Air compressors are mechanical devices that convert kinetic power from an engine (electric, diesel or gasoline) and store it as potential energy in a tank as compressed or pressurized air. This compressed air can be tapped and used as kinetic energy as it is released on command in quick or sustained bursts. This source of energy is the heart of the systems transporting energy around modern machine shops.
Air compressors are used in a wide range of environments—from small shops and garages to major manufacturing plants. It is becoming even more common to find them in home basements and garages. Models are available for every job, from inflating bicycle tires to powering nail guns, impact wrenches and spray guns. The big advantage of air power is that each tool no longer needs to create and store its own power. Each tool can now tap into the power from a monolithic source, making for an easy to use, light and compact system with fewer parts to wear out over time. These systems are less costly, more reliable, and more efficient than maintaining individual sources.
There are numerous methods for compressing air; they are divided into positive-displacement and negative-displacement processes. The most common are positive-displacement compressors. These compressors force air into a chamber which decreases the volume of the chamber, compressing the air and forcing it into a storage reservoir through one-way valves. Piston-type air compressors are a common positive-displacement system, pumping air into an air chamber through the use of the constant motion of pistons.
A negative displacement compressor uses a hydraulic system to push the air into the container. The increased speed formed by the hydraulic propellers is what causes the increase in air pressure. Centrifugal compressors are a typical type of negative displacement compressor. Whereas positive compressors require relief valves to protect the system from over pressurizing, a negative compressor always has a limit above which it cannot pressurize. However, this pressure limit is usually far less than what a positive displacement compressor can reach (and therefore seen by many as a disadvantage). Negative displacement air compressors might have the disadvantage of not being able to reach the same level of pressure as a positive displacement compressor, but they are easier to operate and less expensive. It is really up to the operating situation and environment that dictates the type of compressor required.
One of the major expenses with air compressors is in the maintenance of compressor oils or lubricants. One way to save money with air compressors is to use aftermarket oils or lubricants instead of the OEM brands. Compressor fluids, oil or synthetic lubricants keep the numerous internal parts of the compressor system safely operating at high speeds and under extreme pressures. A properly lubricated compressor helps the machine run more efficiently, keeps temperatures under control, and reduces wear and tear. If the oil is not changed regularly (in order to save money), it will varnish up. This is due to a breakdown in additives that make it too thick to run. If this occurs, a clean run of up to 500 hours is necessary in order to clean out the compressor’s air end. Proper Oil/Lubricant replacement is required to prevent this from happening. Oil replacement is scheduled per number or run time in hours, but usually works out to about 1-2 times per year.