Leaks are a hidden nuisance in a compressed air system that can cause thousands of dollars in electricity per year. These leaks on average can account for up to 30% of the operation cost of a compressed air system. A leak will usually occur at connection joints, unions, valves, and fittings. This not only is a huge waste of energy but it can also cause a system to lose pressure along with lowering the life span of the compressor since it will have to run more often to make up for the loss of air from the leak.
There are two common ways to calculate how much compressed air a system is losing due to leaks. The first way is to turn off all of the point of use compressed air devices; once this has been complete turn on the air compressor and record the average time that it takes the compressor to cycle on and off. With the average cycle time you can calculate out the total percentage of leakage using the following formula.
The second method is to calculate out the percentage lost using a pressure gauge downstream from a receiver tank. This method requires one to know the total volume in the system to accurately estimate the leakage from the system. Once the compressor turns on wait until the system reaches the normal operating pressure for the process and record how long it takes to drop to a lower operating pressure of your choosing. Once this has been completed you can use the following formula to calculate out the total percentage of leakage.
The total percentage of the compressor that is lost should be under 10% if the system is properly maintained.
Once the total percentage of leakage has been calculated you can start to look at the cost of a single leak assuming that the leak is equivalent to a 1/16” diameter hole. This means that at 80 psig the leak is going to expel 3.8 SCFM. The average industrial air compressor can produce 4 SCFM using 1 horsepower of energy. Adding in the average energy cost of $0.25 per 1000 SCF generated one can calculate out the price per hour the leak is costing using the following calculation.
If you base the cost per year for a typical 8000 hr. of operating time per year you are looking at $480 per year for one 1/16” hole leak. As you can see the more leaks in the system the more costly it gets. If you know how much SCFM your system is consuming in leaks then that value can be plugged into the equitation instead of the assumed 3.8 SCFM.
If you’d like to discuss how EXAIR products can help identify and locate costly leaks in your compressed air system, please contact one of our application engineers at 800-903-9247.
Cody Biehle Application Engineer EXAIR Corporation Visit us on the Web Follow me on Twitter Like us on Facebook
Leaks in a compressed air system can be a substantial source of wasted energy. A facility that hasn’t maintained their compressed air system will likely have a leak rate around 20-30% of the total air production. But with a leak detection plan you can reduce air leaks to less than 10% of the compressor output.
Along with the energy waste, leaks will contribute to higher operating cost. Leaks cause a drop in system pressure, which can make air tools operate poorly, harming production cost and time. In addition, by forcing the equipment to cycle more often, leaks shorten the life of almost all system equipment, including the compressor. Increased running time can also lead to added maintenance and increased downtime. Finally, leaks can lead to adding unnecessary compressor volume.
Since air leaks are almost impossible to see, other methods must be used to locate them. The best way to detect leaks is to use an ultrasonic acoustic detector, Like EXAIRUltrasonic Leak Detector (ULD). This unit can recognize the high frequency hissing sounds associated with air leaks. A person using the ULD only needs to point it in the direction of the suspected leak. When a leak is present, an audible tone can be heard with the use of the head phones, and the LED display will light. Testing various unions, pipes, valves and fittings of a complete system can be done quickly and effectively at distances up to 20’ away!
The advantages of ultrasonic leak detection include flexibility, speed, ease of use, the ability to test the system while machines are running, and the ability to find a wide variety of leaks. They involve very little training, operators often become competent after 10 minutes of training.
Due to the nature of ultrasound, it is directional in transmission. For this reason, the signal is loudest at its source. By scanning around a test area, it is possible to very quickly target in on a leak site and pin point its exact location. For this reason, ultrasonic leak detection is not only fast, it is also very accurate.
An active leak prevention program will embrace the following components: identification, tracking, repair, verification, and employee participation. All facilities with a compressed air system should establish an aggressive leak reduction program. A team involving managerial representatives from production should be formed to carry out this program.
A leak prevention program should be part of an overall program intended to improve the performance of compressed air systems. Once the leaks are found and repaired, the system should be started from the beginning until all leaks are addressed.
A good compressed air system leak repair program is very important in maintaining the efficiency, reliability, stability and cost effectiveness of any compressed air system.
“First a Plant Engineer or Maintenance Supervisor must realize that leak repair is a journey, not a destination. An ongoing compressed air leak monitoring and repair program should be in place in any plant that has a compressed air system.” Explains Paul Shaw, a General Manager for Scales Industrial Technologies’ Air Compressor Division, and an Advanced CAC Instructor, “Leak identification and remediation with a high quality repair can lead to substantial energy savings that typically has a very rapid payback, usually a year or less. In the hundreds of leak audits and repairs that we have done we’ve found that the quality of the repair is critical to ensuring the customer receive the most value for his investment and that the leak remains repaired for as long as possible. From there, constantly monitoring for compressed air leaks and repairing them as they occur can help the plant continue to reap the energy benefits.”
