LUBRICATING METHOD FOR LUBRICATING TYPE TWO-STAGE SCREW COMPRESSOR

PROBLEM TO BE SOLVED: To prevent drain from being occurred in an oil separator by setting the discharge temperature of a high-stage compressor to a dew point or more in lubricating oil quantity to the compressor and lubricating oil distribution to each stage and by approximately equalizing the discharge temperature of a low-stage compressor with the high-stage compressor. SOLUTION: An oil separator 3 and an aftercooler 4 are connected to a discharge side of a two-stage compressor composed of a low-stage compressor 1 and a high-stage compressor. The oil separator 3 is constituted of a separator element 5 and an oil sump 6, and the oil sump 6 and the low-stage/high-stage compressors 1, 2 are connected together by an oil pipe 8 via an oil cooler 7. The weight ratio per unit hour of the oil fed to the compressor to the discharge air quantity is reduced from 6:1 to 3.5:1-4.5:1 and the discharge temperature of the high-stage compressor 2 is set to the dew point or more. The lubricating oil distribution to the low-stage compressor 1 and the high-stage compressor 2 is set to 1:1.5-1:2.5 so that the discharge temperature of the low-stage compressor 1 is set equal to that of the high-stage compressor 2.