Partial Pen Weld BTC-P5

[nhtr86]

Looking at AWS D1.1 2010 pg 80. Figure 3.3, Joint Designation BTC-P5.

It shows minimum plate thickness as 5/16", minimum root face of 1/8", and effective weld size of S1+S2-1/4. So 5/16"-1/8"-1/4" should be the effective weld size for 5/16" plate but that number is negative. The 5/16" minimum plate thickness also doesn't seem to make sense when you compare the table for double bevel groove pjp to the table for double V groove pjp.

Also, Table 3.4 suggests that minimum E dimension for 1/4"-1/2" plate is 3/16", which isn't possible for 5/16" plate.

Clearly I don't understand the purpose of the 5/16 min. value for T1 in the table.

What do the values in the table for BTC-P5 mean?

In Table 3.4, where it lists minimum E values, does that apply to both pjp welds in a double bevel groove weld, or could that be interpreted that the combination of both pjp welds (Total Weld Size)needs to match the value in Table 3.4 (the size of each pjp in a double bevel can be half of the minimum size shown in Table 3.4)?

I did some googling, and nothing obvious came up.
Thanks

 

[dhengr]

Nhtr86:
If you dig deeply enough into AWS I think you’ll find that you can’t use the full detailed throat size (depth) on those small grooves and with this process, you just can’t always penetrate all the way down to the root or get good fusion there, so you have to reduce the theoretical throat by a 1/16th or so. Thus, the 1/4” reduction in the weld size, is made up of 1/16” on one throat + 1/8” for ‘f’ + 1/16 on the other throat, would be my guess. Also, the total weld size is S1 + S2 – the fore-mentioned 1/4", not S1 + S2 - f - 1/4". I’ve not used the latest eds. of the AWS very much so you better verify my thinking. Unless you use those tables and sections of the code frequently enough, they are confusing and complicated. You do have to read all the foot notes, etc. for minor variations and exceptions. The upshot is that the double groove PJP weld shown in that BTC-P5 sketch is just not a practical weld for that thin a plate. By the way, they do show the lack of full penetration/fusion to the roots in that sketch and that’s not shown in other sketches where it is less of a problem.