To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
The Rotary Scroll compressor is a popular style compressor and is used primarily for air conditioning refrigerant systems. Recently, since it is very efficient, quiet and reliable it has been adopted by industrial air compressor manufacturer’s to expand their product offering for their smaller, high-efficiency product line.
They operate on the principle of two intermeshing spirals or scrolls with one being stationary while the other rotates or orbits in relation to it. They are mounted with 180° phase displacement between them which forms air pockets having different volumes. Air enters through the inlet port located in the rotating/orbiting scroll which fills the chambers and as is moved along and compressed along the scroll surfaces.
Some of the key advantages of a Rotary Scroll Compressor are:
Pulsation free delivery due to the continuous flow from the suction port to the outlet port.
No metal to metal contact thereby eliminating the need for lubrication
Low noise levels
Fewer moving parts means less maintenance
The largest disadvantage is they are available in a limited range of sizes and the largest SCFM outputs are around 100 SCFM.
This is exactly where EXAIR shines, we offer 15 product lines of highly efficient & quiet point of use compressed air products and accessories to compliment their limited output volume of air. All EXAIR products are designed to use compressed air efficiently and quietly, many of which reduce the demand on your air compressor which will help control utility costs and possibly delay the need to add additional compressed air capacity.
As an example, EXAIR’s Super Air Knives deliver exceptional efficiency by entraining ambient air at ratios of up to 40:1 and they are able to deliver an even laminar flow of air ranging from a gentle breeze to exceptionally hard-hitting force.
EXAIR’s Super Air Amplifiers are able to entrain ambient air at ratio’s up to 25:1. The model 120024 – 4″ Super Air Amplifier developes output volumes up to 2,190 SCFM while consuming only 29.2 SCFM of compressed air @ 80 PSI which can easily be operated on a 100 SCFM output compressor.
For your blow off needs EXAIR’s Super Air Nozzle lineup has an offering that will fit nearly any need or application you may have. Nozzles are available in sizes from M4 x 0.5 to 1 1/4 NPT and forces that range from 2 ounces of force up to 23 Lbs at 12″ from the discharge. We offer sixty two nozzles that could all be operated easily from the limited discharge or a rotary scroll compressor.
If you need to reduce your compressed air consumption or you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call. We would enjoy hearing from you!
If you need to operate at a different pressure because you require less or more force or simply operate at a different line pressure, this formula will allow you to determine the volume of air being consumed by any device.
Lets first consider the volume of the 1100 Super Air Nozzle at a higher than published pressure. As shown in the formula and calculations it is simply the ratio of gauge pressure + atmospheric divided by the published pressure + atmospheric and then multiply the dividend by the published volume. So as we do the math we solve for 17.69 SCFM @ 105 PSIG from a device that was shown consume 14 SCFM @ 80 PSIG.
Now lets consider the volume at a lower than published pressure. As shown it is simply the ratio of gauge pressure + atmospheric divided by the published pressure + atmospheric and then multiply the dividend by the published volume. So as we do the math we solve for 11.04 SCFM @ 60 PSIG from a device that was shown to consume 14 SCFM @ 80 PSIG.
When you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call. Experience the EXAIR difference first hand and receive the great customer service, products and attention you deserve! We would enjoy hearing from you.
On any given day myself and my Application Engineering Brethren here at EXAIR have discussions with customers on air starvation of any given EXAIR Product. The calls generally start off the same, “The Line Vac is not performing like it should”. We at EXAIR absolutely want to help you get the most out of our products and we certainly want them to perform to your expectation. However they must be supplied with clean/dry compressed air at sufficient pressure and volume.
Just the other day I was discussing a performance issue with a customer on a 1″ Line Vac. The customer thought he needed a larger Line Vac. I asked the questions regarding the diameter of his Supply Line and if he was using Quick Connect or Push Lock connectors. He was attempting to feed this Line Vac with 1/4″ Poly Tubing through a elbow Push to Loc fitting.
This 1″ Line Vac was being severely starved for air and therefore not performing as expected. The 1″ Line Vac require’s 14.7 SCFM @ 80PSI to reach the rated performance of 42″ of water column.
Below is a table for Pipe/Hose sizing from the Line Vac installation manual that you can use as a reference guide. It is recommended that if using hose for the supply air to go up to the next size over the pipe recommendation.
Don’t forget that quick connects and Push Lock fittings are not recommended and could restrict the air flow which will have a negative impact on performance.
Flow rate is the quantity of material that is moved per unit of time. Generally, the quantity of material can be expressed as a mass or a volume. For example, mass flow rates are in units of pounds per minute or kilograms per hour. Volumetric flow rates are stated in cubic feet per minute or liters per hour. The trick begins when volumetric flow rates are used for a compressible gas. In this blog, I will go over the various acronyms and the reasons behind them.
