Thinning calculation of bend when pipe is purchased with MWT 1

[lgracio]

Hi,

I would appreciate support for the following case. A pipe bend has to be performed for a pipe NPS 4" purchased with MWT of 17,78mm (AWT of 20,32mm).

The bend radius is 305mm and the material is SA335P91. The design conditions are T=579ºC and P=19,13 MPa. I know that for thinning calculation it shall be according ASME B31.1 §102.4.5, which is 12,7mm (extrados) but the minimum wall thk of this ordered pipe is MWT = 17,78mm, what can I use as limit for thinning?

In other hand, the Min. Wall thk calculated by §104.1.2 eq.(7) = 11,21mm (which is less 17,78mm) shall governs as the minimun design thick for the straight pipe or for any strain zone of the bend.

Luís Grácio
Mechanical Engineer (Engineering Solutions)
Portugal-Setúbal

 

[LittleInch]

I'm having a little difficulty following your post as it has a lot of abbreviations and seemingly random figures, but usually what you do is choose the thickest pipe before you bend it. You don't state the radius you are bending it to, but the thinning seems to be quite large to me.

Can you set out the question a bit clearer please.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way