Stainless Steel - General Information - St St Butt Weld Fittings

St St Butt Weld Fittings

What are Butt Weld Fitttings? - Butt Weld Fittings are a family of fittings used in connecting and creating pipe-work systems whereby they are welded into the system using circumferential butt welds.
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.

What manufacturing standard is required and is the fitting seamless or welded?

Wrought pipe fittings are 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 are 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:

WP-S: Made from seamless pipe to ASTM A312 (Austenitic) or ASTM A790 (Duplex).

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.

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.

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.

WP: Means Wrought Pipe
CR: Means Corrosion Resistant

What markings will be on the fittings? - The full identification of the fitting should be marked on it including:
Nominal Pipe Size (Nominal Bore)
Schedule (Wall Thickness)
Method of Manufacture (Seamless or Welded)
Heat Number
Manufacturer’s Name or Symbol

Datasheet Search

Last Datasheet Revision

18 July 2019


This Data is indicative only and as such is not to be relied upon in place of the full specification. In particular, mechanical property requirements vary widely with temper, product and product dimensions. All information is based on our present knowledge and is given in good faith. No liability will be accepted by the Company in respect of any action taken by any third party in reliance thereon.

Please note that the 'Datasheet Update' date shown above is no guarantee of accuracy or whether the datasheet is up to date.

The information provided in this datasheet has been drawn from various recognised sources, including EN Standards, recognised industry references (printed & online) and manufacturers’ data. No guarantee is given that the information is from the latest issue of those sources or about the accuracy of those sources.

Material supplied by the Company may vary significantly from this data, but will conform to all relevant and applicable standards.

As the products detailed may be used for a wide variety of purposes and as the Company has no control over their use; the Company specifically excludes all conditions or warranties expressed or implied by statute or otherwise as to dimensions, properties and/or fitness for any particular purpose, whether expressed or implied.

Advice given by the Company to any third party is given for that party’s assistance only and without liability on the part of the Company. All transactions are subject to the Company’s current Conditions of Sale. The extent of the Company’s liabilities to any customer is clearly set out in those Conditions; a copy of which is available on request.