What acronyms will be covered?
CFM – Cubic Feet per Minute
SCFM – Standard Cubic Feet per Minute
ACFM – Actual Cubic Feet per Minute
ICFM – Inlet Cubic Feet per Minute
The volumetric component of the flow rate is CFM or Cubic Feet per Minute. This term is commonly used for rating air compressors. From history of air compressors, they could calculate the volume of air being drawn into the air compressor by the size of cylinder. With the volume of the compression chamber and the rotations per minute of the motor, RPM, they could calculate the volumetric air flows. As conditions change like altitude, temperature, and relative humidity, the value of CFM changes. To better clarify these conditions, compressor manufacturers decided to add terms with definition. (For your information, air compressors still use CFM as a unit of air flow, but now this is defined at standard temperature and pressure).
The first letter in front of CFM above now defines the conditions in which the volumetric air flow is being measured. This is important for comparing pneumatic components or for properly sizing pneumatic systems. Volume is measured with three areas: temperature, pressure, and relative humidity. We can see this in the Ideal Gas Law: P * V = n * R * T or Equation 1:
V = n * R * T / P
V – Volume
n – Number of molecules of gas
R – Universal Gas Constant
T – Absolute Temperature
P – Absolute Pressure
The volume of air can change in reference to pressure, temperature, and the number of molecules. Where is the relative humidity? This would be referenced in the “n” term. The more water vapor, or higher RH value, the less molecules of air is in a given volume.
SCFM is the most commonly used term, and it can be the most confusing. The idea of this volumetric air flow is to set a reference point for comparisons. So, no matter the pressure, temperature, or relative humidity, the volumetric air flows can be compared to each other at that reference point. There have been many debates about an appropriate standard temperature and pressure, or STP. But as long as you use the same reference point, then you can still compare the results. In this blog, I will be using the Compressed Air and Gas Institute, CAGI, reference where the “Standard” condition is at 14.5 PSIA, 68 deg. F, and 0% RH. Since we have a reference point, we still need to know the actual conditions for comparison. It is like having a location of a restaurant as a reference, but if you do not know your current location, you cannot reach it. Similarly, we are “moving” the air from its actual condition to a reference or “Standard” condition. We will need to know where the air began in order to reach that reference point. We will talk more about this later in this blog.
ACFM is the volumetric air flow under actual conditions. This is actually the “true” flow rate. Even though this term is hardly used, there are reasons why we will need to know this value. We can size an air compressor that is not at “Standard” conditions, and we can use this value to calculate velocity and pressure drop in a system. We can correlate between SCFM and ACFM with Equation 2:
ACFM = Actual Cubic Feet per Minute
SCFM = Standard Cubic Feet per Minute
Pstd = standard absolute air pressure (psia)
Pact = absolute pressure at the actual level (psia)
Psat = saturation pressure at the actual temperature (psi)
Φ = Actual relative humidity
Tact = Actual ambient air temperature (oR)
Tstd = Standard temperature (oR)
ICFM is one of the newest terms in the history of air compressors. This is where devices are added to the inlet of an air compressor, affecting the flow conditions. If you have a blower on the inlet of an air compressor, the volumetric flow rate changes as the pressure and temperature rises at the “Inlet”. If a filter is used, then the pressure drop will decrease the incoming pressure at the “Inlet”. These devices that affect the volumetric flow rate for an air compressor should be considered. The equation to relate the ACFM to ICFM is with Equation 3:
ICFM = ACFM * (Pact / Pf) * (Tf / Tact)
ICFM = Inlet Cubic Feet Per Minute
Pf = Pressure after filter or inlet equipment (PSIA)
Tf = Temperature after filter or inlet equipment (°R)
Examples of these different types of flow rates can be found here in this EXAIR blog by Tyler Daniel.
To expand on my explanation above about SCFM and ACFM, a technical question comes up about the pressure when using SCFM. The reference point of 14.5 PSIA is in the definition of SCFM. Remember, this is only a reference point. The starting location is actually required. This would be the ACFM value where the air values are true and actual. As an example, two air nozzles are rated for 60 SCFM. An EXAIR Super Air Nozzle, model 1106, is cataloged at 80 PSIG, and a competitor is cataloged at 60 PSIG. By comparison, they look like they use the same amount of compressed air, but actually they do not. To simplify Equation 2, we can compare the two nozzles at the same temperature and RH at 68 Deg. F and 0% RH respectively. This equation can be reduced to Equation 4:
Even though the SCFM is the same amount, you are actually using 21% more air with the competitive nozzle that was reported at 60 PSIG. So, when it comes to rating compressed air products or air compressors, always ask the conditions of pressure, temperature and RH. The more you know about volumetric flow rates, the better decision that you can make. If you need help, you can always contact our application engineers at EXAIR.