In the sustained case, in terms of direct loss of pressure integrity - i.e. at the lug - you'd have to have a generally poorly supported pipe structure, or (relatively) thin wall piping, or some combination of the two. Possible, yes, but it seems that multiple bad decisions would have to have been made to achieve this effect that doesn't fall exclusively onto the lug design.

I don't envy your position. Ascertaining the full range of allowable loads for a huge variety of variables is a daunting task.

1- Fx
2- Fy
3- Fz
4- Mx
5- My
6- Mz
7- OD
8- WT
9- Allowable stress 1
10- Allowable stress 2
11- Differential thermal expansions
12- Lug weld length
13- Lug weld size
14- Lug plate thickness

WRC might get you into the neighborhood, but you'll likely want to select artificially low inputs and follow up with any lugs that fall outside of the established limits.