelligent Compressed Air Products™. Like the airplane wing, our curved surface will also create a low pressure. How does this help? Well, high pressure will always travel to low pressure. Instead of lift, we use the low air pressure to entrain ambient air. This ratio is what we call the amplification ratio. The higher the amplification ratio, the higher the efficiency for a blowing device. Two main compressed air products that EXAIR manufactures use this type of profile; Air Knives and Air Amplifiers. I will cover both below.
The Air Knives that use the Coanda profile blows air along the length of the knife at a 90o angle from the exit. We offer two types; the Standard Air Knife and the Full Flow Air Knife. The Standard Air Knives are made in Aluminum or Stainless Steel with blowing widths up to 48” (1219mm). The inlet ports are at each end; so, the overall length is 1” (25mm) longer. The Full Flow Air Knives have the port or ports on the back. The air blows out the entire length of the air knife. The maximum length is 36” (914mm).
Both types of air knives use the Coanda profile to generate a low pressure as the air exits the gap and “hugs” the curve (reference photo above). This low pressure draws ambient air into the air stream at a 30:1 amplification ratio for both the Standard Air Knife and Full Flow Air Knife. So, for every one part of compressed air, we entrain 30 parts of ambient air. Besides efficiency, it also adds mass to the air stream for a hard-hitting force. With this engineered profile, the air stream is laminar which gives a consistent force across the entire length and reduces noise levels. Not only will they save you money, but they are also OSHA safe.
The Air Amplifiers use the Coanda profile in a circular form to pull in dramatic amounts of free surrounding air. The Coanda effect is able to generate a low pressure to blow air for cooling, cleaning or removing smoke and debris efficiently and quietly. The Air Knives above blow a flat stream of air while the Air Amplifiers will blow a conical air stream. They can reach amplification ratios up to 25:1. The Super Air Amplifiers use a patented shim to increase efficiency.
Unlike fans, they blow a laminar air stream for quick cooling. They do not have any moving parts or motors to wear, so they are very quiet. EXAIR manufactures five different sizes from ¾” (19mm) to 8” (203mm). The Adjustable Air Amplifiers have a plug that can be adjusted to control the blowing force from a breeze to a blast. For cleaning surfaces, this is a nice feature to “dial” in to exactly what you need. We also manufacture five different sizes in aluminum and stainless steel ranging from ¾” (19mm) to 4” (102mm). Both Air Amplifiers can be attached to ducts to remove debris, heat or smoke from the area.
Utilizing the Coanda effect allows for massive compressed air savings. Whether it is a flat or round air stream, EXAIR can do this with high amplification ratios. If you would like to discuss further how our Air Knives or Air Amplifiers can help you in your applications, please contact us. An Application Engineer will be happy to help you. History has shown us a way to increase efficiency when using compressed air. And you can take advantage of it with the Coanda profile. Thank you Mr. Henri Coanda.
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 between an EXAIR Super Air Knife to a common drilled pipe. 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 Total Project Cost is the cost of the product with the labor to install. In our example, we will use a 24” (610mm) wide blow-off device. One device will be an inexpensive drilled pipe and the other will be a high-efficiency EXAIR Super Air Knife. The drilled pipe had (48) 1/16” (1.6mm) diameter holes spaced ½” (13mm) apart. EXAIR manufactures the model 110024 Super Air Knife with a .002” (.05mm) slot along the entire length. Both have a blowing width of 24” to cover the conveyor. The model 110024 has a retail price of $491.00 each. The cost of the drilled pipe was around $50.00. What a difference in price! But, how could EXAIR remain a leader in this industry for over 35 years?
Let’s continue on with the Return on Investment. The amount of time required to install the Super Air Knife across the conveyor only took a maintenance staff about one hour to mount. 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 the knife is $75.00. The Total Project Cost can be calculated as follows: ($491 – $50) + $75.00 = $516.00. The next part of the equation, Total annual savings, is a bit more in-depth, but the calculation is shown below.
EXAIR manufactures engineered products to be efficient and safe. The Super Air Knife has a 40:1 amplification ratio which means that 40 parts of “free” ambient air is entrained for every 1 part of compressed air. For comparison, the Super Air Knives are to compressed air systems as LED lightbulbs are to electricity. In that same way, the drilled pipe would represent an incandescent lightbulb. The reason for this analogy is because of the amount of energy that the EXAIR Super Air Knives can save. While LED lightbulbs are a bit more expensive than the incandescent lightbulbs, the value for the Return on Investment is at a higher percentage, or in other words, a short payback period. On the other hand, the drilled pipe is less expensive to make, but the overall cost for using it in your compressed air system is much higher. I will explain how below.
To calculate the Total Annual Savings, we will use the same blow-off scenario as above. The amount of compressed air used by the drilled pipe is around 174 SCFM (4,924 SLPM) at 60 PSIG (4.1 Bar). The model 110024 Super Air Knife has an air consumption of 55.2 SCFM (1,563 SLPM) at 60 PSIG (4.1 Bar). At an electrical rate of $0.08 per Kilowatt-hour, we can figure the cost to make compressed air. Based on 4 SCFM per horsepower of air compressor, the electrical cost is $0.25 per 1000 standard cubic feet, or $0.25/1000SCF. To calculate an annual savings, let’s use a blow-off operation of 8 hours/day for 250 days a year. Replacing the drilled pipe with the model 110024 Super Air Knife, it will save you (174 SCFM – 55.2 SCFM) = 121.8 SCFM of compressed air. To put this into a monetary value, the annual savings will be 121.8 SCFM *$0.25/1000SCF * 60 Min/hr * 8hr/day * 250 day/yr = $3,654 per year.
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 = ($3,654 – $516.00) / $516.00 * 100
ROI = 608%
With a percentage value that high, we are looking at a payback period of only 52 days. You may look at the initial cost and be discouraged; but in a little over a month, the model 110024 will have paid for itself. And after using it for one year, it will save your company $3,654.00. Some things that may be overlooked are safety issues. With some inexpensive blow-off devices, the noise levels are over the OSHA limits. The drilled pipe had a noise level of 91 dBA while the Super Air Knife only had a noise level of 65 dBA.
In my experience, a loud blowing noise from your equipment is generally coming from an inefficient and safety-concerned product. 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 promote safety, an Application Engineer can help you to get started.
Whenever there is a discussion about fluid dynamics, Bernoulli’s equation generally comes up. This equation is unique as it relates flow energy with kinetic energy and potential energy. The formula was mainly linked to non-compressible fluids, but under certain conditions, it can be significant for gas flows as well. My colleague, Tyler Daniel, wrote a blog about the life of Daniel Bernoulli (you can read it HERE). I would like to discuss how he developed the Bernoulli’s equation and how EXAIR uses it to maximize efficiency within your compressed air system.
In 1723, at the age of 23, Daniel moved to Venice, Italy to learn medicine. But, in his heart, he was devoted to mathematics. He started to do some experiments with fluid mechanics where he would measure water flow out of a tank. In his trials, he noticed that when the height of the water in the tank was higher, the water would flow out faster. This relationship between pressure as compared to flow and velocity came to be known as Bernoulli’s principle. “In fluid dynamics, Bernoulli’s principle states that an increase in the speed of fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluids potential energy”1. Thus, the beginning of Bernoulli’s equation.
Bernoulli realized that the sum of kinetic energy, potential energy, and flow energy is a constant during steady flow. He wrote the equation like this:
Not to get too technical, but you can see the relationship between the velocity squared and the pressure from the equation above. Being that this relationship is a constant along the streamline; when the velocity increases; the pressure has to come down. An example of this is an airplane wing. When the air velocity increases over the top of the wing, the pressure becomes less. Thus, lift is created and the airplane flies.
With equations, there may be limitations. For Bernoulli’s equation, we have to keep in mind that it was initially developed for liquids. And in fluid dynamics, gas like air is also considered to be a fluid. So, if compressed air is within these guidelines, we can relate to the Bernoulli’s principle.
Steady Flow: Since the values are measured along a streamline, we have to make sure that the flow is steady. Reynold’s number is a value to decide laminar and turbulent flow. Laminar flows give smooth velocity lines to make measurements.
Negligible viscous effects: As fluid moves through tubes and pipes, the walls will have friction or a resistance to flow. The surface finish has to be smooth enough; so that, the viscous effects is very small.
No Shafts or blades: Things like fan blades, pumps, and turbines will add energy to the fluid. This will cause turbulent flows and disruptions along the velocity streamline. In order to measure energy points for Bernoulli’s equation, it has to be distant from the machine.
Compressible Flows: With non-compressible fluids, the density is constant. With compressed air, the density changes with pressure and temperature. But, as long as the velocity is below Mach 0.3, the density difference is relatively low and can be used.
Heat Transfer: The ideal gas law shows that temperature will affect the gas density. Since the temperature is measured in absolute conditions, a significant temperature change in heat or cold will be needed to affect the density.
Flow along a streamline: Things like rotational flows or vortices as seen inside Vortex Tubes create an issue in finding an area of measurement within a particle stream of fluid.
Since we know the criteria to apply Bernoulli’s equation with compressed air, let’s look at an EXAIR Super Air Knife. Blowing compressed air to cool, clean, and dry, EXAIR can do it very efficiently as we use the Bernoulli’s principle to entrain the surrounding air. Following the guidelines above, the Super Air Knife has laminar flow, no viscous effects, no blades or shafts, velocities below Mach 0.3, and linear flow streams. Remember from the equation above, as the velocity increases, the pressure has to decrease. Since high-velocity air exits the opening of a Super Air Knife, a low-pressure area will be created at the exit. We engineer the Super Air Knife to maximize this phenomenon to give an amplification ratio of 40:1. So, for every 1 part of compressed air, the Super Air Knife will bring into the air streamline 40 parts of ambient “free” air. This makes the Super Air Knife one of the most efficient blowing devices on the market. What does that mean for you? It will save you much money by using less compressed air in your pneumatic application.
We use this same principle for other products like the Air Amplifiers, Air Nozzles, and Gen4 Static Eliminators. Daniel Bernoulli was able to find a relationship between velocities and pressures, and EXAIR was able to utilize this to create efficient, safe, and effective compressed air products. To find out how you can use this advantage to save compressed air in your processes, you can contact an Application Engineer at EXAIR. We will be happy to help you.