Compressed air has many uses and can be found anywhere from your local gas station to the mechanics. The use of an air compressor in power tools such as sprayers and sanders to just filling up a gas tank has hugely simplified our workloads.
The most common use of the air compressor in the average household is as a tire inflator. Car tires need inflating from time to time and the air compressor does just the trick.
However, air compressors are not like your typical air pump. Below we?ve discussed how air compressors work and the merits of using one as a tire compressor.
Everything About An Air Compressor
What Is An Air Compressor?
An air compressor converts the electric energy produced by your battery or engines into potential energy and stores it as pressurized air.
When this pressurized air is used, the stored energy is converted into kinetic energy. This kinetic energy can be used to do all sorts of things like filling gas cylinders, tires, or powering tools such as jackhammers.
Air compressors are not to be confused with air pumps. Air pumps move air from one place to another without pressurizing it, for example when you?re pumping up your air mattress.
What Is A Tire Inflator?
The tire inflator is a specific type of air compressor used for pumping up your car tires. The use of pressurized gas removes the need for strenuous pumping to fill your tires to the right pressure.
Tire inflators can come in all shapes and sizes. Small handheld ones can easily fit in the boot of your car and are useful in an emergency. Larger tire inflators may not fit in your car but can reliably pump up your tires in record speed.
Anatomy Of An Air Compressor
These are the basic parts of most common air inflator:
A crankshaft is driven by an electric motor or engine. In turn, the force from the crankshaft makes the piston work and the piston compresses the air. This allows the air to be delivered to the nozzle at a high pressure.
Most air compressors will also come with an air tank. The air tank holds air within a certain pressure range. The compressed air in the air tank can be used to power your tools.
As the air in the tank is being used up, the pressure will decrease. This will signal to the motor to automatically turn on again so that the pressure within the tank is kept constant. Once the desired pressure is reached, the motor will turn off.
The gauge tells you the pressure. Gauges can be digital so it?s easy to read off the pressure level of the gas. But if you?ve got an analogue one, it?s important that the scale is legible so that you know when to stop the air compressor.
Some air compressors say they have a high psi. This does not equate to more power. The high psi only tells you that your gauge is capable of measuring a high psi, not that it is capable of inflating that much.
So, if you need to inflate something (e.g. road bike) to 120 psi, you want a model with a gauge that can read that high.
How Air Compressor Works
Air compressors work by a process called positive displacement. A reciprocating piston is used and the air pressure is gradually increased by reducing the amount of volume available.
Air flows into the compressor and is compressed by a piston which is driven by a crankshaft. The piston moves down and creates a vacuum above the piston. This allows air from the outside of the air compressor to flow in.
The piston moves up and compresses the air above the piston. This increases the pressure of the air and stops any outside air coming in. A valve that leads to the air storage tank opens and the compressed air moves into this tank.
Each stroke of the piston puts more air into the tank and increases the pressure of the compressed air.
Technical Aspects Of Air Compressors
The following paragraphs contain some very general information on air compressors that will allow for a more informed decision concerning the type and size of compressor being considered.
Portable Vs Stationary Air Compressor
This is one of the primary distinctions between different air compressors.
Portable Air Compressor
Most portable air compressors are quite light, weighing in at 2 to 6 pounds. Most have a handle for easy carrying and some even have wheels.
They are quite small which is good if you have a limited amount of space in your garage or if you want to store the air compressor in your car.
Unfortunately, their small size limits the use of portable air compressors to inflating objects to a relatively low pressure, such as car tires (32 psi).
Stationary Air Compressor
Stationary air compressors are meant to be permanent fixtures in a workshop. These come with large air tanks and powerful motors. These are very heavy so when you?re deciding where to place your air compressor, you have to be absolutely certain you won?t need to move them again in future.
They also come at a much greater cost and need to be wired to an electricity supply in order for the air compressor to receive enough power to function.
Gas Vs Electric Air Compressor
Some other factors to consider when looking at motors is difference between gas and electric air compressors.
Gas Air Compressor
Gas air compressors are a good choice if you don?t have access to an electric power source. They work in a similar way as an electric air compressor but the main difference is that gas air compressors do not have start/stop regulation.
Instead, they have valves which can be opened or closed and this determines the pressure in the tank. Having the motor constantly running and pressurizing the air is useful for tools which need a continuous flow of air, such as paint sprayers.
