OSHA 29 CFR 1910.95 (a) – It’s a Noise Exposure Standard, Not Just a Confusing Number

Strings of numbers and characters can often appear daunting.  For instance, if I wrote in binary code it would be a string of ones and zeros.  (01000101 01101110 01100111 01101001 01101110 01100101 01100101 01110010 01101001 01101110 01100111 00100000 01101001 01110011 00100000 01000001 01010111 01000101 01010011 01001111 01001101 01000101.) That can look like gibberish and cause concern if unknown or it can make sense to programmers and people familiar with binary code.

Other alphanumeric strings may cause some concern for industry professionals.  Take, for instance, OSHA standards. The OSHA standard 29 CFR 1910.95 (a) may be unfamiliar to some, and thus concerning. Many Environmental Health and Safety Engineers will recognize this code.  It is an OSHA standard that revolves around the amount of time an employee is permitted to be exposed to specific sound levels. These sound levels are all based on the weighted sound level of the noise the operators are exposed to. To better understand how the octave and frequency of the sound play into this, there is a chart provided below.

Equivalent A-Weighted Sound Level Chart – (1)

The weighted sound level is the level at which a Digital Sound Level Meter will read the current level of noise within an environment. This scale is then used to move further into the OSHA directive that we focus on helping companies meet to best provide safe environments for their employees to work in.

If you notice, the lowest weighted sound level is 90 dBA, this is also the lowest-rated noise level that OSHA speaks of in 1910.95(b)(2). It has been shown that noise levels over this level for extended periods will result in permanent hearing loss. The standard then goes on to discuss the duration an employee can be exposed to noise levels even with the use of personal protective equipment as well as even impulsive or impact noise.  The table of permissible time limits is shown below.

Permissible Noise Exposures (2)

As you can see from the table above provided by OSHA, any noise level that an operator is exposed to for eight hours cannot exceed 90 dBA. Noises within an industrial environment can also be variable throughout the day. For instance, the operator stands outside of a sheet metal press and the concussive strike on the press gives off a 90 dBA strike for every stroke of the press. This would not be a continuous noise level. Maybe the operator is operating a CNC machine that is cutting a nest of parts and uses a handheld blowgun to remove debris and coolant from the parts before taking them from their fixture. This blowgun is not used continuously and therefore would not be rated as such for the exposure time. A time study would be conducted on the average length of time the operator is utilizing this gun along with the level of noise it produces during use. OSHA then gives a calculation to use to appropriately combine the sound level while the gun is being used and when it is not in use. That equation is written out below.

Mixed Environment Exposure Fraction
C1/T1+C2/T2+… = ____
Total Exposure Fraction
Cn/Tn = ____

Where:
C1 = Duration of time for a specified noise level
T1 = Total time of exposure permitted at that level
Cn = Total time of exposure at a specified noise level
Tn = Total exposure time permitted at that level

Should the summation of the fractions for different exposures be greater than the Total Exposure fraction, the summation value should be used. As mentioned above, a time study on exposure to noise levels will be needed to obtain the information needed for this type of study. Once the study is done the process can proceed to the next level within the OSHA standard which is a hearing conservation program.

I would like to interject a small side-step at this point. Rather than rolling straight into the implementation of PPE which is proven to be the lowest reliable factor of protection by the CDC and NIOSH. If any of these noise levels being generated are due to the use of compressed air points of use, EXAIR can potentially lower the noise of these point of use applications. In the events, open blowoffs or “band-aid” fixes are in place to keep processes running, and Engineered Solutions can easily be implemented that will reduce the noise level produced by this operation. Whether it is on the handheld Safety Air Gun in the hands of a CNC operator, or if it is a part/scrap ejector that is blowing the sheet metal press out after every strike, we have products that have proven time over time using an Engineered Solution will save air, reduce noise levels, and still get the job done.

If you would like to discuss OSHA directives revolving around compressed air, share with us a recent citation you received from an inspector for this standard, or just discuss compressed air usage in general, contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

1 – Equivalent A-Weighted Sound Level Chart – Retrieved from OSHA.Gov – https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=9735&p_table=standards

2 – Permissible Noise Exposures – Retrieved from OSHA.Gov – https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=9735&p_table=standards

 

Calculating CFM of Air Needed for Cooling

It’s easy to know that EXAIR’s vortex tubes can be used to cool down parts and other items, but did you know that our air knifes can be used to cool down these same things? It’s the same process that we do every day to cool down hot food by blowing on it. Every molecule and atom can carry a set amount of energy which is denoted by physical property called Specific Heat (Cp); this value is the ration of energy usually in Joules divided by the mass multiplied by the temperature (J/g°C). Knowing this value for one can calculate the amount of air required to cool down the object.

Starting out you should note a few standard values for this rough calculation; these values are the specific heat of Air and the specific heat of the material. Using these values and the basic heat equation we can figure out what the amount of energy is required to cool. The specific heat for dry air at sea level is going to be 1.05 J/g*C which is a good starting point for a rough calculation; as for the specific heat of the material will vary depending on the material used and the composition of the material.

