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.
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.
In the past your typical industrial air compressor was rated to run at 100 psi and it was not often that this pressure was exceeded. Lately with modern advances pressures have slowly crept up and have surpassed this threshold. Unfortunately this has proven costly to the industrial user of compressed air.
To clarify this point, if a compressed air system is set to maintain 102 psi it will cost the plant 1% more in electric costs than if the system ran at 100 psi. Also noteworthy is that unregulated air demands consume about 1% more flow for every psi of additional pressure.
So why is the air pressure getting so high and what can you do about it? Here are some possible causes and solutions:
Devices that do require more than 100 psi: It may not be the pneumatic device at all. If these devices are connected with restrictive fittings or there are excessive leaks in the system this can cause up to a 30 psi increase in line pressure just to make up for the poor piping. If this can be corrected it is possible that the pressure can be reduced.
Applications that are believed to be high pressure: Plant workers sometimes think that a higher air pressure is required than actually necessary. This can be caused by a lack of training or perhaps the trainers are simply repeating what they have been taught in error. It is good practice to review all locations that are using a higher pressure to determine if it is really necessary.
Loss due to undersize pipes: If your plants compressed air supply lines are undersized for the volume demand, this can cause a significant restriction and raise the line pressure. The EXAIRDigital Flow Meter can assist in recording how much demand is for a given point in time which will clarify usage.
Filter/Dryer restrictions: If the Dryer or Filter/Separators are dirty and/or undersized the compressor operating pressure is typically raised to overcome these restrictions. EXAIR has six sizes of Filter/Separators to ensure they are properly sized for the SCFM required by the devices that are connected to them. Five of the models feature an automatic drain system and of course we carry the replacement filter elements and rebuild kits to keep them in top operating condition.
Temporary demands: There may be occasional peak compressed air demands in the plant that may be caused by a different or special compressed air process or machine. If the demand is greater than the supply, the pressure may be pulled down to unacceptably low levels. In an attempt to make up for the increased demand a plant may raise the operating pressures. The best way to cope with temporary demands is to install a receiver tank that stores compressed air that can be released when the demand calls for it.
Factory default settings: It is common for compressor manufacturers to set the air pressure at or very near the maximum pressure rating for that compressor. There is no reason for this other than to verify that the air compressor will perform at its rated maximum pressure. To save on air and maintenance costs the compressor should be set only as high as the maximum pressure for approved uses in the facility.
In the compressed air industry, EXAIR provides tools and products with quick payback times.
If you would like to discuss increasing the efficiency of your compressed air usage, quieter compressed air products and/or any EXAIR product, I would enjoy hearing from you…give me a call.
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.
EXAIR’s Digital Flow Meter offers an easy way to measure, monitor and record compressed air consumption. The Digital display shows the current amount of compressed air flow, allowing for tracking to identify costly leaks and/or inefficient air users.
How exactly does the Digital Flow Meter work? The unit falls under the category of Thermal Mass or Thermal Dispersion type flow meters. Below shows the backside of a unit.
Thermal mass flow meters have the advantage of using a simple method of measuring flow without causing a significant pressure drop. The EXAIR units have (2) probes that are inserted through the pipe wall and into the air flow. Each of the probes has a resistance temperature detector (RTD.) One of the probes measures the temperature of the air flow. The other probe is heated to maintain a preset temperature difference from the temperature measured by the first probe. The faster the air flow, the more heat that is required to keep the second probe at the prescribed temperature. From Heat Transfer principles, the heat energy input required to maintain the preset temperature is based on the mass velocity of the air. Using basic physical properties for compressed air, the volumetric rate can be determined (SCFM), and displayed.
It is important to note that the compressed air should be filtered to remove oils, and dried to remove water, as these liquids have different physical properties from air, and will cause erroneous readings.
If you have any questions about the Digital Flow Meter or any of the 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.