The downside of a gas air compressor is that the noise and fumes prevent them from being used indoors.
Electric Air Compressor
Electric air compressors require a nearby power source to run, making them less portable than a gas air compressor but are a lot cheaper to run and maintain.
The motor can automatically turn itself on or off to regulate the pressure inside the tank. The motor can also automatically turn off if no tools are being used.
An annoying issue with electric air compressors is that it is strongly advised that they not be used with extension cords. This is because the length of the power cord to the air compressor is determined by the type of air compressor.
An extension cord that is too long can?t draw enough power, which causes the motor to overheats and fail. Cords that are too short cause the compressor to turn off to protect itself from overheating damage or it can burn out.
Air compressors work primarily from air stored in the storage tank. The style of tank will depend on the type or power requirements of your compressor.
The pancake style tank is small, light and very portable. With a volume of 1 to 6 gallons, they?re good for small repairs and as tire inflators but do not have the capacity to run large power tools.
Little maintenance is required for pancake compressors since there are no belts and they use an oil free pump.
The wheelbarrow air compressor is made from two tanks placed along the length of the compressor, with the arrangement looking kind of like a wheelbarrow.
Wheelbarrow air compressors have powerful motors and are designed for heavy duty use. As such, they?re also quite heavy and difficult to move.
The hotdog compressor has just one cylindrical tank so it?s another small air compressor however it is still heavier than the pancake compressor.
The small tank allows the compressor to power small tools but not large ones. Similar to the pancake compressor, little maintenance is required for these air compressors.
The twin-stack air compressor is the same as the hot dog compressor except it has two tanks stacked one on top of the other.
Naturally, twin-stack compressors have a much larger capacity and are able to power larger tools.
Single Stage Vs Two Stage Air Compressors
Single Stage and Two Stage is in reference to the compressor pump type.
A single stage air compressor draws in air and compresses it into the final pressure using only one piston stroke. Air can be compressed up to 150 psi.
They typically have a higher CFM than 2 stage compressors since every cylinder is drawing in air and compressing with each rotation of the pistons.
These compress air in two stages. The first step draws in air and compresses it to an intermediate pressure. The air is then piped to a cooler chamber for the air to cool down before the second compression step to the final pressure.
Air can be compressed up to 200 psi. Two stage air compressors are more efficient at higher pressures since the air is cooled between compressing.
Oiled Vs Oil Free Air Compressor
Compressors require lubrication and so some compressors use an oil bath.
Oiled compressors splash oil onto the bearings and cylinder walls as the crank turns. The pistons have rings to separate oil from the air but they?re not perfect and a little oil sometimes gets through.
A little oil isn?t too bad since some air tools need oiling anyway. However, the oiled air compressors are high maintenance as they require regular oil checks and oil changes. They also need to be used on a level surface.
Some tools or situations require oil free air, such as when spray painting. In these cases, an oiled compressor is not very suitable. Oil free compressors use permanently lubricated bearings instead of an oil bath
Understanding the physics behind how an air compressor works is a lot easier when you know the technical terms. We?ve defined a few of the more common terms that will crop up.
PSI stands for ?pounds per square inch? and is a unit which is used to measure pressure. 1 psi is equivalent to 6894.76 Pascals.
The tire pressure of the average car is typically 32 psi.
CFM stands for ?cubic feet per minute?. This measures the volume of air passing over an area in one minute.
It is not always easy to use the CFM and so the SCFM is preferred. This is because the CFM is measured in the actual conditions of the environment in which the air flow is taking place.
This can cause a huge difference in calculations and comparisons since the air density changes with the pressure and temperature of the air. This can make comparing the CFM readings difficult.
SCFM is the ?standard cubic feet per minute?. The ?standard? means that standard conditions apply to the air. Typically, the standard conditions are 1 atm and 25 C (68 F) although some industries use a different definition of standard conditions.
Placing the gas under standard conditions means that the air density is always the same and so a fixed amount of gas flows through regardless of the composition of the gas and other conditions which may affect the air flow.
Thus, the SCFM is easier to use when you want to compare air flow rates and other conditions.
Horsepower is used to measure how powerful an engine is and the performance of the engine. It is equivalent to about 746 watts.
