For B31.3 expansion stress, I typically would evaluate the total temperature difference, for example T cold = -20F, T install = 70F, T hot = 200F, Temp difference would be dT = 220 F. The way I read B31.11 piping (restrained or unrestrained) I would compare the maximum of T hot - T install or T cold - T install. So in the example above, dT would be 130F. Is this the correct interpretation of B31.11?