API 6D - Pipeline and Piping Valves
API 6D is the American Petroleum Institute specification for pipeline and piping valves used in petroleum and natural gas industries. It covers ball, check, gate and plug valves for pipeline transportation systems, defining requirements for design, manufacture, testing and documentation.
What API 6D covers
The specification applies to valves intended for full isolation, double block and bleed, and pigging operations. It defines pressure-temperature ratings, bore sizes matched to pipe internals, seat and seal capability in both directions, cavity relief provisions and actuator interface requirements. Valves certified to API 6D carry monogram marking traceable to a license agreement with the API.
Key tests
| Test | Requirement |
|---|---|
| Hydraulic shell test | 1.5 x rated pressure, no visible leakage |
| Seat test | 1.1 x rated pressure, defined leakage rates by class |
| Functional test | Smooth operation at rated torque |
Why it matters for buyers
For pipeline and trunkline projects, API 6D is usually a contractual requirement rather than an option. When comparing manufacturers, verify a valid API 6D license (checkable on the API composite list), the monogram on nameplates, and the testing documentation package including torque curves and cavity relief data.
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