or temporary. Permanent markings are those
petroleum solvent. Change the rinse water
markings that remain during the entire service
frequently to prevent a buildup of acid or alkaline
life of the part. They are applied during man-
in the water. Air-dry the engine parts, and then
ufacturing or after modification of parts.
coat them with a corrosion preventive if they are
Temporary markings maintain identification of
not to be processed further.
parts or reference positions during ordinary
handling, storage, and final assembly. Temporary
Decarbonizing loosens most hard carbon
markings ensure parts may be returned to original
deposits remaining after decreasing. The complete
assembly position. If a part is going to be cleaned,
removal of all hard carbon deposits generally
inspected, and repaired, temporary markings will
requires brushing, scraping, or grit blasting. Use
probably be removed by solvents during cleaning.
caution during these procedures to avoid
If part identification needs to be maintained,
damaging parts. In particular, do not use wire
attach tags or place parts in separate containers.
brushes or metal scrappers on machine surfaces
or bearings.
Temporary Markings
Abrasive Blasting
Certain materials must be used for temporary
marking during assembly and disassembly. Use
Use abrasive blasting to remove hard carbon
only approved pure dye markers to mark engine
or lead deposits, rust, and heat scale. The
hardware. Using nonapproved markers can leave
type (wet or dry) and size of abrasives vary
harmful elements on engine parts. You may
for different engine parts. Mask all openings,
use layout dye (lightly applied) to mark parts
identification markings, and other areas as
that are directly exposed to the engine gas path.
required before blasting. Grit materials such
Some exposed items are the turbine blades
as ground corn, apricot or peach pits, walnut
shells, clover seed, and cracked wheat or rice are
and disc, turbine vanes, and combustion chamber
liners.
in general use.,
NOTE: Do NOT use any temporary
Dry grit blasting is sometimes done in a sand-
marking method that leaves a heavy carbon
blast cabinet. The part must first be degreased or
deposit. Do NOT use any marking that
put through a decarbonizing solution, and then
leaves a deposit of copper, zinc, lead, or
rinsed and dried thoroughly. After grit blasting,
similar residue, such as pencil or black
remove the dust by air blasting, and clean with
grease pen. These deposits may cause
petroleum solvent or hot water. Some types
carbonization or intergranular attack when
of soft grit leave a light grease film on the
the part gets very hot. Parts marked with
part. Remove this film by decreasing if the part
unauthorized materials should have all
is to be subjected to fluorescent penetrant
traces of markings removed before using
inspection.
them.
Wet abrasive blasting is an effective method
to remove heat scale, carbon deposits, and
Permanent Markings
temporary markings, and to produce a uniform
satin finish on metals. This type of blasting
Permanent markings should be positioned in
removes metal, but so slowly that dimensions
the area of lowest stress. Do not apply markings
change very little.
within 0.030 inch of corners, radii, fillet, or edges.
Choose an area where markings will not be worn
off or obliterated by contact with another
MARKINGS
part. If possible, place new markings next to
original markings. Always refer to applicable
Marking engine parts and assemblies aids in
engine manuals and power plant changes for
identification, reassembly, and tracking the
recommended marking met hods and details.
service life of parts. All marks are applied to
Some of the methods of permanent markings
produce maximum legibility and durability
include using a metal stamp, vibropeen, blasting,
without affecting the function or serviceability
and acid-etching.
of the part. Markings are either permanent
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