Single-stage, overhung-impeller (impeller located outboard of the radial bearings, opposite the driver end) designs are available in pressure ratings to approximately 2000 psi and capacities to 50,000 cfm.
Another type of centrifugal compressor is the integrally-geared configuration. This is an overhung-impeller type built around a gear box, with the impellers attached to gear pinion shafts and the impeller housings mounted on the gear box. Possible configurations include two, three, four, and even five stage designs with capacities to 30,000 cfm and pressures to 250 psig. These have typically been used as packaged-air or nitrogen compressors. The overall arrangement of this type varies significantly between manufacturers.
Major features of the integrally geared design include:
• Open impellers—maximum head developed
• volute diffusers for optimum efficiency
• different pinion speeds to optimize impeller efficiency