So how does an air compressor work? Sure the name suggests it makes air smaller but what the heck does that mean?
An air compressor is a machine designed to store air under pressure and release the pressurized air in a controlled fashion. The pressurized air is used to drive air powered tools, air-powered painting devices and/or air accessories like nozzles and inflation needles. A properly used compressor will help you finish a task much faster and with far less labor. Like any power tool, air compressors demand user respect and a high level of safety awareness. In other words, read the user manual before you use a compressor!
At a minimum, all compressors offer:
- An air pump, to move air into an air tank for storage
- An air tank for storing air compressed by the pump
- A pressure gauge that shows the pressure of the air stored in the tank
- A switch that starts and stops the air pump
- A safety valve to prevent excessive pressure buildup of the stored air
- A moisture drain valve on the air tank
Many compressors offer a regulator valve, which is used to control the level of air pressure coming out of the air tank.
When connecting an air hose to a compressor, and when connecting a fitting or accessory to an air hose, it is critical to use Teflon tape on all threaded connections. This prevents pressure loss due to air leaks and makes connections and disconnections easier.
User Tip: All new air compressors have a start-up procedure that must be followed prior to first use. This procedure helps ensure that the motor is properly lubricated and broken in before a load is placed on it.
Selecting the Right Compressor
Selecting the right compressor for your needs can be downright confusing. Do you choose on horsepower, gallons, PSI or CFM? Oiless or oil drive? One stage or two stage?
One selection method you might consider is:
- Determine what tools you want to run
- Consider where you’ll be using the compressor
- Consider how often you’ll be using the compressor
1. Determine what tools you want to run
To run properly, air tools such as impact guns, ratchets and sanders require a certain amount of air pressure, measured in PSI (Pounds per Square Inch), and a certain amount of air volume (measured in CFM (cubic feet per minute).
Most compressors supply air pressure (PSI) of at least 100 PSI, which is sufficient air pressure to operate an air tool. Therefore, air volume (CFM) is the most important consideration for proper air tool performance.
For compressors, air volume (CFM) ratings measure how fast the air pump pushes air into the air tank for storage. Note that most compressors have two CFM ratings: one at around 40 PSI that will be a higher number, and another at around 100 PSI that will be a lower number. That’s because as the air pressure increases inside the air tank, the air pump has to work harder and harder to force more air into the tank.
The other consideration is tank volume (GAL), measured in gallons. The air tank only stores pressurized air; so as long as the compressor is delivering the air volume required by the tool, it’s impossible to run out of air no matter what the tank size is. A smaller tank will get up to pressure quicker and is more portable than a larger tank.
However, for air tools that require continuous use, such as grinders or sanders, a larger air tank reduces the amount of times the pump has to start up and run to maintain a given pressure. This results in longer pump life due to reduced component stress and operating temperatures.
2. Consider where you’ll be using the compressor
The two key considerations here are portability and space requirements.
If you need to use a compressor outdoors, on a job site or at different locations, then a portable air compressor may be the right choice. Even the most “portable” compressor can weigh upwards of fifty pounds, so strategically placed wheels, handles and tanks can help ease the burden of moving your compressor.
A portable compressor will not offer the tank volume of a stationary unit. That makes them a less desirable choice for running continuous tools such as air sanders and grinders.
User Tip: When using a compressor for remote work, it’s important to use a longer air hose to connect the air tool with the compressor. Don’t use a longer power cord to move the compressor away from the power outlet.
Both portable and stationary compressors offer space saving options when shop space is at a premium. Vertical tank units have air pumps mounted to the top of the tank to save space. “Pancake” style tanks take up less room than horizontal tanks. Twin tank compressors stack tanks vertically in a space-saving design.
3. Consider how often you’ll be using the compressor
Compressors are available in a wide price range. So what’s the difference between a 5-gallon compressor that produces 7 CFM at 40 PSI for $129.00, and a 5-gallon compressor that produces 7 CFM at 40 PSI for $249.00?
High-end (and more expensive) compressors designed for continuous daily use have heavy duty, oil-lubricated pumps that can withstand high heat and constant start cycles. The compressor units may be belt driven by the motor rather than directly connected to and driven by the motor. This permits the compressor pump unit to run at a different speed than the motor.
For DIY’ers and pros that don’t run their compressors all day every day, a less expensive model should get the job done. Oil lubricated units offer better durability than oil-less units without a lot of additional maintenance.
Regardless of the size or type of air compressor you buy, you're sure to enjoy the convenience and speed with which you'll get the job done.
Shop our selection of air compressors.