Manual for Induction Motors and Generators
102 -
Trouble Shooting
3BFP 000 050 R0101 REV E
8.2.6 Use
Causes for bearing leakages, apart from being installation-related, some causes are 'use' related.
***Following paragraphs for bearing type: Sleeve bearing with flood lubrication
Oil pressure
The inlet oil pressure for each bearing is calculated according to the desired oil flow, and
therefore the oil pressure should be adjusted accordingly during commissioning.
The specific oil pressure value for each machine must be verified from the documentation
provided with the machine.
***Following paragraph for bearing type: Sleeve bearing with self lubrication
Oil level
The oil level of a self-lubricated sleeve bearing needs to be checked regularly, see
Oil temperature
The correct lubrication oil temperature is essential in keeping the bearing at the correct
operating temperature, in ensuring sufficient lubrication effect, and correct viscosity of the
lubrication oil, see
Chapter 7.5.2.1 Lubrication oil temperature
.
Vibrations
All machines are subjected to, and designed to withstand vibrations. Large vibrations might
cause the various parts in the bearing to function different as intended.
Heavy vibrations can cause different phenomena in the oil film between the shaft and the white
metal, but this will rather seldom lead to oil leakages, but to bearing failures.
Heavy vibrations can cause the bearing housing parts to set, or to 'loosen up' just enough to
allow the oil to enter the split surface between the upper and the lower bearing housing halves.
The vibrations will cause the bearing housing parts to move in respect of each other. This can
cause a 'pumping' effect in such a way, that oil will be pumped in and out from the split surface.
This will eventually remove the sealant, and cause the bearings to leak.
Air pressure inside bearing
The bearing housing is not a hermetic compartment, and therefore any overpressure inside the
bearing housing will escape the bearing housing via the labyrinth seals. In escaping, the air will
bring oil mist with it, thus causing the bearing to leak.
Overpressure inside the bearing is normally caused by other components than the bearing itself.
The most common reason for overpressure inside the bearing is overpressure in the oil return
piping.
Air pressure outside of bearing
Similar to overpressure inside the bearing, under pressure outside the bearing will 'suck' air out
from inside the bearing, thus bringing oil with it, and causing the bearing to leak oil.
