ULTRASONICS
CASE STUDIES
At the Department of Energy's Y-12 nuclear weapons plant in Oak Ridge,
Tennessee, ultrasonic cleaning with aqueous detergents has replaced
about 95% of the vapor degreasing with chlorinated solvents. The Y-12
plant has many small ultrasonic cleaners and five large automated
systems. The initial cost of these systems ranged from $10K to $150K.
Martin Marietta Energy Systems, Inc., who manages the Y-12 plant, found
that ultrasonic cleaning with aqueous detergents works as well or better
than vapor degreasing with chlorinated solvents. NST (Oakite Products
Inc., Berkeley Heights, NJ) is used for nonferrous materials cleaning.
Micro (International Products Corp., Burlington, NJ) is used for
cleaning ferrous parts. While most ultrasonic cleaners operate at
40 kHz, Martin Marietta has found that 20-kHz ultrasonics is more
effective at removing tenacious oils. Aqueous detergent can usually be
discharged to the sewer where it readily biodegrades.
Vaccari, John. 1993. Ultrasonic Cleaning with Aqueous Detergents; a
Government Plant has Almost Entirely Replaced the use of Chlorinated
Solvents, and Cleaning Performance is at Least as Good as Before,
American Machinist, 137(4):41-42.
A Connecticut manufacturer of precision steel components needed to
eliminate the use of two 1,1,1-trichloroethane (TCA) vapor degreasers.
The degreasers were centrally located and used to clean parts at
various stages of the production process. After evaluating the
cleaning needs of the factory, several changes were made. Cleaning was
eliminated for parts that were in transit from one machining process
to the next. Cleaning was decentralized, allowing alternate methods
for a department's specific needs to be developed. Aqueous methods
were substituted for the TCA vapor degreasers in 95% of the cleaning
applications. Several systems were developed using emulsifying
alkaline solutions, nonemulsifying alkaline solutions, rust inhibitors,
ultrasonics, and immersion cleaning. Some of the clients of this
manufacturer required lubricants that could not be removed by aqueous
chemistries. A small TCA degreaser was kept for this fraction (5%) of
"special" cleaning.
Elliott, Bradley T. (Capsule Environmental Engineering). 1991.
Solvent Waste Reduction Through Process Substitution. Presented at the
Environmental Technology Expo '91, Chicago, Illinois, April.
The Ross Gear plant in Greeneville, Tennessee, manufactures fluid power
components that are extremely sensitive to contamination. To remove
the soils produced during the lapping operation, Ross Gear had been
using a trichloroethylene vapor degreaser. Ross Gear discontinued the
use of trichloroethylene in the Greeneville plant in 1987. The plant
now cleans with an aqueous system using an alkaline solution and
ultrasonics. The plant eliminated health hazards associated with
trichloroethylene use, reduced overall hazardous waste by 50%, and
realized significant savings in material and waste disposal costs.
Hartman, Frank and Rad Clanton (TRW Ross Gear Division). 1988.
The Elimination of a Trichloroethylene Vapor Degreasing Operation.
Tennessee Governor's Award for Excellence in Hazardous Waste Management,
WRATT, University of Tennessee.
Digital Equipment Corporation (DEC) has replaced chlorofluorocarbon
(CFC) cleaning systems at its Colorado Springs, Colorado, and
Kaufbeuren, Bavaria, Germany, facilities. The alkaline aqueous system
it installed at these locations consists of one cleaning, three
rinsing, and two drying stations. The cleaning station consists of a
heated ultrasonic tank filled with an alkaline detergent-surfactant.
Cleaning is followed by a rough spray rinse, immersion in a high-purity
water ultrasonic tank, and finally a spray rinse with high-purity
water. Drying is accomplished in two stages. First, excess water is
blown off the parts using pressurized clean, dry air. Infrared
radiation then heats the parts surface to 160øF to speed up evaporative
drying. The system incorporates a water purification and reclamation
system. Wastewater is nonhazardous and can be sent directly to sewer,
provided the parts being cleaned contain no hazardous contaminant. The
aqueous system surpasses the CFC system in removing particles and is at
least equal to the CFC system in overall efficiency.
Vosper, Fred C. and David J. Vickers. 1992. Developing Precision
Aqueous Cleaning of Hard-Disk Electromechanical Components.
Microcontamination, 10(10):31-34.
In a joint research effort, the U.S. EPA and APS Materials, Inc., have
investigated the use of a limonene cleaner to replace TCA and methanol.
APS Materials, Inc., is a metal finishing company that plasma coats
parts for use in hostile environments. In the biomedical parts
division, cobalt/molybdenum and titanium parts are coated with a porous
titanium layer for use as orthopedic implants. APS Materials has
converted to the terpene cleaner as a result of the investigation.
Cleaning efficacy is excellent with a slight increase in bonding
strength for the limonene-cleaned parts. Changing to the aqueous
required the addition of rinse and dry stations. The new system cost
$1,800 to install with annual operating expenses of $850. Net savings
are $4,800 per year.
Brown, Lisa M. (EPA), Johnny Springer (EPA), and Matthew Bower (APS
Material, Inc.). 1992. Chemical Substitution for 1,1,1-Trichloro-
ethane and Methanol in an Industrial Cleaning Operation. Journal of
Hazardous Materials, 29:179-188.
Torrington Bearing in Newington, CT has implemented a phase out of all
solvents. A new aqueous ultrasonic cleaning system installed to clean
turbine engine bearings allows better detection of micro cracks in the
bearing surface. The cost of the new cleaning system was less than the
annual solvent expense for the old vapor degreaser. Torrington Bearing
has also eliminated the use of a petroleum based rust inhibitor, replacing
it with an aqueous alternative.
Paulhus, Jack/Lewis Corporation, Source Reduction: Aqueous Replacement of
Solvent Cleaning Systems, Third Annual Workshop on Solvent Substitution,
Phoenix, Arizona, December 8-11, 1992.
Since 1988, Allied-Signal Aerospace in Kansas City, Missouri has used a
volatile aqueous cleaner for wiping work surfaces of laminar flow work
stations, finger cots, latex gloves, and fixtures to remove light soils
and particulates. The volatile aqueous cleaner consists of 12.5%
isopropyl alcohol, 0.82% surfactant, and the remainder is deionized water.
The solvent removes both organic and inorganic soils. The previous
solvent, CFC-113, was consumed at the rate of 2000 lb/month and has been
completely eliminated for wiping. The volatile aqueous cleaner is also
used in ultrasonic baths to clean complicated machined assemblies.
Allied-Signal Aerospace reports better cleaning and lower cost, about
$1.00/gallon.
Hand, Tom and Bohnert, George/Allied-Signal Aerospace, Case Study #3:
Development and Use of a Volatile Aqueous Cleaner, EPA/ICOLP Eliminating
CFC-113 and Methyl Chloroform in Aircraft Maintenance Procedures, EPA-430-B-93-006, October 1993, pp. 161-162.
PROCESS UNIQUE INFORMATION
Economics for this alternative and related process equipment.
Environmental information concerning regulations and disposal.
General information concerning the process and its uses.
References containing information related to this alternative.
Safety information on operator/process issues.
OTHER INFORMATION
GLOSSARY || STATE INFORMATION ||
PROCESS CONVERSION CHECKLIST
Last update: 18 March 1995
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URL: http://clean.rti.org/ul_case.htm
