Technical data

• When using the PMB method of paint removal
on non-metal (composite) surfaces, it is im-
portant to limit the amount of time the surface
is exposed to the PMB blast. To limit this
“dwell time” and still allow paint to be re-
moved, operators should use the primer coat
as a “flag.” That is, when the primer begins to
become visible, the PMB blast should be
aimed at another section of the surface to be
stripped. This results in all paint being re-
moved and only a portion of the primer. Most
importantly, limiting the dwell time prevents
damage to the composite material being
stripped.
• To minimize dwell time, avoid “low pressure-
long standoff distance-shallow angle” combi-
nation of parameters.
2.11.5.4 To maintain a constant removal rate and limit the
amount of time which the PMB blast impinges on any given
surface (dwell time), the following relationships are impor-
tant to remember:
2.11.5.5 As stand off distance increases (decreases), pres-
sure should increase (decrease) to maintain a constant re-
moval rate.
2.11.5.6 As the angle of incidence decreases towards 0°
(increases towards 90°), the pressure should increase (de-
crease) to maintain a constant removal rate.
2.11.6 Operation Safety Requirements. Proceed as
follows.
a. Keep all sources of ignition a minimum of 50 feet away
from the area when PMB is in progress.
b. All blasting equipment, work stands, and the aircraft,
equipment, or components being blasted shall be prop-
erly electrically grounded per TO 00-25-172 and the
applicable aircraft or equipment manual during the
entire PMB operation.
c. All power shall be removed from the aircraft or equip-
ment while PMB is in progress.
d. Titanium and steel alloy surfaces will spark when
subjected to PMB. When a PMB operation involves a
combination of these and other metals, the titanium and
steel alloy surfaces shall be blasted first and then the
other metal surfaces.
e. The facility used for PMB shall have adequate air flow
and ventilation to prevent build up of an explosive dust
mixture. The Base Bioenvironmental Engineer shall be
consulted for proper ventilation requirements. For addi-
tional reference criteria, see the Air Force Corrosion
Facility Reference Guide on the Air Force Corrosion
Prevention and Control office’s website.
f. Personnel involved in PMB shall wear coveralls with
full length sleeves, gloves with gauntlets, and full air
supplied respirator type hoods and hearing protection
which meet AFOSH STD 48-137 requirements. Hoods
shall be put on prior to entering the blasting area and
shall not be removed until after exiting the blasting area.
Hoods shall be stored in a clean dust free area and shall
be cleaned to remove all dust accumulations on them
prior to storage after use. All personnel entering the
blasting area while PMB is in progress, even though not
involved in the operation, shall comply with these
personnel protection requirements. The Base Bioenvi-
ronmental Engineer and Base Fire Department will
define the PMB blasting area when the PMB equipment
is located within a larger facility and is not segregated
from other areas. Protective clothing worn during PMB
shall remain in the work area and shall not be taken
home for cleaning.
g. Blast nozzle operators shall never direct a nozzle at
other personnel. If more than one blast nozzle operator
is involved in an operation at the same time, they shall
be located on opposite sides and/or ends of the aircraft
or equipment being blasted to ensure safe separation of
personnel.
h. Dust and media residue generated during PMB opera-
tions create very slippery conditions. Walking on top of
aircraft or equipment during PMB operations shall be
avoided if at all possible, and shall be done with extreme
caution by personnel wearing fall protection devices if it
is absolutely required by the operation. All work stands
shall be equipped with guard rails to prevent falls.
2.11.7 Personnel Qualifications. PMB shall be per-
formed only be personnel thoroughly trained in the operation
of PMB equipment and thoroughly indoctrinated in PMB
requirements and techniques specified in this technical order
and any other system peculiar aircraft or equipment technical
order applicable to the job to be performed.
2.11.8 Pre-blast Preparation. Proceed as follows.
a. Prior to masking for PMB, thoroughly clean the aircraft,
equipment, or component per TO 1-1-691 to remove all
grease, oil, hydraulic fluid, and dirt from surfaces to be
blasted. Every effort shall be made to stop all fluid leaks
noted at this time. Surfaces shall be allowed to fully dry
prior to masking and input of the item into the blasting
facility. Water and other fluids contaminate blasting
media and may damage separation equipment.
b. Prior to starting PMB, properly mask the aircraft,
equipment, or component to prevent blast media and
dust from penetrating into interior areas and causing
contamination or damage to equipment, systems, or
structure susceptible to damage by media impingement.
Masking shall be accomplished in accordance with
TO 1-1-8
2-22