Sound Power Level and Sound Pressure

Energy…all day (and night) long, we humans are surrounded by – and bombarded by – all kinds of energy. Sometimes, the effects are pleasant; even beneficial: the warmth of the sun’s rays (solar energy) on a nice spring day is the sure-fire cure for Seasonal Affective Disorder, and is also the catalyst your body needs to produce vitamin D. Good things, both. And great reasons to get outside a little more often.

Sometimes, the effects aren’t so pleasant, and they can even be harmful. Lengthy, unprotected exposure to that same wonderful sun’s rays will give you a nasty sunburn. Which can lead to skin cancer. Not good things, either. And great reasons to regularly apply sunblock, and/or limit exposure if you can.

Sound is another constant source of energy that we’re exposed to, and one we can’t simply escape by going inside. Especially if “inside” is a factory, machine shop, or a concert arena. This brings me to the first point of today’s blog: sound power.

Strictly speaking, power is energy per unit time, and can be applied to energy generation (like how much HP an engine generates as it runs) or energy consumption (like how much HP a motor uses as it turns its shaft) For discussions of sound, though, sound power level is applied to the generation end. This is what we mean when we talk about how much sound is made by a punch press, a machine tool, or a rock band’s sound system.

Sound pressure, in contrast, is a measure of the sound power’s intensity at the target’s (e.g., your ear’s) distance from the source. The farther away you get from the sound’s generation, the lower the sound pressure will be. But the sound power didn’t change.

Just like the power made by an engine and used by a motor are both defined in the same units – usually horsepower or watts – sound power level (e.g. generation) and sound pressure (e.g. “use” by your ears) use the same unit of measure: the decibel.  The big difference, though, is that while power levels of machinery in motion are linear in scale, sound power level and pressure scales are logarithmic.  And that’s where the math can get kind of challenging.  But if you’re up for it, let’s look at how you calculate sound power level:

Sound Power Level Equation

Where:

Wis reference power (in Watts,) normally considered to be 10-12 W, which is the lowest sound perceptible to the human ear under ideal conditions, and

W is the published sound power of the device (in Watts.)

That’s going to give you the sound power level, in decibels, being generated by the sound source.  To calculate the sound pressure level:

Sound Power Level to Sound Pressure Equation

Where:

Lis the sound power level…see above, and

A is the surface area at a given distance.  If the sound is emitted equally in all directions, we can use the formula for hemispheric area, 2πrwhere r=distance from source to calculate the area.

These formulas ignore any effects from the acoustic qualities of the space in which the sound is occurring.  Many factors will affect this, such as how much sound energy the walls and ceiling will absorb or reflect.  This is determined by the material(s) of construction, the height of the ceiling, etc.

These formulas may help you get a “big picture” idea of the sound levels you might expect in applications where the input data is available.  Aside from that, they certainly put into perspective the importance of hearing protection when an analysis reveals higher levels.  OSHA puts the following limits on personnel exposure to certain noise levels:

Working in areas that exceed these levels will require hearing protection.

EXAIR’s line of Intelligent Compressed Air Products are engineered, designed, and manufactured with efficiency, safety, and noise reduction in mind.  If you’d like to talk about how we can help protect you and your folks’ hearing, call us.

 

EXAIR Leads the Way with Product Standards

Standards seem to continually get introduced and updated. There is an ever increasing number of local, regional, federal, and even global standards to comply with.  We pay close attention to these standards and have the largest number of standards upon our products.

meets or exceeds oshaThe standards the every EXAIR product meets or exceeds are the OSHA standards for dead-end pressure as well as allowable noise level exposure.  The dead-end pressure directive is OSHA standard 29 CFR 1910.242 (b).  The standard refers to the fact that compressed air can be dangerous when the outlet pressure of a hole, hose or copper tube is higher than 30 psig (2 BAR).  In the event the opening is blocked by a hand or other body part, air may enter the bloodstream through the skin, resulting in a serious injury.  All of the compressed air products manufactured by EXAIR have been designed for safety.  All are safe to be supplied with higher pressure than 30 psig and still meet or exceed the OSHA standard.

The OSHA standard 29 CFR – 191.95 (a) refers to the maximum allowable noise exposure that an operator is permitted to be exposed to for a given period of time.   The chart of allowable exposure times is shown below.   All EXAIR products are engineered to create the minimum amount of noise while efficiently utilizing compressed air.   Many times blow offs are cross drilled to permit air to escape in order to meet the OSHA standard for dead end pressure, this process increases the noise level generated by that blow off considerably.

