When trying to explain or state a number associated with how loud a sound or noise is it can be somewhat confusing or at the very least, ambiguous. This blog will help to make it clear and easy to understand the difference between Sound Power and Sound Pressure.
Sound Power is defined as the speed at which sound energy is radiated or transmitted for a given period of time. The SI unit of sound power is the watt. It is the power of the sound force on a surface of the medium of propagation of the sound wave.
Sound Pressure is the sound we hear and is defined as the atmospheric pressure disturbance that can vary by the conditions that the sound waves encounter such as furnishings in a room or if outdoors trees, buildings, etc. The unit of measurement for Sound Pressure is the decibel and its abbreviation is the dB.
I know, the difference is still clear as mud! Lets consider a simple analogy using a light bulb. A light bulb uses electricity to make light so the power required (stated in Watts) to light the bulb would be the “Sound Power” and the light generated or more specific the brightness is the “Sound Pressure”. Sound just as with the light emitting from the bulb diminishes as the distance increases from the source. Skipping the math to do this, it works out that the sound decreases by 6 dB as the distance from the sound source is doubled. A decrease of 3dB is half as loud (Sound Pressure) as the original source. As an example sound measured at 90 dB @ 36″ from the source would be 87dB at 54″ from the sound source or 84dB at 72″.
We at EXAIR specialize in making quiet and efficient point of use compressed air products, in fact most of our products either meet or exceed OSHA noise standards seen below.
EXAIR also offers the model 9104 Digital Sound Level Meter. It is an easy to use instrument for measuring and monitoring the sound level pressures in and around equipment and other manufacturing processes.
A glass cutting facility was having issues with small shards of glass leaving the cutting machine. After scribing and breaking individual panes, small pieces of glass would come apart from the edges of the glass. These glass fragments would go downstream causing cuts on transport wheels as well as creating blemishes in the surface of the glass. They needed a non-contact way to clean the glass as the panes left the cutting machine.
Their operation started with a 156” (3.96m) wide sheet of glass placed at the front of the cutting machine. The glass was moved into the machine where it would scribe different dimensions and sizes to minimize any scrap. As the machine was scribing, a protective separator would close off the cutting machine to protect the operators. Once finished, the protective separator would open, allowing the glass sheet to exit on the other side of the machine. As the glass was coming out, a break device would “crack” the glass panes on the scribed lines. They wanted to clean the surface as the glass sheet was coming out to keep the fragments in the machine.
EXAIR has always been the leader in manufacturing the longest air knives in the industry. The EXAIR Super Air Knives can be manufactured up to 108” (2.74m) long in one continuous length. But, for this application, we had to tackle it in a different manner to reach across the entire width of 156” (3.96m). EXAIR had a solution, the model 110900 Coupling Bracket Kit. This can combine aluminum Super Air Knives for additional length. It has all the hardware to securely attach the Super Air Knives end-to-end to get a continuous air flow along the entire length. With the Coupling Bracket Kit, I recommended a model 110072, 72” (1.83m) long aluminum Super Air Knife with a model 110084, 84” (2.13m) aluminum Super Air Knife. The customer was now able to clean the entire section of glass just in front of the exit of the cutting machine. With the air knives directed to blow at a slight angle in the counter-flow direction, this non-contact form of cleaning was able to keep the shards inside the machine without scratching the surfaces.
The Super Air Knives are designed to be the most efficient air knives in the market place. It has a 40:1 amplification ratio which entrains 40 parts of ambient air to every 1 part of compressed air. So, it will save you compressed air which in turn, will save you money. Here at EXAIR, we like to go one step further for our customers. EXAIR offers an Optimization product line to save the customer even more money, to reduce even more waste, and to become even more energy efficient. For this customer above, I recommended an Electronic Flow Control, EFC. This uses a photoelectric sensor to turn on a system only when compressed air is needed. It is a small PLC unit with a timer control. I recommended the model 9064-2 which has two solenoid valves to operate each Super Air Knife. The photoelectric sensor can be adjusted for light and dark object, but for glass, we had to look for an alternative way. I was able to have the customer place it on the protective separator. Now, the Super Air Knives will remain turned off until after the scribing was completed. When the separator moved up, it would trigger the timing operation of the EFC. By adding the EFC to their system, they were able to reduce the amount of compressed air by one-half.
