The Three Types of Air Compressors
Choosing the right air compressor for the job is a difficult decision without knowing which type of air compressor you need. The uses of these different types can vary widely from small personal around the house jobs to large industrial full operation jobs. Having a background knowledge on the types of compressors is essential to have before going out and making any type of purchase. There are three main types of air compressors. They consist of the rotary screw air compressor, the reciprocating compressor, and the centrifugal compressor. Types of compressors vary and can be compared side by side in accordance to several different factors. These can be:
- amount of compression stages (typically either one or two stages)
- lubrication (oil or oil free)
- the cooling method (does it use water, air or oil?)
- drive process (engine, steam, motor etc.)
- Horse Power (amount of power)
We have compiled this resource as a guide to help you pick the right type of air compressor and why you should make that decision.
What are Rotary Air compressors?
Rotary Screw air compressors as they are most commonly called typically are middle of the road sized compressors often used for general industrial jobs and for high powered air tools. You will often find them being used at construction sites in trailer mounted units or for other industrial uses. Rotary compressors are considered positive displacement compressors, meaning that they work by forcing air into a chamber in which the volume decreases to compress air. The most common rotary compressors are single stage gas compressors that use two helical screws or rotors to compress the gas internally. Oil seals the clearances between the screws and cools the inside of the compressor. Because of this, rotary screw air compressors never experience high operating temperatures and maintain a continuous air cooled or water cooled component which can be a real advantage.
A rotary compressor is easily maintained and operated. The use of gas for the compression process of the screw is a continuous motion which creates very little pulsation for smooth operation unlike other types of piston compressors. Combined with the ability to be compact in size and provide a high volume of output over a very long life, the rotary screw air compressor provides a surplus of advantages. They can operate for 24 hours a day, 365 days a year for years upon years. Because they can be so compact but also provide large volume as well, rotary compressor can range from sizes of only a few cubic feet per minute to thousands. Between the two other types of compressors, rotaries are used where higher airflow is required than of smaller reciprocating compressors, but do not typically produce as much as centrifugal.
The most common types of uses of rotary screw compressors are for high power air operated industrial machinery. Largely found at construction sites they can be used for jackhammers and similar large power tools that require a constant continuous source of compressed air. These compressors will often be diesel powered and hauled in trailers. In addition, rotary air compressors are becoming ever more popular for use in power plants and waste treatment plants because of their high output and lower power saving expenses. If you are working an industrial job that will require compressed air at a continuous rate for hours upon hours, rotary is the way to go for you. This could include any sized production facility, garages, or workshops. If you are not constantly using air for your job, or just using a compressor for do it your self projects or for air hand tools, the rotary screw may not be what you need.
What are Reciprocating Air Compressors?
Reciprocating compressors can vary in size but are consistently the most widely known for personal use. You will generally find them in small workshops, on construction sites for nail guns/staple guns and also are used for small do it yourself at home projects. Reciprocating air compressors are also positive displacement machines. Reciprocating compressors are often piston driven, using a cylinder to compress and displace the air volume. The gas is pulled in via suction in which it then flows into a compression cylinder. This is then compressed by the piston by a crankshaft in a “reciprocating” motion and then exits.Â Head to our reciprocating air compressor guide for a more in depth analysis.
Single Stage vs Two Stage Reciprocating Air Compressors
Reciprocating compressors can be either single stage or dual stage compressors. Single stage means air is compressed in 1 motion from stagnant pressure to the working pressure. Single stage reciprocating air compressors are much cheaper in cost than dual stage. Often single stage reciprocating compressors are used in small do it yourself jobs and for small handheld air power tools. Dual compressors use a multi-step compression process that are more often used for larger commercial or industrial jobs. Single stage compressors and dual stage compressors are both available for consumer purchase, but single stage will generally not provide near the amount of pressure that dual or 2 stage will. In terms of power output reciprocating units generally put out between 1-50 HP. Anything larger than that is typically reserved for rotary screw or centrifugal compressors. Head on over to our guide to the best single stage and dual stage reciprocating air compressors for more in depth information.
Engines in these compressors can be both gas powered or electric powered. Both can have advantages, but gas powered will often be found in areas with out electrical plugins like construction sites. However gas powered air compressors do tend to create more noise and output exhaust fumes. Electric and gas powered reciprocating compressors can both be portable, although many of the gas powered ones tend to be larger and more difficult to haul around. These are not as ideal if you are moving around from place to place to use air power tools. Reciprocating units can be both oil-free and oil-flooded although oil-flooded is definitely more common and practical.Â Overall, reciprocating compressors tend to be relatively small compared to other types. If you’re in the market for a compressor for a do it yourself project or for small business like projects, reciprocating would be the way to go. If compressed air is not used in a continuous fashion, even if they are larger tools that are only used sparingly, reciprocating will fit the model best.
What are centrifugal compressors?
Centrifugal air compressors are not as individual consumer driven but deserved to be talked about as they are incorporated into the 3 different types of air compressors. You will generally find centrifugal air compressors in gas turbines or aux power units, diesel engine turbochargers, pipeline compressors, and large air conditioning and refrigeration units. Centrifugal compressors are dynamic compressors that depend on the transfer of energy from a spinning rotor to the air. By using dynamic displacement, a centrifugal compressor produces high pressure discharges of air. These compressors rotate at much higher speeds than other types of compressors and therefore have higher capacity to accompany for the continuous flow of air. Unless you are building a jet engine, or working a large industrial driven job, centrifugal air compressors will probably not be on your radar. For everyday construction and do it yourself jobs, you’ll want to stick to a reciprocating or rotary compressor.
|Use||Do it Yourself, At Home, Small to Average Sized Workshops||Large Workshops, Industrial Use, Construction Sites||Heavy Industrial, Turbines, Oil Refineries,|
|Capacity in CFM (Cubic Feet/Min)||Up to 75 CFM||20 to 500||>500|
|Pressure (PSI)||1500 psi||150 psi||Varies -- can be much greater than 1500 psi|
|Power (HP)||1-10 Horsepower||50-150 Horsepower||>150|
Best Air Compressor Choice
Overall, unless you are in a large commercial or industrial type job and require huge amounts of output from your air compressor, you’ll probably stick to a reciprocating or rotary compressor rather than a centrifugal air compressor. From there it really depends on the type of job, the type of tools you’ll be using and the amount of time you’ll be consistently using those tools. For higher pressure on and off again compression, you’ll want to stick with a reciprocating air compressor like something from the Central Pneumatic line of products. However if you need around the clock air compression with lower pressure, a rotary screw compressor may fit the bill. Head over to our guides to see the best types of reciprocating and rotary air compressors.Â The rest is up to you!