Marine SDNR Valve
The medium flows in through the inlet, pushing the valve disc upward (for a lift-type design) , allowing the fluid to pass through smoothly. In manual opening mode, the operator rotates the handwheel to raise the valve stem, relieving pressure on the valve disc and allowing the medium to flow.
When the outlet pressure exceeds the inlet pressure or the pump stops operating, the medium attempts to flow backward. At this point, under the combined action of the valve disc’s own weight, and the reverse pressure of the medium, the valve disc rapidly closes and seals against the seat, preventing backflow.
Overview
Material Types:
Stainless Steel SDNR Valve:
Body material: Typically made of stainless steel 304 or stainless steel16
Marine stainless steel SDNR valves are suitable for water, steam, oil, and mildly corrosive media; some models can withstand nitric acid-based media. They operate at temperatures up to 200°C and are rated for pressures ranging from 1.6 to 6.4 MPa. They can also be used with conventional marine media such as seawater and freshwater.
Cast Steel SDNR Valve:
Body Material: Typically made of ZG230-450 or ZG275-485 cast steel.
Suitable Media: Fresh water, fuel oil, lubricating oil, and high-temperature steam (≤400°C).
Features: High strength and high-pressure resistance; suitable for main power systems and high-temperature, high-pressure operating conditions.
Bronze SDNR Valves:
Body Material: The valve body, bonnet, and disc are typically made of cast tin bronze (e.g., ZCuSn10Zn2, ZCuSn5Pb5Zn5), while the valve stem is usually made of aluminum bronze (e.g., QA19-2).
Suitable Media: Seawater, fresh water, lubricating oil, fuel oil, and low-temperature steam (≤250°C).
Features: Excellent resistance to seawater corrosion; commonly used in out-of-hull water systems, cooling water systems, and submarine piping.
Type of Connections:
Flange Connection: The most common type, offering good sealing performance and ease of disassembly and maintenance; suitable for medium- and high-pressure piping systems.
Threaded Connection: Primarily used for small-diameter, low-pressure piping systems; easy to install.
