What is Sound, and How Can You Reduce It?

Many manufacturing plants have a strong focus on safety for their workers.  One major safety concern that is commonly overlooked is noise.   Occupational Safety and Health Administration, or OSHA, has a directive that defines the noise exposure over a time-weighted average; 29CFR 1910.95(a).   For an eight-hour day, the maximum noise level is 90 dBA.  The Center for Disease Control, CDC, reports that “approximately 18% of all manufacturing workers have hearing difficulty”1.

What is sound?  In the simplest of terms, a decibel is one-tenth of a bel.  Historically, bel was a unit created to honor Alexander Graham Bell, who invented the telephone.  Like the frequency waves that travel through telephone wires, pressure waves travel through the air as sound.  This sound pressure is what our ears can detect as loudness.  EXAIR offers a Digital Sound Level Meter, model 9104, that is calibrated and can measure sound in decibels.  It is very important to know the sound level, as it can permanently damage your ears.

Here is a test for you.  If you go and stand in your plant, you can probably hear loud noises coming from your compressed air system.  EXAIR has an engineered product to solve most of them.  On the Hierarchy of Controls for NIOSH, Personal Protection Equipment, PPE, is the least effective.  A better control would be to isolate your operators from the hazard with an engineered product.  EXAIR can offer that solution for many of your blow-offs and pneumatic discharges to reduce noise levels.  This would include; but not be limited to; Super Air Nozzles, Safety Air Guns, Super Air Knives, and Super Air Amplifiers

Let’s look at a ¼” open copper tube.  It can create a sound level of over 100 dBA.  They are commonly used because they are readily available and inexpensive to make.  But they waste a lot of compressed air, as well as creating a hazard for your operators.  Just by adding a model 1100 Super Air Nozzle to the end of the copper tube, we can reduce the noise level to 74 dBA at 80 PSIG (5.5 bar).  Wow!  Not only will it remove the hazard, but it will reduce the amount of compressed air usage; saving you money.  Here is a quick video to show the importance of the EXAIR Super Air Nozzles.

At EXAIR, we have a statement, “Safety is everyone’s responsibility.”  EXAIR manufactures engineered products with high quality, safety, and efficiency in mind.  To keep your operators safe, 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 you can use to contact an Application Engineer at EXAIR.  We will be happy to help to reduce your sound levels. 

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Note 1: https://www.cdc.gov/niosh/topics/ohl/manufacturing.html

EXAIR Super Air Knife Helps Bakery Protect Sheet Pan Coating

A bakery had a process where they cleaned baking sheets after they made cakes, breads, and donuts.  The system consisted of scraping the pans with brushes prior to running them through a washing system.   The excess crust material had to be removed as it could cause problems with the washing machine.  The baking sheets had a non-stick coating to help in the baking process.  The issue that they were having was that the brushes would start to remove the non-stick coating over time, causing the pans to rust.  If you needed more iron in your diet, this would not be the proper way.  The baking sheet was 18” (457mm) wide by 36” (914mm) long.  They contacted EXAIR to see if we had a better way to clean these sheets without damaging the coating. 

EXAIR has been supplying powerful non-contact ways to clean, dry, and cool products.  For this application, I recommend the model 110218SS Super Air Knife Kit.    The kit includes an 18” (457 mm) 303SS Super Air Knife, a filter, a regulator, and a shim set.  The stainless-steel construction would protect against the harsh detergents that are used in the process.  If additional protection is required, EXAIR also provides 316SS material.  The unique feature of the Super Air Knife is that it entrains ambient air at a rate of 40:1 to deliver a hard-hitting force with a small amount of compressed air.  In addition, the filter would capture any contamination from the compressed air line to keep the surface clean.  The regulator and shim set would be used to control the amount of force required to remove the debris. 

The Super Air Knife was placed just before the washing system to remove the baked contamination.  The brush system was removed.  As a bonus, they realized that they did not need to replace the brushes quarterly, which added replacement costs and maintenance time.  Sometimes these savings are overlooked.  The setup was really easy, as they only had to run compressed air to the Super Air Knife and mount anywhere from 3” (76mm) to 12” (305mm) from the sheet instead of having to periodically adjust the brushes due to the bristles shortening.

