We’ve blogged about sound and what exactly it is before, see the link. Understanding that sound is vibration traveling through the air which it is utilizing as an elastic medium. Well, rather than me continue to write this out, I found a great video to share that is written in song to better recap how sound is created.
Now that we have that recap and understand better what sound is let’s dig a little deeper to better understand why some sounds may appear louder to a person when they may not appear different on a sound scale that is shown by something like a Digital Sound Level Meter.
Loudness is how a person perceives sound and this is correlated to the sound pressure of the frequency of the sound in question. The loudness is broken into three different weighing scales that are internationally standardized. Each of these scales, A, C, and Z apply a weight to different frequency levels.
The most commonly observed scale here in the USA is the A scale. A is the OSHA selected scale for industrial environments and discriminates against low frequencies greatly.
Z is the zero weighting scale to keep all frequencies equal, this scale was introduced in 2003 as the international standard.
C scale does not attenuate these lower frequencies as they are carrying the ability to cause vibrations within structures or buildings and carry their own set of risks.
To further the explanation on the A-weighted scale, the range of frequencies correlates to the common human hearing spectrum which is 20 Hz to 20kHz. This is the range of frequencies that are most harmful to a person’s hearing and thus were adopted by OSHA. The OSHA standard, 29 CFR 191.95(a), that corresponds to noise level exposure permissible can be read about here on our blog as well.
When using a handy tool such as the Digital Sound Level Meter to measure sound levels you will select whether to use the dBA or dBC scale. This is the decibel reading according to the scale selected. Again, for here in the USA you would want to focus your measurements on the dBA scale. It is suggested to use this tool at a 3′ distance or at the known distance an operator’s ears would be from the noise generation point.
Many of EXAIR’s engineered compressed air products have the ability to decrease sound levels in your plant. If you would like to discuss how to best reduce sound levels being produced within your facility, please contact us.
When I see turbulent flow vs. laminar flow I vaguely remember my fluid dynamics class at the University of Cincinnati. A lot of times when one thinks about the flow of a liquid or compressed gas within a pipe they want to believe that it is always going to be laminar flow. This, however, is not true and there is quite a bit of science that goes into this. Rather than me start with Reynolds number and go through flow within pipes I have found this amazing video from a Mechanical Engineering Professor in California. Luckily for us, they bookmarked some of the major sections. Watch from around the 12:00 mark until around the 20:00 mark. This is the good stuff.
The difference between entrance flow, turbulent flow and laminar flow is shown ideally at around the 20:00 mark. This length of piping that is required in order to achieve laminar flow is one of the main reasons our Digital Flowmeters are required to be installed within a rigid straight section of pipe that has no fittings or bends for 30 diameters in length of the pipe upstream with 5 diameters of pipe in length downstream.
This is so the meter is able to measure the flow of compressed air at the most accurate location due to the fully developed laminar flow. As long as the pipe is straight and does not change diameter, temperature, or have fittings within it then the mass, velocity, Q value all stay the same. The only variable that will change is the pressure over the length of the pipe when it is given a considerable length.
Another great visualization of laminar vs. turbulent flow, check out this great video.
If you would like to discuss the laminar and turbulent flow please contact an Application Engineer.
In industrial settings, having a single air nozzle or other blowoff product is often not the scenario that is seen. Many applications require multiple points of blowoff, even if not in the same direction or for the same position within the machine. In the scenario where multiple nozzles are used, sound levels can get tricky to calculate and is often thought of as a mystery. If you follow our blog then you may have seen this excellent blog that shows all the math behind calculating the total decibels when multiple sources of noise will be present. The video below gives a demonstration of utilizing two of the EXAIR model 1100 – 1/4″ FNPT Super Air Nozzle.
In the video you see a model 1100 being operated and producing a sound level of 74 dBA from 3′ away from the nozzle point. When the second nozzle is turned on (also producing 74 dBA individually), the pressure is adjusted back up to the same input pressure and the sound level meter registers 78 dBA from 3′ away. Following the math laid out in the “excellent blog” link above, the sound level calculated comes out to be the same 78 dBA that is shown in the video using EXAIR’s Digital Sound Level Meter.
If you would like help determining the sound levels within your facility, check out the EXAIR Digital Sound Level Meter as well as reach out to an Application Engineer.
Air… We all breathe it, we live in it, we even compress it to use it as a utility. What is it though? Well, read through the next to learn some valuable points that aren’t easy to see with your eyes, just like air molecules.
Air is mostly a gas.
Comprised of roughly 78% Nitrogen and 21% Oxygen. Air also contains a lot of other gases in minute amounts. Those gases include carbon dioxide, neon, and hydrogen.
Air is more than just gas.
While the vast majority is gas, air also holds lots of microscopic particulate.
These range from pollen, soot, dust, salt, and debris.
All of these items that are not Nitrogen or Oxygen contribute to pollution.
Not all the Carbon Dioxide in the air is bad.
Carbon Dioxide as mentioned above is what humans and most animals exhale when they breathe. This gas is taken in by plants and vegetation to convert their off gas which is oxygen.
Think back to elementary school now. Remember photosynthesis?
If you don’t remember that, maybe you remember Billy Madison, “Chlorophyll, more like Bore-a-fil.”
Carbon dioxide is however one of the leading causes of global warming.
Air holds water.
