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2 MediTEST User Guide Page 9
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9.2.5 GROSS LEVEL
The GROSS LEVEL parameter is used to define the minimum force reading a pack must exhibit to not
be judged a gross leak. This test is required as a large leak path can cause the air content of a pack to
dissipate before the Decay Test is reached and the sample may appear to be intact. This test is carried
out at the end of the decay Phase.
Generally the force generated is proportional to the vacuum applied. A pack exhibiting a gross leak will
not reach this level of force during a test so this simple criteria is a good way of easily judging it. Also
larger packs exert larger forces so this parameter is widely adjustable to allow testing of a wide range
of packs. Figure 9.4 illustrates this.
Normally all
“
good
”
packs will exhibit a characteristic ability to generate the specified initial force level
during the evacuation time. However a pack may:
1.
Not achieve the initial force due to containing a medium to large leak path (air is removed from
the pack during evacuation).
2.
Achieve the initial force, but may then lose pressure during stabilisation (medium sized leak or
sudden failure).
3.
Have abnormally low air content, and therefore cannot expand enough to produce the required
initial force in the specified evacuation time.
TEST METHODS
Figure 9.4