Heat Flow Equation
Using the standard heat equation above add in your variables for the item that needs to be cooled down. In the example I will be using a steel bar that is 25 kg in mass rate and cooling it down from 149 °C to 107 °C. We know that the specific heat of steel is 0.466 J/g°C therefore we have everything needed to calculate out the heat load using air temperature of 22 °C.
Calculating Joules/min
Using the heat rate, we can convert the value into watts of energy by multiplying the value by 0.0167 watts/(J/min) which gives us 16,537.18 watts. Furthermore, we can then convert our watts into Btu/hr which is a standard value used for cooling applications. Watts are converted into Btu/hr by multiplying by 3.41 Btu/hr/watt, giving us 56,391.77 Btu/hr.
Converting Joules to Btu/hr
Once you have Btu/hr you can plug the information into a re-arranged Cooling power formula to get the amount of CFM of air required for cooling.
Calculating CFM
As you can see in order to cool down this steel bar you only need to 343 CFM of air at 72°F. This can be done very easily and efficiently by using one of EXAIR’s Air Amplifiers or Air Knife. Sometimes you don’t need to use a vortex tube to cool down an object; sometimes simply blowing on it is good enough and its pretty simple to calculate out which product would fit your application the best.

If you have any questions about compressed air systems or want more information on any EXAIR’s of our products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Webinar by EXAIR: Use This, Not That – Four Common Ways to Save Compressed Air in Your Plant

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Not much in life is free anymore. So, make sure and take advantage of EXAIR’s upcoming FREE webinar at 2:00 PM ET on 10/17/2019. Not only are we providing it for free, but in this webinar we’ll be discussing how you can save money by reducing your compressed air consumption. Something for free, that will help save you money? Almost unheard of these days!!! Hosted by one of our highly-trained Application Engineers, Jordan Shouse, you’ll learn about four common ways that you can easily save air in your facility.

Compressed air is often referred to as the fourth utility in industry. When used improperly, compressed air is extremely expensive. Homemade devices such as open-ended and drilled pipes, inefficient air nozzles, leaks, etc. all contribute to increased energy costs. In addition to being wasteful, these devices are not safe and compliant with OSHA standards and regulations. By using an Intelligent Compressed Air Product, you’ll be both saving money and creating a safer environment for your operators.

In this webinar, you’ll gain an understanding of the places in your facility that are wasting the most compressed air. We’ll educate you on the various engineered solutions available from EXAIR to help eliminate unnecessary compressed air usage. You’ll gain the knowledge necessary to determine the best solution based on the application, sound level, compressed air usage, and compliance with OSHA safety requirements. You’ll also learn about the various solutions available to help understand and optimize your compressed air system. You can’t begin implementing a plan to reduce air consumption until you fully understand the usage in your own facility and processes. EXAIR’s line of Optimization products are ideal to help you gain a baseline measurement and begin implementing new products and processes that’ll only help add to your bottom line.

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After the conclusion of the webinar will be a brief Q&A session where you can ask any questions you have about any of the topics covered. Unable to attend the webinar live? Don’t let that stop you from registering! Afterwards, each registrant will receive a link via e-mail where they’ll be able to access the full webinar at any time. Make sure and take advantage of this opportunity to gain some knowledge about the usage of your compressed air. You’ll be glad you did!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Applying a Vortex Tube and Adjusting Temperature

Throughout my tenure with EXAIR there are may days where I have tested different operating pressure, volumetric flow rates, back pressures, lengths of discharge tubing, generator compression, and even some new inquiries with cold air distribution all on a vortex tube.  These all spawn from great conversations with existing customers or potential customers on different ways to apply and applications for vortex tubes.

Many of the conversations start in the same spot… How exactly does this vortex tube work, and how do I get the most out of it?  Well, the answer is never the same as every application has some variation.  I like to start with a good idea of the area, temperatures, and features of exactly what we are trying to cool down.  The next step is learning how fast this needs to be done.  That all helps determine whether we are going to be looking at a small, medium, or large vortex tube and which cooling capacity to choose.   After determining these factors the explanation on how to adjust the vortex tube to meet the needs of the application begins.

This video below is a great example of how a vortex tube is adjusted and what the effects of the cold fraction have and just how easy it is to adjust.  This adjustment combined with varying the air pressure gives great versatility within a single vortex tube.

The table below showcases the test points that we have cataloged for performance values.  As the video illustrates, by adjusting the cold fraction lower, meaning less volumetric flow of air is coming out of the cold side and more is exhausting out the hot side, the colder the temperature gets.

EXAIR Vortex Tube Performance Chart

This chart helps to determine the best case scenario of performance for the vortex tube.  Then the discussion leads to delivery of the cold or hot air onto the target.  That is where the material covered in these two blogs, Blog 1, Blog 2 comes into play and we get to start using some math.  (Yes I realize the blogs are from 2016, the good news is the math hasn’t changed and Thermodynamics hasn’t either.)  This then leads to a final decision on which model of vortex tube will best suit the application or maybe if a different products such as a Super Air Amplifier (See Tyler Daniel’s Air Amplifier Cooling Video here.)is all that is needed.

Where this all boils down to is, if you have any questions on how to apply a vortex tube or other spot cooling product, please contact us.  When we get to discuss applications that get extremely detailed it makes us appreciate all the testing and experience we have gained over the years.  Also, it helps to build on those experiences because no two applications are exactly the same.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF