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| The SDF Welded Check Valve represents a pinnacle in fluid control engineering, specifically designed to provide absolute, unidirectional flow protection within high-pressure and extreme-temperature piping architectures. In critical process lines—where operating pressures can peak up to PN160 (Class 900) and temperatures fluctuate dynamically—standard bolted or flanged connections frequently present severe operation liabilities. Over time, traditional flange gaskets degrade due to thermal fatigue, and flange bolts relax under pipeline vibration, causing fugitive emissions and expensive system downtime. The SDF series completely eliminates these structural vulnerabilities by featuring a robust butt-weld end connection design. By welding the valve body directly into the pipeline, it creates a permanent, monolithic bond that guarantees a leak-proof, zero-emission boundary layer, making it the premier choice for capturing volatile, high-cost, or hazardous media where environmental and operational safety is paramount. | |||||||||
SDF
Engineered to endure severe thermal cycling without thermal deformation or structural micro-cracking, the pressure-retaining body shell is cast or forged from premium-grade Carbon Steel (WCB/A105) or high-temperature Alloy Steel (15CrMo/F11/F22). Specifying 15CrMo alloy steel delivers outstanding creep resistance while preventing surface oxidation during prolonged exposure to extreme temperatures up to $550^\circ\text{C}$.
The internal sealing architecture incorporates a heavy-duty swing-disc design suspended from a robust hinge pin. To eliminate "wire-drawing"—the process where high-velocity steam cuts deep, leaking channels through soft metallic surfaces—both the seat ring and the disc interface undergo specialized thermal hard-facing with a thick overlay of cobalt-base Stellite™ alloy. This generates an ultra-hard seating boundary that resists scoring from welding slag, pipe scale, and abrasive line particulates. Fully compliant with GB/T 12236, ASME B16.34, and global design codes, this valve serves as a critical safety barrier to block dangerous backflow and protect costly upstream equipment, such as pumps and compressors, from reverse pressure shocks.
Zero-Leakage Integrity: The butt-weld connection completely removes flanged joints, eliminating ongoing maintenance costs associated with gasket replacements and bolt re-torquing.
Extreme Thermal and Creep Resilience: Advanced 15CrMo alloy steel construction enables the valve body to retain exceptional tensile strength under superheated steam conditions reaching up to $550^\circ\text{C}$.
Stellite™ Hard-Faced Internals: Wear-resistant internal seating faces withstand high-velocity erosion and wire-drawing, ensuring tight shut-off over an extended service life.
Heavy-Wall Structural Safety: Reinforced body wall thicknesses offer a generous corrosion allowance and withstand high-pressure surges, line bending moments, and water hammer shockwaves.
Technical Parameter | Standard Specification | Options / Available Upgrades |
Nominal Diameter Range | DN20 – DN500 (3/4" – 20") | Custom large-bore configurations available up to DN1200 |
Body / Bonnet Metallurgy | Carbon Steel (WCB, WCC) / Alloy Steel (15CrMo, WC6) | Stainless Steel (CF8M, CF3M) for aggressive media |
Sealing Trim Interface | API 600 Trim No. 5 (Full Co-Cr Stellite™ Overlay) | Trim No. 8 (13%Cr vs Stellite™) available |
Pressure Ratings | PN16, PN40, PN63, PN100, PN160 (Class 150 to Class 900) | Ultra-high pressure Class 1500 / 2500 configurations |
Design Compliance | GB/T 12236, ASME B16.34, BS 1868 | Fully certified under CE-PED and ISO 9001 |
End Connection Styles | Butt-Weld Ends (BW) matching specified pipe schedules | Socket-Weld (SW) available for small diameters |
Sealing Leakage Class | API 598 (Liquid and Gas Testing standards) | High-pressure gas seat testing optional |
The heavy-duty welded profile makes this non-return valve the ideal choice for severe service installations where pipelines are permanent and routine maintenance access is restricted:
Power Generation Main Steam: Safeguards supercritical boilers and turbine extraction manifolds against back-flowing superheated steam and sudden water surges.
Petrochemical Refining Processing: Reliably manages high-temperature hydrocarbon loops, catalytic cracking units, and hydrogen-rich process lines.
High-Pressure Boiler Feedwater: Positioned directly on multi-stage pump discharge lines to immediately isolate backpressure shocks during emergency pump shutdowns.
District Heating Infrastructures: Essential for large-scale, high-temperature water distribution grids subject to extreme thermal expansion and pipe movement.
Adhere to these technical guidelines during system design to maintain optimal hydraulic flow and safeguard your welded joints:
Select check valves based on actual volumetric flow velocity rather than matching line size. Oversizing the valve results in insufficient flow velocity to hold the swing disc stably in the fully open position. This causes the disc to "flutter" or chatter against its hinge pins, causing rapid wear on internal pivot bearings. Always confirm that continuous system flow velocity exceeds the manufacturer’s minimum full-lift threshold.
Because the valve is welded directly into the line, strict field welding procedures are mandatory for alloy steels like 15CrMo.
Technical Note: Technicians must execute precise Pre-Heat and Post-Weld Heat Treatment (PWHT) around the butt-weld joints. Inadequate thermal cooling management will create a brittle Heat-Affected Zone (HAZ), leading to micro-cracking under subsequent high-pressure line surges.
The SDF Welded Swing Check Valve relies on gravity combined with fluid backpressure to seat the disc correctly.
Horizontal Piping: The valve must be installed with the bonnet cover facing vertically straight up.
Vertical Piping: Installation is only permitted if the media flow travels upward. Never install a swing check valve in a vertical line with downward flow, as gravity will hold the disc open and completely negate non-return functionality.
Although the valve shell is welded permanently into the pipeline, the top bonnet features a fully bolted arrangement. Always ensure adequate overhead clearance above the valve. This enables service personnel to easily unbolt the cover, lift out the hinge pin assembly, and inspect or lap the seating surfaces without cutting the valve body out of the pipe run.
Extensively deployed in high-pressure steam supply grids, boiler feedwater lines, compressed air infrastructure, and critical chemical utility loops.
We typically provide a quotation within 4 hours of receiving your inquiry. Urgent requests are given top priority.
Yes. We support OEM and customized valve manufacturing according to your drawings, technical specifications, and specific operating conditions.
Normally, production is completed within 15 working days after order confirmation, depending on the product type and quantity.
Our products comply with GB, ANSI, API, JIS, DIN, BS, and other major international standards.
Pressure: Class 150 – 3500 | Size: DN10 – DN3000 | Temperature: -196ºC to 610ºC
We are ISO 9001 and CE certified, and we provide third-party inspection and material test reports upon request.
Delivery terms: EXW, FOB, CFR, CIF
Payment terms: T/T (30% deposit + 70% balance), L/C, or other terms by mutual agreement.
Yes. We offer 24/7 technical support and maintain a supply of spare and consumable parts for long-term service.
