Did you know that the earth is able to process air much like a compressor? In other words, the weight of our atmosphere actually compresses air, generating 14.7 psi of air pressure per square inch at sea level. An air compressor processes the same air we breathe to store energy in pretty much the same way.
How? You ask.
That’s a great question, and one that we are about to answer right here. But first…
What’s an Air Compressor, exactly?
Air compressors are basically devices that are designed to take in a large amount of air at atmospheric pressure, and convert it into a smaller volume at a much higher pressure. This requires a diesel or electric powered motor, and stores it a storage tank as a form of compressed air which can then be used as energy. After the pressure within the storage tank has reached its upper limit, the motor shuts off automatically and the high-pressure air that is now trapped in the storage tank can be used as a power source for all types of applications. High-pressure air can be used to power pneumatic tools such as sanders, airbrushes, blow guns, nail guns and air hammers etc. it can also be used to inflate car tires and pool toys. Now, that we’ve gotten to the bottom of what an air compressor is, let’s get back on track by telling you how air compressors work.
How does an air compressor work?
Whether it’s a professional or home user, pneumatic tools are an invaluable piece of equipment simply because rather than using electric or gas power sources, they use the power of air, more specifically, compressed air. Besides, since pneumatic tools are smaller and lighter while being just as powerful, it makes them the most preferred option as compared to electric-powered tools. Apart from that, there is very little that can go wrong while using pneumatic tools and since there are no capacitors or brushes to replace they are more durable and require low maintenance. In fact, pneumatic tools that are powered by compressed air, when used properly can easily outlast any of the electric or gas powered tools. So, now that we’ve made the case that air compressors are to pneumatic tools what Trump is to fascists or Hillary is to ANTIFA, let’s continue.
Many DIY enthusiasts and professionals use air compressors to spray paint surfaces or to seal wood, concrete etc. Air compressors are considered to be essential tools when it comes to spray painting projects. This is also the reason who portable air compressors are so popular amongst contractors since them can provide compressed air power that can be utilized for various needs on a job site. In this way, air compressors can be seen as a transition of power from the traditional electric and gas sources to a more fuel-efficient source of energy.
By compressing the air, energy is produced, which results from the pressure difference in the tank of the compressor and its surrounding atmosphere. But, the biggest advantage of using pneumatic tools is that these tools are able to produce a high amount of torque. Apart from that, pneumatic tools do no generate the heat that is produced by electric powered tools, meaning when a pneumatic tool is on even under extreme conditions, the extra load does not cause the tool to overheat. Since air compressors are essential when it comes to using pneumatic tools, it pays to find out exactly how air compressors work to power pneumatic technology.
The Technology Behind Air Compressors
While some compressors use a device known as an impeller pump for compressing air, others use a reciprocating piston for achieving the same results. Those compressors that use reciprocating pistons operate in very much the same way as in internal combustion engine does. Similar, to a gas-powered engine, there are a few components that make up a piston air compressor. These components are: a crankshaft, cylinder, valve head, connecting rod and a piston. While some air compressors use an electric motor, there are some that use a gas engine to power the crankshaft. As the shaft rotates, the connecting rod pushes the piston up and down within the cylinder causing two distinct effects. The valve head used has two valves, one is the inlet and the other the outlet.
As the piston motions downward, it creates a vacuum in the head. During this time, an inlet valve is opened that allows air to enter the vacuum that’s been created. While on the upward motion, the air is then compressed by the force of the piston that’s pushing against it. During the compression stroke, an outlet valve is opened allowing air to be forced towards the compression tank. With every up and down motion, more air is compressed into the tank, which causes the air within the tank to increase.
Lubrication for Air Compressors
Similar to the engine in a car, the cylinder that’s in the compressor also needs to be lubricated. Traditionally, air compressors have always used oil for lubricating the pistons, but nowadays, oil-free lubrication are more commonly used in air compressors.
Compressors that use oil to lubricate the piston have an oil sump or oil bath. The oil is then pulled up by the motion of the piston and splashed on the walls of the cylinder to lubricate it. Microscopic particles of oil are also pushed and mix with the air which is being compressed despite being preventing from entering the valve head by the piston rings. The oil that escapes can prove to be useful in some cases, but there are times when the presence of oil in the air has a negative impact on the functions of air compressor.
