Respected Chuck Becht sir,John Breen sir,Anindya sir,
My query is about Consideration of Hoop stress in Expansion stress but not in sustained stress...
As per B31.3 ,Sustained Longitudinal stress to be compared with Sh....so it is clear that as per code Hoop and radial not to be included in Sustained stress because it is stating"Longitudinal".
and
for Expansion Stress Hoop stress is considered.

please share your opinion in this matter...Why Sustained stresses computation skipped Hoop and Radial stresses..

and Why Hoop stress is considered in computation of Expansion stresses.

Thanks in advance.

Does expansion stress calculated with hoop stress? I guess not.
For B31 piping code, thickness will cover the hoop stress...

this link will might help you

http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=230

Anybody on this forum..
Kindly add your opinion..

A guess? The sustained stress state is easier to calculate by hand and was the first check to the system. If you had a sufficiently low sustained stress case, you had a much better chance at receiving a full-blown passing stress design.

Even the (B31.3) expansion stress equation does not consider hoop stress. The expansion stress (which is a stress range not an actual stress) is determined from bending and torsion stresses only.