Tarry drum is due to short run length.
The scenario is simultaneous power and steam failure which is a possibility and even though after recovery of power after an hour or so, steam recovery takes enough time.
Getting water into drum without steam stripping can be possible only after power recovery. But it is said that one should not get water into unconverted VR/ partially converted VR.
A more detailed description about my question could be that since due to short run length the materials inside drum would still be pitch like material. After power and steam failure, even though transfer line would be flushed by available steam header pressure, but as soon the steam pressure would fall down, the resid material from the drum would roll back into transfer line. Now if steam recovery takes enough time the resid material would plug/choke the transfer line completely and this scenario could be really dangerous and tedious to deal with.
How to mitigate from this kind of situation