Stainless Steel Butt Weld Fittings

Butt weld fittings are a family of fittings used for forming circumferential butt weld joints in pipework systems.


They are used only in conjunction with ANSI pipe and are available in the same size range. They are used in areas where pipe-work is permanent and are designed to provide good flow characteristics.

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Manufacture of Butt Weld Fittings

Materials

Fittings may be made from forgings, bars, plates, or seamless or welded tubular products, provided the materials conform to the chemical composition requirements of ASTM A240.

The steel may be melted by electric- furnace, or vacuum-furnace, or by either of these followed by vacuum or electroslag- consumable remelting.

Forming

Fittings may be formed by hammering, pressing, piercing, extruding, upsetting, rolling, bending, fusion welding, machining or any combination of these processes.

Heat Treatment

All fittings are heat treated in accordance with the heat treatment table. All welding must be done prior to heat treatment.

Manufacturing Standards

Wrought Pipe Fittings

Manufactured to dimensions and tolerances in ANSI B16.9 with the exception of short radius elbows and return bends which are made to ANSI B16.28. Light-weight corrosion resistant fittings are made to MSS SP43.

Butt Weld Fittings

Available to ASTM A403, ASTM A815 and MSS SP43. These standards require the fittings to be manufactured as follows:

  • Seamless austenitic fittings are made from seamless pipe to ASTM A312.
  • Welded fittings in austenitic grades are manufactured from welded pipe to ASTM A312 or plate to ASTM A240. Note that welded fittings manufactured from plate may have two-welds.
  • Duplex (ferritic/austenitic) grades are manufactured from pipe to ASTM A790 or plate to ASTM A240.
  • ASTM A403/A815 butt weld fittings are sub-divided into four classes:
  1. WP-S: Made from seamless pipe to ASTM A312 (Austenitic) or ASTM A790 (Duplex).
  2. WP-W: Manufactured from welded pipe to ASTM A312 (Austenitic) or ASTM A790 (Duplex). There is no requirement for radiography unless a manufacturer’s weld has been introduced or there are welds made with the addition of filler metal.
  3. WP-WX: Of welded construction. All welds must be 100% radiographed in accordance with Paragraph UW-51 of Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code.
  4. WP-WU: Of welded construction. All welds must be 100% examined ultrasonically in accordance with Paragraph UW-51 of Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code. Note that this Class only applies to austenitic fittings made to ASTM A403.
  • CR fittings are manufactured to the requirements of MSS SP43. These are light- weight fittings and do not require radiography.

Note:

WP: Wrought pipe, CR: Corrosion resistant

Markings on Tube & Fittings

The full identification of the fitting should be marked on it including:

  • Nominal Pipe Size (Nominal Bore)
  • Schedule (wall thickness)
  • Specification
  • Grade
  • Method of manufacture (seamless or welded)
  • Heat Number
  • Manufacturer's Name or Symbol

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