API 6D Swing Check Valve

1. Design Features‌

• ‌Disc and Hinge Mechanism‌:

  • A swinging disc (clapper) mounted on a hinge pin or pivot arm.
  • The disc swings freely in the flow path, opening with forward flow and closing automatically when flow stops or reverses.
  • Gravity and flow dynamics ensure closure (no external actuation required).

• ‌Full-Bore Design‌:

  • Typically full-port (full-bore) to minimize pressure drop and turbulence, critical for high-flow applications.

• ‌Body Construction‌:

  • Bolted cover or pressure seal, depending on size and pressure class.
  • Designed to meet ASME B16.34 pressure-temperature ratings.

• ‌Seat Design‌:

  • Metal-to-metal seating for tight shutoff (standard).

• ‌End Connections‌:

  • Flanged ends per ASME B16.5/B16.47 or butt-weld ends per ASME B16.25.
  • Optional hub, threaded, or other connections as specified.

• ‌Face-to-Face Dimensions‌:

  • Compliant with API 6D/ASME B16.10 standards.

2. Material Specifications‌

• ‌Body and Trim‌:

  • Carbon steel (e.g., ASTM A216 WCB), stainless steel (e.g., ASTM A351 CF8M), or alloy materials (e.g., Duplex, Inconel) for corrosive or high-temperature services.
  • Hinge pins and disc arms are often made of hardened stainless steel for wear resistance.

• ‌Seat and Disc‌:

  • Hard-faced surfaces (e.g., Stellite) for erosion resistance in high-velocity or abrasive services.

• ‌Non-Metallic Seals‌:

  • Elastomers (NBR, Viton) or PTFE for sealing, compliant with NACE MR-0175 for sour service if required.

‌3. Performance and Testing‌

• ‌Pressure Testing‌:

  • ‌Shell Test‌: Hydrostatically tested to 1.5× the valve’s pressure rating.
  • ‌Seat Test‌: Tested for leakage at 1.1× rated pressure (liquid) or 0.6 MPa (gas).
  • Optional low-pressure gas test (0.05–0.1 MPa) for fugitive emissions compliance.

• ‌Fire-Safe Design‌:

  • Optional compliance with API 6FA or API 607 for fire-safe performance (metal seats and fire-resistant materials).

• ‌Cyclic Testing‌:

  • Valves may undergo endurance testing to verify repeated opening/closing reliability.

‌4. Optional Features

• ‌Counterweighted Disc‌:

  • For vertical installation, a counterweight ensures proper closure against gravity.

• ‌Spring-Assisted Closure‌:

  • Accelerates disc closure to prevent water hammer in fast-flow systems.

• ‌Drain and Vent Plugs‌:

  • For pipeline draining or pressure relief.

• ‌Lifting Lugs or Eye Bolts‌:

  • Facilitate safe handling and installation.

• ‌Locking Device‌:

  • Allows the valve to be locked open/closed for maintenance.

• ‌Coating/Internal Lining‌:

  • Internal epoxy coatings or corrosion-resistant linings for harsh environments.

5. Compliance and Certification‌

• ‌API 6D Requirements‌:

  • Design, manufacturing, testing, and documentation comply with API 6D (24th/25th edition).
  • Optional API Monogram for certified valves.

• ‌Additional Standards‌:

  • NACE MR-0175 for sour service (H₂S environments).
  • ISO 14313 (equivalent international standard)

6. Advantages of API 6D Swing Check Valves‌

• ‌Low Pressure Drop‌: Full-bore design minimizes flow resistance.
• ‌Durability‌: Robust construction for high-pressure and high-temperature services.
• ‌Maintenance-Friendly‌: Bolted-cover designs allow easy access to internal components.

7. Applications‌

• Oil and gas pipelines, refineries, petrochemical plants, and offshore platforms.
• Suitable for horizontal or vertical upward flow (orientation-specific designs available).

Assembly Drawing