acceptable as a vac test before every run.
which is entirely different from “commissioning” (or recommissioning as in OP’s use case). @Voidx is on point.
(also) testing vac while in a dry ice slurry is advised as well. I’ve had multiple systems that would pull atmosphere into the solvent tanks when they got cold. Tuffsteel gaskets solved that for our robot-with-a-bomb.