Non-destructiveTo detect microleaks in hermetically sealed packages by measuring electrical discharges between the food product and device electrodes.
To scan packages and seals in the ultrasonic C-scan reflection or pulse-echo mode using different transducers to obtain images and attenuated signals.
To eliminate external disturbances and subject to changes in external pressure.> 10 μm channel, > 50 μm pinholesReal-time, > 10 s, on-line> $100,000
The laser-acoustic inspection system operates on the principle that fill materials affect the vibration of the container in a measurable and predictable way. Typically, the density, viscosity, and elastic properties of the fill material affect the frequencies at which vibration resonances occur and the amplitudes of those resonances. Vibrations are induced in objects by broadband white noise emanating from an ordinary loudspeaker is usually positioned as close to the inspected object as is practical. This distance is typically several inches but has been as far as several feet.
Ultrasonic waves are mechanical vibrations, so ultrasonic testing is especially suited to detection of elastic anomalies and measurement of physical properties such as porosity, structure and elastic constants.
- Oscilloscope with alarm system
- Place packages in a chamber to eliminate external disturbances and subject to changes in external pressure.
- Air movement through small holes in package wall generates ultrasonic sound waves.
- A microphone senses the vibration.
- Audiofilters eliminate all frequencies except those of interest.
Ultrasonic images of different types of packages with different standard defects are shown in Figures 1, 2, and 3. In general, all defects were easily identified and further characterized by the UI technique. Limit of detection (LOD) of the UI technique for microchannel leaks was 10 μm in all package types tested. The LODs for pinholes in Figures 1, 2, and 3 packages were 60, 50, 50 μm, repectively.
PACKAGE TYPES AND DEFECTS
Rigid plastic container
|Plastic Can (Double-seam Metal End)||Paperboard|
|Double Seam Defects*|
|Foreign Matter Inclusion|
|Loose Flap or Ear|
|Seal Defects (Blister)|
|Seal Defects (Blocked)|
|Seal Defects (Burnt)|
|Seal Defects (Compressed)|
|Seal Defects (Contaminated)|
|Seal Defects (Convolution/Embossing)|
|Seal Defects (Creep)|
|Seal Defects (Crooked)|
|Seal Defects (Incomplete)|
|Seal Defects (Misaligned/Deformed)|
|Seal Defects (Nonbonding/Weak)|
|Seal Defects (Plastic Lumps)|
|Seal Defects (Seal-width Variation)|
|Seal Defects (Stringy)|
|Seal Defects (Uneven Impression)|
|Seal Defects (Uneven Juncture)|
|Seal Defects (Wrinkle)|
|Swell (Swollen Package)|
- Packaging Technologies and Inspection. 145 Main Street Tuckahoe, New York, 10707. TEL (800)-532-1501 (http://www.ptiusa.com/)Sonoscan Inc. 2149 E. Pratt Blvd., Elk Grove Village, IL 60007. TEL (847)-437-6400 (http://www.sonoscan.com/index.html)MeadWestvaco Corporation. 501 South 5th Street, Richmond, VA 23219-0501. TEL (804) 444-1000 (http://www.meadwestvaco.com/index.htm)Ayhan Z and Zhang QH. 2003. Evaluation of heat seal quality of aseptic food containers by ultrasonic and optical microscopic imaging. Eur Food Res Technol (2003)217:365-368.
- Song, Y. and Sadler, G. 2005. Ultrasonic imaging for seal quality and imperfections in hermetically sealed flexible and semi-rigid food packages. Poster presented at the IFT Annual Meeting, July 15-20, New Orleans, LA.