B31.3 Weld Metal Impact Test Exemptions

[posershadow]

I have some 3 and 4" Sch. STD A-106 Gr. B pipe with a design minimum temperature of -20F per curve B of Figure 323.2.2A. I am planning to use para 323.2.2(b) and Figure 323.2.2B to calculate my stress ratio and exempt it from impact testing with a new design minimum temperature of -50F.

Looking at Table 323.2.2, I believe it falls under Column A with material type 3. For the weld metal, A-3(b) states that impact testing is required if the design minimum temperature is less than 0F unless Note 3 or 4 is satisfied or if the weld consumable requires impact testing at or below the design minimum temperature.

Without knowing my filler metal at this point, I was attempting to satisfy Note 3. This essentially points me back to para. 323.2.2.(h). As long as my stress ratio is low enough, I believe I can use -50F for the base metal design minimum temperature. My question is in regards to the statement "For carbon, low alloy, and intermediate alloy steel welds that require impact testing in accordance with Table 323.2.2, Box A-3(b), the temperature reduction from Figure 323.2.2B shall be applied to -29C(-20F).

Does that mean I subtract my temperature reduction from -20F (hopefully achieving -50F)? Or does that mean -20F is the lowest allowed design minimum temperature for the weld metal?

I interpreted it as the former, but then I found this: Link
That website seems to indicate they interpret -20F as the lowest limit for the weld metal. If that is true, then I suppose my only options are to impact test the weld metal or use a filler that requires impact testing at or below design minimum temperature.

 

[VQ35]

You will calculate coincident ratios for the 2 parts you are joining. The maximum of those coincident ratios gives you your allowable reduction per Figure 323.2.2B That reduction (say it is 50°F) is applied to each of your components.
Pipe: -20°F - 50°F = -70°F (but limited to -55°F per 323.2.2(h))
Non impact qualified weld: Start at -20°F per 323.2.2(h) - 50°F = -70°F (but limited to -55°F per 323.2.2(h))

I do not believe that link is interpreting correctly. The first sentence in paragraph (h) specifically includes welds. If welds were limited to -20°F they would only be mentioned in the second sentence which specifically addresses welds.