Vacuum Decay Method


Vacuum Decay Method (VDM) is a non-destructive Container Closure Integrity (CCI) testing practice applicable to most pharmaceutical package systems.
Bonfiglioli Engineering developed the VDM system in accordance with the ASTM approved test method F2338 that is recognized by Food and Drug Administration (FDA) as a consensus standard for pharmaceutical packages integrity.
CCI testing is performed while the package itself is held within an hermetically sealed test chamber.
In the presence of failure in the package closure integrity (leakage), as a consequence of the application of vacuum within the test chamber and hence of 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 packaged liquid that partially or fully occludes 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 end of the testing phase, points out a leakage.
Once the test chamber is loaded with the package to be tested and hermetically closed, the VDM process comprises 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 decision-making 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 leakages) 
if Δ > THR the PFS is classified as defective (a micro leakage is detected) 
In 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 leakage is detected)

NEW FEATURE AVAILABLE:
When dealing with prefilled syringes, the system is equipped with an unique technical solution preventing the plunger movement during Vacuum Decay testing phase.