Hi

I would like to know if it is necessary to check the occasional cases such as earthquake or wind while we are checking the "lift up" condition of our piping system.

regards

Hi Pooria

In my opinion if some support lift in occasional case for that reason no need to go for stress check again (lift off case).
Like if we check operating stress according to B 31.3 appendix P there is no need for additional lift off stress checking.
Pure occasional effect in piping is ( (ope+wind)-ope)) hence it already take care of pipe lift off.