My case is this:
Piping is fabricated at 21^C, After installation, the piping experienced a temperature of 85^C due to hot climate,during operation the piping is subjected to -90^C.
My argument is this:
The piping will experience both expansion & contraction. Is it correct to calculate the expansion stress range from 85^C to -90^C and compare it to the code allowable ?
What I believe right now is that it should not be, because the piping will go back to the undeflected position;i.e at 21^C, before it contracts. Pls correct me if I am wrong.

Regards,
delpilar