API 6D Trunnion Mounted Ball Valve

Structural Features

• ‌Trunnion-Mounted Ball‌: The ball is fixed by two trunnion bearings, reducing operating torque and ensuring stability in high-pressure conditions.
• ‌Sealing Mechanism‌: Utilizes bidirectional or unidirectional sealing, depending on application requirements. Common sealing materials include PTFE, reinforced polymers, or metal-to-metal designs.
• ‌Actuation Options‌: Manual, gear-operated, electric, pneumatic, or hydraulic actuation.

Applications

• High-pressure differential systems
• Critical sealing applications (e.g., hydrocarbon pipelines)
• Extreme temperature environments (cryogenic or high-temperature)
• Oil and gas transmission pipelines
• Chemical processing and refining

Design Requirements

• ‌Pressure-Temperature Ratings‌: Must comply with ASME B16.34 or equivalent standards.
• ‌Sealing System‌: Design must prevent leakage under maximum pressure and temperature conditions.
• ‌Fire-Safe Design‌: Optional fire-tested per API 607/6FA for valves used in flammable environments.

Material Requirements

• ‌Body Materials‌: Carbon steel (e.g., ASTM A216 WCB), alloy steel (e.g., A352 LCC), stainless steel (e.g., A351 CF8M), or specialty alloys as per service conditions.
• ‌Sealing Materials‌: PTFE, RPTFE, PEEK, or metal seals (for high-temperature/pressure applications).
• ‌Fasteners‌: Bolts, nuts, and studs must meet API 20E/20F or equivalent standards.

Manufacturing and Testing

• ‌Production Processes‌: Casting, forging, welding, and heat treatment must comply with API 6D and ASME standards.
• ‌Non-Destructive Testing (NDT)‌:
  • Ultrasonic Testing (UT) for critical sections.
  • Radiographic Testing (RT) for weld joints.
  • Magnetic Particle (MT) or Liquid Penetrant Testing (PT) for surface defects.
• ‌Pressure Testing‌:
  • ‌Shell Test‌: 1.5 times the rated pressure to verify structural integrity.
  • ‌Seat Test‌: Conducted with air or water at 1.1 times rated pressure to ensure zero leakage.
  • ‌Low-Pressure Closure Test‌: For bidirectional sealing validation.

Marking and Documentation

• ‌Valve Identification‌: Must include manufacturer name, size, pressure class, material grade, serial number, and API 6D compliance mark.
• ‌Required Documentation‌:
  • Material Test Certificates (MTCs) for all components.
  • NDT and pressure test reports.
  • Compliance certificates (e.g., fire-safe, fugitive emissions).