API 6D Ball Valves

1. General Structure and Operation

• ‌Spherical Closure Member‌: Ball valves in API 6D have a solid one-piece spherical closure member (ball) that rotates on an axis perpendicular to the direction of flow.
• ‌Rotation Mechanism‌: The ball is designed to rotate within the valve body to control the flow. When the ball's bore is aligned with the flow path, fluid flows freely; when perpendicular, flow is blocked.
• ‌Fire-safe Design‌: Fire-safe design to meet API 6FA or API 607 standards.
• Anti-static Device: Ball valves shall have electrical resistance not to exceed 10Ω.
• Cavity Pressure Relief: If liquid or multi-phase fluid trapping is possible, the valve will be provided with automatic cavity-pressure relief. For design temperature up to 250 °F (121 °C) the valve cavity relief shall not exceed 33% differential pressure above the valve pressure rating.
• ‌Locking Device‌: Can be provided to lock the valve in the open or closed position.
• ‌Position Indicator‌: Visual or mechanical indicator to show the position of the ball (open or closed).
• ‌Extended Stem‌: For below-ground applications, an extended stem with a protective housing is available.

2. End Connections

• ‌Flanged and Welding Ends‌: Ball valves covered by API 6D are available with flanged or welding ends to suit different piping systems and application requirements.

3. Sealing and Seat Design

• ‌Seat Types‌: Ball valves can be equipped with single or double seats, depending on the sealing requirements.
• ‌Bidirectional or Unidirectional‌: The valve can be designed for bidirectional or unidirectional flow.
• ‌Seal Materials‌: A variety of seal materials are available, including soft seats and metal-to-metal seats, to suit different media and operating conditions.

4. Pressure and Temperature Ratings

• ‌Pressure Rating‌: API 6D Ball valves conform to ASME B16.34 pressure rating standards, with classes ranging from 150 to 2500.
• ‌Temperature Rating‌: The valves are designed to operate within a specified temperature range, with materials selected to maintain performance across this range.

5. Materials of Construction

• ‌Body and Closure Member‌: Commonly made from cast or forged steel, with options for stainless steel, alloy steel, and other corrosion-resistant materials.
• ‌Internal Components‌: Seats, stems, and other internal components are also made from materials suitable for the intended service conditions.

6. Testing and Validation

• ‌Hydrostatic Shell Test‌: Performed to ensure the structural integrity of the valve body and end connections.
• ‌Seat Tightness Test‌: Verifies the sealing capability of the ball and seat under specified pressure and temperature conditions.
• ‌Additional Testing‌: Depending on the application, valves may undergo additional testing such as fire testing, low-temperature testing, and cavity relief testing.

7. Marking and Documentation

• ‌Valve Marking‌: Each valve is marked with information including valve type, size, pressure class, material, and manufacturer details.
• ‌Certification and Documentation‌: Provided with a certificate of conformance, material test reports, and pressure test reports as required by the specification.