Check valves open autonomously by the pressure which is exerted by the working medium upon the valve disc. They start to open at a differential pressure of 0.01 to 0.05 bar and are fully open between 0.1 and 0.2 bar. As soon as the flow is interrupted or the flow direction is reversed, the valve closes automatically. The closing function is supported by the elastic force of the spring or by the valve disc’s own weight. RVZ check valves are designed for installation between two counterflanges that are attached directly to the valve housing. With this design the medium flow is not is not being diverged as it is the case for other check valve types. AWP check valves are designed for installation in the refrigerant circulation of industrial refrigeration systems. They are installed on the pressure or suction side of compressors or in pipes in which only one direction of flow is intended.