Hi all,

As per ASME B31.3 code buried piping analysis shall be carried out? I dont find any topics regarding this in B31.3 code..

Horizontal loop can be considered in buried pipes?

Can anyone explain?

Please be more specific on "doubts" you have.
I interpret "I dont find any topics regarding this in B31.3 code" as you cannot find NONMANDATORY APPENDIX VII, PROCEDURES FOR THE DESIGN OF RESTRAINED UNDERGROUND PIPING.
For pipelines you can consider "Z" shaped loops that must be analyzed taking into consideration the pipeline-soil interaction and documented as passing Code requirements.

Sorry, I tried to mention B31.1 which has a Non-mandatory Appendix on this subject. Anyway, an underground piping would be required to be documented by calculation and the principles remain the same, regardless the Code. However, under normal circumstances in a plant aren't important underground pipelines under B31.3 jurisdiction.

Mariog,

Thanks for your Guidance.I am new to underground piping stress analysis.currently I am doing stress analysis of 12" (API 5L) CS pipe with oil service.

Followings are my doubts

1.How to decide Anchor block location in buried portion?
2.can we define support span in buried portion? if so how can we edit?

You can consider the old Schnackenberg's article "How to calculate stress in above/below ground transition". Fortunately, this reference article is included in Pipeline rules of thumb handbook.
The key parameter considered in article is "the longitudinal resistance of the soil that needs to be known".
In fact, Schnackenberg's model is a simple linear one, where the stress difference between "fully restrained" and "unrestrained" points (multiplied by pipeline metal sectional area) generates a tendency to "elongate" to the ends of pipeline (typically toward pig stations).
In case you decide to fight with that "elongation", you may consider an anchor block in front of pig station. In case you decide to accept that elongation, you would rather consider a "Z" shaped loop in that zone; the only "difficulty" is that the pipeline leg and nearby bends must be properly analyzed taking into consideration the pipeline-soil interaction.