What is the manufacturing process of ASTM A234 WPB pipe fittings?

The WPB is not short hand for any process. It is simply an identifier developed by ASTM. The fittings in question are manufactured in the same manner as the companion pipe for this specification.

ASTM A234 WPB pipe fittings

In very large sizes, the fittings may be manufactured in pieces and welded together as is the case for many large fittings.

The term used for the manufacturing is called “wrought” which means it is worked as opposed to being cast or forged.

As to the W standing for weldable, I’m not sure that is correct since that are many, many pipe fittings that are weldable but carry designations other than a W. Note the reference below.

Forging is the manufacturing process of ASTM A234 WPB pipe fittings.

W = WELDABLE / wrought
P = RELATED TO P NUMBER OF ALLOY MATERIAL
B = REFER TO MINIMUM YIELD OF MATERIAL

LATEST STANDARD IS:

ASTM A234/A234M-07
Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service

This standard covers wrought carbon steel fittings of seamless and welded construction which are manufactured to the dimensional specifications of ASME B16.9 and B16.28. These fittings are primarily for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures.

ANSI/ASME B16.25 Standard covers the preparation of butt welding ends of piping components to be joined into a piping system by welding. It includes requirements forwelding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and tolerances).

Coverage includes preparation for joints with the following:

(a) no backing rings
(b) split or noncontinuous backing rings
(c) solid or continuous backing rings
(d) consumable insert rings
(e) gas tungsten arc welding (GTAW) of the root pass Details of preparation for any backing ring must be specified when ordering the component.

ANSI/ASME B16.25 Standard applies to any metallic materials for which a welding procedure can be satisfactorily qualified, but does not prescribe specific welding processes or procedures. Unless otherwise specified by the purchaser, it does not apply towelding ends conforming to ASME B16.5, B16.9, or B16.47.