Control Of Bearings; Removal And Replacement Of Components And Component Assemblies; Removal And Re-Assembly Of The Pmg; Replacing The Bearings - Sincro SK315 Serie Manual De Uso Y Mantenimiento

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 stresses that will reduce its
lifespan.
IMPORTANT!
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;
• disconnect Exc+ and Exc- leads from the AVR (red
28
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 mechanical parts used for
IMPORTANT!
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.