API Spec 6A 20th Edition

ANSI/API SPECIFICATION 6A
20th Edition, October 2010, Effective Date 1-April-2011
Specification for Wellhead and Christmas Tree Equipment

CONTENTS
  1. Scope
  2. Normative References
  3. Terms, Definitions And Abbreviated Terms
  4. Design and performance - General requirements
  5. Materials - General requirements 
  6. Welding - General requirements
  7. Quality control
  8. Equipment marking
  9. Storing and shipping
  10. Equipment-specific requirements 
  11. Repair and re-manufacture 

SUMMARY

1.1 PURPOSE
  • specifies requirements and gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling, storing, shipment, purchasing, repair and re-manufacture of wellhead and christmas tree equipment for use in the petroleum and natural gas industries.
  • not apply to field use, field testing or field repair of wellhead and christmas treeequipment.
1.2  APPLICABILITY
  1. wellhead equipment: casing-head housings, casing-head spools, tubing-head spools, cross-over spools, multi-stage head housings and spools;
  2. connectors and fittings: cross-over connectors, tubing-head adapters, top connectors, tees and crosses, fluid-sampling devices, adapter and spacer spools;
  3. casing and tubing hangers: mandrel hangers, slip hangers;
  4. valves and chokes: single valves, multiple valves, actuated valves, valves prepared for actuators, check valves,chokes, surface and underwater safety valves and actuators, back-pressure valves;
  5. loose connectors [flanged, threaded, other end connectors (OEC), and welded]: weld neck connectors, blind connectors, threaded connectors, adapter and spacer connectors, bullplugs, valve-removal plugs;
  6. other equipment:  actuators, clamp hubs, pressure boundary penetrations, ring gaskets, running and testing tools (see Annex H), wear bushings (see Annex H).
1.3 Service Conditions: This International Standard defines service conditions, in terms of pressure, temperature and material class for the well-bore constituents, and operating conditions.
1.4 Product Specification Levels (PSL): PSL 1, 2, 3, 3G, and 4 define the different levels of technical quality requirements. Annex A provides guidelines (not requirements) for selecting an acceptable PSL.
4.1 Performance Requirements : para 4.2 to 4.7 and Clause 10 (P & T ranges and used, test fluids consistent with the material class in Table 3). Other requirements specified by the purchaser may include load capability, cycles, lubrication and operating force or torque. Performance requirement levels: PR1 and PR2.
4.2 4.2 Service conditions
4.2.1 Pressure Ratings : maximum rated working pressures (ksi: 2, 3, 5, 10, 15, 20),  threaded connection limitation (limited by thread sizes and rated working pressures in Table 1 -- rating do not include tubing and casing hangers)

 4.2.2 Temperature Ratings : min. (the lowest ambient temperature to which the equipment may be subjected) and max. (the highest temperature of the fluid that may directly contact the equipment) temperatures specified in Table 2 or as agreed between the purchaser and manufacturer.

4.2.3 Material Classes : designed with materials, including metallics, that meet the requirements set forth in Table 3

  • class AA: stainless steels and/or CRA materials and classes BB: carbon and low-alloy steels
  • material classes DD, EE, FF and HH shall meet ISO 15156 (all parts) (NACE MR0175; see Clause 2) -->  the designation and marking the maximum allowable partial pressure of H2S in units consistent with the rated working pressure markings and prefixes
  • example, “FF-10” :indicates material class FF rated at 10 kPa H2S maximum allowable partial pressure. Where no H2S limit is defined by ISO 15156 (all parts) (NACE MR0175; see Clause 2) for the partial pressure, “NL” shall be used for marking (i.e. “DD-NL”).
  • resistance to cracking caused by H2S is influenced by a number of other factors: pH; temperature;  chloride concentration; elemental sulfur.
  • material classes ZZ : a specific sour-service application that is outside the parameters defined in ISO 15156 (all parts) (NACE MR0175; see Clause 2). The manufacturer shall meet material specifications supplied or approved by the purchaser, and shall maintain traceable records (regardless of PSL).
4.3 Design methods4.3.1 Connections: Flanges, Clamp hub and outlet end connections, Clamps
4.3.2 Casing hangers, tubing hangers, back-pressure valves, lock screws and stems4.3.3 Other end connectors, bodies and bonnets
4.3.3.5 Design qualification by proof test: as an alternative to the analytical methods above, the pressure rating of equipment may be determined by the use of a hydrostatic test at elevated pressure. It shall not previously have been subjected to a pressure greater than 1,5 times the desired or anticipated maximum allowable working pressure.
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