Ramesh,
If the corrected hydrotest pressure for the shell side is lower than the design pressure of the tube side then a PSV would be required considering a tube rupture case for the shell-and-tube exchanger.
Corrected hydrotest pressure is defined as follows:
Pcorrected = Phydrotest x (σscenario / σhydrotest)
Where:
Pcorrected = Corrected hydrotest pressure, kPag
Phydrotest = Hydrotest pressure, kPag (Current ASME Code for pressure vessels defines as 1.3*MAWP)
σscenario= Material stress at the overpressure scenario temperature, MPa
σhydrotest = Material stress at the hydrotest temperature, MPa
Hope this helps.
Regards,
Ankur.