Oil-Free Rotary Screw Compressors

The air compression process of oil-free rotary screw compressors is similar to that of oil-injected rotary screw compressors, but oil isn't injected into the air compression chamber.

The intermeshing rotors in oil-free rotary screw compressors are not allowed to touch, and their relative positions are maintained by lubricated timing gears outside to the compression chamber. Since there is no fluid injected to remove the heat of air compression, most designs use two stages of compression, with an intercooler between them and an aftercooler following the second stage.

Oil-free rotary screw compressors typically range from 25 – 500 HP or 90 – 2,400 CFM. Single stage units can operate up to 50 PSIG, whereas two-stage air compressors generally can achieve up to 150 PSIG. They utilize lubricant for lubrication of bearings and gears, which are isolated from the air compression chamber.

Advantages:

• Complete packages

• Designed to deliver 100% oil-free compressed air

• Do not require any special foundations

• Condensate oil/water separation systems are not required

• Environmentally friendly design

Disadvantages:

• Higher initial costs compared to oil-injected rotary screw compressors

• Less efficient than oil-injected compressors

• Limited to load/unload capacity control

• Maintenance costs may be higher than oil-injected units in the long term