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.
There is rarely a day that goes by that I don’t receive a call from someone who has a need for a compressed air product and when I state the SCFM requirements of the device they respond back with the psi rating of their air compressor. Many technicians simply do not understand the difference between the two. Simply put psi (pounds square inch) is force and CFM (cubic feet per minute) is flow.
A simple illustration would be to contrast a 12 VDC powered air compressor that many people carry in their trunks to inflate car tires. They will inflate your car tire to 35 psi in a matter of minutes. While the air compressor at a tire shop can inflate a car tire in a minute or less. What is the difference?
Simply put, the flow. Both inflate the tire to the desired pressure but the one with largest flow (volume) does it much faster. In the case of a compressed air product such as an air nozzle, the pressure required to operate is only one part of what is necessary to operate the device effectively, you need to have enough flow or CFM.
Let us now consider an EXAIR 1100 Super Air Nozzle, its rated performance of 13 ounces of force at 12″ distance from the nozzle is derived from supplying 14 SCFM @ 80 psi. The typical home use air compressor that runs on 110 VAC (Generally 2 HP maximum) will not generate the flow (volume /CFM) at 80 psi to run the nozzle at peak force, just as it would not generate enough flow to fill the tire as quickly as the industrial compressor at a tire shop.
When an open tube, pipe or inefficient nozzle is placed at the end of an air line to provide blow off for cooling or cleaning it demands much greater volume from the compressor. If the compressor cannot keep up the force (pressure) of the system will decline. Replacing an open tube or pipe with an EXAIR engineered nozzle will require less compressed air volume which, in turn, will give the compressor more ability to provide full pressure and force upon your application.
If you would like to discuss air consumption of any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.
“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!
EXAIR 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.
Sound meters convert the movement of a thin membrane due to the pressure waves of sound into an electric signal that is processed and turned into a readable output, typically in dBA. The dBA scale is the weighted scale that most closely matches the human ear in terms of the sounds and frequencies that can be detected.
To protect workers in the workplace from suffering hearing loss OSHA has set limits to the time of exposure based on the sound level. The information in the OSHA Standard 29 CFR – 1910.95(a) is summarized below.
The Digital Sound Meter can be used to monitor and measure sound levels of manufacturing processed such as blowoffs for cooling or drying. Many blowoffs, especially open or drilled pipes are very inefficient and can be identified as a source of excessive noise, outside the OSHA exposure ranges. Once the noise violators are identified, a review can be done and the implementation of engineered solutions such as Super air Nozzles or Super Air Knives can be investigated. Keeping harmful noise levels in check benefits everyone involved.
The EXAIR Digital Sound Level Meter is an accurate and responsive instrument that measures the decibel level of the sound and displays the result on the large optionally back-lit LCD display. There is an “F/S” option to provide measurement in either ‘slow’ or ‘fast’ modes for stable or quickly varying noises. The ‘Max Hold’ function will capture and hold the maximum sound level, and update if a louder sound occurs.
Certification of accuracy and calibration traceable to NIST (National Institute of Standards and Technology) is included.
There is an informative Video Blog, presented by @EXAIR_LE that can be found here.
If you have questions about the Digital Sound Level Meter, or would like to talk about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
On November 2, 2017 at 2 PM EDT, EXAIR Corporation will be hosting a FREE webinar titled “Optimizing Your Compressed Air System In 6 Simple Steps”.
During this short presentation, we will explain the average cost of compressed air and why it’s important to evaluate the current system. Compressed air can be expensive to produce and in many cases the compressor is the largest energy user in a plant, accounting for up to 1/3 of the total energy operating costs. In industrial settings, compressed air is often referred to as a “fourth utility” next to water, gas and electric.
Next we will show how artificial demand, through operating pressure and leaks, can account for roughly 30% of the air being lost in a system, negatively affecting a company’s bottom line. We will provide examples on how to estimate the amount of leakage in a system and ways to track the demand from point-of-use devices, to help identify areas where improvements can be made.
To close, we will demonstrate how following six simple steps can save you money by reducing compressed air use, increasing safety and making your process more efficient.