Vacuum Decay Method (VDM) is a non-destructive Container Closure Integrity (CCI) testing practice applicable to many sealed package types, including food, beverage, industrial and pharmaceutical packages, among others. Vacuum Decay is the primary leak test method for filled/sealed container inspection, including seal integrity testing and/or container integrity testing.
While ALPS does offer vacuum decay testing for empty plastic containers, Vacuum Decay testing for filled/sealed containers is offered under the Bonfiglioli Engineering brand.
Bonfiglioli Engineering developed their Vacuum Decay Method system in accordance with the ASTM approved test method F2338 that is recognized by the Food and Drug Administration (FDA) as a consensus standard for filled package integrity testing. CCI testing is performed while the package itself is held within a hermetically sealed test chamber.
If a leak is detected in a package, as a consequence of the application of a vacuum within the test chamber forming a differential pressure between the inside and the outside of the package, the air moves from the high pressure zone (within the package) to the low pressure zone (outside the package), causing a progressive pressure rise (that is a vacuum decay) outside the package.
Vacuum decay can also result from the volatilization of a packaged liquid that partially or fully obstructs the leak path. In this case, vacuum decay will occur if the chamber test pressure is lowered below the liquid’s vaporization pressure.
A vacuum decay greater than a given threshold at the end of the testing phase indicates a leak.
Once the test chamber is loaded with the package to be tested and hermetically closed, the VDM process consists of the following phases:
- Vacuuming: the period of vacuum setting within the test chamber;
- Stabilization: the time necessary to get a homogeneous vacuum distribution within the test chamber;
- Testing: the time frame in which the vacuum level is monitored by means of a dedicated transducer; two measurements are taken respectively at the beginning (1st reading) and at the end (2nd reading) of this phase.
Following the testing phase the VDM pass/fail decision is performed by means of comparing the vacuum decay DELTA “Δ” (Δ = 1st - 2nd reading) to a predetermined threshold THR:
if Δ ≤ THR the PFS is classified as conforming (no detectable leaks)
if Δ > THR the PFS is classified as defective (a micro leak is detected)
In the case that a preset minimum level of vacuum (M_LEV) is not reached at 1st reading time, the package is classified as defective as well (a large leak is detected)
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For more information on Bonfiglioli Engineering's Vacuum Decay machines, please visit their website, www.bonfiglioliengineering.com, or find out how Vacuum Decay can help meet your leak detection needs by Asking Us a Question.