Okay, I will admit, the title may be a tad bit leading. The fact is, it can be done. I speak to customers almost daily who are struggling with the noise levels produced from open pipe blowoffs. With Noise Induced Hearing Loss (NIHL) a significant problem among manufacturing workers, reducing the noise form compressed air can be a simple solution and contribute toward reducing overall noise exposure levels. Many of these calls and emails revolve around reducing these exact noise levels, sometimes the open pipes have existing threads on them to install the solution immediately.
To reduce these noise levels, we need to simply reduce the amount of energy that is being expelled through the pipe. How do we do this you might ask? The use of an air nozzle will reduce the energy being dispersed from an open pipe. This will result in lower air consumption as well as lower sound levels while actually increasing velocity as the pipe will maintain higher operating pressures. Be cautious about the air nozzle you choose, however, they are not all created equal. EXAIR’s engineered air nozzles are among the quietest and most efficient air nozzles available.
What size pipes can we fit nozzles to? That’s a great question. We have nozzles that range from a 4mm straight thread all the way up to 1-1/4″ NPT thread. This also includes nearly any size in between especially the standard compressed air piping sizes. For instance, a 1/4″ Sched. 40 pipe that has 1/4″ MNPT threads on it can easily produce over a 100 dBA noise level from 3 feet away. This can easily be reduced to below 80 dBA from 3′ away by utilizing one of our model 1100 Super Air Nozzles. All it takes is a deep well socket and ratchet with some thread sealant.
This doesn’t just lower the sound level though, it reduces the amount of compressed air expelled through that open pipe by creating a restriction on the exit point. This permits the compressed air to reach a higher line pressure causing a higher exit velocity and due to the engineering within the nozzle, this will also eliminate dangerous dead-end pressure and complies with OSHA standard 29 CFR 1910.242(b).
All in all, a 30-second install can make an operator’s work station considerably quieter and potentially remove the need for hearing protection. If you would like to discuss how to lower noise levels in your facility, contact us.
Sound levels and ROI don’t immediately link together in a quick thought. Unless you are me and things seem to link up that don’t always go together, like peanut butter and a cheese burger. (Trust me, just try it, or if you are near West Lafayette, Indiana just go try the Purvis Burger across the street from Purdue University.) The truth behind tying sound levels being reduced and ROI together is actually pretty simple.
For this example, I am going to stay fairly high level as we could get into some pretty deep measurements of what exactly could be a cost savings. If we reduce the sound level being generated by point of use compressed air products that is easiest to do by implementing engineered blow off products as well as reducing the operating pressure. Let’s use this example: A 1/4″ copper tube that is being used as a blow off will give off a noise level of over 100 dBA from 3′ away. The table below shows that at an 80 psig inlet pressure the same tube will also consume 33 SCFM of compressed air.
By installing a model 1100 1/4″ FNPT Super Air Nozzle on the end of this copper tube, we reduce the noise level generated by the blow off to 74 dBA. This measurement is at the same 80 psig inlet pressure and from 3′ away, which is well below the OSHA standard for allowable noise level exposure. This also gives a broader more defined pattern to the air stream which may permit a reduction in compressed air pressure.
The other factor this changes is that the air consumption is reduced by 19 SCFM of compressed air which then results in energy savings. This ultimately ends in a simple ROI equation where we are simply using the compressed air reduction as the only variable for the return.
By reducing the air consumption of a process that operates 24/7, 250 days a year that equates to a savings of 6,840,000 SCFM per year and that equates to $1,710.00 USD. This does not account for any reduction in paying for hearing protection that may no longer be needed, or increase in production because the application functions better.
So you see, reducing noise levels in a facility can easily amount to a sizable cost savings in energy going towards compressed air consumption. If you would like to walk through any potential applications, please contact us.
Over the years, EXAIR has come across a variety of different types of blow-off devices. We have seen copper tubes, pipes with a crushed end, fittings with holes drilled into them, and modular flex lines. For compressed air use, these are very dangerous and very inefficient. In many instances, companies will go through a mixed bag of items to make a blow-off device for their application. It is inexpensive to do. But what they do not realized is that these items are very unsafe and will waste your compressed air, costing you much money in the long run.
