Marine Screw Down Non-Return Valve
Marine screw down non-return valves are controlled by manual, electric, or pneumatic actuators to open and close the valve. They not only regulate the flow and shut off the medium but also prevent reverse flow of the medium within the piping system.
Marine screw down non-return valves are widely used in systems that require prevention of reverse flow to ensure safe system operation. Examples include ship hydraulic systems and oil-water separation systems.
Overview
Applications:
Pump Set Discharge Piping: Installed at the discharge ports of seawater pumps, freshwater pumps, fuel transfer pumps, and lubricating oil pumps, these valves can be manually closed using a handwheel for maintenance and automatically prevent backflow of the medium from impacting the impeller when the pump is shut down.
Fuel and Lubricating Oil Systems: Used in the supply and return lines of main and auxiliary engines to prevent oil backflow that could cause the pump to run dry or result in system pressure imbalances; typically suitable for temperatures ≤250°C or higher.
Seawater and Ballast Water Systems: Used in outboard water intake and ballast water exchange lines; the bronze or stainless steel construction resists seawater corrosion and prevents seawater from flowing back into the system when the ship heels or the pump is shut down.
Auxiliary Steam and Condensate Systems: Used in low-pressure steam lines and condensate recovery sections where temperatures do not exceed 250°C–300°C, combining throttling regulation with backflow prevention functions.
Space-Constrained Piping Sections: Replaces the series combination of a “globe valve + check valve,” saving installation space and reducing potential leak points in narrow compartments or complex piping systems.
Inappropriate Applications:
Large-Diameter Piping Requiring Low Pressure Drop: Due to the relatively high flow resistance of the globe valve structure, this valve is not suitable for main circulation pipelines that require extremely low pressure loss.
Applications Requiring Frequent and Rapid Opening/Closing: The manual operating mechanism has a slow response time, making it unsuitable for explosion-proof or safety relief systems that require emergency rapid shutoff.
Ultra-high-temperature, high-pressure steam: Bronze globe check valves are generally not suitable for high-temperature, high-pressure main steam pipelines.