If you have a wide area that needs to be blown off, cooled, or dried; EXAIR may have a solution for you. For the customer above, EXAIR was able to combine Super Air Knives with optimization for an efficient and effective way to clean a wide surface. If you would like to discuss a solution for your “wide” application, you can contact an Application Engineer at EXAIR to discuss.
Keeping noise levels in check and at safe levels is very important to ensure employee safety and well being. OSHA (the Occupational Safety and Health Administration) through standard 29 CFR-1910.95(a) has studied the situation and set Maximum Allowable Noise Exposure limits in Hours per Day based on the Sound Level, in dBA, of exposure.
For existing processes, a Digital Sound Meter is a valuable tool to measure the sound level to ensure that the source of loud noises can be quickly identified and isolated for immediate corrective action.
For new processes, or changes to an existing process, it is important to estimate the sound level prior to installation and start-up, so that precautions can be taken as needed.
For example, let’s say we are going to add a blow off station to clean off a part on a conveyor to improve the process and increase the throughput. A typical set-up might be a 12″ Super Air Knife (model 110012) blowing off the top and a pair of Super Air Nozzles (model 1100) to blow off the sides.
If we look at the performance data for the (2) different blow off devices, we find that the Super Air Knife is rated at 69 dBA and the nozzles at 74 dBA, when operated at 80 PSIG of compressed air supply.
When asked, “what is the sound level for (1) of the knives, and (2) of the nozzles” a little Acoustic Engineering is in order. The decibel scale is logarithmic, and determining the total sound level when all (3) devices are in operation is not as easy as adding up the three sound level values (which would equal 218 dBA, way off the charts!). Thankfully, both the actual sound level and the numerical value are determined another way. I’ll spare you a lot of the math but the equation is as below.
… where SL1, SL2, SL3, … are the sound levels in dBA of the each sound makers, for as many that are being combined (in our example SL1 = 69, SL2 = 74 and SL3 = 74)
Plugging in the numbers into the equation, the combined sound level works out to be a quiet 77.65 dBA — well within the OSHA limit for exposure for a full 8 hour period.
A manufacturing company had a pressure decay leak system to check for leaks in compressed air housings. Their detector was able to find leaks as small as 0.02 cc/min. The leak program was designed for recording each housing with a batch/lot number and the corresponding leak data. If the housing reached or surpassed the leak limit, the part would be marked and quarantined. The pressure decay leak detector was a sensitive instrument, but it could not tell the operator where the leak was occurring.
How the pressure decay leak detector worked was by pressurizing the housing to a target pressure. The flow valves would shut, isolating the housing. After the pressure stabilized, the sensitive pressure sensors would pick up any loss in pressure over time. If the leak limit wasn’t reached, a green light would indicate a good leak test. If the limit was reached, a red light would indicate a failed leak test, and the housing would have to be segregated.
The housing design used a head, a bowl, a drain, and a differential pressure gauge. The leak paths were numerous. It could be at the drain, between the drain and the bowl, between the head and bowl, at the differential pressure gauge, and even in the casting of the head. The heads were made from a die-casted aluminum. If the process was not done properly, porosity could occur in the head. The leak detector was sensitive enough to find any voids that would allow air to pass through the head casting. With these many areas of potential leaks, it could be problematic if the reject rate was high.
For the application above, it is important to find where the leaks are occurring in order to create a corrective action. In order to find the leaks, they purchased a model 9061 Ultrasonic Leak Detector from EXAIR. Instead of pressure decay, the Ultrasonic Leak Detector uses sound. Whenever a leak occurs, it will generate an ultrasonic noise. These noises have a range of frequencies from audible to inaudible. The frequencies in the range of 20 Khz to 100 Khz are above human hearing, and the Ultrasonic Leak Detector can pick up these high frequencies, making the inaudible leaks, audible. The model 9061 has three sensitivity ranges and a LED display; so, you can find very small leaks. This unit comes with two attachments. The parabola attachment can locate leaks up to 20 feet (6.1 meters) away. And the tube attachment can define the exact location. With this application, they used the tube attachment to locate the leaks. After retesting the failed housings, they found that 80% of the rejects were from a sealing surface. They were able to replace or repair the o-rings. 10% of the leaks were coming from the drain. 3% of the rejects were leaking at the differential pressure gage. Both the drains and the pressure gages could be replaced with new units. 7% of the housings had a porosity problem in the head of the housing. For these, they were shipped back for evaluation to create a modification for a better casting. The production manager shared with me that an extra vent hole was required to reduce the void. This was a huge savings for the die-caster and manufacturing plant.
