Second Stage Buckets The second stage buckets on the
frame 7F suffer from a similar problem as the 7EA
buckets. In both engines, the shrouds lift due to the cen-
trifugal forces acting on them, resulting in misalignment
of the Z notch contact faces. The repair developed for this
type of damage involves applying material by the LPM
process to realign the contact faces and restoring the
contacts surfaces by hard face welding (Figure 12e48).
During this repair, it is possible to realign the shroud to
lower the stresses and reduce the tendency for future
shroud lift.
FIGURE 12e46 Cracking and oxidation damage at the tip of a frame 7F
first stage bucket. (Source: Liburdi Engineering.)
FIGURE 12e47 Weld repair of tip damage on a frame 7F first stage
bucket. (Source: Liburdi Engineering.)
Chapter | 12 Maintenance, Repair, and Overhaul 727
The typical workscope for repair of these buckets would
include:
l Incoming inspection
l Strip coating
l Fluorescent penetrant inspection
l LPM reinforcement
l Weld hard facing
l Rejuvenation heat treatment
l Finish to contour
l Reapply coating
l Final inspections
Nozzles While the geometry of the nozzles in the frame
7F turbine are different than those in the EA model, the
materials and construction and general features are very
similar. The repair of these components, therefore, is
similar to that described for the 7EA components described
above. The differences in geometry, of course, require
different tooling (Figure 12e49).
The typical workscope for repair of 7F nozzles
includes:
l Incoming inspection
l Remove cooling inserts
l Strip coatings
l Fluorescent penetrant inspection
l Welded and LPM repair
l Finish to contour
l Rejuvenation heat treatment
l Coating
l Final inspection
Second Stage Buckets The second stage buckets on theframe 7F suffer from a similar problem as the 7EAbuckets. In both engines, the shrouds lift due to the cen-trifugal forces acting on them, resulting in misalignmentof the Z notch contact faces. The repair developed for thistype of damage involves applying material by the LPMprocess to realign the contact faces and restoring thecontacts surfaces by hard face welding (Figure 12e48).During this repair, it is possible to realign the shroud tolower the stresses and reduce the tendency for futureshroud lift.FIGURE 12e46 Cracking and oxidation damage at the tip of a frame 7Ffirst stage bucket. (Source: Liburdi Engineering.)FIGURE 12e47 Weld repair of tip damage on a frame 7F first stagebucket. (Source: Liburdi Engineering.)Chapter | 12 Maintenance, Repair, and Overhaul 727The typical workscope for repair of these buckets wouldinclude:l Incoming inspectionl Strip coatingl Fluorescent penetrant inspectionl LPM reinforcementl Weld hard facingl Rejuvenation heat treatmentl Finish to contourl Reapply coatingl Final inspectionsNozzles While the geometry of the nozzles in the frame7F turbine are different than those in the EA model, thematerials and construction and general features are verysimilar. The repair of these components, therefore, issimilar to that described for the 7EA components describedabove. The differences in geometry, of course, requiredifferent tooling (Figure 12e49).The typical workscope for repair of 7F nozzlesincludes:l Incoming inspectionl Remove cooling insertsl Strip coatingsl Fluorescent penetrant inspectionl Welded and LPM repairl Finish to contourl Rejuvenation heat treatmentl Coatingl Final inspection
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