Maintenance Of Bearings; Dismantling Operations; Reassembly Operations - MarelliGenerators MJB 160 Instrucciones Y Advertencias De Seguridad

5.2 Maintenance of bearings

The lifetime of bearings is determined by multiple factors and specifically by:
The lifetime of the grease.
The environmental conditions and working temperature.
The external loads and vibrations.
The bearings (D.E. and N.D.E. side are prelubricated sealed type (life lubrication), with sufficient grease quantity for a long operating
time.
The life expected time is, in case of normal operating condition, of about 30.000 hours for all bearings.
In case of complete overhaul of genset, the bearing of the generator should be changed.

5.3 Dismantling operations

Before dismantling the machine, examine the views in cross-section.
Check that the lifting means available are suitable for the movement of all parts which have to be handled.
Check also that all the working conditions are suitable to operate without dangers for safety of personnel.
On disassembly, mark the components if believed necessary, in order to identify their correct positions during successive
assembly.
Then uncouple the generator from the prime mover, removing the bolts securing the flange and feet; remove the bolts fixing the
coupling and disconnect the terminals of the power leads on the terminal board.
Next, remove the generator from the prime mover.
Disconnect the leads whites (+) and (-) connecting the exciter stator to the voltage regulator, and take the clamps off.
For two bearing generators:
- Remove the half coupling from shaft extension and remove the key (223).
- Remove the bolts fixing the shields (4-5) to the frame.
- Then remove the shields having care to sustain the rotor in order it will not fall heavily on the stator.
- Using proper lifting means, remove the rotor (3) from the main stator, through the D.E. side, taking special care to avoid any
damage to the windings.
For single bearing generators:
- Remove the bolts fixing the N.D.E. shield to the frame.
- Remove the shields having care to sustain the rotor in order it will not fall heavily on the stator. The rotor can be extracted from
the stator, from D.E. side.
ATTENTION! It should be remembered that the exciter stator is fixed to the N.D.E. shield: special care should be taken to avoid any
damage to its windings when removing the N.D.E. shield; furthermore be sure the connections or the exciter stator are free to slide out
from terminal box.
If a bearing needs to be replaced, remove it with a suitable puller or on the inner cover of the bearing (where present).

5.4 Reassembly operations

Carry out the operations described above for dismantling in reverse order.
- Place the pre-loading spring into on the N.D.E. shield and fixing it by some grease.
- The fixing screws have to be fixed with LOCTITE type 243 (on the threaded surface).
- If a bearing was removed, always install a new one.
- To make assembly easier, the bearings should be heated to about 80 - 90° C.
ATTENTION!: Bearings should be assembled with the utmost care in order not to damage them.
If a locking element has to be replaced, make sure that the new one is of the same type and same resistance class of the original.
The following table indicates the tightening torques valid for locking screws and nuts:
Fixing of electrical connections
Fixing of screws in low strength material components
(aluminium).
Fixing of components (shields, bearing caps, etc).
Fixing of feet or flange.
Assembly of discs is carried out directly on the shaft-end
(on MJB 160 only)
SIN.UM.017.11
Tightening torques in Nm
Application Thread diameter
M 6 M 8 M10
(cl.8.8)
10 22
5 12
11 26 48
/ /
26
ENGLISH
M10 M12
(cl.12.9)
/ / /
/ / /
/ 85
/ 75 /