Non-destructiveTo detect microleaks in hermetically sealed packages by measuring electrical discharges between the food product and device electrodes.> 20 μm pinhole, > 50 μm micro-channelReal-time, on-line> $20,000
External pressure methods are classified into the pressure decay sensor method and the proximity sensor method. In the pressure decay sensor method, a package is placed inside an enclosed chamber where a pressure is applied to create a pressure differential across the package wall. Gas will flow into the package if there is a leak or a weak seal, because the pressure inside the package (at about 1 atmosphere) is lower than the pressure in the chamber. The decay of pressure inside the chamber is monitored using a pressure sensor (Figure 1). In the proximity sensor method, an open channel is created around the seal of a package by using a clamp system, and compressed gas is applied into the channel. If there is a leak or a weak seal, the compressed gas will enter into the package and cause its upper wall to move. The movement can be detected by a proximity sensor (Figure 2).
Compared to the external vacuum method, both external pressure methods do not require residual gas to be present in the package. In addition, the compressed gas can easily enter the package even when a channel or a pinhole is plugged up with food particles, whether liquid or solid.
- A chamber equipped with a pressure decay sensor
- A clamping system coupled with a proximity sensor
- Put the package into a enclosed chamber or in the clamping system.
- Apply external pressure to the chamber or the open channel.
- Monitor the pressure decay or the upper wall movement.
If the pressure of the chamber decreases or the proximity sensor detect the movement, the package leaks.
If the pressure of the chamber decreases or the proximity sensor detect the movement, and the package is good sealed, it may be caused by the unsealed chamber.
If the pressure of the chamber maintains the same or the proximity sensor do not detect the movement, the package is good sealed.
If the pressure of the chamber maintains the same or the proximity sensor do not detect the movement, the leaking channel may be plugged.
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)|
- TM Electronics, Inc. 45 Main Street , Boylston, MA, 01505. TEL (508)-869-6400 (http://www.tmelectronics.com/)Moncon. 7500 Mendelssohn Ave N., Minneapolis, MN 55428 USA. TEL (763)-493-6370 (http://www.mocon.com/index.php)UNITED STATES, Teledyne TapTone Headquarters. 49 Edgerton Drive, North Falmouth, MA 02556, USA. TEL (508)-563-1000 (http://www.taptone.com/)ASTM F2338 - 09 Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum Decay Method
- ARNDT., G.W. JR. 1998. Chapter 22C Examination of Flexible and Semirigid Food Containers for Integrity. FDA Bacteriological Analytical Manual (8th Ed)
- Blakistone and C. Harper. 1995. Pressure differential technique for package integrity inspection. In Plastics Package Integrity Testing, Assuring Seal Integrity. FPA, Washington, DC.
- Tetra Pak Technical Bulletin 1991. Issue 1. Tetra Pak, Sweden.