Screw compressor

A screw compressor comprising:

• a first stage compressor;
• an intercooler for cooling working air compressed by said first stage compressor;
• a second stage compressor for compressing the working air cooled by said intercooler;
• an aftercooler for cooling the working air compressed by said second stage compressor;
• speed increasing gears for transmitting motive power of an electric motor to the respective stage compressors;
• and an integral casing for accommodating said first and second stage compressors, said integral casing including working gas flow passages through which the working gas sucked into said first stage compressor flows out from said aftercooler.

A screw compressor comprising:

• at least one stage compressor;
• a capacity control valve provided upstream of the first stage compressor;
• a check valve provided downstream of the final stage compressor;
• a blow-off valve capable of releasing air discharged from the final stage compressor to ambient atmosphere from a location between the final stage compressor and the check valve, a secondary side of said blow-off valve being connected to a primary side of said capacity control valve;
• an aftercooler for cooling the air discharged from the final stage compressor;
• and an integral casing for accommodating said first and second stage compressors, said integral casing including working gas flow passages through which the working air sucked into said first stage compressor flows out from said aftercooler.