When EXAIR started to manufacture compressed air products in 1983, we created a culture in making high quality products that are safe, effective, and efficient. Since we stand by our products, we created a program called the Efficiency Lab. We test blow-off devices against EXAIR products in noise levels, flow usage, and force measurements. With calibrated test equipment, we compare the data in a detailed report for the customer to review. If we are less effective, we will state that in the report, but this is very rare. With this quantified information, we can then determine the total amount of air savings and safety improvements that EXAIR products can offer.
With our Efficiency Lab, it is quite simple to do. For starters, you can go to our Product Efficiency Survey on our website to give the conditions for testing. If you wish for a side by side analysis, you can place your pneumatic device in a box and send it to EXAIR. We will run the tests at the specified conditions or in a range of settings. We will then return your pneumatic device back to you with a report of the comparison. This report can be used to show managers, executives, HSE, etc. on the improvements that EXAIR can provide in cost savings and safety.
In a recent Efficiency Lab, a customer sent us a water jet nozzle that he was using to blow off product passing on a conveyor (reference photo above). The customer supplied us with the required information to test. They had three water jet nozzles on a manifold that had ¼” NPT male connections. The air pressure was set at 75 PSIG (5.2 bar), and the air pattern was round. Their annual usage for this blow-off device was 7000 hours continuous, and their electric rate for their facility was $0.10/KWh. The reason that they sent their nozzle to EXAIR was because the operation was very loud, and they believed that they were wasting compressed air. They asked me for a recommendation and what the payback period might be with my selection.
I recommended the model 1101 Super Air Nozzle as our standard round pattern with a ¼” NPT male connection. With our engineered design, the Super Air Nozzle can entrain the “free” ambient air into the air stream to generate a hard-hitting force; using less compressed air. Also, with this suggestion, they will not have to redesign their blow-off station; just remove the water jet nozzles and replace them with the Super Air Nozzles. We tested the water jet nozzle, and we found that it used 17.5 SCFM (496 SLPM) at 75 PSIG (5.2 bar). The noise level was measured at 91.2 dBA for a single nozzle. As a comparison, the model 1101 Super Air Nozzle will only use 13.3 SCFM (376 SLPM) of compressed air at 75 PSIG (5.2 bar); and, the noise level was reduced to 73 dBA for each nozzle.
The first thing that is important to me is safety. High noise levels will cause hearing damage. OSHA generated a standard 29CFR-1910.95a with a chart for Maximum Allowable Noise Exposure. To calculate the noise level for three nozzles, I will reference a previous blog that I wrote: “Measuring and Adding Sounds”. With three water jet nozzles, the total sound is 96 dBA. From the OSHA table above, the usage without hearing protection is less than 4 hours a day. With the Super Air Nozzles, the noise level will be 78 dBA for all three nozzles; well below the requirement for 8 hours of exposure. It is difficult to put a monetary value on safety, but using PPE should never be the first step as a solution.
For the annual savings and the payback period, I will only look at the electrical cost. (Since the Super Air Nozzle is using less compressed air, the maintenance and wear on your air compressor is reduced as well).
The air savings is calculated from the comparison; 17.5 SCFM – 13.3 SCFM = 4.2 SCFM per nozzle. With three nozzles, the total compressed air savings will be 12.6 SCFM for the blow-off station. An air compressor can produce 5.36 SCFM/KW of electricity at a cost of $0.10/KWh. For an annual savings, we have the figures from the information above; 7000 hours/year * 12.6 SCFM * $0.10/KWh * 1KW/5.36 SCFM = $1,645.52/year. For the payback period, the model 1101 Super Air Nozzle has a catalog price of $44.00 each, or $132.00 for three. The customer above did not disclose the cost of the water jet nozzles, but even at a zero value, the payback period will be just under 1 month. Wow!
Not all blow off devices are the same. With the customer above, they were able to reduce their noise levels and compressed air consumption. If your company decides to select an unconventional way to blow off parts without contacting EXAIR, there can be many hidden pitfalls; especially with safety. Besides, if you can save your company thousands of dollars per year as well, why go with a non-standard nozzle? If you have a blow off application and would like to compare it against an EXAIR product, you can discuss the details with an Application Engineer. What do you have to lose?
EXAIR offers the model 9104 Digital Sound Level Meter. It is an easy to use instrument for measuring and monitoring the sound level pressures in and around equipment and other manufacturing processes.
