Definition and details of Butt Weld Fittings

Buttweld Fittings general

A pipe fitting is defined as a part used in a piping system, for changing direction, branching or for change of pipe diameter, and which is mechanically joined to the system. There are many different types of fittings and they are the same in all sizes and schedules as the pipe.
Fittings are divided into three groups:

  Image of most used buttweld fittings.
Standard Buttweld Fittings

1. Elbow 90° long radius   2. Elbow 45°   3. Elbow 90° short radius
4. Elbow 180° long radius   5. Elbow 180° short radius
6. Tee straight   7. Tee reducing
8. Reducer concentric   9. Reducer eccentric
10. End cap   11. Lap joint Stub End

Applications of Buttweld Fittings

Buttweld Fittings

A piping system using buttweld fittings has many inherent advantages over other forms.

Bevelled Ends

The ends of all buttweld fittings are bevelled, exceeding wall thickness 4 mm for austenitic stainless steel, or 5 mm for ferritic stainless steel. The shape of the bevel depending upon the actual wall thickness. This bevelled ends are needed to be able to make a "Butt weld".

  Image of typical bevel types.
Typical bevel types

ASME B16.25 covers the preparation of buttwelding ends of piping components to be joined into a piping system by welding. It includes requirements for welding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and dimensional tolerances). These weld edge preparation requirements are also incorporated into the ASME standards (e.g., B16.9, B16.5, B16.34).

Material and Performance

The most common materials used in fittings produced is carbon steel, stainless steel, cast iron, aluminium, copper, glass, rubber, the various types of plastics, etc..

In addition, fittings, like pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the fitting themselves, which are "lined fittings".

The material of a fitting is basically set during the choice of the pipe, in most cases, a fitting is of the same material as the pipe.