OSHA Noise Level

One of the most stringent compliance that EXAIR has upon its products is the UL/CUL listings and recognition.  All EXAIR Cabinet Cooler Systems are UL listed, we were the first to insure your electrical cabinet’s NEMA integrity remained by putting our Cabinet Cooler systems to the UL test. This means that the Underwriters Laboratories have deemed these products safe for operation throughout the US and Canada per their standards that are applicable for each of the product groups.   The products undergo numerous tests and scenarios to ensure that an operator will be safe during the normal operation of the units.   The tests for the Cabinet Cooler Systems includes environmental exposure for the given NEMA type of the enclosure along with many other tests.  The Static Eliminator Power Supplies are also UL listed.

cULlistedcULrecognized

CE is another standard which EXAIR pays great attention to to meet or exceed. CE is a standard that is normally preferred when dealing with countries outside of the US but is gaining popularity within the states as well.  CE being a European standard actually stands for a french phrase, “Confrmité Eurpéene” which is translated to “European Conformity”.  Any EXAIR product displaying the CE mark conforms where there are applicable directives.CE

The RoHS directive is targeted on heavy metals that are generally found within electronics.  Substances like Mercury, Lead, Polybrominated biphenyls, Cadmium, or Hexavalent chromium.  In order to meet the RoHs directive a product must have 100 parts per million or less of mercury and for other substances there must be less than 0.01% of the substance by weight in a raw homogeneous materials level. All EXAIR products which are electronic or contain electronic devices are compliant to the 2002/95/EC RoHS directive, also including the amendment outlined in the European Commission decision L 214/65.  This includes all EXAIR Static Eliminators, Electronic Flow Control, and Electronic Temperature Control products.ROHS_Vector

EXAIR maintains records to be sure our supply chain is providing product which meets the conflict mineral free guidelines of the Dodd-Frank Act.  EXAIR supports Section 1502 of the Dodd-Frank Wall Street Reform and Consumer Protection Act and we are committed to compliance with the conflict minerals rule in order to curb the illicit trade of tin, tantalum, tungsten and gold in the DRC region. EXAIR is using the CMRT 3.02 template to document our supply chain and commitment to conflict free products. When requested we will even provide the needed forms to support our customer’s efforts in complying with the Dodd-Frank Act.

conflictfree

REACH, is another European Community Regulation this time on chemicals and their safe use.  REACH is targeted to ensure personnel and environmental health by identifying the intrinsic properties of chemical substances easily.  REACH stands for Registration, Evaluation, Authorization and Restriction of Chemical substances and was written into law in 2007. EXAIR products are not required to be registered per Title II, Article 7, paragraph 1  of the legislation since they do not contain substances that are intentionally released.   This is to ensure compliance with Regulation (EC) No 1907/2006 Title I, Article 3, paragraph 3, the European Union requires registration of chemicals and substances imported into the EU to ensure a high level of protection of human health and environment.

Reach

 

To conclude, when there is a safety audit, safe sourcing directive or some other form of standard/conformance that you need to meet, consider EXAIR compressed air products. Please contact us to find out if we can help you meet or exceed those standards.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Making Safety A Priority

Everyone has heard the term “idiot-proof,” and most of us know what a misnomer it is. No matter how hard we try to ensure that nothing can go wrong with a plan, there’s always going to be that possibility. And when it does, it’s frequently going to be traceable back to human error. Of course, material failures happen, and they can be darn near impossible to predict…anyone who’s ever owned an automobile for any length of time surely knows this.

Sometimes, not keeping up with regular maintenance is to blame...
Sometimes, not keeping up with regular maintenance is to blame…
...but, it can happen to anyone, it seems.
…but, it can happen to anyone, it seems.

In the Navy, we had another term, which, curiously, none of us ever regarded as derogatory: “sailor-proof.” It, of course, meant the same thing, and its use always provoked the same warning about how difficult it was to achieve. Of course, our training, attention to detail, and self-preservation instincts ensured a pretty good track record, as far as safety goes.

I was thinking about all this when I saw, in recent news, that a British submarine shipyard had trapped two workers inside a ballast tank by accident. When banging on the hull with a tool didn’t attract anyone’s attention, one of them was able to find a spot, near the top of the tank, where his cell phone got reception and was able to call for help.

At EXAIR, we’re dedicated to safety. Not only in providing Intelligent Compressed Air Products that comply with OSHA standards in regard to use for cleaning (1910.242(b)) – and noise levels (1910.95(a)), but also in the way we do business here. We have regular “all hands” training on subjects such as hazard communication & forklift safety. We’ve got ready access to Safety Data Sheets on any product used in the shop. Clear and visible signs indicate where personal protective gear (i.e. safety glasses, ear plugs, etc.) are required. Fork lift paths are clearly defined, and nobody operates one without current and specific certification. I’ve said it before and I’m proud to say it again: Getting hurt on the job is the last thing someone has to worry about here, because safety is the first thing everybody is thinking about.

Is your company paying that kind of attention to safety? If you use compressed air products for cleaning, blow off, cooling, etc., we’ll be happy to discuss that aspect with you, just to make sure. Give us a call.

Russ Bowman
Application Engineer
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Aston Martin Vantage S broken down image courtesy Paul Townsend. Creative Commons License.

busted image courtesy Jenny oh. Creative Commons License.

