Stress Indices are used to evaluate peak stresses, which are used for fatigue evaluation. If the equipment is not in cyclic service, then stress indices neednot be included.
If you refer to WRC output, you can have Pm and Pm+Pl and Pm+PL+Q+F. Pm is the stress due to internal pressure, and pm+Pl gives the local membrane stress.
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Regards,
Kunal Shah
New Delhi