TM-1-1500-344-23-2
AIRCRAFT VOLUME II
TECHNICAL MANUAL; CLEANING AND CORROSION CONTROL
APRIL 2009
TM-1-1500-344-23-2 - Page 79 of 240
4-3
NAVAIR 01-1A-509-2
TM 1-1500-344-23-2
15 April 2009
4-5.4.2. PMB Restrictions. The following restrictions
apply to PMB operations:
a. PMB of aircraft component surfaces is authorized
for use ONLY at Intermediate and Depot level
maintenance activities.
b. PMB is NOT authorized for use at Organizational
level maintenance activities.
c. PMB in a walk-in booth (open blasting) is not
authorized at Intermediate level maintenance activities.
At the Intermediate level, only the PMB of aircraft
component surfaces in a blast cabinet (glove box)
designed for plastic media is authorized.
d. PMB of aircraft component surfaces at
Intermediate maintenance level activities is restricted to
metallic surfaces 0.032 inch thick or greater.
e. Nonmetal surfaces, such as composites or
fiberglass, and metal bonded structures are not
authorized for PMB at the Intermediate level.
f. Corroded steel components shall not be
processed in equipment used for aluminum and
magnesium components without first removing all
corrosion products (rust). Plastic media used to remove
paint from rusted steel parts should be completely
purged from blasting equipment, and the equipment
should be thoroughly cleaned prior to blasting aluminum
or magnesium parts. Best practice is to maintain and
use separate equipment for steel components.
g. Plastic media used to remove non-slip, walkway
coatings (such as A-A-59166), is considered
contaminated and the media must be replaced prior to
blasting aluminum or magnesium parts.
4-5.4.3. Fluorescent Penetrant Inspection Limitations.
Because PMB can peen or smear soft metals, it shall
not be used to remove paint from aluminum or
magnesium components requiring subsequent
fluorescent penetrant inspection for cracks (see NAVAIR
01-1A-16) unless specifically directed by the engineering
authority for that component. Distortion caused by PMB
can limit crack detection. PMB is permitted prior to eddy
current inspection. Chemical etching may be used to
reopen cracks after PMB by removing distorted metal,
however, this process shall be performed only in
accordance with specific engineering authority, approval,
and written detailed process and application instructions.
Chemical etching also removes protective coatings
such as anodize and chromate conversion coatings.
Instructions for reapplication of these protective coatings
must also be provided by the engineering authority.
WARNING
Hearing protection and air respirator shall be
worn during plastic media blasting operations.
Contact the local safety and health office for
proper personal protection equipment (PPE).
4-5.4.4. Operator Safety. Operational safety
compliance shall be in accordance with local regulations
and the following:
a. PMB creates airborne particles which may be
hazardous if inhaled or allowed to contact eyes or skin.
Both eye protection (goggles) and respirator are required
for all operating personnel. Do not allow unprotected
personnel to come in contact with dust. Wash hands
thoroughly before eating or smoking.
b. The PMB process is noisy; typically greater than
80 decibels. Hearing protection is mandatory.
c. All PMB equipment and components being blasted
shall be properly grounded to dissipate static electricity.
4-5.4.5. PMB Equipment. The blast cabinet (glove
box) shall be specifically designed for use with plastic
media meeting the requirements of NA 17-600-191-6-2.
The blast cabinet shall be the pressure pot design,
capable of maintaining constant blast pressure and
media flow using a 1/4 inch to 3/8 inch I.D. nozzle. The
blast cabinet shall be equipped with an air pressure
regulator and pressure gage to provide easy adjustment.
The equipment shall allow for several successive cycles,
and shall be equipped with a dust collection system to
remove dust particles (recommend 60 mesh or finer).
The dust collection system shall be accessible for
removal of the collected dust to facilitate proper waste
disposal. A magnetic particle separator shall be an
integral part of the system to remove ferrous particles
from recirculated media.
4-5.4.6. PMB Preparation.
4-5.4.6.1.Prior to PMB, all components to be blasted
shall be thoroughly cleaned to remove dirt, oil, grease,
and other soils. Refer to Chapter 2 for cleaning methods
and materials. If not removed, these soils will contaminate
the plastic media, causing possible damage to the
surface(s) being blasted and leading to malfunction of
the blasting equipment. Allow the surfaces to dry
completely prior to blasting.
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