PURPOSE: To provide a two-stage type oil free screw compressor which is constituted to reduce the number of overhaul times. ;CONSTITUTION: A two-stage type oil free screw compressor comprises an inverter 21 to control the number of revolutions of a rotor of a second compressor body 12; a pressure sensor 23 to detect the pressure on the outlet side of an intercooler 13; and a computing control part 24 to receive a detecting pressure signal indicating a detecting output from the pressure sensor 23 and output a control signal, needing to output a number of revolutions signal for the number of revolutions of a rotor enough to prevent the occurrence of an under-mentioned state to an inverter 21 when a detecting pressure is brought into a state to exceed an allowable pressure range, to a second compressor body 12.;COPYRIGHT: (C)1995,JPO
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