5.2 AIR GAP CHECK
5.2.1 General points
The air gap measurement is not always possible because
of a lack of access. When the air gap can be reached the
measure can be distorted because of paint and resin
coating on the checked surfaces.
Measure the air gap at different points (minimum four
different points spaced of 90°).
Calculate an averaged value (sum of the measures divided
by the number of measures)
Compare the averaged value to each measure
Main field air gap accuracy :
Air gap
(mm)
Acceptable Offset (mm)
20% offset up to an air gap
of 3mm
15% offset for an air gap
from of 4 up to 12mm
10% offset for an air gap
above 18mm
Eg : for a nominal air gap of 3 mm an air gap measured
value of 2.4 mm is acceptable
Eg : for a nominal air gap of 10 mm an air gap measured
value of 8.5 mm is acceptable
Exciter air gap accuracy :
50% of the nominal value (eg: for an a nominal air gap of
3mm a read value of 1.5 mm is acceptable)
Permanent Magnet Generator (optional) air gap accuracy:
50% of the nominal value (eg: for an a nominal air gap of
1mm a read value of 0.5 mm is acceptable)
5.2.2 Double bearing machine
Verification of the air gap is not necessary. The rotor is
mechanically centered by its construction. Even after
dismantling and reassembling the machine, the rotor will
return to its position without verification of the air gap.
The exciter air gap of generators type A60 and A62 can be
adjusted on site by 2 jacking screws.
5.3 ANTI FRICTION-BEARINGS
5.3.1 General points
NOTE:
Few international studies report that more than 80% of
the anti friction bearing installed worldwide for any
duty are prematurely damaged because of lubrication
trouble.
To preserve your machine we recommend to closely
fulfill the recommendations of this manual.
They must be lubricated regularly with the same type of
grease as used in the factory. For information concerning
the lubrication quantity and interval, refer to Section 1:
"Characteristics and Performance".
CAUTION:
LUBRICATION MUST BE CARRIED OUT AS PER
SECTION 1 OR AT LEAST EVERY 6 MONTHS
WHICHEVER COME FIRST
NOTE:
After a regreasing the bearing temperature may
increase of 10 to 20°C
This temporary temperature increase may stay few
tens of hours
NOTE:
In case of a "stand by" duty or generator with short
operation cycles it is recommended to run the machine
during at least 3 hours after each regreasing
NOTE:
For re greasing period lower than 2000 hours we
recommend to install a continuous greasing system to
limit the maintenance operators visit
These type of system must be disable during machine
stop
The grease contained in these systems must not be
stored over a period of 1 year
5.3.2 Cleaning bearings from old grease
This note is applicable when the type of grease is changed.
Dismantle the machine in order to get to the bearing
Remove the old grease with a palette knife.
Clean the lubricator and the grease removal tube.
For greater cleaning efficiency, use a brush with solvent.
NOTE:
Used solvent must be in accordance with local
regulation and environmental standard.
Electric Power Generation
Installation and maintenance
5654
en - 2017.
10
/
a
LSA 5
2
.2
MHV
Industrial Range Alternators
- 4 pole
24
