SDNR Spring Bolted Bonnet Globe Valves are a type of industrial valve designed for regulating and controlling the flow of fluids in pipelines. The term "SDNR" stands for "Straight Double Non-Return," indicating that these valves have two non-return valves in a straight configuration, allowing for efficient and reliable flow control. The spring-loaded design ensures a positive shut-off when the valve is in the closed position.