Manual for Induction Motors and Generators
Trouble Shooting -
103
3BFP 000 050 R0101 REV E
Under pressure inside the bearing is normally not caused by the bearing itself, but by parts
outside the bearing.
Under pressure near the bearing housing is caused by rotational parts moving the air next to
them in such a way that a local under pressure is formed next to the exit of the shaft of the
bearing.
8.2.7 Use verification
Oil
The oil quality must be verified.
***Following paragraphs for bearing type: Sleeve bearing with flood lubrication
The inlet pressure of the oil must be verified and adjusted accordingly.
The normal value for the oil pressure is 125 kPa ± 25 kPa (1.25 bar ± 0.25 bar), but the specific
oil pressure value for each machine must be verified from the documentation provided with the
machine.
***Following paragraphs for bearing type: Sleeve bearing with self lubrication
The oil level in the bearing must be verified.
The temperature of the oil must be verified. A too high temperature will cause the viscosity of
the oil to diminish, thus making it easier to escape from the bearing.
NOTE: Bearings with only one Pt-100 temperature detector normally detect the temperature of
the bearing, not the oil. The temperature of the oil is approximately 10°C (20°F) lower
than the bearing temperature.
***Following paragraph for bearing type: Sleeve bearing with flood lubrication
The normal oil inlet temperature is in the range of 65°C to 75°C (150°F - 170°F), but must be
verified from the documentation provided with the machine.
Vibrations
Vibration readings of the bearing housings should be taken in three directions: axial, transversal
(horizontal) and vertical, see
.
Air pressure inside the bearing
The air pressures inside and outside the bearings should be verified.
Overpressure is, as stated above, normally caused by overpressures in the oil tank. The
overpressure from the oil tank is then transmitted to the bearing via the oil return piping.
The best way to measure the pressure inside a bearing, is from the oil fill entrance or the
inspection glass on top of the bearing.
In case overpressure inside the bearing is found, the following measures should be taken in the
following order:
•
Mount breather in the oil tank if possible. This is not suitable for diesel engine crankcases
•
Make sure the oil return pipe enters the oil tank below the oil level. This is essential for
diesel engine crankcases
