Air compressors are machines that convert power into pressurized air stored in a tank for later use. On a homestead, compressed air powers pneumatic tools, inflates tires, cleans equipment, and operates sprayers. Compressors are specified by tank capacity in liters (gallons), maximum pressure in bar (psi), and the compressor's free air delivery in liters per minute (cubic feet per minute), which is the volume of air the pump delivers at a given pressure. Small Engine Repair and Generator Maintenance list compressed air as a tool for cleaning and testing engine components.
Piston compressors, also called reciprocating compressors, use a piston driven by an electric motor or gasoline engine to compress air in a cylinder. They are the most common type for homestead use, available in tank capacities from 5 to 200 liters (1 to 50 gallons). Single-stage compressors compress air to 100 to 150 psi in a single stroke and are suitable for most pneumatic tools. Two-stage compressors compress air to 175 to 200 psi and are used for higher-demand applications such as sandblasting and production painting. Portable compressors, 5 to 25 liters (1 to 6 gallons), are used for inflation and light-duty nail guns.
Pneumatic tools run on compressed air and include nail guns, impact wrenches, air ratchets, die grinders, air hammers, and spray guns. Air consumption is measured in cubic feet per minute (CFM) at a given pressure. A framing nailer requires 2 to 3 CFM at 80 to 100 psi. An impact wrench requires 4 to 8 CFM at 90 psi. Continuous-operation tools, including sanders and grinders, require 8 to 15 CFM. The compressor's CFM rating at the required pressure must exceed the tool's consumption by at least 30 percent for reliable operation.
Compressor maintenance includes draining the tank daily to remove accumulated moisture, checking and changing the oil on lubricated models, cleaning or replacing the air filter, and inspecting the pressure relief valve. The compressed air tank should be inspected periodically for rust and corrosion, as tank failure can cause catastrophic explosion. OSHA recommends hydrostatic testing of compressor tanks every 5 to 10 years depending on service conditions. Hoses and fittings should be rated for the maximum compressor pressure. Safety glasses and hearing protection are required when using pneumatic tools.