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.
To understand the value of a having a Pressure Regulator at every point of use we should start with identifying the two types of Pressure Regulators, Direct Acting & Pilot Operated. Direct Acting are the least expensive and most common (as shown above), however they may provide less control over the outlet pressure, especially if they are not sized properly. However when sized properly they do an outstanding job. Pilot Operated Regulators incorporate a smaller auxiliary regulator to supply the required system pressure to a large diaphragm located on the main valve that in turn regulates the pressure. The Pilot Operated Regulators are more accurate and more expensive making them less attractive to purchase. The focus of this Blog will be on the Direct Acting Pressure Regulator.
The Direct Acting Pressure Regulator is designed to maintain a constant and steady air pressure downstream to ensure whatever device is attached to it is operated at the minimum pressure required to achieve efficient operation. If the end use is operated without a regulator or at a higher pressure than required, it result’s in increased air demand and energy use. To clarify this point, if you operate your compressed air system at 102 PSI it will cost you 1% more in electric costs than if the system was set to run at 100 PSI! Also noteworthy is that unregulated air demands consume about 1% more flow for every PSI of additional pressure. Higher pressure levels can also increase equipment wear which results in higher maintenance costs and shorter equipment life.
Sizing of the Air Regulator is crucial, if it is too small to deliver the air volume required by the point of use it can cause a pressure drop in that line which is called “droop”. Droop is defined as “the drop in pressure at the outlet of a pressure regulator, when a demand for compressed air occurs”. One commonly used practice is to slightly oversize the pressure regulator to minimize droop. Fortunately we at EXAIR specify the correct sized Air Regulator required to operate our devices so you will not experience the dreaded “droop”!
Another advantage to having a Pressure Regulator at every point of use is the flexibilty of making pressure adjustments to quickly change to varying production requirements. Not every application will require a strong blast sometimes a gentle breeze will accomplish the task. As an example one user of the EXAIR Super Air Knife employs it as an air curtain to prevent product contamination (strong blast) and another to dry different size parts (gentle breeze) coming down their conveyor.
EXAIR products are highly engineered and are so efficient that they can be operated at lower pressures and still provide exceptional performance! This save’s you money considering compressed air on the average cost’s .25 cents per 1000 SCFM.
The primary business benefits of an efficient air compressor system are reduced operational costs, reduced maintenance and increased up-time. With that being said, is your compressed air system costing you more than you think it should? Are you having failures, pressure drops, inadequate volume and/or pressure? You might think from these issues that your system has seen better days and is ready to be replaced. However, it is possible that your existing tried and true compressor system has more life left in it than you think and with a few simple steps you could have it performing like a champ again!
It is estimated that typically plants can waste up to 30 percent of their generated compressed air and that cost is substantial. Considering the average cost to generate compressed air is .25 cents per 1000 SCFM, that translates into .075 cents for every .25 cents spent! Considering that energy costs have doubled in the last five years, it couldn’t be more timely to make your air compressor system more efficient.
So just where is all this waste occurring? The largest source of compressed air energy waste is from unused or leaked compressed air and that is followed by line pressure drops, over pressurization and inadequate maintenance of the compressor.
So how can you identify this issues in your system?
1). Finding leaks can be accomplished by several methods such as soapy water applied to a suspected joint or connection or the EXAIR Ultrasonic Leak Detector. It is a high quality instrument that can locate costly leaks in your compressed air system. When a leak is present and audible tone can be heard in the supplied headphones and the LED display will light. This testing can be done up to 20′ away so need to get on a ladder!
2). Pressure drop is caused by is caused by the friction of the compressed air flowing against the inside of the pipe and through valves, tees, elbows and other components that make up a complete compressed air piping system. If the piping system is to small, the flow (volume) will not be sufficient and the devices will not operate properly. The volumetric demand would need to be added up to determine if the piping is of sufficient diameter to flow the required volume. EXAIR’sDigital Flow Meter is an easy way to monitor compressed air consumption and waste. The digital display shows the exact amount of compressed air being used, making it easy to identify piping that may be undersized. Installing one on every major leg of your air distribution system to constantly monitor and benchmark compressed air usage is a fast and efficient way to see what your volume through that distribution leg is.
3). Over pressurization is also an issue, as the pressure is raised to account for high demand periods, system leaks and pressure drops. Unfortunately operating at higher pressures can require as much as 25 percent more compressor capacity than needed, generating wasted air which is called artificial demand.
You can reduce the leakage rate by running the compressor at lower pressures. If you’re short on air, don’t turn up the pressure. Run your compressor at no higher pressure than what you process requires. To relieve peak demands on your system consider the EXAIR Receiver Tank. It store’s compressed air during low usage times and releases it when the demand is increased without working your air compressor system harder.
4). Finally, a preventative maintenance (PM) program will need to be implemented to keep the air compressor system running properly. Two items that are often neglected are the drive belts and filters. Loose belts can reduce compressor efficiency and dirty filters allow dirt to get through the system and cause pressure drops. EXAIR has replacement elements for our line of filter separators to keep you air clean and line pressure down.
By increasing your awareness of the health of your air compressor system and implementing a PM program you can significantly reduce your costs from wasted energy and avoid costly down time from an out of service air compressor.
If you would like to discuss improving your compressed air efficiency or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.
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.
“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!