The connection between the oil separator and the oil injiection nozzles during the shut down has to be cut off avoid blowing out oil through the suction line.During the start up the oil stop valve should be open as fast as possible to ensure an accurate lubrication and cooling of the compressor.The signal pressure inlet E is connected directly to a connection in the discharge duct of the compressor upstream from the non-return valve .Alternatively,the valve can be opende or closed by signal pressure form a reliable solenoid valve.