Thanks Mr.Samsul for the reference,but i am confused to co-relate the importance of Sustained case with the occasional case.
Please clarify if i am right with the below understanding.
1)As per the ASME.B31.3(2004),says the sum of Longitudinal stresses(SL)& the stresses produced by occasional case may be 1.33times the basic allowables for the particular material.
Can i above co-relate to my understanding that if the system is passing in sustained case for piping lift-off check then there is no need to check for occasional stress(in piping lift-off check) as the ocassional stresses are 1.33 times the basic allowables.
2)If my stresses while Piping lift case in sustained case is passing then there is no need to check the occasional stresses in Piping lift-off case as the sustained case(force driven) remains constant even after the thermal growth(displacement driven) during the life of the piping system and hence we can assume that the scalar summation of occasional case(difference between W+P+T-W+P+T+OCC.CASE(WIND OR SEISMIC)=pure wind & Pure seismic) & sustained case will be safe.

Please clarify if i am wrong or any alternate explanation so that i can understand thoroughly.

Regards.