4A National Standard Swing Check Valve

Description

4A (ASTM A890 Grade 4A / CD3MN) is a ferritic-austenitic stainless steel that offers a superior balance of properties:

• Stress Corrosion Cracking (SCC) Defense: The dual-phase microstructure provides a natural barrier against SCC, a common failure mode in chemical and offshore applications.
• Elite Corrosion Resistance: Provides exceptional protection against pitting and crevice corrosion, specifically in chloride-rich environments like seawater and brine.
• Mechanical Strength: Offers nearly double the yield strength of standard austenitic stainless steels (such as 316L), ensuring the valve body maintains integrity under heavy pressure surges.

Features

• Swing-Type Automatic Operation: The valve features a “swinging” flap (disc) that rotates about an internal hinge pin. It opens fully with forward flow and closes automatically under the force of gravity and backpressure, ensuring instantaneous protection against reverse flow.
• Full Port Flow: The swing design allows the disc to move completely out of the flow path, providing a straight-through bore that minimizes pressure drop and turbulence—ideal for systems where flow efficiency is critical.
• Stellite Hardened Sealing: The seat and disc sealing surfaces are typically reinforced with cobalt-based alloy (Stellite) welding. This provides elite resistance to high temperatures, wear, and “wire-drawing” erosion, significantly extending the service life.
• National Standard Compliance: Manufactured and tested to GB/T 12236, GB/T 9113, and GB/T 12221, ensuring dimensional accuracy and technical reliability for domestic industrial infrastructure.

Specifications

Applications

• Marine & Offshore: Seawater cooling loops, ballast systems, and offshore oil production platforms.
• Chemical Processing: Handling of organic acids, aggressive chemical slurries, and chloride-bearing fluids.
• Desalination: High-pressure reverse osmosis (RO) systems and brine treatment.
• Oil & Gas: Upstream and midstream pipelines requiring high-strength backflow protection.