UG99(g):Except for leakage that might occur at temporary test closures for those openings intended for welded connections, leakage is not allowed at the time of the required visual inspection.Leakage from temporary seals shall be directed away so as to avoid masking leaks from other joints.

does the red lines means identical?

Fred,

This means a leaking temporary closure. For example a blanked nozzle flange, where the blank is not part of the vessel, but only installed for the hydrotest. If in this case the gasket is leaking during the test, it may be accepted. However, the water shall be lead away in order to be able to detect tightness of the flange and it*s welds.
DK

Thanks for reply, Dr. Koelbl, so the temporary seals include bolt-flange sealing with extra blind flange(blank),but, in my opinion, the leaking may be caused by the damage to the sealing face of nozzle flange,then is it acceptable if there is indeed this cause?

Fred,

The result of a damaged flange surface would be some cosmetic grinding, and the pressure test would not need to be repeated.
In my experience it is usually the gasket /O-Ring /sealing tape that is leaking.

If you are in doubt, or if welded repair is required, the test is not accepted, agree?

DK

absolutely, thanks!