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ASME B16.11-2021

Forged Fittings, Socket-Welding and Threaded
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ASME B16.11-2021

Forged Fittings, Socket-Welding and Threaded

PUBLISH DATE 2022
PAGES 34
ASME B16.11-2021

Purpose and Scope of ASME B16.11-2021

ASME B16.11, Forged Fittings, Socket-Welding and Threaded, is part of the ASME B16 series of standards and applies specifically to small-bore, high-pressure fittings manufactured from forged materials. The term "forged" indicates that these fittings possess superior strength, making them suitable for the most severe service conditions encountered in industrial piping.

The standard ensures uniformity and high reliability for fittings used primarily in sizes from NPS 1/8 through NPS 4 (DN 6 through DN 100). It covers:

  • Pressure Ratings (Classes): It establishes distinct pressure classes based on the end connection:
    • Threaded Fittings: Class 2000, 3000, and 6000.
    • Socket-Welding Fittings: Class 3000, 6000, and 9000.
  • Fitting Types: Elbows (45° and 90°), Tees, Couplings, Crosses, Caps, Unions, Plugs, and Bushings.
  • Dimensions and Tolerances: It sets precise dimensions and tolerances for features critical to assembly and welding, such as the minimum wall thickness, socket bore diameter, and center-to-end dimensions.
  • Material Requirements: It sets minimum material standards, typically referencing ASTM/ASME specifications for forged materials like carbon steel (A105), alloy steel, and stainless steel.

The standard does not cover the actual installation welding requirements; those must be found in the applicable ASME Piping Code (like B31.3) governing the piping system.


Application and Use

ASME B16.11 fittings are the primary choice for connections in auxiliary piping, instrument lines, and small-bore lines in high-pressure or high-temperature service where leakage resistance is critical. It is used by:

  • Manufacturers: They use the dimensional and material specifications to forge and machine fittings that meet the strict pressure integrity requirements of the specified class.
  • Engineers and Designers: They specify these fittings for systems requiring extremely high pressure (up to Class 9000), particularly in petrochemical plants, power generation facilities, and process piping where the high strength and leak-tight joint designs (socket-weld or threaded) are mandatory.
  • Installers and Welders: They follow the standard's dimensions to ensure proper pipe fit-up for both the socket-weld (which requires a gap for thermal expansion) and the threaded (NPT) joints, thus preserving the system’s integrity.

The standard provides the high-quality components necessary for critical connections in severe-service piping, complementing the high-integrity design requirements of the ASME Boiler and Pressure Vessel Code and B31 Piping Codes.

SDO ASME: American Society of Mechanical Engineers
Document Number B16.11
Publication Date Sept. 19, 2022
Language en - English
Page Count 34
Revision Level
Supercedes
Committee
Publish Date Document Id Type View
Sept. 19, 2022 ASME B16.11-2021 Revision