For equipment to be designed at a temperature such that the allowable stress values are obtained from time-dependant properties, do I have to perform tensile stress at the design temperature?
If it's so, where can I find a reference in the Code, that clearly requires mechanical test at design temperature?

Cristiana, You will likely get more answers if this question is reposted in one of the "design" related forums, such as for ASME Section VIII Division 1 or Division 2.

Tom, was a good idea. I copied the topic to VIII Div1

DK