In the following blade removal and replace-
thickness along its entire length, except areas
ment procedures, read the numbered steps while
repaired by blending. Stress rupture cracks or
referring to figure 10-14.
deformation of the leading edge are often
mistaken for foreign material impingement
NOTE: Before removing any blades,
damage. When any stress rupture cracks or
match mark all blades and baffles. Install
deformation of the leading edge of the first-stage
the original or its proper replacement in the
turbine blades is found, suspect an overtempera-
original position.
ture condition. Check the individual blades for
stretch, and the turbine disc for hardness and
Steps 1 through 3 refer to figure 10-14, view A.
stretch.
1. Locate and mark damaged blade.
NOTE: Install blades removed for detail
2. Straighten locking strip tab of damaged
inspection or for check of disc stretch in
blade.
the same slots from which they were
3. Straighten locking strip tab of two
removed. Number the blades before
adjacent blades.
removal.
Steps 4 through 6 refer to figure 10-14, view B.
Inspect the turbine blade outer shroud for air
4. Slide leading blade, baffle, and trailing
seal wear. If you find evidence of shroud wear,
blade from slot; weigh damaged blade.
measure the thickness of the shroud at the worn
5. Remove remaining loose blades from
area. Use a micrometer (or another suitable
slots.
measuring device) to be sure of a good reading
6. Remove and discard locking strips. Do
in the bottom of the narrow wear groove. If the
not reuse locking strips.
remaining radial thickness of the shroud is less
than specified in the appropriate technical
Steps 7 through 9 refer to figure 10-14, view C.
manual, replace the stretched blade.
7. Place new locking strip in blade dots.
8. Position baffles and trailing and leading
Turbine Blade Replacement
blades into slot.
9. Slide leading blade, baffle, and trailing
There are two categories of moment-balance-
blade into the last two serration.
weight classifications for turbine blades in axial-
flow engines. These are individually classified
Figure 10-14, view D, is a hydraulic tab bender
blades and sets (two or three) of matched blades.
and consists of a hydraulic foot pump and
The first category includes individual blades with
adjust able tab-bending adapter.
permanently marked moment-balance-weight
classifications. The second category includes sets
Step 10 refers to figure 10-14, view E.
of blades with the same classifications and
temporary markings.
10. Prebend locking strip tabs using special
tool provided or a common screwdriver. Set
NOTE: Never mix blades. Classification of
adjusted tab bender onto tab to be bent. Apply
the two categories does not follow the same
hydraulic pressure with foot pedal until tab is set.
schedule. Always refer to the Turbine
Remove tab bender and check clearance, as shown
Rotor Disc Assembly Service Record to
in figure 10-14, view F.
determine which category applies.
Turbine Stator Vanes
If visual inspection of the turbine assembly
The inspection of turbine vanes is accom-
shows that blade replacement is necessary, use the
plished in the same manner as described in the
following example procedures as a guide. Replace
previous section for the compressor vanes.
any number of blades through 100 percent in the
Damage may be greater as turbine vanes
turbine rotor. Replacement is permissible if the
experience extremely high heat. Blend minor nicks
pan weight of the replacement is within 1 gram
and dents with fine stones or emery cloth. Visually
of the old blade.
10-16
