ULTRASONIC CLEANING PROCESSES AS A SOLVENT ALTERNATIVE
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| Overview: | Ultrasonic cleaning is a process
that enhances immersion cleaning. It improves the cleaning efficiency of
most liquids, including neutral, alkaline, and acidic aqueous solutions,
as well as semi-aqueous solutions. It is a viable alternative to
traditional solvent-based cleaning operations such as vapor degreasing.
Ultrasonics can be used in gross cleaning operations as well as precision
applications and effectively removes particles, machining chips, grease,
oils, and other contaminants.
An ultrasonic cleaning system consists of transducers, a generator, a tank, and a liquid medium. The transducers convert the energy supplied by the generator to sonic energy vibrations. These vibrations are transmitted through the tank and produce cavitation bubbles in the liquid medium in the tank. The formation and collapse of these bubbles create a scrubbing action that is very effective at removing contaminants. The energy provided by the ultrasonics will raise the temperature of the liquid; heaters, thermostats, and cooling coils may be required to control the operating temperature to within a few degrees. Ultrasonic cleaning is usually employed in a multistage process consisting of an ultrasonic wash, rinse, and dry. Depending on the application, the cleaning process may include a prewash to remove gross contaminants and a spray rinse to reduce dragout into the rinse tank. Ultrasonics may be used in the rinse step as well. The drying step may incorporate some combination of air knives, hot-air ovens, and vacuum drying ovens. Ultrasonics can be used to improve the cleaning efficiency of an immersion cleaning process. Special safety equipment must be used if the cleaning solution is flammable or combustible. Additives such as surfactants should be low foaming. Proper fixturing is important to assure uniform cleaning. Improperly designed fixtures may create "shadows" which block the action of ultrasonic waves. Baskets should have a wide mesh with minimal part contact, and parts should be placed to avoid nesting. Delicate parts should be fixed in place to keep them from moving during insertion into and removal from the tank. Ultrasonics work best on sound-reflecting materials such as metal, glass, and plastics. It is less efficient on sound-absorbing materials such as rubber and cloth. |
| Compliance Benefit: | Use of ultrasonic cleaning may
decrease the amount of ODSs used at a facility which will help the
facility meet the requirements under 40 CFR 82, Subpart D and Executive
Order 12843 requiring federal agencies to maximize the use of safe
alternatives to class I and class II ozone depleting substances, to the
maximum extent practicable. In addition, a decrease in solvents may
decrease the need for a facility to obtain an air permit (40 CFR 70 and
71). Switching from a halogenated solvent (i.e., methyl chloroform,
methylene chloride, perchloroethylene, carbon tetrachloride, or
chloroform) may also decrease the need for a facility to meet the NESHAPs
for halogenated solvent cleaning (40 CFR 63). Ultrasonic cleaning
will increase electricity and water consumption. Under EO 12902,
federal facilities are required to reduce energy consumption and implement
water conservation programs.
The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved. |
| Materials Compatibility: | Excessive dwell times may cause cavitation erosion of some materials. Using a sweep frequency can reduce resonant damage caused by standing ultrasonic waves. |
| Safety and Health: | Ultrasonics typically operate
in the 25 kHz to 40 kHz range; hearing protection may be required. Other
safety and health issues depend on the cleaning solution used. Consult
your local industrial health specialist, your local health and safety
personnel, and the appropriate MSDS prior to implementing this
technology.
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| Benefits: |
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| Disadvantages: |
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| Economic Analysis: | Will vary on a case-by-case
basis. Factors affecting capital investment and operating costs are size
of system, number of tanks, cleanliness level, production rate, and
operating temperature.
Standard sizes are available and may range from 5-gallon capacity benchtop units with 240 watts output power to 35-gallon capacity units with 1440 watts output power. Manufacturers can also provide custom configurations designed to meet specific needs. |
| Approving Authority: | Approval is controlled locally
and should be implemented only after engineering approval has been
granted. Major claimant approval is not required.
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| NSN/MSDS: |
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| Points of Contact: | Navy: Mr. Paul Klein Naval Air Warfare Center, Lakehurst Lakehurst, NJ 08733-5091 Phone: (732) 323-2963 FAX: (732) 323-4810 Email: kleinp@navair.navy.mil |
| Vendors: | This is not meant to be a complete
list, as there are other manufacturers of this type of equipment.
CAE Ultrasonics |
| Blue Wave Ultrasonics 960 S. Rolff Street Davenport, IA 52802 Phone: (800) 373-0144 or (319) 322-6144 FAX: (319) 322-7180 URL: http://www.bluewaveinc.com/ | |
| Branson Ultrasonics Corp.,
Precision Processing Division 41 Eagle Road Danbury, CT 06813-1961 Phone: (203) 796-2298 FAX: (203) 796-0320 URL: http://www.bransoncleaning.com/ |
| Sources: | Mr. Paul Klein, Naval Air
Warfare Center, Lakehurst, May 1999. Mr. Peter Bond, Blackstone Ultrasonics Corporation, January, 1998. Mr. John Hurley, Branson Ultrasonics Corporation, January, 1998. Ms. Sandra Geheb, Process Engineer, NAS North Island, CA, January, 1998 Mr. Dan Bojorquez, Naval Facilities Engineering Service Center, Port Hueneme, CA, November 1999. Ms. Mary Jo Bieberich, Naval Surface Warfare Center, Annapolis, MD, May 1996. Fed Log database, Defense Logistics Agency, February 1994. Steve Verosto, Naval Surface Warfare Center, Annapolis, MD, May 1996. |
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