After the installation, they were amazed at the power of the Super Air Knife.  And with the non-contact cleaning, the non-stick surface was able to last much longer without having to replace the pans.  Currently, the baking sheets are lasting twice as long as they were before they started using our product.  If you have an application, where you would like to protect the surface, EXAIR has a variety of products that can create a non-contact way to clean, dry, and cool.  An Application Engineer can assist you. This customer above could now have their cake and eat it, too.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

The Cost of Compressed Air Leaks

As margins get tighter and the cost of manufacturing climbs, industries are looking for ways to be more economical.  A big focus is on the compressed air system.  Compressed air is considered to be the “fourth utility” behind gas, water, and electricity.  Air compressors are necessary to run pneumatic systems, but they are the least efficient of the utilities.  For every $1.00 that is put into making compressed air, you only get roughly 5¢ of work from it.  So, it is very important to use this utility as efficiently as possible. 

One of the biggest problems affecting compressed air systems is leaks.  That quiet hissing sound coming from the pipelines is costing your company a lot of money.  A study was conducted by a university to determine the percentage of air leaks in a typical manufacturing plant.  In a poorly maintained system, they found that 30% of the compressor’s capacity is lost through air leaks on average.  Just to let you know, the majority of companies do not have a leak prevention program, so they will fall into the “poorly maintained” category.  To put a dollar value on it, a leak that you cannot physically hear can cost you as much as $130 per year.  That is just for one inaudible leak in hundreds of feet of compressed air lines.  The chart below shows the amount of money that can be wasted by the size of the hole for larger leaks. Unlike a hydraulic system, compressed air is clean, so leaks will not be visible at the source.  You have to find them by other means. 

Most leaks occur where you have threaded fittings, connections, hoses, and pneumatic components like valves, regulators, and drains.  The Optimization products that EXAIR offers are designed to help optimize your compressed air system, and the most effective way is to find and stop leaks.  We have the Ultrasonic Leak Detectors to find inaudible air leaks and the Digital Flowmeters to check your system and find leak rates.  With both products included in a leak prevention program, you will be able to keep your compressed air system running optimally and reduce the cost caused by wasting compressed air. 

EXAIR Ultrasonic Leak Detector: When a leak occurs, it emits an ultrasonic noise caused by turbulence.  These ultrasonic noises can be at a frequency which is inaudible for human hearing.  The EXAIR Ultrasonic Leak Detector, model 9207, can pick up these frequencies and make the leaks audible.  With a signal strength number and bar graph level display, you can find very minute leaks.  It comes with two attachments; the parabola to locate leaks up to 20 feet away, and the tube attachment to define the exact location in the pipeline.  Once you find a leak, it can be marked for fixing.  This simple-to-use instrument can save you a lot of money and headaches. 

EXAIR Digital Flowmeter: With the Digital Flowmeters, you can continuously watch for waste.  Air leaks can occur at any time within any section of your pneumatic system.  You can do regular checks by isolating sections with the Digital Flowmeter and watching for a flow reading.  Another way to monitor your system would be to compare the results over time.  With the Digital Flowmeters, we have a couple of options for recording the air flow data.  We have the USB Datalogger for setting certain time increments to record the air flows.  Once the information is recorded, you can connect the USB to your computer, and with downloadable software, you can view the information and export it into an Excel spreadsheet.  With the digital flowmeters, we also offer wireless capability.  You can have multiple flow meters that can communicate with your computers to continuously log and record the flow information via one gateway.  Once the flow information starts trending upward for the same process, you can use the Ultrasonic Leak Detector to find the leak.  It can also serve as a preventive measure if a pneumatic system is starting to fail.

Leaks in compressed air will cost you in terms of performance, compressor life, and electrical costs.  It is important to have a leak prevention program to check for leaks periodically, as they can happen at any time.  The EXAIR Ultrasonic Leak Detector and the Digital Flowmeters will help you accomplish this and optimize your compressed air system.  If you need more information, you can contact an Application Engineer at EXAIR.  Once you find and fix all your leaks, you can then focus on improving the efficiency of your blow-off devices with EXAIR products.  It will save you even more money. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Photo: Soap bubble and pencils by Carola68Pixabay license

Controlling Temperature & Flow on a Vortex Tube

How a Vortex Tube Works

Vortex Tubes are unique items that use an ordinary supply of compressed air to create two streams of air, one hot and one cold.  We can drop the temperature by as much as 129oF (71.1oC) below inlet temperature on the cold end. It can also be raised as much as 195oF (107.9oC) above the inlet temperature on the hot end.  And this can be done without any moving parts, motors, or Freon. Compressed air would be the only input.  In this blog, I will cover how to adjust the Vortex Tubes and the resulting effects. 

