Two basic methods to set up a compressed air operation for turning off is the ball valve and the solenoid valve. Of the two, the simplest is the ball valve. It is a quarter turn, manually operated valve that stops the flow of the compressed air when the handle is rotated 90°. It is best for operations where the compressed air is needed for a long duration, and shut off is infrequent, such as at the end of the shift.
The solenoid valve offers more flexibility. A solenoid valve is an electro-mechanical valve that uses electric current to produce a magnetic field which moves a mechanism to control the flow of air. A solenoid can be wired to simple push button station, for turning the air flow on and off – similar to the manual valve in that relies on a person to remember to turn the air off when not needed.
Another way to use a solenoid valve is to wire it in conjunction with a PLC or machine control system. Through simple programming, the solenoid can be set to turn on/off whenever certain parameters are met. An example would be to energize the solenoid to supply an air knife when a conveyor is running to blow off parts when they pass under. When the conveyor is stopped, the solenoid would close and the air would stop blowing.
The EXAIR EFC (Electronic Flow Control) is a stand alone solenoid control system. The EFC combines a photoelectric sensor with a timer control that turns the air on and off based on the presence (or lack of presence) of an object in front of the sensor. There are 8 programmable on/off modes for different process requirements. The use of the EFC provides the highest level of compressed air usage control. The air is turned on only when an object is present and turned off when the object has passed by.
By turning off the air when not needed, whether by a manual ball valve, a solenoid valve integrated into the PLC machine control or the EXAIR EFC, compressed air usage will be minimized and operation costs reduced.
If you have questions about the EFC, solenoid valves, ball valves or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
For most industrial enclosure cooling applications, a temperature of 95°F (35°C) is sufficient to be below the rated maximum operating temperature of the electrical components inside the cabinet. EXAIR Thermostats are preset to 95°F (35°C) and are adjustable. Maintaining the cabinet at 95°F (35°C) will keep the electronics cool and provide long life and reduced failures due to excessive heat. But if 95°F (35°C) is good, why not cool the cabinet to 70°F (21.1°C)?
When cooling an enclosure to a lower temperature, two things come into play that need to be considered. First, the amount of external heat load (the heat load caused by the environment) is increased. Using the table below, we can see the effect of cooling a cabinet to the lower temperature. For a 48″ x 36″ x 18″ cabinet, the surface area is 45 ft² (4.18 m²). If the ambient temperature is 105°F (40.55°C), we can find from the table the factors of 3.3 BTU/hr/ft² and 13.8 BTU/hr/ft² for the Temperature Differentials of 10°F (5.55°C) and 35°F (19.45°C). The factor is multiplied by the cabinet surface area to get the external heat load. The heat load values calculate to be 148.5 BTU/hr and 621 BTU/hr, a difference of 472.5 BTU/hr (119.1 kcal/hr)
The extra external heat load of 472.5 BTU/hr (119.1 kcal/hr) will require the Cabinet Cooler System to run more often and for a longer duration to effectively remove the additional heat. This will increase, unnecessarily, the operating costs of the cooling operation.
The other factor that must be considered when cooling an enclosure to a lower temperature is that the Cabinet Cooler cooling capacity rating is effected. I won’t go into the detail in this blog, but note that a 1,000 BTU/hr Cabinet Cooler (rated for 95°F (35°C cooling) working to cool a cabinet down to 70°F (21.1°C) instead of 95°, has a reduced cooling capacity of 695 BTU/hr (174 kcal/hr). The reduction is due to the cold air being able to absorb less heat as the air rises in temperature to 70°F instead of 95°F.
In summary – operating a Cabinet Cooler System at 95°F (35°C) provides a level cooling that will keep sensitive electronics cool and trouble-free, while using the least amount of compressed air possible. Cooling to below this level will result in higher operation costs.
If you have questions about Cabinet Cooler Systems or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
From the main page, hover the mouse pointer over ‘KNOWLEDGE BASE‘ and the pop-up menu will appear as seen below. Select ‘APPLICATIONS’
On the left hand side of the screen you will see a gray navigation pane that shows Application with a list underneath. Scroll down the main page and you will see a second heading in the navigation pane labeled “Industry”. You can select your industry from the list provided. For today’s example we will select Aerospace.
Once the industry is selected there will be a new list of applications that are displayed in the center of the page. Simply select the application you would like more information on and the details will display.
Below, we showcase the application from a machine manufacturer for the Aerospace industry. This customer manufactured the production equipment of a flexible, porous material that is continuously passed through a wash tank prior to cutting to length. They were interested in speeding the drying process of this strand, and considered blowing hot air onto it. It was not feasible to install an electrically powered hot air blower or gun. They needed an air flow of approximately 15 SCFM at 200°F, and had 70 psig air supply with a large volume available. They utilized a Vortex Tube installed over the strand after it exited the dip tank. The Vortex Tube was oriented with the hot air exhaust blowing on to the strand to dry the strand. The customer stated that they not only met their expectations but exceeded the original hopes and were able to dry the product quicker and safer than expected.
