Removal And Replacement Of Components And Component Assemblies; Replacing The Bearings; Removal Of The Main Rotor; Removal Of The Rectifier Diodes - Sincro SK225 Serie Manuel D'utilisation Et De Maintenance

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 Replacing the bearings

Removal of the NDE bearing
• Turn the rotor in position that that one pole is touching
the stator;
• Remove the cover grille present on the shield rear of the
generator;
• 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 4 screws that fasten the end-shield to the
housing;
• Apply simultaneously two screws (M6 for SK225 series,
M10 for SK250 series, at least 75mm long) on the two
threads (M6 for SK225 series, M10 for SK250 series)
placed on the shield, and slowly start to remove the end-
shield from the bearing.
• Pay particular attention when the bearing is almost
completely out of seat on 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 DE 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 that one pole is touching
the stator;
• 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 of regreasable bearing, follow the
procedure as described above, taking into
account to place back additional mechanical
parts used for bearing lubrication in the same
IMPORTANT!
position like they were prior to dismounting.
Apply the quantity and type of grease as
indicated on the generator nameplate.
26

7.2.2 Removal of the main rotor

• Turn the rotor in position that the poles centerline is in
vertical position;
• Dismount the shields (NDE and DE) from the generators
as previously described;
• 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.
Reassembly
Reassembly of the rotor should be made in reverse order
of the operation described above taking in the account the
following cautions:
• in case that any part of the rotor have been changed, the
complete rotor must be re-balanced;
• in case of single bearing alternators, check if the coupling
discs are damaged.
It's important that the rotor is additionally
supported by crane since, once the rotor is
out of the stator core, it may slip and cause
damage to persons or materials.
IMPORTANT!

7.2.4 Removal of the rectifier diodes

• Remove generator end-shield cover;
• unscrew the 4 screws that fasten the NDE-shield to the
housing;
• apply simultaneously two screws (M6 for SK225 series,
M10 for SK250 series, at least 75mm long) on the two
threads (M6 for SK225 series, M10 for SK250 series)
placed on the shield, and slowly start to remove the end-
shield from the bearing. This process should be applied
until the end-shield comes out max. 20mm. In this position
there is enough space to change the rotating bridge.
• Pay special attention not to drive the end-shield too
much to avoid to slips from bearing since in that moment
becomes free and could be damaged or even cause the
injuries to persons.
• As a precaution, using the lifting bolt on the top of the
end-shield, secure the end-shield before starting of this
process;
• unscrew the 3 + 2 screws that hold the diode leads
together with rotor exciter leads;
• to remove the rectifier diodes of the SK225 series
unscrew the screw at the centre. For the SK250
the 2 screws on the sides of the diode bridge.
Reassembly
Reassembly of the rectifier diodes should be made in reverse
order.
NOTE: The procedure of the replacing the rectifier diodes
can be also made in a way that the complete end-shield is
removed. In this case follow the procedure as it's described
in the NDE bearing replacement and after the end-shield has
been removed, follow the procedure of changing the diodes
plates out as it is described above.
unscrew