Weld joint strength reduction factor,W

[insider79]

Hello members,

Can you kindly help me out with below query?

1. I have to calculate the WT for A358-321 CL.1 pipe at design conditions of 800degC at 49.7psig. Am I correct in understanding that value of W must be linearly interpolated from values in the row "Austenitic stainless grade 3xx and N088xx nickel alloys [Notes (7) and (8)]"in table 302.3.5, which mentions 0.55 at 788°C and 0.5@ at 816°C?

2. If I use A312-TP321 EFW, I can substantially reduce the thickness since W=1 for all temp ranges. However, If I chose A312-TP321 EFW pipes, then should I specify that the welded wrought fittings A403-WP321 are mandatorily fabricated or made from welded mother pipes that have been fabricated without using filler metal? ASTM A403 gives the option of both. I am worried about the WT wrought fittings being affected due W factor stated in point 1.

Thanks
Regards

 

[EdStainless]

Isn't the W=1 for seamless product?
I want to recall that all welded product has some weld factor.

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P.E. Metallurgy, consulting work welcomed

 

[david339933]

That would be Ej not W. W only comes into play at elevated temps.

 

[insider79]

Ej=1 since the longitudinal seam is X-rayed.I’m referring to table 302.3.5 in ASME B 31.3. Design temp is 800degC. For material A358-321H, am I correct in understanding that value of W must be linearly interpolated from values in the row "Austenitic stainless grade 3xx and N088xx nickel alloys [Notes (7) and (8)]"in table 302.3.5, which mentions 0.55 at 788°C and 0.5@ at 816°C?
Thanks

 

[david339933]

Sorry, was replying to Ed. You must satisfy Note 6 to use a value of 1.

 

[insider79]

Thanks David for the reply.
my doubt still persists. Let me make it simpler. Pipe ASTM A358-321 which I intend to use is a austenitic SS welded pipe using filler material., in which case I must refer to the row stating "Austenitic stainless grade 3xx and N088xx nickel alloys [Notes (7) and (8)]"in table 302.3.5 of B31.3 which mentions W=0.55 at 788°C and W=0.5@ at 816°C. Is my understanding correct?

Thanks

 

[XL83NL]

There’s some debate, iirc, on when W needs to be applied. That is, either for long or circ seams. I think the current general consensus is that it applies to long seams, as that’s where the industry failures, that led to the W factor, came from. However at discretion of the designer, circ seams may be taken into account as well.
B31.3 currently has more guidance on it, but a paper from Charles Becht had more background on this. Not sure if it could help, but here’s a link to that paper;

https://asmedigitalcollection.asme....uction-Factors-in-the?redirectedFrom=fulltext

PS: at those temperatures you essential need 321H. The design code will require more than 0.04%C (or 0.08; not sure, but it’s in the Code). For plain or straight grade 321, this essentially means you’re tight to 321H as probably no mill will make 321 with that chemistry.

Huub
- You never get what you expect, you only get what you inspect.

 

[davefitz]

The reason for calculating W for longitudinal joints is the "law of the hot dog". Just as a hot dog splits along its longitudinal length, the primary stresses on a longitudinal weld are 2x the primary stresses on a circumferential joint. Since the W for some alloys over 600 C are not much more than 0.5, it is likely that the W should also be considered for any weld that is not a true circumferential joint, such as for fabricated tees. If the pipe also has significant axial stresses ( due to gravity loads or other structural loads) then it would be prudent to calculate W also for circumferential welds.

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