This is just one of many applications that are showcased in the Application Database for the Aerospace industry. Those are just a small sampling of the thousands of applications that can be researched through the database. If you would like to share your application to the database, feel free to contact an Application Engineer.
If you have questions about any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
Since all compressed air systems will have some amount of leakage, it is a good idea to set up a Leak Prevention Program. Keeping the leakage losses to a minimum will save on compressed air generation costs,and reduce compressor operation time which can extend its life and lower maintenance costs.
There are generally two types of leak prevention programs:
Leak Tag type programs
Seek-and-Repair type programs
Of the two types, the easiest would be the Seek-and-Repair method. It involves finding leaks and then repairing them immediately. For the Leak Tag method, a leak is identified, tagged, and then logged for repair at the next opportune time. Instead of a log system, the tag may be a two part tag. The leak is tagged and one part of the tag stays with the leak, and the other is removed and brought to the maintenance department. This part of the tag has space for information such as the location, size, and description of the leak.
The best approach will depend on factors such as company size and resources, type of business, and the culture and best practices already in place. It is common to utilize both types where each is most appropriate.
A successful Leak Prevention Program consists of several important components:
Baseline compressed air usage – knowing the initial compressed air usage will allow for comparison after the program has been followed for measured improvement.
Establishment of initial leak loss – See this blog for more details.
Determine the cost of air leaks – One of the most important components of the program. The cost of leaks can be used to track the savings as well as promote the importance of the program. Also a tool to obtain the needed resources to perform the program.
Identify the leaks – Leaks can be found using many methods. Most common is the use of an Ultrasonic Leak Detector, like the EXAIRModel 9061. See this blog for more details. An inexpensive handheld meter will locate a leak and indicate the size of the leak.
Document the leaks – Note the location and type, its size, and estimated cost. Leak tags can be used, but a master leak list is best. Under Seek-and-Repair type, leaks should still be noted in order to track the number and effectiveness of the program.
Prioritize and plan the repairs – Typically fix the biggest leaks first, unless operations prevent access to these leaks until a suitable time.
Document the repairs – By putting a cost with each leak and keeping track of the total savings, it is possible to provide proof of the program effectiveness and garner additional support for keeping the program going. Also, it is possible to find trends and recurring problems that will need a more permanent solution.
Compare and publish results – Comparing the original baseline to the current system results will provide a measure of the effectiveness of the program and the calculate a cost savings. The results are to be shared with management to validate the program and ensure the program will continue.
Repeat As Needed – If the results are not satisfactory, perform the process again. Also, new leaks can develop, so a periodic review should be performed to achieve and maintain maximum system efficiency.
In summary – an effective compressed air system leak prevention and repair program is critical in sustaining the efficiency, reliability, and cost effectiveness of an compressed air system.
If you have questions about a Leak Prevention Program or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
It is important to know the cost of compressed air at your facility. Most people think that compressed air is free, but it is most certainly not. Because of the expense, compressed air is considered to be a fourth utility in manufacturing plants. In this blog, I will show you how to calculate the cost to make compressed air. Then you can use this information to determine the need for Intelligent Compressed Air® products.
There are two types of air compressors, positive displacement and dynamic. The core construction for both is an electric motor that spins a shaft. Positive displacement types use the energy from the motor and the shaft to change the volume in an area, like a piston in a reciprocating compressor or like rotors in a rotary compressor. The dynamic types use the energy from the motor and the shaft to create a velocity energy with an impeller. (You can read more about air compressors HERE). For electric motors, the power is described either in kilowatts (KW) or horsepower (hp). As a unit of conversion, there are 0.746 KW in 1 hp. The electric companies charge at a rate of kilowatt-hour (KWh). So, we can determine the energy cost to spin the electric motors. If your air compressor has a unit of horsepower, or hp, you can use Equation 1:
hp * 0.746 * hours * rate / (motor efficiency)
hp – horsepower of motor
0.746 – conversion to KW
hours – running time
rate – cost for electricity, KWh
motor efficiency – average for an electric motor is 95%.
If the air compressor motor is rated in kilowatts, or KW, then the above equation can become a little simpler, as seen in Equation 2:
KW * hours * rate / (motor efficiency)
KW – Kilowatts of motor
hours – running time
rate – cost for electricity, KWh
motor efficiency – average for an electric motor is 95%.
As an example, a manufacturing plant operates 250 day a year with 8-hour shifts. The cycle time for the air compressor is roughly 50% on and off. To calculate the hours of running time, we have 250 days at 8 hours/day with a 50% duty cycle, or 250 * 8 * 0.50 = 1,000 hours of running per year. The air compressor that they have is a 100 hp rotary screw. The electrical rate for this facility is at $0.08/KWh. With these factors, the annual cost can be calculated by Equation 1:
In both equations, you can substitute your information to see what you actually pay to make compressed air each year at your facility.
The type of air compressor can help in the amount of compressed air that can be produced by the electric motor. Generally, the production rate can be expressed in different ways, but I like to use cubic feet per minute per horsepower, or CFM/hp.
The positive displacement types have different values depending on how efficient the design. For a single-acting piston type air compressor, the amount of air is between 3.1 to 3.3 CFM/hp. So, if you have a 10 hp single-acting piston, you can produce between 31 to 33 CFM of compressed air. For a 10 hp double-acting piston type, it can produce roughly 4.7 to 5.0 CFM/hp. As you can see, the double-acting air compressor can produce more compressed air at the same horsepower.
The rotary screws are roughly 3.4 to 4.1 CFM/hp. While the dynamic type of air compressor is roughly 3.7 – 4.7 CFM/hr. If you know the type of air compressor that you have, you can calculate the amount of compressed air that you can produce per horsepower. As an average, EXAIR uses 4 CFM/hp of air compressor when speaking with customers who would like to know the general output of their compressor.
With this information, we can estimate the total cost to make compressed air as shown in Equation 3:
C = 1000 * Rate * 0.746 / (PR * 60)
C – Cost of compressed air ($ per 1000 cubic feet)
1000 – Scalar
Rate – cost of electricity (KWh)
0.746 – conversion hp to KW
PR – Production Rate (CFM/hp)
60 – conversion from minutes to hour
So, if we look at the average of 4 CFM/hp and an average electrical rate of $0.08/KWh, we can use Equation 3 to determine the average cost to make 1000 cubic feet of air.
Once you have established a cost for compressed air, then you can determine which areas to start saving money. One of the worst culprits for inefficient air use is open pipe blow-offs. This would include cheap air guns, drilled holes in pipes, and tubes. These are very inefficient for compressed air and can cost you a lot of money. I will share a comparison to a 1/8” NPT pipe to an EXAIR Mini Super Air Nozzle. (Reference below). As you can see, by just adding the EXAIR nozzle to the end of the pipe, the company was able to save $1,872 per year. That is some real savings.
Making compressed air is expensive, so why would you not use it as efficiently as you can. With the equations above, you can calculate how much you are paying. You can use this information to make informed decisions and to find the “low hanging fruit” for cost savings. As in the example above, targeting the blow-off systems in a facility is a fast and easy way to save money. If you need any help to try and find a way to be more efficient with your compressed air system, please contact an Application Engineer at EXAIR. We will be happy to assist you.
My Application Engineer colleagues and I frequently use a handy table, called Discharge of Air Through an Orifice. It is a useful tool to estimate the air flow through an orifice, a leak in a compressed air system, or through a drilled pipe (a series of orifices.) Various tables and online calculators are available. As an engineer, I always want to know the ‘science’ behind such tables, so I can best utilize the data in the manner it was intended.
The table is frequently found with values for pressures less than 20 PSI gauge pressure, and those values follow the standard adiabatic formula and will not be reviewed here. The higher air pressures typically found in compressed air operations are of interest to us.
For air pressures above 15 PSI gauge the discharge is calculated using by the approximate formula as proposed by S.A. Moss. The earliest reference to the work of S.A. Moss goes back to a paper from 1906. The equation for use in this table is-Where:
For the numbers published in the table above, the values were set as follows-
C = 1.0, p1 = gauge pressure + 14.7 lbs/sq. in, and T1 = 530 °R (same as 70 °F)
The equation calculates the weight of air in lbs per second, and if we divide the result by 0.07494 lbs / cu ft (the density of dry air at 70°F and 14.7 lbs / sq. in. absolute atmospheric pressure) and then multiply by 60 seconds, we get the useful rate of Cubic Feet per Minute.
The table is based on 100% coefficient of flow (C = 1.0) For well rounded orifices, the use of C = 0.97 is recommended, and for very sharp edges, a value of C = 0.61 can be used.
The table is a handy tool, and an example of how we use it would be to compare the compressed air consumption of a customer configured drilled pipe in comparison to that of the EXAIR Super Air Knife. Please check out the blog written recently covering an example of this process.
If you would like to talk about the discharge of air through an orifice 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.
An important part of operating and maintaining a compressed air system is taking accurate pressure measurements at various points in the compressed air distribution system, and establishing a baseline and monitoring with data logging. A Pressure Profile is a useful tool to understand and analyze the compressed air system and how it is functioning.
The profile is generated by taking pressure measurements at the various key locations in the system. The graph begins with the compressor and its range of operating pressures, and continues through the system down to the regulated points of use, such as Air Knives or Safety Air Guns. It is important to take the measurements simultaneously to get the most accurate data, and typically, the most valuable data is collected during peak usage periods.
By reviewing the Pressure Profile, the areas of greatest drop can be determined and the impact on any potential low pressure issues at the point of use. As the above example shows, to get a reliable 75 PSIG supply pressure for a device or tool, 105-115 PSIG must be generated, (30-40 PSIG above the required point of use pressure.) As a rule of thumb, for every 10 PSIG of compressed air generation increase the energy costs increase 5-7.5%
By developing a total understanding of the compressed air system, including the use of tools such as the Pressure Profile, steps to best maximize the performance while reducing costs can be performed.
If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.