Valve Plates Valves are used within a compressor to allow gas flow to and from the cylinder area. About Valve PlatesThey operate based on pressure difference: if the pressure below the valve is greater than the pressure above plus the spring force, it opens. The valves function as spring-loaded non-return valves, with the gas only being able to flow in one direction.Valve plate works with suction valves to compress low pressure suction gas into high pressure discharge gas.