The "magic" that "protects" the lateral is likely the complexity of variability.

Laterals are not covered dimensionally by ASME, thus it's difficult to expect a piping code to try to keep up with something that isn't standardized.

I would expect that at some point it might be possible to develop a function that would cover SIFs and flexibility factors that would be a function of OD1, OD2, WT1, WT2, crotch radius1, crotch radius 2, crotch radius 3, crotch radius 4, lateral offset, and approach angle.

However, until then, we do what we must to move forward. I have also seen the doubling of SIFs.

I've attached images depicting CL/CL intersection, weld center, and OD/CL intersection. At a minimum, we should be incorporating an offset to not take credit for the length between red and green, but likely red and blue makes more sense from a conservative standpoint.

But for those 2 sharp corners whose location are dependent on the angle. Or that long, sharp edge where the two cylinders are coming together. Are we certain for what range a SIF + safety factor of 2 is accurate?