EXAIR Ultrasonic Leak Detector is a great tool. It can be used in a variety of applications including compressed air systems, bearing wear, circuit breakers, refrigerant leaks, and gas burners to name few. For the company above, it was a great tool to improve their assembly and testing process for their housings. If you have an application where you need to find an ultrasonic noise, you can speak with an Application Engineer to see if the model 9061 Ultrasonic Leak Detector could help.
A few weeks ago, we posted a blog discussing how artificial demand and leaks can lead to poor performance and expensive waste. Today, I’d like to review how following a few simple steps can help optimize your current compressed air system and reduce compressed air usage.
The first step you want to consider is measuring the air usage in the system. To do this, you want to start at the compressor and check individual leads to each drop point to a blowoff device, record your findings to track the demand. By measuring your compressed air usage, you can locate the source of high usage areas and monitor the usage on each leg of the system. If the demand exceeds the supply, there is potential for problems to arise, such as lowered pressure and force from compressed air operated devices leading to irregular performance.
EXAIR’s Digital Flowmeters are designed to measure flow continuously and accurately to give you real-time flow measurements of your compressed air system to help identify problems areas.
Step 2 is to locate the source of waste. Again, compressed air leaks can result in a waste of up to 30% of a facility’s compressor output. A compressed air leak detection and repair program can save a facility this wasted air. Implementing such a program can be used as a way for a facility to “find” additional air compressor capacity for new projects. Whenever a leak occurs, it will generate an ultrasonic noise.
Our Ultrasonic Leak Detector is designed to locate the source of ultrasonic sound emissions up to 20’ away. These ultrasonic sound emissions are converted to a range that can be heard by humans. The sound is 32 times lower in frequency than the sound being received, making the inaudible leaks, audible through the included headphones and the LED display gives a visual representation of the leak.
The 3rd step involves finding the source of noisy and wasteful blowoffs, like open pipes or homemade blowoffs, and replacing them with an energy efficient, engineered solution. By replacing these devices, you are not only reducing the amount of waste but also improving operator safety by complying with OSHA safety requirements.
EXAIR’s Digital Sound Level Meter is an easy to use instrument that measures and monitors the sound level pressure in a wide variety of industrial environments. The source of loud noises can be quickly identified so that corrective measures can be taken to keep sound levels at or below OSHA maximum allowable exposure limits.
The easiest way to reduce compressed air usage and save on operating expense is to turn off the compressed air to a device when it isn’t needed, step 4 in the process. Not only will this save money, in many cases, it can also simplify a process for the operator.
A simple manual ball valve and a responsible operator can provide savings at every opportunity to shut down the air flow.
For automated solutions, a solenoid valve can be operated from a machine’s control. For example, if the machine is off, or a conveyor has stopped – close the solenoid valve and save the air.
A foot pedal valve offers a hands free solution to activate an air operated device only when needed, such as being implemented in an operator’s work station.
For even more control, you can use a device like our EFC or Electronic Flow Control. This helps minimize compressed air usage by incorporating a programmable timing controlled (0.10 seconds to 120 hours) photoelectric sensor to turn off the compressed air supply when there are no parts present. It is suited for NEMA 4 environments and can be easily wired for 100-240VAC.
Step 5, intermediate storage. Some applications require an intermittent demand for a high volume of compressed air. By installing a receiver tank near the point of high demand, there is an additional supply of compressed air available for a short duration. This will help eliminate fluctuations in pressure and volume.
EXAIR offers a 60 gallon, ASME approved vertical steel tank with mounting feet for easy installation near high demand processes.
Many pneumatic product manufacturers have a certain set of specifications regarding performance at stated input pressures. In many applications, or in the case of using a homemade blowoff device like open pipe, these wouldn’t necessarily require the full rated performance of the device or full line pressure. Controlling the air pressure at the point-of-use device will help to minimize air consumption and waste, step 6.
By simply installing a pressure regulator on the supply side, you can start off at a low pressure setting and increase the pressure until the desired result is achieved. Not only will this help to conserve energy by only using the amount of air required for the application, it also allows you to fine tune the performance of the point-of-use device to match the application requirements.
If you have any questions, please contact an application engineer at 800-903-9247.
