Hi John,
All your assuptions are correct!
I have already discussed this matter with the process engineer and know the cause and source of the fire but dont agree with some of his assumptions relating to the flex (fire)temperature distribution in the piping system, however I have to accept his figures.
The fire is expected to be localised at a vessel and heats up the contents of the piping all down the pipe rack. We have springs in this system but away from the source of the fire, and yes, I have already considered the spring over travel due to the flex temp.
All cases have been considered, but only by considering the flex temperature (350C) as the maximum operating temperature. I am still not convinced that I should analyse the system to the lower temperature which is the process design temperature of 235C.
Now, I am coming back to my original question, do I ignore the flex temperature?
I am beginning to feel as if I am flogging a dead horse here.
Incidentally for what its worth, this is not the first time I have come across a fire case in the line list, its quite common in front end engineering, perhaps due to a greater involvement of the HSE.

Regards
A