Hi Aslam
WNC may have significant effect if there is spring in model otherwise I guess will not have much effect on piping stress.

For example if there is top pump discharge line ( long vertical length) & we introduce spring to reduce vertical operating/sustain weight on pump nozzle.
Now when that particular pump is in standby condition or plant is in shutdown condition (no fluid in vertical leg of piping) may produce unacceptable upward load at nozzle because spring may still be in active condition.

To accommodate tank settlement if spring is used WNC may again have some serious effect That's why sometime bellow is considered as preferred solution for settlement issue.

Regards

Habib