Those pneumatic tools which need lubrication while operating can benefit from the present of oil contained in the compressed air. That being said, some pneumatic tools such as spray guns that use paint can be impacted negatively by the presence of oil in the air. That’s because the oil inhibits the ability of the pain to adhere to the surface.
While using certain pneumatic tools, a filtration system is used to remove the oil from the compressed air. But, those air compressors which do not use oil lubrication can eliminate this problem altogether. Contrary to popular belief, this type of compressor is treated with a longer-lasting lubricant which is silicone based rather than oil based. However, the compressors that are lubricated by oil are considered to be more durable since the oil which is used for lubricating the pistons can be changed on a regular basis. But, this will require a maintenance program to ensure that the piston remains lubricated properly for the entire lifetime of the engine.
On the other hand, those air compressors that do not use oil are sealed with the silicone-based lubricant being added in the cylinder beforehand. This of course, means that the lubricant cannot be replaced. Despite the oil-free lubrication being less durable, it is still the preferred option for many people when it comes to air compressors. That’s because there is no risk of the air within the compressor being contaminated with oil, neither does one have to check the level of the oil, or change the oil, which means less time spent on maintenance.
Now that we’ve covered the positive and negative aspects of having oil in a compressor, there are other contaminants that should be avoided at all costs so that the air compressor is able to function at optimum levels. These contaminants are dust and other solid particles that are present in the atmosphere, which can seriously harm the components within the pneumatic tool being used. If there are particles in the air, spray paint applications will not be able to deliver the best results, which will show in the inferior quality of the pain job. An air filter is used to prevent any dust or other particles in the atmosphere from entering the compressor tank. This air filter is fitted in the air intake of the compressor. The type of filters that can be used may vary depending on the brand. While some manufacturers use simple air filters that are cheap, while others use commercial-grade air filters that cost more, but deliver more in terms of performance.
It is also possible to retrofit your device with a more efficient air filter to get the desired results. Professionals normally opt for multi-tier air filtration systems to ensure the highest level of quality while using a paint gun.
This might sound surprising, but even water can be harmful to both the durability of the pneumatic tool and the quality of the paint job. Air compressors create heat with its motor and the friction that’s caused by the piston. The heat that’s created in turn, causes an increased in evaporation of water molecules in the surrounding air. Once the air cools within the air compressor’s tank, the water then condenses and then settles to the bottom of the tank. Once the amount of water starts to increase in the tank, it mixes with the air, escaping from the tank.
Some air compressors use specially designed cooling fins that are used to cool the air before it enters the air compressor’s tank. This in turn, helps reduce the amount of condensation within the tank, but does not remove the water completely. This is why all air compressor tanks are fitted with a special drain valve, which is fitted at the bottom of the tank and its function is to extract any water that collects inside the tank. Users can also use a water trap that can be fitted to the air outlet, and uses a venturi effect to suck the suspended water in the compressed air into a reservoir that’s at the bottom of the trap, which in turn, prevents any water from entering the pipe that leads to the pneumatic tool that’s being used. But, even after all this effort the truth of the matter is that water almost always builds up in the tank and is unavoidable. But the good news is that it can be managed. But, the tank first needs to be drained after regular intervals. Just how often the tank needs to be drained will mainly depend on the air intake cooling system, and for how long the compressor is worked. Large compressor tanks will require less frequent draining because of the large volume of the tank, which means that’s there is a lower water to air ratio in the tank.
Compressor Volume and Pressure
Different pneumatic tools work differently, while some require a High Volume Low Pressure or HVLP, others require Low Volume Low Pressure or LVLP. These pneumatic tools are usually spray guns that are used for spray painting surfaces. Another type of tool are the orbital pneumatic tools that vary in both pressure and volume requirements, depending on the size and the power of the pneumatic tool. These tools also have adjustable valves which allow the users to control the pressure and volume of the air that’s used in these machines. In normal conditions, these tools operate within ranges between 60 PSI to 90 PSI.
