I'm not an expert and below is just what I know

Thermal expansion stress is a 'secondary stress', which is not a collapsing load. It means only single affect of thermal stress will not cause severe(or direct) damage to the system.

Because of self-limiting, your piping system can endure small local yielding or minor distortion caused by thermal displacement. Find stress range of secondary stress and see its behaviour, it does have pre-stresses/residual strsses you mentioned but it'll be ok until the stress reach two times of Sy(yield strength) of material.

Piping will be contracted to original position when the system cools down with small local yieldings or plastic strains.
Unless your pipe slide off the supports when it expanded, and after cool down it can't get its original position. It could cause serious problem.

If the calculating expansion is too excessive, add more loops or use springs(guess its on the field, so spring might not be usuable) to absorb expansion.


To get more detail, please refer this thread http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=230