A separate hydraulic power pack for providing at least one user with an oil flow. The hydraulic unit includes a motor, a hydraulic pump driven by the motor, a tank, an oil inlet, an oil outlet, a heat exchanger, and a first conduit system for oil. The first conduit system connects at least the oil inlet, the heat exchanger, the oil tank, the hydraulic pump and the oil outlet. The heat exchanger is provided for liquid cooling of the oil. A cooling liquid inlet for connection to a cooling liquid source, a first cooling liquid outlet and a second conduit system for a cooling liquid.