Method for controlling an oil-injected compressor device

A method for controlling an oil-injected compressor device (1) with at least one compressor element (2) with an inlet (7) for gas to be compressed and an outlet (9) for compressed gas and with a variable speed controller (5), whereby the compressor device (1) is provided with an oil circuit (14) with an oil separator (12) with an input that is connected to the outlet (9) of the compressor element (2) and an output to which a compressed gas consumer network is connected, whereby this oil separator (12) comprises a pressure vessel (11) in which oil (15) separated from the compressed gas is received and from which the oil (15) is guided to a cooler (18) and is then injected into the compressor element (2), whereby this cooler (18) is cooled by a coolant that is guided through the cooler by means of a fan (19) or pump (30), wherein a bypass pipe (20) for the oil (15) is provided across the cooler (18), wherein the method comprises determining a temperature (T) at the outlet (9) of the compressor element and when this determined temperature (T) at the outlet (9) is less than a preset value (Tset), the following steps are taken successively:

• first the fan (19) or pump (30) is switched off or its speed is decreased for as long as the temperature (T) at the outlet (9) is less than the preset value (Tset) and a minimum speed of the fan (19) or pump (30) is not reached;
• then the temperature (T) at the outlet (9) of the compressor element (2) is determined again and, when this temperature (T) at the outlet (9) is still less than the preset value (Tset), the oil (15) is driven through the bypass pipe (20) to the compressor element (2) or an increasing proportion of the oil (15) is driven through the bypass pipe (20) to the compressor element (2) for as long as a maximum quantity of the oil (15) has not been reached;
• then, when the maximum quantity of the oil that is driven through the bypass pipe (20) to the compressor element (2) is reached, the temperature (T) at the outlet (9) of the compressor element (2) is determined again, and when this temperature (T) at the outlet (9) is less than the preset value (Tset), the quantity of oil (15) that is injected into the compressor element (2) is reduced until the temperature (T) at the outlet (9) is at least equal to the preset value (Tset) or a minimum quantity of the oil is reached.