B31.8 does not address combined stresses in onshore-buried pipelines, as explicitly mentioned in code interpretation no 11-1. Combined stress intensity in high temperature high-pressure pipelines can therefore exceed the material yield strength even if the hoop stress is within code limits. May I know the industry practice regarding limit on stress intensity in buried pipelines designed per B31.8? Will it be appropriate to refer B31.4 and chapter VIII of B31.8 that impose such a limit?
I shall be thankful for valuable guidance from the learned fellow members.

Thanks