Early one morning we received a call from a local metal stamping company that had a problem. They had outstripped the volumetric capacity of their (2) 50 HP air compressors.
They were using open copper tubes to facilitate separating the part from the die on the upstroke and then blow the part backwards into the collection chute. The (5) 1/4” copper tubes were all connected to a single manifold with a valve to control each tube. Compounding their compressed air shortage was that this setup was duplicated on approximately (8) presses. Per the plant they run the presses for approximately (4) hours per day. The volume of air required for one press was calculated as:
One 1/4” open copper pipe consumes 33 SCFM @ 80 PSIG, therefore:
Due to the award winning design of EXAIR’s engineered air nozzles the plant achieved faster separation of the part from the die and greater efficiency moving the part to the collection chute, while averting the need to purchase a larger air compressor. They are saving air, reducing energy costs and lowering the noise level in their facility.
If you would like to discuss saving air and/or reducing noise, I would enjoy hearing from you…give me a call.
Last week, the EXAIR Blog featured an article about the OSHA Standard 1910.242(b) – Reduction of Air Pressure below 30 psi for Cleaning Purposes. This week, we will review another OSHA standard that affects many of you in manufacturing and other industries.
OSHA 29 CFR 1910.95 – Standard on Occupational Noise Exposure discusses the effects of noise and sets limits for exposure. Occupational noise can cause hearing loss, and also interfere with concentration and communication, disrupting the job performance. Below is a summary from the standard of the Permissible Noise Exposure (OSHA Table G-16)
From the chart, the time an employee can be exposed to loud noise is greatly reduced as the sound level goes up. The use of hearing protection is helpful but relies on the operator to use consistently and correctly. Ear plugs or ear muffs can be uncomfortable and hot, leading to possible reduced usage. OSHA can come on site, and if violations to the sound level exposure limits are found, they can impose fines and mandate corrective action be taken place.
The recommended course of action when an operator is subjected to sound exceeding those in the chart above is to enable feasible administrative or engineering controls. Engineering controls is the arena in which EXAIR can be a great resource.
The first step in understanding and addressing any sound level issues is to measure the sound. The easy to use Digital Sound Meter, model 9104 shown below, allows for accurate testing of noise levels throughout the facility. Noisy areas can be quickly identified, leading to review, design and implementation of the engineering controls.
Some of the worst offenders for noise violations is compressed air usage. A prime example would be inefficient blowoffs, used for cooling, drying, or cleaning. Open pipe, copper tube or drilled pipe are a few of the common culprits. Not only do they consume excessive amounts of compressed air, they can produce noise levels above 100 dBA.
EXAIR manufactures a wide variety of engineered products that utilize compressed air and deliver it in a controlled manner. This allows for the most efficient use of compressed air and keeps the sound levels much lower than the inefficient methods. A Super Air Knife can replace a drilled pipe, reducing sound by as much as 20 dBA, while using 50-70% less compressed air. An engineered Super Air Nozzle can replace an open pipe or copper tube and reduce sound levels down to 74 dBA, and even down to 58 dBA for the smallest available nozzles.
EXAIR has been providing Intelligent Compressed Air Products since 1983.
If you have questions regarding noise limits and how to solve any issue with an EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
In May of 1976, The Who performed a concert in London that Guiness’ Book of World Records used to certify them as the World’s Loudest Band. A sound level of 126 decibels was recorded and documented at a distance of 32 feet from the stage. That’s right at the boundary of the threshold of pain. Which I’m sure is what they were going for.
There are a variety of charts available that relate common noises to the decibel levels they could be expected to produce. For instance, a DC-9’s engines produce a sound level of about 120 decibels at takeoff or landing. Now, imagine if such a plane were to land at the aforementioned concert: would the sound level, at a given distance, be equal to those two decibel levels added together?
The answer, of course, is no, because we’re talking about sound pressure level. It’s not EXACTLY the same as fluid pressure, but a decent analogy is that, if you have an air compressor supplying your system with 100psig compressed air, turning on your other, identical air compressor won’t result in 200psig in your system.
