Tag: dba

A Sound Reckoning Of The Super Air Knife

Published on by Russ BowmanLeave a comment

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.

The Super Air Knife entrains air at a rate of 40:1, relative to its compressed air consumption.
The Super Air Knife entrains air at a rate of 40:1, relative to its compressed air consumption.

If you’d like to find out more about how EXAIR Intelligent Compressed Air Products such as the Super Air Knife can reduce your air consumption AND your sound levels, give me a call.

Russ Bowman
Application Engineer
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Video Blog: Features and Positioning of EXAIR’s Digital Sound Level Meter

Published on by Lee EvansLeave a comment

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.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Reduce Noise Exposure with Super Air Nozzles

Published on by Russ BowmanLeave a comment

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.

*Engineered air nozzles, such as EXAIR’s Super Air Nozzles, solve this problem by design:

air nozzle flow

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!

Russ Bowman
Application Engineer
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(800)923-9247 toll free
(513)671-3363 fax
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Award Winning Compressed Air Nozzle Saves Hundreds of Dollars Annually

Published on by Dave WoernerLeave a comment

awards2013_1126_400wide

 

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.

*Assuming 24 hours a day and 250 working days

Dave Woerner
Application Engineer
Davewoerner@EXAIR.com
@EXAIR_DW