SECTION VIII, DIV.1 - Cap size larger than 4" NPS; what are my spec options?

[timsch]

I've been told by others more experienced in my industry than myself that to make a pressure vessel cap (most similar to UG-34(h)) that is larger than 4" NPS, that SA-182 forged bar had to be used rather than our typical SA-479 bar. When looking at UG-6(b), the same limitations apply as to the bar. I don't what they are basing their statement on.

What is my best option for these larger caps? They need to be custom made in our shop.

 

[XL83NL]

Code case 2156-1 allows for the use of rod & bar larger than NPS 4" (since UG-14(b) proohibits it in the first place).

 

[timsch]

This CC does not actually mention caps, but only hollow cylindrical shaped parts. Our caps are solid, with a number of small holes bored through them axially.

On another note, this code case was approved in 2006. I don't see why UG-14 wasn't just revised in later releases of the code to add the wording from this CC.