Sound meters convert the movement of a thin membrane due to the pressure waves of sound into an electric signal that is processed and turned into a readable output, typically in dBA. The dBA scale is the weighted scale that most closely matches the human ear in terms of the sounds and frequencies that can be detected.
Noise induced hearing loss can be a significant problem for many workers in manufacturing and mining. To protect workers in the workplace from suffering hearing loss OSHA has set limits to the time of exposure based on the sound level. The information in the OSHA Standard 29 CFR – 1910.95(a) is summarized below.
The EXAIR Digital Sound Level Meter is an accurate and responsive instrument that measures the decibel level of the sound and displays the result on the large optionally back-lit LCD display. There is an “F/S” option to provide measurement in either ‘slow’ or ‘fast’ modes for stable or quickly varying noises. The ‘Max Hold’ function will capture and hold the maximum sound level, and update if a louder sound occurs.
If you have questions about the Digital Sound Level Meter, or would like to talk about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
If you have ever walked into a manufacturing facility and heard the hiss or even worse the banshee scream of compressed air being exhausted to ambient, whether it be from a cylinder discharge, a timed drain going off, or a bypass valve being activated, they all could be hushed with a muffler. A muffler for compressed air comes in several shapes and sizes. EXAIR offers four separate types from stock to help attenuate the noise disruption within your facility.
The OSHA standard for allowable noise exposure is 29 CFR-1910.95(a) and outlines the number of hours per day any individual can be exposed to a particular noise level. These noise levels are expressed in decibels (dbA).
The first type I would like to showcase are the Reclassifying Mufflers. These are ideal for cylinder exhausts or valves which commonly contain an oil mist within the air stream which can easily contaminate the surrounding area. The patented design of the removable element separates oil from the exhausted air so virtually no atomized oil is released into the environment. They also attenuate the exhaust noise level up to 35 decibels. The filter element helps the exhaust to meet the OSHA Standard 29 CFR 1910.1000, a worker’s cumulative exposure to oil mist must not exceed 5 mg/m³ by volume in any eight hour shift of a forty hour work week.
The chart below helps to properly size the Reclassifying Muffler for a pneumatic cylinder. One key to proper installation of these mufflers is they must be installed vertically in order to properly trap and drain the oil.
The next type of muffler to discuss are the Sintered Bronze Mufflers that are offered in ten different sizes. These are an excellent low cost solution which easily install into new or existing ports. Each size is designed to provide minimal back pressure and restriction for the individual port size. The quick pick chart below helps to easily select the correct size for attenuating the exhaust of a pneumatic cylinder. One key difference between these and the Reclassifying Mufflers is, these do not have to be oriented vertically as they do not collect the oil out of the exhaust air.
If the process air needs to be directed or plumbed away from the operator then the Straight Through Mufflers are the ideal selection as they offer an NPT threaded inlet and exhaust. They are available in three standard NPT sizes from stock. These mufflers can be installed in any orientation and work well with our Vortex Tubes to help pass the cold air through while lowering the operating sound level of the tube. The average noise reduction of the Straight-Through Mufflers is 20 dB. This can easily reduce the noise level of an operation to below the OSHA standard requiring hearing protection for operators in the area.
The final option for mufflers from EXAIR are the Heavy Duty Mufflers. These are available in two sizes from stock and are constructed of corrosion-resistant aluminum with a stainless steel internal screen. These can be installed in any orientation and are ideal for protecting exhaust ports from contaminants that may clog or damage the device they are attached to. The typical noise reduction from installation is 14 dB with these mufflers.
These are available in two sizes from stock and are constructed of corrosion-resistant aluminum with a stainless steel internal screen. These can be installed in any orientation and are ideal for protecting exhaust ports from contaminants that may clog or damage the device they are attached to. The typical noise reduction from installation is 14 dB with these mufflers.
To summarize, EXAIR offers a multitude of options when it comes to lowering sound levels in operation areas that are caused by exhausted compressed air. Each of the mufflers discussed above are shipped same day from stock to meet your immediate need. If you are unsure of which muffler to use for your application, feel free to contact an Application Engineer.
In physics, sound is a wave of pressure. It occurs in a medium, which can be a solid, liquid or gas. Sound cannot travel through a vacuum, such as in space. The wave of pressure reaches our ears and causes the ear drum to vibrate, which then goes through a complex process to ultimately be perceived as audible sound.
