Thanks Richard for that very nice explanation.

For expansion stress, yes, the pressure terms (Hoop Stress & Radial Stress) will drop down from the equation of Maximum Stress Intensity (considering pressure as the primary load).

For Sustained Stress, the equation considers pressure terms which can include radial pressure stress (0,-P,-P,0) and can be the minimum principal stress S3.

Anyway, it's still a good idea to include in the output of the software the Maximum Stress Intensity (S1-S3). Normally, this is higher than the Code Stress, and I observed that the Max. SI is somewhat near to the Hoop Stress Value, which makes sense because S1 is a function of both hoop and longitudinal stress. This is a useful tool for the evaluation of fatigue and Creep.

Thanks,