The volume that is produced by the air compressor can be measured in Cubic Feet per Minute or CFM, which tells us just how many cubic feet of air is being forced into the tan per minute. Large pistons that have a high horsepower motor can produce more CFM. While using pneumatic tools, the size of the tank is what makes an impact on the amount of work that can be done with the device. Even if the compressor is able to produce a low air volume it can be compensated for by using a larger tank. While, a high volume of compressed air in a tank usually means that it will most likely take longer for the air pressure to drop in the tank. It will also be easy to add any additional tanks to the outlet of the compressor to increase the volume of the compressed air that can be stored in the tank.
All air compressors are fitted with pressure control, spring-loaded switches that help control the start and stop of the pump in the compressor. The valve that is placed on the tank is used to direct air into the switch. As the pressure builds within the tank, the spring is compressed. This spring is connected to a lever that either opens or closes the switch. This spring has been set at the lowest and highest pressure setting.
Once the spring is compressed to the maximum pressure that is rated for the particular tank, which is usually between 120 PSI and 125 PSI, the switch is opened automatically to cut the power form the motor. As the air is released from the tank of the air compressor, the spring decompressed until it reaches the minimum pressure that is rated for the tank, which is usually between 90 PSI and 95 PSI. Once the pressure of the tank reaches this point, the switch is closed once again and the power is supplied to the motor.
Some air compressors are also fitted with a regulator which is placed at the outlet and is used to set the pressure in the tank. Typically, this type of compressor has two gauges, one is used as an indicator for the tank pressure and the other is used as an indicator for the pressure in the output line. These compressors also come fitted with safety cut-offs as an extra precaution in circumstances when the pressure control switch malfunctions. When the pressure within the tank exceeds its maximum safety point, the power is automatically switched off, while a pressure relief valve opens and releases the air that’s built up in the tank. The pressure relief valve remains open until the air pressure in the tank reaches a safe level.
Air compressors vary in size. They can be either portable and used as handheld devices for light-duty jobs. Small, handheld air compressors are only capable of supplying just about enough compressed air to run a light-duty staple gun or nail gun. On the other hand, industrial-grade air compressors are much larger and can produce enough energy to power almost any pneumatic tool. That being said, there are many sizes that fall within the two size ranges for air compressors.
Silent Air Compressors
Portable, handheld air compressors are popular amongst contractors and DIY enthusiasts since it is lightweight and takes up less space. There are also some portable air compressors that are classified as silent air compressors, albeit they are not entirely silent, but they are silent enough to be used in an enclosed space without waking up the neighbors. Silent air compressors produce a noise of such less frequency that it does not disturb a normal conversation between two people. But, they are unable to produce the amount of power necessary for larger pneumatic tools. This is why it is important to choose the right size when using an air compressor by factoring in not just the price, but the size of the pneumatic tools that you are going to use along with the air compressor.
Amount of Pressure
Another factor to pay attention to is the amount of pressure generated by the air compressor. For instance, while using a spray gun, you will need a constant pressure, as even a slight drop in pressure could lead to disastrous results with the paint job. Large volume tanks are often preferred when using spraying tools since there’s a more gradual drop in air pressure which does not affect the quality of the paint finish. Low CFM compressorsmay result to delays since it may require you to wait for the tank to build up pressure if a large volume of air is being used.
Service Pressure Range
Air compressors can be divided into three distinct types based on the amount of pressure that they are able to produce:
- Low – The discharge pressure in these compressors range between 125 to 150 PSI. This type of compressor is normally used to carry out small tasks such as inflating balloons, inflating bike or car tires, or inflating pool toys, and also to power small, hand-held cleaning electronic equipment.
- Medium – The discharge pressure of these compressors range between 150 to 1000 PSI. This type of compressor is used for powering pneumatic tools that are responsible for more demanding tasks such as spray painting or sand blasting.
- High – The discharge pressure of this type of air compressor is higher than 1000 PSI, which is a lot of power and is usually used for industrial and commercial purposes or workshops.
Well, there you go. This is all you need to know about the complex and extremely technical inner workings of an air compressor. So, the next time your buddies at the bar ask you, “Hey, how does an air compressor work anyway?” you can spend the rest of the night explaining it to them, or better still, forward them this blog. YW!