Compressor surge is a form of aerodynamic instability in axial compressors or centrifugal compressors. Dynamic displacement air compressors include centrifugal compressors and axial compressors. Rotary screw compressors are also positive displacement compressors. The speed lines of gas turbine centrifugal compressors typically exhibit choke. It is commonly used by manufacturers of blowers and compressors. Reciprocating compressors are piston-style, positive displacement compressors. The presence of multiple cylinders in reciprocating compressors reduces suction and discharge pulsations. They often came fitted with compressors and generators. Magnetic bearing (magnetically levitated) and air bearing centrifugal compressors exist. Of particular interest are applications which contain pumps, fans, compressors and turbines. In 1981, Sanden began manufacturing the first commercially available scroll compressors for automobile air conditioners. We know what the tanks, pumps, compressors and other parts look like. Such installations are known as inverter compressors. Improvements in centrifugal compressors have not been achieved through large discoveries. Tilting pad bearings are used as radial bearings for supporting and locating shafts in compressors.