AWP constant pressure valves are autonomously working regulating devices (constant pressure function) within the oil management systems of screw compressor packages, to ensure defined minimum differential pressure (e. g. 3 bar, 4 bar etc.) or oil injection pressure during the start-up phase and running of the screw compressor. The constant pressure valve is equipped with a back-pressure compensation sealing element. The valve is opened by the pressure of the operating medium below the valve disc and depends on the set opening pressure of the valve (spring-loaded). The set pressure is determined by the customer and is set by the manufacturer.