When it becomes necessary to use wind and seismic values in the load cases? Is it the stress analyst's discretion or certain conditions that require their use.

Yes, it is necessary based on the site condition.

Say if ur site falls under seismeic free zone no need to analysize earthquake LC. Also if ur pipe is inside building no need to consider wind/Snow load cases.

However if pipe exist outside building obviously wind/snow could act on it based on the site condition. Irrespecive of inside or outside when site is likely to have earthquake, pipes will suffer the same.

Like wise, suitably pipe needs to be analysized for all these LC considering the site condition.

Dear Shancert,

Please tell me why we no need to consider wind or snow load inside the building? I think we are only igorne about seismic.

Thanks.

Wind load depends on the piping elevation in which wind pressure vary according to the elevation. Siesmic should be consider whether it is inside in the building or not but wind and snow, I don't think so. Think about it. Read and understand the piping stress analysis specification.