Pipe thk claculation for SS347 Pipe at 649 deg C

[Pipingclassic]

Hi All,

We are designing a pipe for high temperature service and using the base material as SS 347 for a temperature 649 deg C / 300#. The pipes seamless pipes are as below,
A312 Gr.TP347 (Seamless)
A358 Gr.347 CL.1 (Welded)
For Pipe wall thickness calculation we have used the B31.3 Table A-1

- For welded points the allowable are taken considering heat treatment requirement above 538 deg. C.
- The Y factor taken as 0.7
- The Weld Joint factor as 0.77
But the thickness getting are much more than the existing pipe used. So is there any requirement I have to consider in high temperature pipe thk. calculation or heat treatment has any impact on allowable stress values of SS347 at high temperature.

 

[davefitz]

You might try specifying 347H instead of 347.
Also, above a 15 mm thick wall, there is a concern regarding "RC" relief cracking of 347H

"Whom the gods would destroy, they first make mad "

 

[metengr]

First off, use only seamless pipe material and you don't have a weld joint factor.

 

[Pipingclassic]

Thanks for quick reply @ davefitz, metengr
@ davefitz

Actually the existing pipe is used with A312 TP347 hence the calculaion is considering that material.

@ metengr
We are using the seamless pipe but for 24" and above (upto 42") the welded pipes are used.

 

[metengr]

Ok, you have your answer. If the minimum wall is x by code calculation, that is it.

 

[birken]

PipingClassic,

You may like to use PetroPipe software to get you calculation verified.
It does the calculations for required thickness according to different piping codes including ASME B31.1, B31.3, B31.4 & B31.8.
It's a freeware.

Birken

 

[ijzer]

You could do a 1000hrs creep test on a welded joint as allowed by ASME B31.3 par. 302.3.5 (f)(1)to get a higher factor than .77

 

[XL83NL]

or, as C. Becht IV wrote in his book "Process Piping: The Complete Guide to ASME B31.3", 3rd edt., para 3.4 on WJSRF;

A few highlights of the table follow:
..
..
.
5. Reference is made to permit use the Section III, Subsection NH, Tables I-14.10 A-xx, B-xx and C-xx factors specified for 100,00 hour duration. Observing figure 3.3, and in particular the 304B line (304 welded with 316 weld metal), this can give higher factors for combinations of base metal and weld metal.

So, if your plant/pipe life is less than say 20 yrs (200.000hrs), you might want to look into ASME III Div 1 sub NH. Not sure though if 347 as a amaterial is listed in there, to permit a higher WJSRF.