The walls and ceiling of the building are not insulated. The office
space was built within the building and is located in the northeast
comer of the building. The offices have 8 foot ceilings. The
office area was insulated with two-foot wide batts of insulation.
This insulation was placed on the top of the ceiling tiles and ceiling
joists and so was exposed to the work area of the building. Samples
were taken of the insulation, and it was determined to be
fiberglass.
An inspection of this facility was conducted and there were no
sources of asbestos found. Background air samples collected prior
to disassembly showed no airborne asbestos fibers.
2.3. Overhaul work personnel
All work was done by, and under the supervision of, mechanics
experienced in jet engine overhaul work. The owner of the facility
where this work was done has approximately 20 years experience
working on jets, has attended aviation school in Miami for both
power plant and airframe training, and has worked on Pratt &
Whitney JT3D engines his entire career. The owner reported that
much of the work done by this facility is on the newer JT8D engine
type, but JT3D engines are routinely overhauled at this facility, and
he expected to perform about 12 such overhauls in during the year
of this study.
The owner oversaw all aspects of the overhaul work. He was assisted
by the company’s director of quality assurance, and by a
supervisor. The workers who performed the overhaul were all
mechanics with experience in engine mechanical work ranging
from 7 to 36 years.
2.4. General description of work and sampling
The overhaul was performed in accordance with accepted
industry standards, and with the guidelines published in the Pratt
& Whitney engine manuals. The exception was that upon completion
of the overhaul, the engine was not returned to flight readiness.
While all engine components were reassembled, some
time-consuming procedures normally part of an overhaul, principally
installation of safety wiring, disassembling and weighing
each individual blade from each compressor and turbine section,
rebalancing each compressor and turbine section, testing the integrity
of parts, rebalancing moving parts, torqueing of bolts, alignment
testing of bearings, and balancing of compressor and
turbine vane assemblies were not performed. This had no effect
on the assessment of airborne asbestos exposure since no asbestos-
containing part removal, replacement, or disturbance is associated
with these activities.
Work of this type requires a number of specialized tools. The
facility where the work was done had originals of these specialized
tools, or replicas of them. The work practices used were the same
as those used at any point in the history of this engine, according
to the owner of the facility and the two aviation experts on-site.
2.5. Overhaul
The overhaul took place over a three week period. During the
first week of the project, the mechanics disassembled the JT3D engine.
The disassembly work took approximately 6–7 business days.
No work was done during the intervening weekend. The disassembly
was conducted in accordance with the procedures set forth in
the Pratt & Whitney engine manuals (Pratt and Whitney, 1997),
and accepted industry standards.
Weeks two and three of the project were spent reassembling
the engine. Reassembly proceeded in reverse from disassembly,
and was conducted in accordance with the procedures set forth
in the Pratt & Whitney engine manuals, and accepted industry
standards. Original replacement parts were used whenever
possible.
During the period of time between disassembly and reassembly,
no work was performed on the engine or any of its components,
except that all the appropriate large, metal pieces were cleaned.
Cleaning of these components is a normal part of an overhaul,
and presents no opportunity for asbestos exposure. Accordingly,
no air sampling was performed during this period of time.
2.6. Gear box rebuild
Once removed from the engine, the gear box for most jet engine
types, including the JT3D, is typically rebuilt in a separate area,
concurrent with the remainder of the engine rebuild. The gear
box for this engine was rebuilt in this fashion. It was taken to a separate
room, described earlier, and a mechanic whose specialty is
this type of work performed the rebuild.
The gear box rebuild was done in one day. On the same day, and
in the same room, some minor components of the engine such as
the fuel control, the fuel pump, and the fuel oil cooler, were rebuilt
as well.
Separate personal air samples were collected during the rebuild
of the gear box and other components from the mechanics that
performed the work. Area air samples were collected in proximity
to this work in conjunction with the overhaul, as were samples
from the two outdoor locations.
2.7. Sample collection and analysis
2.7.1. Bulk sampling
During the overhaul work, representative bulk samples of all
types of parts removed and parts installed that could have contained
asbestos were collected. These samples were collected to
determine whether asbestos was present in the parts, and, if present,
the type and amount. Bulk samples of the engine parts were
collected by placing either the entire part, or a sufficient portion
of it, in a clear plastic, resealable bag. By representative parts we
mean that we sampled at least one of each type, though many
identical parts may have been used on the engine. For example,
if an insulated clamp was removed from the engine, that sample
represented all such similar gaskets on all the same type of insulated
clamp. If a second type of insulated clamp was found, this
second type was sampled. This continued until at least one sample
had been collected for all types of insulated clamps encountered.
Bulk samples were collected on various days during the overhaul
work from any potential ACM present in the facility. These
samples were collected to determine whether building components
and/or materials could contribute to any airborne asbestos
levels measured.
2.7.2. Air sampling
Air sampling was conducted to determine the airborne fiber
concentrations in during the overhaul. Area sampling was conducted
at four locations centered on the engine overhaul. The area
samples were initiated at approximately the same time as work
began, and were terminated at the end of the work day. Sampling
was also conducted outside the buildings to allow comparison between
outdoor and indoor fiber levels.
Personal air sampling was conducted to provide information
regarding the airborne asbestos fiber exposure of persons performing
the engine overhaul or service work. The personal air samples
used to assess potential asbestos fiber exposure were collected in
duplicate, i.e., using side-by-side personal sampling pumps and
collection media. One set of these personal samples was submitted
for analyses, and the other set was archived.