Oil-free compressor is provided with two series-connected pressure stages, i.e. low and high pressure stages, each with suction and pressure sides

摘要

The oil-free compressor is provided with two series-connected pressure stages, i.e. low and high pressure stages (2,3), each with suction (12) and pressure sides (13). The pressure side of the low pressure stage is connected to the suction side of the high pressure stage. Each pressure stage has at least one rotor (6) located by means of a shaft (7) in a rotor housing (5). At least on the pressure side of the high pressure stage, between the shaft and the rotor housing, a sealing device (9) is provided comprising at least two friction-less seals (10a-10d) and a number of chambers (11a-11c) extending around the shaft and which are separated from each other by the seals. At least on the pressure side of the high pressure stage, one of the chambers via a backflow conduit is connected with a location in the compressor where the pressure from the compressed gas is maintained between atmospheric pressure and the pressed pressure of the high pressure stage. The other chambers are closed.