Hi Piyush,
The METHODOLOGY described in the papers by LC Peng and described in B31.1 Appendix VII for modeling piping systems for analysis are GENERALLY applicable to underground piping within a plant. If the refinery is located in a jurisdiction that prescribes B31.3 as the applicable Code for design, fabrication, erection, examination and testing (and the owner chooses so) then the ASME B31.3 Process Piping rules will apply. I can see no conflicts in applying these methodologies to buries refinery piping.
There may be other issues (e.g., environmental issues) that will require other considerations in the design of underground piping systems. It would therefore be prudent to talk with your local environmental authorities regarding requirements for such things as double containment and leak detection. The corrosion protection of the piping may also be a consideration and you may need to look into cathodic protection and other methods of protecting piping against corrosion.
There are several books available that address all the aspects of the design of underground piping.
Regards, John.
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John Breen