Valve Standard Reference
API 6A
AmericanSpecification for Wellhead and Christmas Tree Equipment
API 6A is the fundamental specification for wellhead and Christmas tree equipment used in oil and gas well drilling and production.
Overview — API 6A
API 6A is the fundamental specification for wellhead and Christmas tree equipment used in oil and gas well drilling and production. It covers all equipment installed at the top of a well casing — including casing heads, tubing heads, Christmas trees, choke valves, gate valves, and actuators — that must contain wellbore pressures that can reach 20,000 psi. API 6A valves are subjected to far more rigorous qualification testing than standard process plant valves and must be tested at the rated working pressure of the equipment, not a fraction of it. The standard is mandatory for virtually all oil and gas wellhead equipment worldwide.
Scope
Covers all valves, chokes, and other pressure-controlling equipment installed at or above the wellhead flange including gate valves (slab and expanding), ball valves, plug valves, choke valves, and their actuators. Working pressure ratings range from 2,000 psi (PSL 1) to 20,000 psi (PSL 4). Temperature classes range from −60°C to 180°C.
Applicable Valve Types
Gate Valves — slab and expanding type wellhead
Ball Valves — wellhead and Christmas tree
Choke Valves — adjustable and positive
Plug Valves — wellhead service
Applicable Pressure Classes
Key Requirements — API 6A
Product Specification Level (PSL): 1, 2, 3, 3G, or 4 — each with escalating quality, testing, and documentation requirements
Working pressure classes: 2000, 3000, 5000, 10000, 15000, and 20000 psi
Temperature classes: K (−60 to 82°C), L (−46 to 82°C), P (−29 to 82°C), R (−18 to 121°C), S (0 to 60°C), T (−18 to 82°C), U (0 to 121°C), V (2 to 180°C)
Material classes: AA (general service), BB (H₂S partial, CO₂), CC (H₂S full, NACE), DD, EE, FF, HH per NACE MR0175
All load-bearing and pressure-containing parts must meet minimum yield strength per temperature class
Traceability: full heat/lot traceability required for PSL 2, 3, 3G, 4
Factory acceptance test (FAT): hydrostatic body test + seat test at rated WP for all PSL levels
Third-party certification mandatory for PSL 3, 3G, 4
Testing Requirements — API 6A
Hydrostatic body (shell) test at 1.5× rated working pressure
Seat (gate/seat interface) test at rated working pressure, both upstream and downstream seats
Low-pressure gas seat test at 100–200 psi for PSL 3G/4
Functional test: full open-to-close-to-open cycle under rated pressure
Extended cyclic pressure test for PSL 3G and 4 qualification
Documentation Required for API 6A Compliance
API 6A monogram license (API monogram on equipment)
Material Mill Test Reports (MTR) per EN 10204 3.1
Full hydrostatic test report with witnessed pressure charts
Third-party inspection certificate (PSL 3/3G/4)
NACE MR0175 compliance report when CC/DD/EE/FF/HH material class is specified
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