4A National Standard Check Valve is a high-performance duplex stainless steel non-return valve designed for the most challenging industrial environments. By utilizing 4A Duplex Steel (CD3MN) and adhering to the GB/T 12235 standard, this valve offers exceptional mechanical strength and elite resistance to localized corrosion, making it the ideal choice for seawater, brine, and aggressive chemical processing.
Description
4A (ASTM A890 Grade 4A / CD3MN) is a ferritic-austenitic stainless steel that provides a superior balance of properties compared to standard 300-series alloys:
- Stress Corrosion Cracking (SCC) Defense: The dual-phase microstructure provides a natural barrier against SCC, a common cause of failure in pressurized chemical systems.
- Twice the Mechanical Strength: The yield strength of 4A duplex is approximately double that of standard austenitic steels like 316L, allowing the valve to withstand higher pressure surges and mechanical stress.
- Elite Chloride Resistance: Specifically engineered to resist pitting and crevice corrosion in high-chloride environments, such as marine offshore platforms and desalination plants.
Features
- Automatic Backflow Prevention: Operates autonomously based on fluid dynamics. The valve opens under forward pressure and closes instantly when flow ceases or reverses, protecting critical equipment like pumps and compressors from damage.
- Stellite Hardened Sealing: The seat and disc (flap) sealing surfaces are reinforced with cobalt-based alloy (Stellite) welding. This creates a surface that is extremely wear-resistant, corrosion-resistant, and capable of maintaining a tight seal at high temperatures.
- GB Standard Compliance: Manufactured and tested in full accordance with GB/T 12235, ensuring standardized flange dimensions and reliable technical performance for domestic and international industrial projects.
- Versatile Design Options: Available in various structural forms (such as lift or swing types) and connection styles to meet specific pipeline requirements and medium conditions.
Specifications
| Feature | Specification |
| Design Standard | GB/T 12235 |
| Flange Dimensions | GB/T 9113 / JB/T 79 |
| Face-to-Face | GB/T 12221 |
| Body Material | 4A Duplex Steel (CD3MN / 022Cr22Ni5Mo3N) |
| Pressure Rating | PN16, PN25, PN40, PN64 |
| Sealing Material | Stellite (Cobalt-based alloy) |
| Testing Standard | GB/T 13927 / JB/T 9092 |
Applications
- Marine & Offshore: Seawater cooling systems, ballast water management, and offshore oil production.
- Chemical Processing: Handling organic acids, acidic slurries, and chloride-bearing chemical streams.
- Desalination Plants: High-pressure reverse osmosis (RO) systems and brine handling loops.
- Oil & Gas: Upstream and midstream pipelines where high-strength, corrosion-resistant backflow protection is mandatory.
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