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. 43 psi, 58 psi, 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.