Take particular care in selecting a cleaning method to ensure that
anodizing or dichromating is not removed from the surfaces. Do not
use caustics on aluminum, magnesium, ceramiccoated, aluminized,
painted, nitrated, or carbonized parts. In most cases the engine
manual prescribes the approved cleaning procedure to be used. Most
engine parts may be cleaned by using the following methods.
a. Vapor degreasing. Used only on unpainted metal parts or
aluminumpainted steel parts, vapor degreasing using heated
trichloroethylene, type II, or perchloroethylene, specification No.
OT634, removes oil, grease, and sludge. The hot vapor condenses on
metal surfaces, liquefies, and carries away the oil, grease, and
sludge. Parts may be flushed while held in the vapor. To prevent
corrosion, the parts should not be removed from solvent vapors until
they have reached the temperature of the vapor.
b. Solvent immersion. In another cleaning method, the parts
are immersed in Carbon Removing Compound MILC19853, to remove
carbon, gum, grease, and other surface contaminants. This method is
used on steel and stainless steel parts. Parts with painted finishes
should not be cleaned by this method, because the carbon cleaning
compound attacks the paint.
c. Vapor blasting. An abrasive method used to clean
combustor parts, vapor blasting must not be used on ceramic,
magnesium, painted, or aluminum surfaces. Be sure that metal is not
removed during cleaning and that cooling slots, holes, ridges, and
overlap areas do not become clogged with blasting grit.
d. Drycleaning solvent. All metal parts may be cleaned with
drycleaning solvent, PD680 Type I. This method is suitable for
removing heavy oil and grease deposits from most parts, including
flexible hoses and carbon seals. Drycleaning solvent leaves an oily
film that protects steel parts from corrosion for a short time.
3.10.
CLEANING COMPRESSOR ROTOR BLADES
When a particular engine's performance decreases to or below
the point specified in the applicable TM, and the EGT increases
steadily during normal operation, the compressor rotor blades need
cleaning. Compressor rotor blades should also be cleaned whenever
the engine has been operating in areas where the air is salt laden,
or when the engine has been subjected to contamination with fire
extinguishing agent residue (chlorobromomethane and soda ash).
Cleaning can be accomplished while the engine is installed in the
aircraft.
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