CCIT testing method

The CCIT described here, is based on the detection of container lid deflection. Deflection means the difference in position between two consecutive container lid profiles, when the container itself is placed inside the hermetic testing chamber and a sequence of vacuum levels are applied in succession. These vacuum levels, are predetermined according to the features of the container to be tested.

Application of the vacuum, establishes a pressure gradient between the inner and outer surfaces of the container. Deflection may or may not occur, depending on the container integrity and on the lid tightness. Specifically, integrity defects or failures, caused by the formation process (such as holes, cracks, incomplete welding and cuts) cause air trapped in the area of higher pressure (inside the container – atmospheric pressure) to move towards the area of lower pressure (in the testing chamber – established vacuum level). Defects, that are larger in size, correspond to a proportional leak (the larger the hole, the larger the leak) and, respectively, to a partial deflection (presence of micro-defect) or close to zero deflection (presence of macro-defect) during the performance of CCIT.

Deflection movements (differential reading of the lid profile for each Cij cell), are detected by means of the S_ACQ, whose sensitive touch membrane of the S_ACQ finds itself in contact with the container during CCIT. The force exerted by each Cij cell of the container in the S_ACQ, is both a quantitative indicator of the container integrity and a specific mark of the defect location.

A phase called “model calculation”, which takes place prior to the CCIT execution, aims to provide the system with a rational, in order to decide whether the containers tested are conforming or not. The model calculation, determines a conformity range, to represent all of the possible behaviors of the lid for each conforming Cij cell. This phase is, therefore, performed by using surely non leaking containers (model sample) under the same conditions as those of the CCIT cycle. The number of model samples is adjusted, to ensure the process gaussianity and to allow reliable statistical evaluation. The conformity range is, therefore, defined as {[μij-(K)*σij];[μij+(K)*σij]} = {[THR-;THR+]} where:

μij is the average of lid deflection for a generic Cij cell

σij is the standard deviation of lid deflection for a generic Cij cell

K is the parameter that determines the extent of the conformity range.

During CCIT, the difference (Δij=deflection) between the forces exerted by the lid of a Cij cell, is compared with the conformity range limit values (THR- e THR+). The purpose of this, is to declare conformity (container intact) or non-conformity (container not intact).

Once the container to be tested has been loaded into the testing chamber and the chamber has been brought to the hermetic closure condition, the CCIT cycle is performed. The duration of the cycle is T0 (T0 = T1+T2+T3+T4), according to the sequence of phases indicated in Figure 4 and described below: 

Figure 4. Possible progress of the vacuum and lid in the CCIT cycle

a. 1st  reading acquisition: the shape of the lid is detected without generated deformations (atmospheric pressure condition)

b. vacuuming: the vacuum level V0 is generated in the testing chamber (T1) by the action of the Pump

c. stabilization: the action of the vacuum on the container is made homogeneous (T2)

d. change of vacuum level in the testing chamber: the vacuum level is switched from V0 to V1 (V0 > V1) by the action of the EPR and then V1 is kept (T3)

e. 2nd reading acquisition: the shape of the lid is detected with generated deformations (modified pressure condition)

f. process: the difference between the 2nd and 1st readings is calculated for each Cij cell (2nd – 1st = Δij = lid deflection value)

g. display: the CCIT results for each Cij cell are shown in a graphic matrix (Figure 5) on the HMI

h. decision making:

if all Δij are within the range [THR-; THR+] the container is declared as conforming

if there is at least one Δij for which the condition (Δij < THR-) exists the container is declared as non-conforming

the case in question does not consider the condition (Δij > THR+)

i. unloading: the testing chamber is restored to atmospheric pressure conditions (T4)

j. start of a new operation.

Figure 4 shows of lid deformation trends for a generic Cij cell with reference to:

an intact container (green)

a container with a micro-defect (red)

a container with an intermediate defect (blue)

a container with a macro-defect (yellow)

The graphic matrix, shows a set of “Points of Interest” (POI), which corresponds geometrically to the structure of the container(s) in terms of the position of the relative Cij cells (Figure 5).

The color of the reference POI’s outline indicates the status of the corresponding Cij cell:

green: Cij cell conforming after the last CCIT cycle performed

blue: Cij cell non-conforming after the last CCIT cycle performed

The fill color of the POI, indicates the difference (Δij) between the forces exerted by the lid of the Cij cell in the S_ACQ.

A red cross, on the reference container, states that the container is non-conforming.

 

     

Detection of intact containers

Detection of micro-defects in cells C15, C17 and C19

Detection of a macro-defect in cell C15

Figure 5. Graphic matrix and possible configuration of the results of the CCIT cycle

For each POI shown, information can be obtained regarding (Figure 6):

Pressure POI: the value of Δij detected in POIij during the CCIT cycle

Model Pressure: the value of Δij detected in POIij during the model calculation cycle

Minimum Pressure: the minimum force exerted by Cij in the S_ACQ during the CCIT cycle

Maximum Pressure: the maximum force exerted by Cij in the S_ACQ during the CCIT cycle

The position of THR+ (red marker)

The position of Δij detected in POIij during the CCIT cycle (upper end of the green bar)

The position of THR- (cyan blue marker)

 

Figure 6. Result indicators for a reference POI