Not long ago while checking out of a motel my laptop bag that was attached to the handle on my suitcase fell forward and the impact shattered the screen on the laptop. Upon turning the computer on I realized that a new screen was in order.
I waited until I arrived at home and found what I thought to be the correct monitor and quickly ordered it. It arrived two days later and I painstakingly took the laptop apart and exposed the mounting frame. The removal of the broken screen and the installation of the new was not too difficult but the cable connector was less than robust and was very tight. Carefully I worked it back and forth and it came free.
Installation and reassembly went quickly and then I powered up the machine. I was only greeted with a series of very loud and annoying beeps. At that point I shut it down and called the company I purchased the screen from and described the issue. They determined that the resolution of the screen was incorrect for my laptop and that I needed a different model. They said I could return the incorrect one and upon inspection receive a credit less the return shipping. At that point I ordered the correct screen and packaged up the wrong one and dropped it off at the parcel delivery service.
The new model arrived and it installed easily and worked perfectly. I waited patiently and never did see a refund so I called the company and they said that it was an oversight on their end and that it would be corrected within 48 hours. Sure enough they issued the credit and money was credited back to my account with one exception, the 40% restocking fee!
I can tell you that EXAIR is not that way! If you order the wrong item or are not satisfied for any reason and the item was purchased within the last 30 days we will facilitate the return and ZERO restocking fee. There are a multitude of reasons our customers would want to take advantage of our 30 day guarantee and we make it a simple transaction if you need to take advantage of it too. Testing is one reason a customer would use this 30 days, other customers may have ordered incorrectly or released product inadvertently, they may have wanted a small sample for a meeting or demonstration at a customers location.
“To measure is to know – if you cannot measure it, you cannot improve it.” -Lord Kelvin, mathematical physicist, engineer,and pioneer in the field of thermodynamics.
This is true of most anything. If you want to lose weight, you’re going to need a good scale. If you want to improve your time in the 100 yard dash, you’re going to need a good stopwatch. And if you want to decrease compressed air consumption, you’ll need a good flowmeter. In fact, this is the first of six steps that we can use to help you optimize your compressed air system.
There are various methods of measuring fluid flow, but the most popular for compressed air is thermal mass air flow. This has the distinct advantage of accurate and instantaneous measurement of MASS flow rate…which is important, because measuring VOLUMETRIC flow rate would need to be corrected for pressure in order to determine the true compressed air consumption. My colleague John Ball explains this in detail in a most excellent blog on Actual (volume) Vs. Standard (mass) Flows.
So, now we know how to measure the mass flow rate. Now, what do we do with it? Well, as in the weight loss and sprint time improvements mentioned earlier, you have to know what kind of shape you’re in right now to know how far you are from where you want to be. Stepping on a scale, timing your run, or measuring your plant’s air flow right now is your “before” data, which represents Step One. The next Five Steps are how you get to where you want to be (for compressed air optimization, that is – there may be a different amount of steps towards your fitness/athletic goals.) So, compressed air-wise, EXAIR offers the following solutions for Step One:
Digital Flowmeter with wireless capability. This is our latest offering, and it doesn’t get any simpler than this. Imagine having a flowmeter installed in your compressed air system, and having its readings continually supplied to your computer. You can record, analyze, manipulate, and share the data with ease.
Digital Flowmeter with USB Data Logger. We’ve been offering these, with great success, for almost seven years now. The Data Logger plugs into the Digital Flowmeter and, depending on how you set it up, records the flow rate from once a second (for about nine hours of data) up to once every 12 hours (for over two years worth.) Pull it from your Digital Flowmeter whenever you want to download the data to your computer, where you can view & save it in the software we supply, or export it directly into Microsoft Excel.
Summing Remote Display. This connects directly to the Digital Flowmeter and can be installed up to 50 feet away. At the push of a button, you can change the reading from actual current air consumption to usage for the last 24 hours, or total cumulative usage. It’s powered directly from the Digital Flowmeter, so you don’t even need an electrical outlet nearby.
Digital Flowmeter. As a stand-alone product, it’ll show you actual current air consumption, and the display can also be manipulated to show daily or cumulative usage. It has milliamp & pulse outputs, as well as a Serial Communication option, if you can work with any of those to get your data where you want it.
Stay tuned for more information on the other five steps. If you just can’t wait, though, you can always give me a call. I can talk about compressed air efficiency all day long, and sometimes, I do!