Horsepower was first used to compare the work output of a horse with the work output of an engine that can be used to replace the horse.
Peak horsepower is the maximum output of your air compressor and can be a misleading way of determining the performance of your compressor. This is because peak horsepower can be 5 times greater than the actual running horsepower of your compressor.
Running the motor at peak horsepower for an extended period of time can cause damage and overheating to your air compressor and so it is not a very useful indicator of what the motor can output over a long period of time.
Try to use the running horsepower rating for your air compressor as it will be a more reliable indicator of what your air compressor can sustain.
Usage Of A Tire Inflator
With an air compressor you can complete your construction, maintenance, automotive repair, hobby, and craft projects faster than with traditional tools.
Tire Inflators On The Market
Before making any purchase, you should check out this list that describes the tire inflators available in the market.
Cordless tire inflators are extremely convenient. They come with rechargeable batteries and most have 12V and 120V adapters. This allows you to recharge your batteries at home or in the car.
Electric 120V tire inflators can be plugged into your sockets at home for easy use. They?re more powerful than a 12V tire inflator and so they can inflate faster.
They?re capable of inflating car tires but not an RV.
12V Tire Inflator
12V tire inflators plug into your car?s 12 V outlet (also known as the car cigarette lighter). These tire inflators are more compact to carry around in your car while still displaying good performance.
These small tire inflators may even be better than the larger ones that connect to a car?s battery ? while those are better performance, they are bigger, pricier and some people don?t feel comfortable connecting things up to the car battery.
With all of the choices of tire inflators available, we compiled a list of the best ones.
Kensun produces portable and easy to store air compressors for use in the car or at home. They come with power adapters so you can use them in the car or inside your house.
Adapter nozzles are also included so you can use your air compressor for your tires, rafts and mattresses.
Campbell Hausfeld boasts a very wide range of air compressors so you can easily find one for the right use. Whether it?s for heavy duty mechanical work or you just want an emergency air compressor, Campbell Hausfeld have you covered.
Their air compressors are all electric, so you?ll need a handy power source if you?re going with a Campbell Hausfeld air compressor.
ENGREPO air compressors are convenient, handheld compressors with rechargeable pumps so you can use them on the go.
They also come with adapters so you can use them anywhere, at home or on the road side.
Bon-Aire air compressors have high psi digital gauges, making for easy readings when you?re inflating those car tires at a higher pressure.
They can plug into the 12V outlet in your car but not into the wall at home so these are designed for the purposes of roadside assistance.
To make sure that your tire inflator runs smoothly without leaking air, it is important to check your equipment every time you use it. Things you may want to look out for include:
- Air leaks or oil leaks
- Changing air compressor oil (if applicable)
- Changing the air filter
- Replacing a worn compressor belt
Changing Air Compressor Oil
Turn on for a few minutes ? this will warm up the oil so that it is not too viscous. But don?t leave the air compressor running for too long.
- Remove the fill cap so air can get in
- Drain the oil into a container
- Fill the tank with the manufacturer?s recommended oil
- Make sure you fill it with the right amount of oil
Replacing A Worn Compressor Belt
- Check for cracks, wear and tear in the compressor belt
- Grasp the belt firmly
- Pull it over the largest wheel in the pulley system and at the same time, rotate the pulleys
- The belt should come off easily. Put the new belt on the smallest pulley and then onto the biggest one by turning the wheels in a forward?s motion
- Wear protection for your eyes and ears
- Don?t use your air compressor in a wet area ? this can cause the tank to rust, making it more likely to combust, damage tools or electrical circuitry
- Ensure all hose fittings are tight. Loose fittings can decrease performance and cause danger
- Keep your hose clean to lengthen your hose life
- Change the oil / refuel when the machine is cool. Don?t do it while the machine is running or it has just been used
- Make sure the trigger on your tools isn?t pulled when you turn on the air compressor
- Plug into properly grounded electrical circuit
Air compressors are quite simple machines but the amount of work they do is amazing. You should now have more insight into the workings of an air compressor and things to consider when you are shopping for your own one to use as a tire inflator.
With the numerous uses of an air compressor, it seems practical to have one handy to use to inflate your car tires. It?ll save a lot of time and money driving to the nearest service station to have your tires pumped.
Don?t forget to check out our buying guide for more help on selecting the best tire inflators for your vehicle.