There are several characteristics of sound waves that can be measured and help define the sound. A sound wave can be visualized as a repeating sinusoidal wave (see below), and can be described by these properties – frequency and wavelength, amplitude, and speed.
Frequency is the number of cycles in 1 second, and is measured in Hertz (Hz)
Wavelength is the distance over which 1 cycle occurs, and for audible sound is between 17 m and 17 mm long
Amplitude is the measure of its change over a single period, and normally a measure of sound loudness
Speed is the distance traveled per unit time
The speed of sound in air can be found using the equation: a = Sqrt (γ•R•T)
where for air: γ = ratio of specific heats = 1.4, R = gas constant = 286 m²/s²/K T = absolute temperature in °K (273.15 + °C)
At room temperature, 22°C (71.6°F), the speed of sound is 343.8 m/s (760 mph)
Some interesting facts about sound:
Sounds generally travels faster in solids and liquids than in gases.
You can estimate the distance from a lightning strike by counting the seconds that pass between seeing the lightning flash and hearing the thunder. Take this duration an divide by 5 to get the distance away, in miles.
Humans normally hear sound frequencies between 20 Hz and 20,000 Hz.
Sound waves above 20,000 Hz are known as ultrasound, and sound waves below 20 Hz are known as infrasound.
Sound travel through water close to 4 times faster then through air.
The sound of a cracking whip occurs because the speed of the tip has exceeded the speed of sound.
Sound that is too loud can be a problem. The Occupational Safety and Health Administration (OSHA) has set limits on the noise exposure that an employee can be subjected. Exceeding these values can cause permanent damage to your ears and cause noise induced hearing loss. So, knowing and reducing the sound levels within a manufacturing operation is important.
EXAIR has many products that can help reduce the sound levels in your processes. With products such Air Knives, Air Wipes, Air Amplifiers, Air Nozzles and Jets, and Safety Air Guns, strong, quiet and efficient blowoff, drying, and cooling can be performed.
If you have questions about sound and keeping your sound levels in check or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
In the simplest of metric terms, a decibel is one-tenth of a bel. But, historically, bel was a unit created to honor Alexander Graham Bell who invented the telephone. In the early days with telephone wires, they noticed that the signal strength would decay over a long distance. In order to determine power requirements to connect people for communications, they determined that they could use the ratio of power levels. As a start, it had to be based on a minimum amount of power required for a person to hear on the telephone. They found that the signal power level to generate an angular frequency of 5000 radians per second would be that minimum value as determined by an average number of people. They used this mark as a reference point in the ratio of power levels. Because of the large variations in values, they simplified the equation on a base-10 log scale and dividing the bel unit by 10. Thus, creating the measurement of decibel.
Today, this same method is used to measure sound. Like frequency waves that travel through the telephone wires, pressure waves travel through the air as sound. This sound pressure is what our ears can detect as loudness, and it has a pressure unit of Pascals (Pa). As an example, a small sound pressure would be like a whisper while a large sound pressure would be like a jet engine. This is very important to know as high sound pressures, or loudness, can permanently damage our ears.
With sound pressures, we can determine the Sound Pressure Level (SPL) which is measured in decibels (dB). Similar to the equation for the telephone power signals above, the SPL also uses a ratio of sound pressures in a base-10 logarithmic scale. For a minimum reference point, an average human can just start to hear a sound pressure at 0.00002 Pa. So, the equation for measuring sound levels will use this minimum reference point as shown in Equation 1.
L = 20 * Log10 (p/pref)
L – Sound Pressure Level, dB
p – Sound pressure, Pa
pref – reference sound pressure, 0.00002 Pa
Why is this important to know the decibels? OSHA created a chart in 29CFR-1910.95(a) that shows the different noise levels with exposure times. This chart was created to protect the operators from hearing loss in work environments. If the noise level exceeds the limit, then the operators will have to wear Personal Protection Equipment (PPE), or suffer hearing damage. EXAIR offers a Sound Level Meter, model 9104, to measure sound levels in decibels. It comes calibrated to accurately measure the sound to determine if you have a safe work environment.
There is a term that is used when it comes to loud noises, NIHL. This stands for Noise Induced Hearing Loss. Once hearing is damaged, it will not come back. To keep your operators safe and reduce NIHL, EXAIR offers many different types of blow-off products that are designed to decrease noise to a safe level. So, here’s to Alexander Graham Bell for creating the telephone which can be used to contact EXAIR if you have any questions.