TURBINE SECTION REPAIRS
exceed 3 inches in length. Repair cracks more than
3 inches long and exceeding 75 percent of the
Inspect turbine sections and components
entire circumference of the duct by gas fusion
thoroughly because of the extreme heat en-
welding. When repairing a duct, use a silicone
countered in this section. Turbine sections can
carbide grinding wheel. Grind a 90-degree "V"
groove, 0.035-inch deep, for the entire length of
be replaced in whole or in part. The turbine rotor
is usually repaired by changing individual blades
the crack. It is permissible to remove some of the
or an individual rotor. It is not feasible to describe
parent material when grinding. Adequate depth
all of the damage conditions that may be found
is necessary to be sure that the grinder removes
in the turbine. If the damage is within prescribed
all material from the crack. Repairs must not
limits, but there is doubt about the rework, you
result in distortion or misfit of the parts at
should replace the turbine rotor or part.
assembly. File out any distorted hole, as a result
Some first-stage turbine blades are coated with
of welding, to restore it to the original configura-
a protective coating to prevent sulfidation. Alpak
tion. See figure 10-10 for an example of inner and
is normally used for coating these blades. Without
outer ducts repair limits.
Figure 10-10.-Combustion chamber inner and outer duct.