Wall thinning in fittings and bends

[alchemon]

In looking through a few welded steel pipe fitting catalogs: I see that for ASME B16.9/ASTM A234 WPB 3R fittings, the manufacturers list the wall thickness as the same as the fitting WT (for example for 6” schedule 40 - WT is shown as 0.280” WT). Is there no thinning in the pipe wall due to the fitting fabrication?

 

[KevinNZ]

The thickness refers to the thickness at the weld prep.

Butt weld fittings must either be designed to pressure equipment codes or the design is proof tested so attached pipe will always fail before the fitting. In either case the thickness in the body of the fitting will be thicker than the normal thickness at the weld.

 

[davefitz]

Thinning at the extrados of bends is normal and is usally permitted to some extent. First of all, the pressure stress equation to be used is a toriodal equation, not a cylindrical equation, and that proves a thinner wall is permitted . Secondly , the bending process usually cuases work hardening at the extrados, and that also improves strength for most metals.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick