on August 7 2013
Air compressor power air tools, also called pneumatic tools, which are generally faster, lighter and more powerful than traditional power tools. The key to choosing the ideal compressor is to match the unit to the job demands. Portable compressors are ideal for the home and the job site while stationary compressors provide the high volume of air needed for powering automotive and production air tools. This buying guide will explain the factors to consider when selecting an air compressor, so you can feel confident you’re choosing the right compressor for your needs.
Factors to Consider
– Stationary or portable
• Power Source
– Electric or gas-powered
• Performance Ratings
– SCFM, PSI and horsepower
• Tank Size
– No tank, small tank or large tank
• Pump Type
– Continuous operation, stop/start operation, single stage, two-stage, oil-lubricated and oil-free
Portability is a key factor when choosing an air compressor. Air compressor units fall into two broad categories:
|Portable compressors are available in a variety of shapes and sizes. Smaller models are light enough to carry, and larger ones are equipped with wheels that make them easy to move from project to project. For applications like powering a brad or finish nail gun or inflating tires, consider a lightweight, oil-free compressor with a 2–6 gallon tank. For more demanding jobs, like powering a frame nail gun, you’ll need a portable compressor with more power. A wheelbarrow compressor with a 4–5 gallon tank provides adequate air flow, but is still easy to maneuver around a job site. If you’re looking for a portable compressor suited to working on a car in your garage, you’re going to need more power and greater air storage. Consider a space-saving vertical compressor with wheels and a 20–30 gallon tank
|Stationary compressors are designed to be bolted into a fixed area and wired directly to a building’s electrical circuit. Generally, they’re equipped with 60-80 gallon tanks and 4-10 HP motors. Stationary compressors are ideal for garages and workshops because they make it simple to use a variety of air tools that cost less and provide greater performance than equivalent electric tools.
Air compressors are either powered by electricity or gasoline.
|Electric compressors generally run on standard household voltage, between 110–120V. Compressors with motors that exceed 2 running horsepower require a 220–240V outlet. Since electric compressors don’t emit fumes, they are the better choice for indoor applications.
|Gas-powered compressors are generally used by builders and remodelers because of there high output and convenience at the jobsite. However, these compressors emit exhaust and should only be operated outdoors or in well-ventilated work areas.
Once you’ve decided on the portability and power source for your air compressor, you can determine which model works best for you based on a comparison of key performance ratings.
The most important rating to consider when matching a pneumatic tool’s requirements to an air compressor’s capabilities is how much air the compressor can deliver, which is measured in Standard Cubic Feet per Minute, or SCFM. Tools powered by air compressors also have SCFM ratings, which indicate the air flow required for optimal operation. The actual SCFM changes depending on the pressure of the air in the compressor (represented as pounds per square inch, or psi). Look for the “SCFM at 90psi” number when comparing SCFM ratings.
Smaller tools usually require between 0-5 SCFM, while larger tools can require 10 or more SCFM. To gauge the minimum compressor SCFM rating you need, examine the SCFM requirements of all the tools you intend to use. Multiply the highest tool rating by 1.5 to get the minimum compressor SCFM for your needs. This gives you a little buffer, which is important, since actual SCFM varies during compressor operation.
If you expect to operate multiple pneumatic tools at the same time, you’ll need more power. In this case, calculate the minimum SCFM compressor rating by adding up the SCFM requirements for each tool that you’ll use simultaneously. Most light-duty home compressors are designed to power only one tool at a time, but larger professional-grade compressors can handle multiple tools.
The air pressure the compressor generates inside the tank is measured in Pounds Per Square Inch, or PSI. Light-duty compressors generally have 90 psi, which is typically sufficient for pneumatic tools for simple household tasks, including nailers. More powerful compressors may generate 150 psi or higher.
While not as important as the SCFM rating, a compressor’s horsepower (HP) rating can give you a relative sense of the model’s power. Horsepower indicates how powerful the motor is, while the SCFM rating tells you how much power the compressor actually provides to your tools. Compressors generally have horsepower ratings between 1.5–6.5 HP. Stationary oil-lubricated compressors with a rating above 2 HP require a 230/240v power source to supply the high volume of air needed for high consumption air tools like sanders, grinders and sandblasters.
The size of a compressor’s tank is important because it determines how long air tools can run before the compressor turns back on. Tank sizes are rated in gallons, and run from 1 gallon all the way up to 80 gallons.
Keep these basic guidelines in mind:
If you will be using air tools that require a high volume of air for continuous use, than you should consider a larger tank. If you only intend to use the tool for intermittent use, your compressor can have a smaller tank size. Having a large enough tank with a compressor pump that exceeds the SCFM requirement of the tools will allow the compressor time to cool between cycles.
Tools that require only quick bursts of air, like pneumatic brad and finish nailers, drain the air tank much more slowly. For these tasks, tank sizes between 2-6 gallons are sufficient.
Variations in pump design can make a difference in compressor performance. Here are some key points to keep in mind.
Single-Stage vs. Two-Stage
• Single-stage compressors can have one or more cylinders producing compressed air at the same output
• Two-stage compressors have at least two cylinders. The first-stage cylinder(s) feed air to a second-stage
cylinder that further compresses air to 135 psi and the second stage increases the pressure to 175 psi.
The benefit is more air stored in the same size tank, allowing tools to run longer. This is useful for
high-demand work, such as continuous tool operation in an auto shop.
Oil-Lubricated vs. Oil-Free
• Oil-lubricated compressors require oil to operate, just like a car or lawn mower engine. The oil lubricates the
moving parts in the pump to prevent excessive wear.
• Oil-lubricated compressors are generally larger and heavier than equivalent oil-free models, and oil must be
monitored and changed to prevent premature failure.
• Oil-free compressors typically use special piston rings, made from a material similar to what's used in non-stick
frying pans, to lubricate the cylinder. Because there is no oil, oil-free compressors are much smaller and lighter
than oil lubricated compressors, making them a popular choice for home and job site applications where
portability is important.
• Air-Cooling System:
Cools pumping machinery to extend motor life
• Thermal Overload Switch:
Automatically shuts off motor if it overheats, increasing tool life and protecting your
• ASME Certification:
Indicates high-quality material and craftsmanship, identified on the tank with a certification
label stating that the unit meets the standards of the American Society of Mechanical Engineers
• Roll Cage:
Protects the compressor from being crushed or battered on the job site
As with any power tool, safety is paramount when operating pneumatic tools and an air compressor. Keep these guidelines in mind:
• When appropriate, use gloves, goggles, earplugs or a respirator.
• If you purchase an electric compressor, make sure you use an electrical outlet with the specified voltage.
• Powering an electric compressor with a generator can damage the motor.
• Don't exceed the recommended pressure for the job or the tool.
• With oil-lubricated compressors, always check the oil level to ensure sufficient lubrication.
• Use a belt guard to provide protection during use.
• When finished, open the drain cock to get rid of moisture. This will prolong the life of the tank.
• Safety relief valves allow air to escape automatically if pressure is too high.