ASME B31.1-Design of Straight Pipe-minimum required wall thickness and bending factor

[sunstorm80]

Good morning to everybody,

I have a doubt about the minimum wall thickness method per designing the straight pipe under internal pressure (art. 104.1.2): I'm considering longitudinal electrowelded pipe without filler metal. How must I take into account the bending factor to compensate for thinning in bends, refer to para. 102.4.5.? Only in case of a completed bend (I mean for a curve) or also for designing a straigth pipe (e.g. for taking into account possible deviations from rectilinear shape or a circumferential thermal gradient on the across section)?
Thanks.

 

[MJCronin]

I don't believe that your question is clear....

The ASME B31.1/31.3 codes are quite specific about the calculation of minimum wall thickness for your particular system.

If you are fabricating "bends" from straight pipe and you meet the dimensional and ovality limitations after the straight pipe is modified, you have met the code requirements.

An additional minimum wall thickness evaluation need not be done.



MJCronin
Sr. Process Engineer

 

[sunstorm80]

Thanks Cronin.
I'm trying to be more clear.
I would like to properly desing the thickness of a straight pipe, considering an electrowelded pipe without filler metal manufactured by cold rolling.
Reading the paragraph 104.1 of ASME B31.1-2001, regarding the design of Straight Pipe Under Internal Pressure, it explains the design of tm (minimum required wall thickness) should refer to para. 102.4.5 to compensate for thinning in bends: does it means that I must consider a bending factor, multiplying the tm value as per the factor of table 102.4.5, also for manufacturing a straight pipe?

 

[Surachai]

The minimum wall thickness on the bend component under internal pressure is similar to straight pipe as per para. 104.1.2(A). Para. 102.4.6 given the Code user a guideline of the extra-thickness for ordering the pipe required bending process. Ask the forming shop is another solution.