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 percent 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
ranges 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.
Digital Equipment Corporation (DEC) has replaced 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 160 F to speed up evaporative drying. The system incorporates a water purification and
reclamation system. Waste water 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
particulates and is at least equal to the CFC system in overall efficiency.
Vosper, Fred C. and Vickers, David J. Developing Precision Aqueous Cleaning of Hard-Disk Electromechanical
Components, Microcontamination, 10(10): 31-34, 1992.
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.
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.
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