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20th Edition, October 2011

Complete Document

Specification for Wellhead and Christmas Tree Equipment

Includes all amendments and changes through Errata , August 2016

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Product Details:

  • Revision: 20th Edition, October 2011
  • Published Date: August 2016
  • Status: Active
  • Document Language: English
  • Published By: American Petroleum Institute (API)
  • Page Count: 466
  • ANSI Approved: Yes
  • DoD Adopted: No

Description / Abstract:


This International Standard specifies requirements and gives recommendations for the performance, dimensional and functional interchangeability, design, materials, testing, inspection, welding, marking, handling, storing, shipment, purchasing, repair and remanufacture of wellhead and christmas tree equipment for use in the petroleum and natural gas industries.

This International Standard does not apply to field use, field testing or field repair of wellhead and christmas tree equipment.


This International Standard is applicable to the following specific equipment:

a) wellhead equipment:

- casing-head housings,

- casing-head spools,

- tubing-head spools,

- cross-over spools,

- multi-stage head housings and spools;

b) connectors and fittings:

- cross-over connectors,

- tubing-head adapters,

- top connectors,

- tees and crosses,

- fluid-sampling devices,

- adapter and spacer spools;

c) casing and tubing hangers:

- mandrel hangers,

- slip hangers;

d) 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;

e) 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;

f) other equipment:

- actuators,

- clamp hubs,

- pressure boundary penetrations,

- ring gaskets,

- running and testing tools (see Annex H),

- wear bushings (see Annex H).

The nomenclature used in this International Standard for typical equipment is shown in Figures 1 and 2. All parts whose physical dimensions conform to the metric tables incorporated into the body of this International Standard or to the tables in USC units in Annex B are acceptable;

Service conditions

This International Standard defines service conditions, in terms of pressure, temperature and material class for the well-bore constituents, and operating conditions.

Product specification levels

This International Standard establishes requirements for five product specification levels (PSLs): PSL 1, 2, 3, 3G and 4. These five PSL designations define different levels of technical quality requirements. Annex A provides guidelines (not requirements) for selecting an acceptable PSL.