Types of Stationary Air Compressors
There are two main types of stationary air compressor: reciprocating and rotary screw. Reciprocating air compressors are the more common type. This is due in large part to their relatively lower cost. Also known as piston-driven, a reciprocating air compressor is the type most often used in home applications. Air enters and leaves the unit in equal volume, which helps disperse heat. So do inter- and after-coolers between stages. Capacity is lower with a reciprocating compressor due to reduced horsepower and CFM (cubic feet per minute) ratings. In addition, they do not allow continuous duty. This limits the number of minutes per hour they can be operated. Rotary screw air compressors draw in air via two or more interlocking screws. Air compression happens in degrees before being discharged. A rotary compressor has fewer moving parts, which helps reduce heat generated during operation. They also have greater air capacity and continuous duty capability. This makes the rotary type more popular for industrial use despite its higher cost.
Oil-Free or Oil Lubrication?
Like any equipment with moving parts, stationary air compressors require lubrication. You have two options: oil-free and oil lubrication.
- Also known as flooded, oil lubrication is exactly what it sounds like. Oil lubricates the compressor’s moving parts. Filters and the separator help ensure the air remains oil-free, but some crossover contamination is unavoidable.