Selection criteria for oil‐free vacuum pumps

Some high‐vacuum pumps without oil in the swept pumping volume are now available for the evacuation and process pumping of vacuum systems. These pumps are from different principles, i.e., multistage roots blowers, screw compressor, claw pump, dry piston, or molecular drag pump. The selection of the right pump for a given application must take into consideration the different parameters specific to the application or process: contamination by dust and/or oil backstreaming, corrosion resistance, safety, and cost of operation and maintenance. I will compare the basic performances and characteristics of the existing oil‐free vacuum pumps, with emphasis on cleanliness and compatibility to a process as well as the estimation of their cost of operation. I will also examine how to pump large flows of light gases, i.e., hydrogen or helium, with the multistage oil‐free vacuum pumps.