Hydro test pressure should be calculated as follow:
1) Hydro test pressure = 1.5 Times of Design Pressure.
2) For a design temperature above the test temperature, minimum test pressure can be calculated as:
Pt = (1.5 X P X St) / S
Where:-
P: Internal design pressure.
Pt: Minimum Test Pressure.
S: Allowable stress as design temperature.
St: Allowable stress at test temperature.