That’s right, high quality H2O gets suspended within the air molecules causing humidity. This humidity ultimately reaches a point where the air can simply not hold anymore and it starts to rain. The lack of humidity in the air leads to static, while lots of moisture in the air when it gets compressed causes moisture in compressed air systems.
Air changes relative to altitude.
Air all pushes down on the Earth’s surface. This is known as atmospheric pressure.
The closer you are to sea level the higher the level of pressure because the air molecules are more densely placed.
The higher you are from sea level the lower the density of air molecules. This causes the pressure to be less. This is also why people say the air is getting a little thin.
Hopefully this helps to better explain what air is and give some insight into the gas that is being compressed by an air compressor and then turned into a working utility within a production environment. If you would like to discuss how any of these items effects the compressed air quality within a facility please reach out to any Application Engineer at EXAIR.
On June 13, 1831 at 14 India Street, in Edinburgh Scotland James Clerk Maxwell was born. From a young age his mother recognized the potential in James, so she took full responsibility of his early education. At the age of 8 is mother passed away from abdominal cancer, so his father enrolled him in the very prestigious Edinburgh Academy.
James was fascinated by geometry at a early age, many times learning something before he was instructed. At the age of 13 he won the schools mathematical medal and first prize in both English and poetry. At the age of 16 he starting attending classes at the University of Edinburgh, and in 1850 he enrolled at the University of Cambridge.
The largest impact he had on science were his discovery’s around the relationship between electricity, magnetism, and light. Even Albert Einstein credited him for laying the ground work for the Special Theory of Relativity. He said his work was “the most profound and the most fruitful that physics has experienced since the time of Newton.”
Maxwell also had a strong interest in color vision, he discovered how to take color photographs by experimenting with light filters.
But here at EXAIR we are very interested in his work on the theory that a “friendly little demon” could somehow separate gases into hot and cold flows, while unproven in his lifetime, did actually come to fruition by the development of the Vortex Tube. Which does just that.
So here’s to you, James Clerk Maxwell…may we continue to recognize your brilliance, and be inspired by your drive to push forward in scientific developments.
A few weeks ago I was on vacation with my family. My wife and I had taken our three daughters to Columbus, OH for three days after camping in a tent for a few days. One of the focal points to the trip was COSI, the Center of Science and Industry. In case you live anywhere near Columbus, OH and have not heard of how amazing this interactive museum is, you should definitely check it out. This isn’t your normal museum.
While the Mythic Creatures exhibit and the Jim Henson exhibit were both absolutely amazing for my 9, 6 and 4 year old daughters, it was also entertaining for my wife and myself. Now you may be asking what does this interactive science place and trip with kids have to do with EXAIR.
Well, while my daughters and I were watching this enormous pendulum that knocks ball bearings off boxes every few minutes I could hear that all too familiar, gentle sound of compressed air blowing every now and then. I couldn’t however see where the noise was coming from.
As we wandered through the different sections I saw several examples of compressed air use but none were the exact sound or display I had heard. When we were walking through the Space exhibit just above where the pendulum was located and that gentle sound was getting closer. All of a sudden I saw it. Next thing I know I look up and my 6 year old was using a joystick to control a scaled down Lunar Lander propelling it in circles. This was where the sound was coming from.
While I was amazed by this interactive piece I could tell they were using compressed air and I was curious as to how it was working. That’s when I noticed the distinct design of our Nano Super Air Nozzle on the bottom of the Lander. Here’s a close up picture, well as close as the handrail would allow me to get without over reaching.
The interesting part to this is how this setup gives an idea of the amount of thrust given off by a nozzle that only consumes 8.3 SCFM of compressed air when powered at 80 psig inlet pressure. These nozzles can easily be fitted to blast debris or moisture out of small pockets or hard to reach areas. They also can be used to help direct product that may be getting diverted to a new conveyor. And, obviously, they can be used to propel scale models of lunar landers.
If you would like to discuss any application for point of use compressed air, and I do mean ANY, give us a call. If I can’t help with the application we will at the very least do our best to send you in the right direction.
Here at EXAIR, Coandă is a household name that can be heard on any given day multiple times throughout the day. The Coandă effect is fairly easy to visualize with a ligthweight ball and some high velocity airflow. Take the video below for example. This 2″ Super Air Amplifier on a stand powered at 40 psig at the inlet easily lifts this hollow plastic ball and then suspends the ball due to the Coandă effect.
If you were able to see the airflow, you would see it impacting the surface of the sphere at all different points then following the profile of the sphere until it colides with itself and is forced to separate off the surface. The turbulent flow on the top is creating a downward pressure as well. The science behind this was all found and showcased by Henri Coandă. He showcased this with a propulsion device which used a domed hood with airflow to follow the curvature of the dome then exit off the sharp edge or where the separate air streams began to recombine causing a turbulent / low pressure area depending on the angle.
This stream of air following a surface begins to pull in all surrounding and impacted air molecules from around the stream which is called entrainment. This is a key factor for EXAIR products and one reason the Coandă profiles are a key characteristic to obtaining the peak performance and efficiency out of a compressed air product.
Many EXAIR products utilize the Coandă principle to improve their efficiencies and performance. Below you can see the EXAIR product families containing Coandă profiles within their design which increases the ambient air entrainment resulting in an amplified air blowoff.