Removal And Replacement Of Components And Component Assemblies; Replacing The Bearings; Removal Of The Main Rotor; Removal Of The Rectifi Er Diodes - Sincro SK225 SM 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 signifi cant, 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 fi tting 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 fi tting
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.
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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 rectifi er diodes of the SK225 series
unscrew the screw at the centre. For the SK250
unscrew 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.