I mention this for a couple of reasons. One; I’m a BIG fan of The Who, and I heard one of my favorite songs of theirs on the radio this morning: “You Better You Bet,” from their Face Dances album, which came out in 1981 and hence would not have been played at the 1976 Loudest Band concert, but I digress.
The other reason is because of a conversation I had with a caller about the sound levels produced by our Super Air Knives. The published sound pressure level is 69 dBA. “dB” is short for decibels; “A” means the unit is weighted to express the relative loudness of sounds as perceived by the human ear. Anyway, the caller was interested in knowing how much louder our longer Super Air Knives were than their shorter counterparts. The answer is, of course, they’re not louder…for the same reason that your second air compressor doesn’t double the air pressure in your system, which is the same reason that the fictional jet landing at the rock concert wouldn’t double the sound level.
Now, a couple of things to consider: the sound pressure levels that we publish were measured at a distance of 3 feet to the side of the Super Air Knife. Sound levels at a closer distance, and/or in front of or behind the Air Knife, will be different. Also, the Super Air Knife was blowing into free air. If the air flow is impinging on a surface, there will be a sound level associated with that as well. If it’s in excess of the 69 dBA that the Super Air Knife is producing, then that’s what your ears are going to be subject to.
All things considered, though, the Super Air Knife is INCREDIBLY quiet, considering the amount of air flow it’s producing. The science behind this has to do with what makes them so efficient with their use of compressed air: their entrainment ability. The Super Air Knife’s design allows it to use the primary compressed air flow to entrain enormous amount of air from the surrounding environment. This entrained air not only multiplies the resultant flow rate produced, but forms an attenuating boundary layer, which effectively reduces the sound level produced by the high velocity compressed air.
This video explains a few of the features on the EXAIR Digital Sound Level Meter. It also illustrates proper positioning of the meter when taking sound level readings. This sound level meter is an important tool to quantify noise exposure of employees and identifying the sources of noise.
News from the CDC that those of us involved with industrial safety are paying close attention to is the release of their NIOSH (National Institute for Occupational Safety and Health) division’s Hazard Evaluation Program Noise Measurement Database, which contains data obtained through Health Hazard Evaluation surveys performed between 1996 and 2012. It includes hundreds of personal noise exposure measurements (how much noise was received by individuals) and almost as many area noise measurements (how much noise was made.) A comparison of these measurements, of course, is valuable in determining if appropriate measures are being taken to abate the exposure, which is key: there are an awful lot of industrial processes where there’s nothing that can be done about the generation of noise…they’re just simply LOUD. So, they focus on what they can do to limit exposure: Use engineering controls (retrofit open line with engineered nozzles, build sound barriers) , use administrative controls (relocating personnel away from the sound), use personal protective equipment, and spending as little time as possible near the source.
Regardless of what people can get used to, the area noise associated with compressed air use CAN be reduced, while still maintaining the efficiency of the operation. Here’s the deal:
*The most basic form of air blow off is a piece of pipe, tubing, or hose connected to a source of compressed air. When it’s opened to the atmosphere, the compressed air exits with a great deal of force. This makes quite a racket, and the only way to quiet it down is to reduce the air supply pressure. Then you get less force, however, and it might not get the job done.
The compressed air supply (black arrow) uses the Coanda effect when it exits the series of holes recessed in the array of fins (dark blue arrows.) This serves to entrain an enormous amount of air from the surrounding environment (light blue arrows,) which not only results in a high volume flow rate at minimal consumption, but also makes the resultant air flow very quiet.
EXAIR Super Air Nozzles are quiet, efficient, and easy to get…we maintain inventory of anything you see in the Catalog, all available for same day shipment. If you’d like to know how EXAIR products can be easy on your ears…and your wallet…give me a call!
