How Air Compressors Work

Air compressors are used for a wide variety of tasks in the automotive world. They can be used to power anything from nail guns, sanders and drills to impact wrenches, staplers and spray guns. Below, we take a look at exactly how an air compressor works and how it can assist you in a variety of tasks.

The Inner Workings of Air Compressors

While there are some air compressors use rotating impellers to draw in air and create air pressure, the more common type of air compressor, particularly in a DIY automotive setting, is the positive-displacement compressor. With positive-displacement compressors, air pressure increases by reducing the size of the chamber than contains the air. This job is performed by what is called a reciprocating piston.

A conventional positive-displacement piston compressor is just like a small internal combustion engine in the sense that they both operate with a crankshaft, connecting rod, piston, cylinder and a valve head. At the top of the cylinder, there is the valve head which holds two thin metal flaps called the inlet and discharge valves. The inlet port is mounted underneath the valve plate, and the discharge port is mounted on top of the valve plate. As the reciprocating piston moves down, a vacuum is created above it which allows the outside air to push open the inlet valve and fill the area above the piston. When the piston moves up, the above air is compressed which holds the inlet valve shut and pushes the discharge valve open. This air then moves from the discharge port to an air tank. As the piston continues to move up and down, the air pressure in the tank rises, allowing your tools to be connected and powered through it. The air compression motor cycles on and off to maintain the right pressure in the air tank, keeping your power consistent for everyday automotive tasks.

Air Compressor Power

Air compressors deliver volumes of air measured in cubic feet per minute, or cfm. Measurements in cfm can vary depending on the level of atmospheric pressure, dictated by a state of elevation. Cfm can also depend on the temperature and level of humidity in the air. Standard cubic feet per minute, or scfm, is a measurement of air compressor power that is taken within these conditions: sea level, about 68 degrees Fahrenheit and at 36% relative humidity. Scfm measurements, labelled on air compressors, will give you a more universally accurate reading of the amount of air pressure that can power your tools.

Pounds per square inch, or psi, is another important power rating that can dictate which tools will work best with a particular air compressor. Whenever you choose an air compressor, make sure both the cfm and the psi ratings are powerful enough to supply the amount of air and air pressure that your tools need to function properly, whether they be for painting, drilling or welding.

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