PART- IX
PLACEMENT OF LP ROTOR
Measure journal diameter, spigot diameter and coupling hole
sizes.
Ensure centring of temporary bearing support in the LP front
pedestal for placement of LP
rotor.
Place LP rear bearing in position.
Prepare shaft seal compensator along with gaskets (Gasket to
be installed in fully ring shape
only) and position them on LP rotor with the help of supplied
supports of compensator.
Lift LP rotor with the supplied lifting beam in perfectly
level condition and place it in
position. During lowering of rotor ensure radial clearance
with the help of long feeler gauges
in the LP casing.
WELDING OF LP OUTER CASING
The welding of LP outer cover is to be carried out before
placement of LP Rotor in position
to avoid damage to the rotor.
Colour match and remove all high spots of the matching flange
of the LP outer casing.
Ensure good contact between parted diffuser of LP front and
LP rear cover.
Colour match and remove all the high spots of the parted
diffuser/vertical face to ensure
good contact with the compensator at a later stage.
Colour match and remove all burrs and high spots from parting
plane of LP outer casing.
Side flange of LP front and rear cover are to be ensured in
right angle to achieve good
contact with their matching flanges.
Place LP front LP rear cover along with parted diffuser and
ensure feeler tight joint after
tightening the parting plane bolts. The joint must be feeler
tight just after normal tightening
of bolts. Do not over tighten parting plane bolts.
Ensure matching of parted diffuser face on both side of LP
casing. If necessary colour
matching may be carried out to achieve a feeler tight joint.
Drill/ream all the parting plane holes as per drawings and
install all dowel pins.
After fixing of LP front and rear cover measure the dimension
for positioning of both the
centre flanges. The dimensions are to be recorded in such a
way that there is no clearance
after fitting of centre flanges in position on both side with
the LP front and rear cover. The
centre flanges are supplied in extra length on both sides
from the factory and final length
are to be maintained at site only.
Drill/ream dowel pin holes in centre flanges and install all
dowel pins in position. Ensure
drilling and reaming of all dowel pin holes to equal depth.
Fit both the centre pieces of the cover in position.
Achieve the fitting clearances for welding as per laid down
procedure.
Weld/lock LP upper half flange with respect to
lower half casing with the help of metal
cleats to
minimise the distortion during welding of LP cover. The cleats may be welded at
an
interval of
about one meter distance.
Carry out
the welding as per the following welding procedure.
Follow the
welding procedure and sequence of welding as suggested by manufacturer.
ALIGNMENT
AND COUPLING OF LP-IP & HP ROTOR
LP rotor is
to be aligned on pedestal seal bore and LP inner outer casing is to be
centralised
in such a
way that enough clearances are available to LP rotor, during alignment. Now
this
alignment
activity of all the three rotor can be divided as below :
-Preparation
of HP rotor for alignment.
-Preparation
of IP rotor for alignment.
-Preparation
of LP rotor for alignment.
-Alignment
of LP-IP & HP rotors.
-Reaming,
honing of the coupling holes.
-Balancing
of coupling bolts weight.
Alignment
preparation of individual rotor ( i.e HP,IP and LP) to be completed as per OEM
‘s
instruction
manual and this is not discussed here. I am going to the next step.
ALIGNMENT OF
HP, IP AND LP ROTORS
-Ensure
radial and axial run out of all the three rotors are individually in order. If
necessary
Individual
rotor module can be taken out for correction of coupling face run out. Any
Variation on
radial run out of rotor is to be referred to the factory.
-Match
coupling faces of two rotor as per the axial face reading of the rotor. Ensure
that the
higher point
of the rotor coupling face and lower point of another rotor coupling face are
matched
together. This is to be compared with shop protocol also.
-Preliminary
align (radial and axial) all the three rotors and shift them in spigot along
with
the casing to avoid fouling of rotor inside the
casing.
-During
alignment achieve left and right movement of the rotor with the help of shims
in
spherical /
torus piece of the bearing. The up and down movement of the rotor is to be
achieved
with the help of shims in the cylindrical/spherical support of the bearing .
The
adjustment
of shims in the bearing should be within the permissible limits only.
-Ensure
during alignment that the catenaries of the shaft are maintained.
-Check/record
spigot clearance of HP-IP and LP-IP rotors by actually moving them in spigot.
Install four
nos. supplied bolts along with one/two pins in HP-IP and LP-IP coupling. Hand
tighten the
coupling bolts by keeping a gap of > 1.00 mm in coupling faces for
alignment.
Rotate the
rotor system and record the coupling gap at 90 Deg. intervals on left, right
and
top
position. Ensure that the coupling, bolts and pins remain free while recording
the gap of
the coupling
for the alignment purposes.
-Check swing
check value of the HP rotor with alternate bolts in position. The above value
must be
within the prescribed limit only otherwise a correction must be carried out at
site in
consultation
with designer.
-Ensure free
movement of rotor on their bearing. Do not rotate the rotor if it is tight
during
its
rotation.
-Ensue that
the coupling holes are properly aligned to avoid unnecessary enlargement of
holes.
-Ensure
HP-IP-LP rotor radial run out after tightening with alternate clearance bolts.
Release
the
couplings for reaming / honing of couplings.
REAMING /
HONING OF COUPLING
Ensure that
there is no disturbance on coupling during reaming/honing operation.
First
ream/hone two opposite holes of the coupling and install two pins/bolts with
sliding fit
and then
take up all other holes.
Enlarge
coupling holes to the minimum possible diameter and try to make all the holes
to
same dia.
Ensure that
the finished holes are straight and there is no banana shape. This can be
ensured by
checking hole with a straight ground finish pin having 0.02/0.03 mm clearance.
Reaming
,Honing of coupling holes is an expert job for machinist and not the job of
erectors
. Therefore
it will be better to engage professional service to do this job.
BALANCING OF
COUPLING BOLTS
After
fitting the coupling bolts in all the holes these are to be balanced within +/-5
gms
accuracy and
an accurate balance which can take a load of about 20 kg. may be used. During
balancing of
coupling bolts following points are to be taken care.
Final
balancing of the coupling bolts are to be done along with the coupling nut of
individual
bolt.
If all the
coupling bolt hole sizes are same before/after reaming and honing then all the
bolts can be
kept of equal weight.
If necessary
adjust the weight of the bolts by machining the metal from the bolt head.
COLOUR
MATCHING OF THRUST BEARING
After
completion of reaming/honing and preliminary tightening of the coupling bolts,
the
colour
matching of the thrust bearing pad have to be carried out with respect to the
thrust
collar of
the HP Rotor. During colour matching a good contact on all the pads of front
and
rear side
are to be ensured with respect to rotor collar by moving the rotor in +/- direction
during its
hand rotation.
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