ABB AMA Series Manual page 120

Manual for Induction Motors and Generators
Figure 8-1 Verification of air pressure inside and outside of a sleeve bearing
If a large under pressure is found to be inside the machine, e.g. between the end shield and the
machine seal, the situation is tricky; it is normally very difficult to remove the machine seal, and
to re-seal it.
NOTE: In no case should a breather be installed to remedy under pressure in the bearing, as it
will only make the leakage worse.
3BFP 000 050 R0101 REV E Trouble Shooting - 105