Patent ID: 7204678

Claim:
Method for controlling the oil recirculation in an oil-injected screw-type compressor comprising a compressor element ( 1 ), connected thereto an inlet conduit ( 5 ) and a pressure conduit ( 8 ), an oil separator ( 10 ) in said pressure conduit ( 8 ), an oil recirculation conduit ( 17 ) between said oil separator ( 10 ) and the compressor element ( 1 ), in which recirculation conduit ( 17 ) an oil cooler ( 18 ) is installed, and a passage or bypass ( 30 ) bridging-over the oil cooler ( 18 ) in the recirculation conduit ( 17 ), which controlling is performed by means of a thermostatic valve ( 24 ) having a valve element ( 26 ) which can be moved by means of a temperature-sensitive element ( 34 ), whereby the temperature-sensitive element ( 34 ) measures the temperature of the recirculating oil and the valve element ( 26 ), if this temperature is below a certain value, opens the bypass ( 30 ), such that the separated oil from the oil separator ( 10 ) can flow directly towards the compressor element ( 1 ) without having to flow over the oil cooler ( 18 ) and, if the temperature of the oil is above a certain value, which is higher than or equal to the aforementioned value, the valve element ( 26 ) closes off the bypass ( 30 ), characterized in that during the transition of the screw compressor from the unloaded to the loaded condition, the effect of the temperature-sensitive element ( 34 ) temporarily is switched off at least partially, such that the valve element ( 26 ) temporarily takes a position in which, regardless of the temperature of the oil, at least the bypass ( 30 ) is open and thus the recirculation of oil from the oil separator ( 10 ) to the compressor element ( 1 ) temporarily takes place at least through this bypass ( 30 ).