Screw multiple-stage

An oil-free compressor—typically a rotary screw, multiple-stage design... 

Multiple-stage turbo compressors are by far the most frequently used machines in cryogenic air separation. Positive displacement machines are foimd in niche applications, such as piston compressors for oxygen compression and screw compressors for small plants processing less than 4000 m h of air. 

Multiple-screw extruders can involve either two screws (twin-screw design) or four screws. A typical four-screw extruder is a two-stage machine, in which a twin-screw plasticating section feeds into a twin-screw discharge section located directly below it. The multiple screws are generally sized on output rates (Ib/h) rather than on L/D ratios or barrel diameters. 

For the tests of preparing dynamic vulcanizates in the continuous process of reactive extrusion a twin-screw mixer-extruder DSK 42/6D manufactured by Brabender was used. The vulcanizates were produced dynamically in the process of one-stage or two-stage extrusion process, setting the favorable operating parameters for the device, which had been determined based on multiple tests distribution of temperatures in each heating area... 

---