The cold air flow and temperature are easily controlled by adjusting a slotted valve located at the hot air outlet.  Opening the valve (turning it counterclockwise) reduces the cold air flow rate and lowers the cold air temperature.  Closing the valve (turning it clockwise) increases the cold air flow and raises the cold air temperature.  So, how does this apply to cooling? 

To go a little deeper, we have to consider cold air temperature and cooling capacity.  Cooling capacity is the rate at which heat can be extracted.  The higher the cooling capacity, the faster the heat is removed.  This deals with temperatures and mass air flow.  Like stated above, the colder the air temperature that we create with a Vortex Tube, the less cold air is produced. The two are inversely related.  So, we have to find a balance between the temperature and cold air flow. You can find this rate by using Equation 1:

Equation 1:

H’ = 1.0746 * Q * (T2 – T1)

H’ – cooling capacity (BTU/hr)

Q – cold air flow (SCFM)

T2 – Final temperature (oF)

T1 – cold air temperature (oF)

With a Vortex Tube, the temperature difference is based on the inlet pressure and Cold Fraction.  The Cold Fraction is the amount of compressed air entering the Vortex Tube that will blow out of the cold end.  The remaining portion of the air will travel out of the hot end as heated air.  We have a chart below that shows the temperature drop on the cold air side and the temperature rise on the hot air side. 

EXAIR Vortex Tube Performance Chart

Here’s an example.  If we use a model 3240 at two different Cold Fractions, we can see the difference in cooling power.  At 100 PSIG (6.9 Bar), the model 3240 will use 40 SCFM (1133 SLPM) of compressed air.  If we look at two different Cold Fractions: 20% Cold Fraction and 70% Cold Fraction, we can calculate the cooling capacities by Equation 1.  In setting some criteria for our example, we will be using 70oF (21oC) compressed air at 100 PSIG (6.9 Bar).  Also, we will have a target temperature of 95oF (35oC). 

Example 1:  At a 20% Cold Fraction and 100 PSIG, the Vortex Tube will generate a cold air temperature drop of 123oF.  So, with a 70 oF inlet air temperature, the cold air temperature will be 70 oF – 123 oF = -53 oF.  The amount of cold air at 20% Cold Fraction is 0.2 * 40 SCFM = 8 SCFM.  Now that we have this information, we can calculate the cooling capacity.

H’ = 1.0746 * 8 SCFM * (95 oF – (-53 oF)) = 1,272 BTU/hr.

Example 2:  At a 70% Cold Fraction and 100 PSIG, the Vortex Tube will generate a cold air temperature drop of 71oF.  So, with a 70 oF inlet air temperature, the cold air temperature will be 70 oF – 71 oF = -1 oF.  The amount of cold air at 70% Cold Fraction is 0.7 * 40 SCFM = 28 SCFM.  Now that we have this information, we can calculate the cooling capacity.

H’ = 1.0746 * 28 SCFM * (95 oF – (-1 oF)) = 2,889 BTU/hr.

As you can see, Example 1 will give you a much colder air stream, but the cooling capacity is 56% less than Example 2.  Or, in other words, in one hour, the Vortex Tube that is set at 70% Cold Fraction can remove 2,903 BTU of heat from an object.  While the same Vortex Tube set at 20% Cold Fraction, which is much colder, will only remove 1,279 BTU of heat.

In the above examples, we used 95oF as the target temperature for our application. If the target temperature changes, then so does the relative cooling power generated by a vortex tube. We take this into account when we are performing calculations to determine which model and setting for cold fraction would be best for your application.

EXAIR offers a wide range of sizes and cooling capacities with our Vortex Tubes for different applications.  They can be used to cool parts, set materials, and regulate temperatures in environmental chambers.  They provide an instant and reliable flow of cold air at different temperatures.  In this blog, I showed the difference between cold temperatures and the effect of cooling capacity.  If you have an application that requires cooling, you can contact an Application Engineer at EXAIR, and we will be happy to run through these calculations to help you select the correct model. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb