436763116661
liujun@valtone-valve.com
enLanguage
Category
BS 1873 & JIS F7409 Flanged SDNR Valves (Screw Down Non-Return) for Marine Engineering & Steam Boiler Systems

 

SDNR (Screw Down Non-Return) valves combine manual pipeline isolation and automatic backflow prevention within a single cast body. The internal guided disc operates freely as a check valve under normal flow and provides positive mechanical shutoff when the handwheel is engaged. Primarily utilized in marine auxiliary piping, industrial boiler feedwater systems, and multi-pump discharge manifolds to save installation space and reduce flange connections.

 

Key Features
• Dual-function architecture replaces separate isolation and check valves in confined piping layouts.
• Independent stem-to-disc connection allows the disc to react to fluid dynamics while the stem remains fully open.
• Internal piston or swing disc guiding prevents lateral shudder, vibration, and premature seat wear under turbulent flow.
• Rising stem with external position indicator visually verifies valve travel status.
• Renewable seat rings and hardened disc geometry resist wiredrawing in high-pressure steam environments.

 

 
 
Technical Specifications

 

Parameter

Specification

Size Range

DN 15–DN 300 (NPS 1/2–NPS 12)

Pressure Ratings

PN 16, PN 25, PN 40; ASME Class 150, Class 300

End Connections

Flanged to EN 1092-1, JIS B2220, or ASME B16.5; Butt-Weld available

Design Standards

BS 1873, DIN 3356, JIS F7409 (Marine Standards)

Testing Standards

ISO 5208, API 598 — Hydrostatic and Pneumatic Seat Testing

Classification Compliance

ABS, DNV, LR, BV Marine Certificates Available

 

DIN EN13789 SDNR Valve

 

Design & Construction

Body & Bonnet Assembly: Bolted bonnet joint utilizing spiral-wound stainless steel/graphite gaskets for secure sealing under thermal cycling.


Guiding Mechanism: Piston-type or swing-type internal guides ensure the disc returns squarely to the seat center upon flow reversal, preventing slamming.


Stem Interface: Non-rotating rising stem with rolled trapezoidal threads transfers torque without transmitting rotational friction to the seating face.


Backseat Feature: Integral backseat allows safe repacking under normal operating pressure when the valve is fully open.

 

Materials

 

 

Body & Bonnet Castings:

Bronze (Rg5 / CuSn5ZnPb), Cast Carbon Steel (ASTM A216 WCB / GP240GH), Stainless Steel (ASTM A351 CF8M / 1.4408).

 

Trim Materials:

CuSn12 Bronze / Monel for seawater; 13Cr Stainless Steel (AISI 410) / Stellite for steam and thermal fluids.

 

Gaskets & Packing:

Expanded flexible graphite and PTFE-impregnated asbestos-free braided rings.

 

 

Working Principle

 

Isolation Mode: Turning the handwheel downward forces the stem against the disc, locking it mechanically against the seat ring for a standard shutoff.


Check Mode: Retracting the stem to the fully open position allows the internal disc to float. Forward flow lifts the disc. Upon flow reversal, back pressure instantly forces the disc against the seat, blocking reverse flow without operator input.

 

 

Performance / Selection Considerations

Flow Direction: Must strictly follow the body flow arrow indicator; improper orientation disables the non-return check function.


Pressure Drop: Inherently higher flow resistance than standard gate valves due to the internal pocket and disc guiding structure.


Installation Orientation: Specify horizontal or vertical pipelines during ordering, as gravity-dependent disc return designs vary by mounting angle.

Angle Type Boiler Stop Check Valve

 

 
 
Applications

• Marine engine room cooling water, bilge injection, and ballast manifolds.
• Shipboard main and auxiliary steam distribution networks.

• Multi-boiler feedwater discharge systems preventing boiler cross-flow.
• Condensate return and thermal fluid processing loops.

 

Manufacturing & Quality Control

Material Verification:

Positive Material Identification (PMI) conducted on alloy and stainless pressure-retaining components.

Dimensional Checking:

CMM inspection of face-to-face dimensions and flange hole alignment to shipbuilding tolerances.

Pressure Testing:

100% shell testing (1.5x rating) and seat testing (1.1x rating) on automated test benches.

Witness Testing:

Hydrostatic and functional test verification available for classification society surveyor sign-off.

 

OEM / Customization

 

Custom flange drilling patterns matching legacy JIS, DIN, or ANSI marine piping standards.

 

Special copper-nickel or bronze alloy trims for highly corrosive seawater desalination.

 

Yoke-mounted locking devices or limit switches for remote control room status monitoring.

 

 

 

Our Certificate

 

 

productcate-1-1
productcate-1-1
productcate-1-1
productcate-1-1

 

Why Choose Valtone

 

Direct manufacturing control over internal disc guiding tolerances, eliminating binding under pulsating pump loads.
Complete material traceability with EN 10204 3.1 certification provided for every production batch.
Proven supply track record supporting marine skid fabricators and industrial boiler package OEMs.
Engineering verification of cracking pressure and flow coefficients prior to manufacturing.

 

 

FAQ

 

 

Q: What is the primary advantage of an SDNR valve over separate gate and check valves?

A: An SDNR valve combines isolation and check functions in one housing. This reduces overall piping weight, halves the required installation space in congested machinery rooms, and eliminates one set of flanged connections, reducing potential leak paths.

Q: Can an SDNR valve be installed in any orientation?

A: Installation orientation depends on the internal disc design (lift or swing type). Piston-type SDNR valves generally require horizontal lines or vertical upward flow. Verify the specific mounting orientation with engineering drawings prior to installation.

Q: How does the valve protect pumps during an emergency shutdown?

A: When system pumps shut down, reverse flow forces the internal guided disc back onto the seat ring instantaneously. This prevents backflow into the pump discharge line automatically, requiring zero manual intervention.

Q: Is it possible to lock the valve in a specific position?

A: Standard configurations utilize a manual handwheel. However, padlocking devices or limit switch brackets can be engineered into the yoke assembly to prevent unauthorized operation or integrate with plant safety interlock systems.

Q: What class society documentation accompanies marine SDNR orders?

A: Valves destined for marine and offshore applications are supplied with inspection certificates and material test reports validated by major classification societies like ABS, DNV, LR, and BV, based on specific project requirements.

Q: What causes disc chatter, and how is it prevented?

A: Disc chatter occurs when flow velocity is insufficient to keep the disc stable. This is prevented by calculating minimum flow requirements during the selection phase and utilizing precision-machined internal guide ribs that stabilize the disc across standard operating ranges.

As one of the most professional SDNR valve manufacturers and suppliers in China, we have world-leading production equipment and strong manufacturing capabilities. Please rest assured to buy bulk durable SDNR valve for sale here from our factory. We also accept customized orders.

Product Recommended
Send Inquiry
Send Inquiry