Oh, I may finally get what you mean,
you may mean . ajust the fluid density to zero,
meanwhile set the HP pressure to zero,

then Load case:
L3:WW+HP(HYD)
L4:W+HP(HYD) ---- HP in some part is zero
if you want to see the stress and restaints in the portion which do not need hydro test.
,you see L4.

right?