III. Feature Description

A. Trunnion-Mounted (Fixed) Ball Structure: High-Pressure Stability

B. Turbine Gear Drive: Torque Efficiency for Large Diameters

C. WCB Material: High-Temperature & Pressure Tolerance

D. API 6D Compliance: Pipeline Valve Reliability

E. Dual-Seal Flexibility: Adapt to Diverse Media

• PTFE Soft Seal: Ideal for low-to-medium pressure (≤600LB) and ambient-to-moderate temperatures (-29℃~200℃), providing bubble-tight sealing (API 598 Class V) for clean media like potable water or natural gas.
• Stellite 6 Metal Seal: Cobalt-based hard alloy surfacing (hardness ≥58 HRC) withstands high temperatures (up to 350℃) and abrasive media (e.g., crude oil with fine sediments), ensuring wear resistance and maintaining API 598 Class IV leakage even after thousands of cycles.

IV. Manufacturing Processes

A. Material Inspection & Preparation

• WCB Quality Control: Raw WCB billets undergo spectral analysis to verify chemical composition (C: 0.25%~0.35%, Mn: 0.60%~1.00%) and ultrasonic testing (UT) to detect internal porosity or cracks—critical for preventing pressure-induced failure.
• Stainless Steel Verification: 304/316 ball blanks are tested via positive material identification (PMI) to confirm chromium/nickel/molybdenum content, ensuring corrosion resistance meets design requirements.

B. Valve Body Casting & Heat Treatment

• Sand Casting: WCB valve bodies are produced via resin-bonded sand casting—this process minimizes surface defects and ensures uniform wall thickness (≥25mm for DN300, 600LB) to withstand high pressure.
• Normalization Heat Treatment: Cast bodies are heated to 890~950℃, held for 2~3 hours, then air-cooled. This refines the grain structure, reduces internal stresses, and enhances mechanical properties (e.g., impact toughness at -29℃).

C. Precision Machining of Critical Components

• Ball & Trunnions: The stainless steel ball is CNC-turned to a spherical tolerance of ±0.02mm, then lapped to a surface roughness of Ra ≤0.8μm for tight seal contact. Trunnions (integrated with the ball) are ground to a diameter tolerance of h7 (±0.015mm) to ensure smooth rotation in the valve body bearings.
• Valve Seat & Seal Faces: Seat pockets are CNC-machined to match the ball’s curvature; metal seal faces (Stellite 6) are welded via TIG welding, then ground to Ra ≤0.4μm to ensure uniform pressure distribution.
• Turbine Gear Set: Gear teeth are hobbing-machined to AGMA Class 8 precision, with a surface finish of Ra ≤1.6μm to reduce friction and ensure torque efficiency.

D. Assembly & Quality Testing

• Component Assembly: The ball-trunnion assembly is inserted into the valve body, with bearings (bronze with PTFE inserts) installed to reduce trunnion wear. Seats are pressed into pockets, and the turbine gearbox is mounted to the valve bonnet—aligned via laser to ensure 90° ball rotation with no binding.
• Hydrostatic Test: The valve is filled with water; the shell is pressurized to 15.0MPa (1.5×600LB) for 30 minutes, and the seat to 11.0MPa (1.1×600LB) for 15 minutes—no leakage or deformation is allowed.
• Torque & Cycle Testing: Turbine operation is tested to confirm torque ≤800 N·m; 100 open-close cycles are performed to verify consistent sealing and smooth gear operation.
• API 6D Verification: Final inspection includes checking flange dimensions (ASME B16.5), material traceability, and certification documentation to ensure full API 6D compliance.