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EXAIR’s 1 Inch Flat Super Air Nozzle won the Gold Award for Compressed Air from Plant Engineering in 2014. We won the award for the immense savings that our customers reap by using this nozzle to replace open blow offs. While saving compressed air, we also reduce noise level and comply with an OSHA regulation 192.242(b). Do not leave that blow off open. It is costing you everyday in dollars; it may cost you more in OSHA fines later, and it will cost your employees hearing later.
A 1/4″ copper tube can use 33 SCFM at 80 PSIG of inlet pressure. This homemade blow off will use 1,980 standard cubic feet per hour. Typical industrial compressed air cost $0.25 per 1,000 standard cubic feet. That 1/4 copper tube is costing you $0.50 every hour to run. Each year, one 1/4″ copper tube costs $2,970*.
The 1 inch Flat Super Air Nozzle, model 1126, uses 10.5 SCFM or 22.5 SCFM less than 1/4″ Copper tube. Saving your company 22.5 SCFM, is the same as saving $0.34 every hour or $2,025 every year.* Saving 22.5 SCFM also, means that your compressor system doesn’t have to work as hard. A 5 HP compressor will put out 20 SCFM, so replacing one 1/4″ Copper Tube with a model 1126 will save you from upgrading compressor system as your company expands.
Regardless of the $2,025 you just saved by replacing the homemade blow offs with engineered nozzle, it is also an industry best practice because it can lower the noise exposure for personnel and prevent any harm from dead end pressure. OSHA standard 29 CFR – 1910.95(a) requires that if an employee is exposed to greater than 100 dBA for 2 hours, he or she needs to wear hearing protection. A 1/4″ copper tube will easily exceed 100 dBA. The model 1126 will lower the noise level to 77 decibel, 13 dBA lower than the OSHA requirements for an 8 hour day.
Finally, the 1″ Flat Super Air Nozzle cannot be dead ended, which protects your employees from serious injury. In the event, that a compressed air orifice is blocked with no means of escape, air may enter the bloodstream from an open cut or wound in the skin. Compressed air must be kept below 30 PSIG to eliminate this danger when using an open pipe, tube or many commercial air nozzles. With EXAIR nozzles, pressure to the nozzle can remain at line pressure and produce the maximum velocity and force for a successful application.
My sister-in-law and my nephews are traveling from Columbus to Cincinnati for a visit this weekend. My nephews are 18 months and 3 years old, and they will find any sharp, fragile, or flammable object within walking, crawling or climbing distance. Of course they don’t consider these things dangerous. All they see are fun new toys. Yesterday, I battened down the hatches for the nephew hurricane that will be barreling down Interstate 71 this weekend, and there were more dangerous or scary items in the house that the nephews will want to use than I could hide.
At EXAIR, we strive to provide products that intelligently use compressed air, but everyday we have customers who are using compressed air in unsafe manner. We try to educate many of our customers and the industry as whole of the dangers and that can be associated with compressed air. The chief concern is that compressed air may cause an embolism by forcing air into the bloodstream through a break in the skin or body opening. Because of this risk, OSHA has laid down several rules for using compressed air for cleaning purposes inside the work place. To quote the OSHA Instruction STD 1-13.1, “The requirements for dynamic flow are such that in the case when dead ending occurs a static pressure at the main orifice shall not exceed 30 psi. This requirement is necessary in order to prevent a back pressure buildup in case the nozzle is obstructed or dead ended.
An open pipe used for cleaning violates this rule. Yet everyday I speak to a customer who are using open pipes to remove chips, dust or water from parts. If a employees hand is trapped against the open tube, serious injury will result. EXAIR’s Super Air Nozzles are designed with multiple openings and fins to protect those openings, so that air always has a path to escape.
The other safety concern with an open pipe is the noise level. Open pipes can produce noise levels over 100 dBA which violates OSHA’s standard for maximum Allowable Noise Exposure for even 2 hours per day. EXAIR Super Air Nozzles will reduce noise levels to create a safer more productive work environment.