Control Of Bearings; Removal And Replacement Of Components And Component Assemblies; Removal And Re-Assembly Of The Pmg; Replacing The Bearings - Sincro SK315 Série Manuel D'utilisation Et De Maintenance

7.1.4 Control of bearings

During maintenance control the condition of the bearings
and check that no grease has leaked; the lifespan of the
bearings depends on the vibrations and axial strains they
undergo (vibrations can increase considerably with a bad
alignment) and on the working conditions. So check for
any unusual signs: vibrations, unusual noises, clogged air
vents.
If undue vibrations or noises appear after long-term usage,
these could be due to a worn bearing that, if damaged, has
to be replaced
The bearing should always be replaced after 20.000
working hours.
In case of regreaseable bearing, check nameplate for
regreasing period and grass type/quantity.
A bearings lifespan is closely linked to the
working conditions and environment.
IMPORTANT!
Long periods of sustained vibrations can
damage the bearing balls and their seat.
Too high humidity can emulsify the grease
and encourage corrosion.
IMPORTANT!
Intense vibrations caused by the engine
bad alignment of the components in the
generating set put the bearing under
IMPORTANT! stresses that will reduce its lifespan.
7.2 Removal and replacement of components
and component assemblies
The screws tightening torques for all reassembling
procedures are reported in the table of paragraph
6.2.3.

7.2.1 Removal and re-assembly of the PMG

• Remove generator end-shield cover;
• disconnect the electrical connector of the PMG;
• unscrew the four screws that hold the PMG housing on
generator end-shield;
• pull the housing out of the rotor (take care due to the
strong magnetic force that can attract the stator and
cause damage of the stator windings or even cause
operator injury);
• unscrew the three screws that holds PMG rotor to the
main generator shaft and carefully take the rotor out
from the shaft-end.
Reassembly
For reassembling the PMG repeat the above procedure in
reverse. Take care that before assembling the stator PMG,
the rotor PMG is cleaned of metal particles.

7.2.2 Replacing the bearings

Removal of the NDE bearing
• Turn the rotor in position that the poles centerline is in
vertical position;
• remove generator end-shield cover;
• in case of generator equipped with PMG, follow the
procedure as described in 7.2.1;
28
• disconnect Exc+ and Exc- leads from the AVR (red and
black wire) and pull them back out of connection box to
the stator exciter;
• before removing the end-shield, using the lifting bolt on
the top of the end-shield, secure the end-shield from
uncontrolled movements once it will be removed;
• unscrew the 8 (6 on SK315/355 series) screws that
fasten the end-shield to the housing;
• apply simultaneously two screws M12 (at least 75mm
long) on the two threads M12 placed on the opposite
sides of the end-shield, and slowly start to remove the
end-shield from the bearing. Be careful when the bearing
is almost out of the bearing seat of the shield;
• since the weight of the end-shield together with stator
exciter is significant, special care should be taken
during this process to avoid any damage to persons or
materials;
• remove the wave-washer (if present) and circlip;
• remove the bearing using a standard extractor.
Removal of the NDE bearing
• In case that the generator is coupled with drive engine,
to perform following procedure it's necessary to remove
it completely from engine;
• turn the rotor in position that the poles centerline is in
vertical position;
remove the protection grid from the generator DE-shield;
•
• before removing the DE-shield, using the lifting bolt on the
top, to secure the DE-shield from uncontrolled movements
when it will be removed;
• unscrew the screws that fasten the end-shield to the
housing;
• force the end-shield out of the bearing;
• remove the bearing using a standard extractor.
Reassembly of bearings
Reassembly of the bearing should be made in reverse order
of the operation described above taking in the account the
following cautions:
• before fitting the bearing, ensure that the coupling
surfaces both on the bearing and shaft has no signs of
wear;
• heat the bearing to approximately 80° C before fitting it
onto the shaft.
In case that regreasable bearing are used,
follow the procedure as described above,
taking into account to place back additional
IMPORTANT! mechanical parts used for bearing lubrication
in the same position like they were prior to
dismounting. Also apply the quantity and
type of grease as indicated on the generator
nameplate.

7.2.3 Removal of the main rotor

• Turn the rotor in position that the poles centerline is in
vertical position;
• based on the above parts of instructions, dismount the
PMG, shields (NDE and DE) from the generators;
• using appropriately sized belt, support the DE side with it
and carefully start with tracking the rotor out of the stator.
As rotor come out of the stator, change the position of the
belt till the moment when it's approximately on the gravity
center of the rotor. During this process, it's necessary
to support the NDE end of the rotor to guide the rotor
precisely out of the stator to avoid any damages of the
stator or the rotor winding.