Hello Pad75,
Piping flexibility and stress analyses are performed in accordance with the appropriate piping Code. The ANSI/ASME Codes for Pressure Piping, B31, require the cold modulus of elasticity (Young's modulus) to be used in the stress calculations. These pipe stress analyses MUST NOT include design cold spring. These calculations will result in slightly conservative predictions of elastic stresses. It is common in the industry to model the points of attachment to terminal equipment as "rigid" for the piping analyses. This will be conservative for static thermal stress analysis.
After the analyst is confident that the Code requirements for limits on pipe stresses have been satisfied, other issues can be addresses. If spring hangers are to be chosen the analyses models can be used to pick the hanger types. Also, it would be appropriate to calculate the forces and moments (loadings) that the piping will transfer to terminal (sometimes strain sensitive) equipment (e.g., pressure vessels, fin-tube coolers or rotating equipment such as turbines, pumps, turbo expanders, etc. It would be appropriate to use the modulus of elasticity "at temperature" for these analyses. It would also be appropriate to include any (truly creditable) local flexibilities of the terminal equipment in these analyses. If the piping engineer has specified cold spring, it would be included in these analyses (two analyses would be needed as the loadings should be evaluated with the system cold with cold spring, and hot with cold spring). You must be very careful to be sure not to use the pipe stresses calculated by the computer software by these (at temperature, with flexibilities) analyses because they are invalid.
I hope that this addresses your question.
Best regards, John.
