United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-90/052 Mar. 1992
'SrEPA Project Summary
Degreaser System Pollution
Prevention Evaluation
M.F. Szabo and M.T. Nutter
The report gives results of an inves-
tigation of the capability of various en-
gineering changes to an existing vapor
degreaser to reduce solvent emissions
to the atmosphere while remaining
within the established U.S. Air Force
(USAF) exposure limits for 1,1,1-
trichloroethane (TCA). A 1970 vintage
vapor degreasing system, serving a
USAF metal fabrication shop, had been
converted from trichlorethylene to TCA
and fitted with a lip vent exhaust sys-
tem to decrease worker exposure. Sol-
vent consumption by the bath with this
configuration was two to three 55-gal.
(208-L) drums weekly, all presumed to
be emitted to the atmosphere via the lip
vent. In sequence various modifications
to the degreaser and operating proce-
dures were instituted to define their ca-
pability to reduce emissions and comply
with exposure limit requirement. They
include decreasing and eliminating lip
vent suction, a freeboard extension, an
ad-on chiller, and a combined freeboard
extension and add-on chiller.
Although the lip vent lowered work-
place concentrations, it also greatly in-
creased TCA emission rates. Eliminating
the lip vent with the simultaneous addi-
tion of a combined freeboard exten-
sion/add-on chiller provided about
equivalent workplace concentrations of
TCA but with a decreased discharge
rate of TCA. The rate of consumption of
TCA was reduced by about 75% with
this configuration while maintaining the
same degree of worker safety as pro-
vided by the lip vent.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Objective
The purpose of this project was to in-
vestigate the technical and economic fea-
sibility of applying a range of solvent
conservation options to a vapor degreaser
located at Wright Patterson Air Force Base
(WPAFB-4950 TW/AMFSM) while keeping
worker breathing zone concentrations at
U.S. Air Force (USAF) engineering targets
of 25% of Occupational Safety and Health
Administration (OSHA) action limits of 43
ppm for an 8-hour time-weighted average
(TWA) and a short-term exposure limit
(STEL) of 56 ppm for 1,1,1-trichloroethane
(TCA). The degreaser uses TCA as a sol-
vent.
Background
The U.S. EPA and USAF are involved
in a joint program to identify methods of
reducing pollution from USAF depot facili-
ties throughout the U.S. The vapor
degreaser being studied was inspected
and chosen as a test candidate for reduc-
ing emissions of TCA through various pol-
lution prevention options. The degreaser
utilizes a lip vent suction system that re-
sults in excessive loss of TCA. Since TCA
may be phased out of use over the next 10
years, its cost will most certainly rise in the
Printed on Recycled Paper
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interim period, increasing the incentive for
the implementation of solvent conserva-
tion options.
Scope
The scope of the project included base-
line degreaser measurements, effects of
ventilation patterns on solvent loss/worker
exposure, and a series of physical modifi-
cations to the degreaser system, such as
reducing exhaust fan speed, increasing
freeboard area, and installing a freeboard
chiller. The physical modifications were
designed to systematically reduce solvent
consumption at increasing cost levels.
Methodology
Solvent loss and worker exposure mea-
surements were taken during each test. A
portable infrared analyzer (Miran 1A) and
charcoal tubes were used for the solvent
loss/exposure measurements. Various
other ancillary parameters such as exhaust
duct air flow, atmospheric pressure,
degreaser temperature, and solvent level
were measured during each test. Both win-
ter and summer operating conditions were
tested.
Test Description
Initially, four tests were performed dur-
ing the winter and spring from February to
April 1990. A second series of tests were
conducted in late May/early June 1990 to
represent summer conditions. Both sets of
tests included baseline testing at full fan
speed, reduced fan speed, and an increase
in freeboard height. The summer tests in-
cluded the use of a chiller both alone and
in conjunction with the freeboard exten-
sion, and ventilation patterns were altered
to isolate the degreaser room.
Results
Test options controlled worst-case per-
sonal exposure to levels (at degreaser mid-
point) that achieved, or slightly exceeded,
USAF Engineering Target Levels (ETLs):
(1) baseline, (2) reduced lip vent suction,
(3) fan off with freeboard extension, (4)
chiller without fan or freeboard extension,
and (5) chiller with freeboard extension.
One test option did not reduce worst-case
personal exposure to meet the USAF ETLs:
fan off with existing freeboard. Two test
options achieved acceptable control from
a worker comfort standpoint: (1) baseline
operation and (2) chiller with freeboard
extension. The use of a chiller with free-
board extension resulted in a maximum
reduction in solvent consumption of 72%.
Conclusions
Very significant reductions in solvent
use are achievable from the USAF
degreaser using the chiller-plus-freeboard
option, while simultaneously keeping
worker exposure below USAF ETLs, and
with worker acceptance and support of the
physical modifications to the degreaser.
Installing the chiller and freeboard is
technically feasible, requiring only a few
days of down time. The economic payback
for this degreaser is less than 1 year,
based on solvent and heat loss savings.
Recommendations
The degreaser should be operated per-
manently with the chiller and freeboard
extension (no fan). Continued isolation of
the degreaser room with more permanent
materials is also necessary to maintain
current levels of worker exposure. Leaks in
the degreaser system should be repaired
and will likely reduce worker exposure even
further. Keeping better records on
degreaser operation and solvent use would
help identify causes of excessive solvent
consumption.
M. F. Szabo and M. T. Nutter are with PEI Associates, Inc., Cincinnati, OH 45246.
Charles H. Darvin is the EPA Project Officer, (see below).
The complete report, entitled "Degreaser System Pollution Prevention Evaluation,"
(Order No. ADA 242-110/AS; Cost: $26.00, subject to change) will be available only
from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-90/052
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