A (Sample) Lexicon For Compressed Air

Every industry and different technical subject matter comes with it’s own lexicon of terms or vocabulary words.  More often than not, when speaking to an Application Engineer here at EXAIR you are going to hear words within our lexicon. The list I have compiled below is merely a sampling to help translate some terms that we forget not everyone knows.  Some of these are merely acronyms that get thrown around a good amount.

SCFM – Standard Cubic Feet per Minute – This is the unit we use to represent the volumetric flow rate of compressed gas that has already been corrected to standardized conditions of pressure and temperature.

PSIG – Pounds per square inch gauge – This is the unit which we use to represent the operating inlet pressure of the device.  When requesting this, we generally are looking for a pressure gauge to be installed directly on the inlet to the device with no other form of restrictions between the two.  For the most part, catalog consumption values are given in SCFM at 80 psig.  The main exception to that rule are the Vortex Tube based products.

Compressed Air – This is a utility that most industrial manufacturing facilities have available to them.   It is regular, atmospheric air which has been compressed by an air compressor to a higher pressure than atmospheric.  Generally speaking, compressed air systems will be at a range of 85-120 psig.

OSHA – Occupational Safety and Health Administration – This is the main federal agency that enforces two of the major conformance standards that EXAIR products meet or exceed.

29 CFR- 1910.95 (a) – Maximum allowable noise level exposure.  The great majority of EXAIR products meet or exceed this safety standard, our largest Super Air Nozzles
1910.242 (b) – This is the standard which states compressed air blow off devices cannot exceed 30 psig of dead end pressure.  This means, if the exit point of the air can be blocked the operating pressure must be below 30 psig.  The reason for this standard is to prevent air embolism which can be fatal.  All EXAIR products meet or exceed this standard by having multiple orifice discharge.

Coanda Effect – This is the effect that numerous EXAIR products utilize to amplify and entrain ambient air.   The Coanda effect is when a fluid jet (stream of compressed air) tends to be attracted to a nearby surface.  This principle was found by a Romanian aerodynamics pioneer, Henri Coandᾰ.  The picture below shows a Super Air Amplifier blowing a foam ball into the air and suspending it due to the Coanda effect on the surface of the ball.

A Super Air Amplifier's air stream causes a foam ball to be suspended in mid air thanks to the Coandᾰ effect.
A Super Air Amplifier’s air stream causes a foam ball to be suspended in mid air thanks to the Coandᾰ effect.

Rigid Pipe or Hard Pipe – This is the term we will often use when discussing the compressed air line that can be used to support and supply certain EXAIR products.  Generally we are referring to a Schedule 40 steel pipe, Type L copper line, stainless steel tube, or any form of pressure rated hard pipe that can be used for supplying compressed air.

Plenum – the state or a space in which a gas, usually air, is contained at pressure greater than atmospheric pressure. Many of our products feature a plenum chamber. 

Again, this list is only a sample of the terminology you will hear us use when discussing compressed air applications.  If there are any other air/compressed air/fluid dynamic terms you may be unsure of, please contact us.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Award Winning Compressed Air Nozzle Saves Hundreds of Dollars Annually

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

Safety – When You Least Expect It You Need it Most

The cold weather kept me indoors this weekend and I conceded to being a couch potato in front of the TV. One of the shows I watched was the lumberjack competitions – and let me tell you, those guys are crazy. Standing on a board wedged into a notch in the side of a tree, up 40 feet in the air and swinging an ax is just not safe. But, that was the way it was done in the early days before mandated safety rules.

Afterward, I watched a little news only to see hundreds of motorists stranded in their cars due to inclement weather. Folks were on their way home from work and ended up sleeping in their cars. I know it is recommended that you carry an emergency kit in your car but I never gave it any thought it would be needed it in the city. Then I was jolted from my couch when the smoke alarms went off. I forgot about my buffalo wings in the oven. Wow! What if I had left the house?

In the workplace, compressed air safety should be a top priority. Open compressed air lines are extremely noisy and can cause permanent hearing loss which is addressed  OSHA Standard 29 CFR – 1910.95 (a) regarding the allowable noise exposure. High pressure compressed air can pierce the skin and enter the blood stream, causing a dangerous blood embolism – this is why OSHA has standard CFR 1910.242(b), 30 PSI maximum dead end pressure for compressed air blow off.

One of the main issues with regulating all of your compressed air lines to less than thirty psig is, thirty psig does not provide a very effective blow off.  With EXAIR’s  engineered nozzles the air can be kept at higher line pressure and still meet or exceed the OSHA standard. Higher pressure equate to higher velocity and more force upon your application. Because of this, we can solve the application, keep compressed air to a minimum, and keep safety a top priority.

Air Nozzle and Safety Air Gun

EXAIR nozzles are safe, provide very effective blow off, and reduce compressed air consumption. By design they produce output flow up to 25 times the compressed air consumed. For more information or help with your application call our application engineers at 1-800-903-9247

Joe Panfalone
Application Engineer
Phone (513) 671-3322
Fax (513) 671-3363
Web: www.exair.com
Twitter: www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair