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.
The electricity costs associated with the generation of compressed air make it the most expensive utility within an industrial environment. In a poorly maintained compressor system, up to 30% of the total operational costs can be attributed simply to compressed air leaks. While this wasted energy is much like throwing money into the air, it can also cause your compressed air system to lose pressure. This can reduce the ability of the end use products to function properly, negatively impacting production rates and overall quality. Luckily, it’s quite easy to estimate the leakage rate and is something that you should be including in your regular PM schedule.
According to the Compressed Air Challenge, a well-maintained system should have a leakage rate of less than 5-10% of the average system demand. To estimate what your leakage rate is across the facility, first start by shutting off all of the point of use compressed air products so that there’s no demand on the system. Then, start the compressor and record the average time it takes for the compressor to cycle on/off. The compressor will load and unload as the air leaks cause a pressure drop from air escaping. The percentage of total leakage can be calculated using the following formula:
Leakage % = [(T x 100) / (T + t)]
T = loaded time (seconds)
T = unloaded time (seconds)
The leakage rate will be given in a percentage of total compressor capacity lost. This value should be less than 10% for a well-maintained system. It is not uncommon within a poorly maintained system to experience losses as high as 20-40% of the total capacity and power.
A leak that is equivalent to the size of a 1/16” diameter hole will consume roughly 3.8 SCFM at a line pressure of 80 PSIG. If you don’t know your company’s air cost, a reasonable average is $0.25 per 1,000 SCF. Let’s calculate what the cost would be for a plant operating 24hrs a day, 7 days a week.
3.8 SCFM x 60 minutes x $0.25/1,000 SCFM =
$0.06 x 24 hours =
$1.44 x 7 days x 52 weeks =
$524.16 per year
A small leak of just 3.8 SCFM would end up costing $524.16. This is just ONE small leak! Odds are there’s several throughout the facility, quickly escalating your operating costs. If you can hear a leak, it’s a pretty severe one. Most leaks aren’t detectable by the human ear and require a special instrument to convert the ultrasonic sound created into something that we can pick up. For that, EXAIR has our Model 9061 Ultrasonic Leak Detector.
Implementing a regular procedure to determine your leakage rate in the facility as well as a compressed air audit to locate, tag, and fix any known leaks should be a priority. The savings that you can experience can be quite dramatic, especially if it’s not something that has ever been done before!
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.
What is Air? Air is an invisible gas that supports life on earth. Dry air is made from a mixture of 78% Nitrogen, 21% Oxygen, and 1% of remaining gases like carbon dioxide and other inert gases. Ambient air contains an average of 1% water vapor, and it has a density of 0.0749 Lbs./cubic foot (1.22 Kg/cubic meter) at standard conditions. Air that surrounds us does not have a smell, color, or taste, but it is considered a fluid as it follows the rules of fluid dynamics. But unlike liquids, gases like air are compressible. Once we discovered the potential of compressing the surrounding air, we were able to advance many technologies.
Guess when the earliest air compressor was used? Believe it or not, it was when we started to breathe air. Our diaphragms are like compressors. It pulls and pushes the air in and out of our lungs. We can generate up to 1.2 PSI (80 mbar) of air pressure. During the iron age, hotter fires were required for smelting. Around 1500 B.C., a new type of air compressor was created, called a bellows. You probably seen them hanging by the fireplaces. It is a hand-held device with a flexible bag that you squeeze together to compress the air. The high stream of air was able to get higher temperature fires to melt metals.
Then we started to move into the industrial era. Air compressors were used in mining industries to move air into deep caverns and shafts. Then as the manufacturing technologies advanced, the requirements for higher air pressures were needed. The stored energy created by compressing the air allowed us to develop better pneumatic systems for manufacturing, automation, and construction. I do not know what the future holds in compressed air systems, but I am excited to find out.
Since air is a gas, it will follow the basic rules of the ideal gas law;
PV = nRT (Equation 1)
P – Pressure
V – Volume
n – Amount of gas in moles
R – Universal Gas Constant
T – Temperature
If we express the equation in an isothermal process (same temperature), we can see how the volume and pressure are related. The equation for two different states of a gas can be written as follows:
P1 * V1 = P2 * V2 (Equation 2)
P1 – Pressure at initial state 1
V1 – Volume at initial state 1
P2 – Pressure at changed state 2
V2 – Volume at changed state 2
If we solve for P2, we have:
P2 = (P1 * V1)/V2 (Equation 3)
In looking at Equation 3, if the volume, V2, gets smaller, the pressure, P2, gets higher. This is the idea behind how air compressors work. They decrease the volume inside a chamber to increase the pressure of the air. Most industrial compressors will compress the air to about 125 PSI (8.5 bar). A PSI is a pound of force over a square inch. For metric pressure, a bar is a kg of force over a square centimeter. So, at 125 PSI, there will be 125 pounds of force over a 1” X 1” square. This amount of potential energy is very useful to do work for pneumatic equipment. To simplify the system, the air gets compressed, stored as energy, released as work and is ready to be used again in the cycle.
Compressed air is a clean utility that is used in many different applications. It is much safer than electrical or hydraulic systems. Since air is all around us, it is an abundant commodity for air compressors to use. But because of the compressibility factor of air, much energy is required to create enough pressure in a typical system. It takes roughly 1 horsepower (746 watts) of power to compress 4 cubic feet of air (113L) to 125 PSI (8.5 bar) every minute. With almost every manufacturing plant in the world utilizing compressed air in one form or another, the amount of energy used to compress air is extraordinary. So, utilizing compressed air as efficiently as possible is mandatory. Air is free, but making compressed air is expensive
If you have questions about getting the most from your compressed air system, or would like to talk about any EXAIR Intelligent Compressed Air® Products, you can contact an Application Engineer at EXAIR.
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.
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.