API 6D Valves

1. Types of Valves

• ‌Ball Valves‌: Valves with a spherical closure member that rotates on an axis perpendicular to the direction of flow.
• ‌Check Valves‌: Valves with a closure member that responds automatically to block fluid in one direction.
• ‌Gate Valves‌: Valves with a closure member that moves in a plane perpendicular to the direction of flow.
• ‌Plug Valves‌: Valves with a cylindrical or conical closure member that rotates about an axis perpendicular to the direction of flow.

2. Design and Materials

• ‌Design Standards‌: Valves must conform to internationally recognized design codes such as ASME BPVC, Section VIII, or EN standards.
• ‌Material Requirements‌: Metallic materials must meet specified chemical composition, mechanical properties, and impact testing requirements. Nonmetallic materials such as seals must have defined physical property requirements.

3. Manufacturing Processes

• ‌Process Control‌: Manufacturers must have a quality management system in place to ensure conformance with API 6D.
• ‌Welding‌: Welding procedures and welders must be qualified in accordance with industry standards.
• ‌Nondestructive Examination (NDE)‌: Various NDE methods, including radiographic, ultrasonic, magnetic particle, and liquid penetrant testing, are required for different valve components and manufacturing stages.

4. Testing

• ‌Pressure Testing‌: Valves must undergo hydrostatic shell and seat tests to ensure they can withstand specified pressures without leakage.
• ‌Gas Testing‌: High-pressure gas shell and seat tests may be required to demonstrate the valve's performance under extreme conditions.
• ‌Torque/Thrust Testing‌: The maximum torque or thrust required to operate the valve must be measured and documented.

5. Marking and Documentation

• ‌Marking‌: Valves must be marked with the manufacturer's name, material grade, pressure rating, size, and other relevant information.
• ‌Documentation‌: Manufacturers must provide detailed documentation, including material test reports, NDE records, pressure test reports, and assembly drawings.

6. Additional Features and Options

• ‌Double Block and Bleed (DBB)‌: Valves can be designed with DBB features to isolate two pressure sources and bleed/vent pressure between the sealing elements.
• ‌Double Isolation and Bleed (DIB)‌: DIB valves provide two sealing elements to a single pressure source and allow bleeding/venting between the sealing elements.
• ‌Fire Testing‌: Valves can be qualified for fire testing in accordance with API 6FA or API 607 to ensure they can withstand fire exposure without leakage.
• ‌Extended Hydrostatic Shell Test‌: By agreement, valves can undergo hydrostatic shell tests at pressures higher than specified in the standard.
• ‌Custom Design Features‌: The purchaser can specify various custom design features, such as special end connectors, drain connectors, lifting provisions, and antistatic devices.