Hydro-test pressure and holding times vary for different design codes. For example, the ASME SEC VIII Div.1 general hydro-test pressure will be1.3 x design pressure (minor factors may vary for this equation as well) and for piping design codes, the hydro-test pressure will be ASME B31.4,B31.8 1.5 xdesign pressure.
Bellows of an expansion joint going through a hydro-test pressure.