Usually, there is little air in the bag, so this can cause 2 problems:
1-1 When we make the immersion test in an ASTM D3078 vacuum chamber, we may not be able to create enough pressure differences across the container walls to observe leaks. This will depend on the size of the bag and the volume of air left inside.
1-2 Although conditions are ideal for testing in a vacuum chamber, if there is a leak, only a few bubbles will come out of the bag for 5 to 10 seconds. The pressures will quickly equalize and all the air will have been sucked out. Therefore, the operator must be attentive and observant.
👉🏼 The test becomes very subjective.
Solution: test by injecting air -> internal pressurization in the bag with a needle: ASTM F2096 standard
2- Low viscosity index of the product.
The other difficulty is the product it contains.
The lower the viscosity index of the product: gel or peanut butter, the more likely the product itself (packaging) will block any leaks and prevent air expulsion (bubbles) or product flow. Unfortunately, this phenomenon is difficult to detect. The only solution is to do validation tests with empty products or with a product with a higher viscosity index.
So, as you can see, it’s not easy.
If it suits you, I can quote you a CDV2 (28x20x20cm) SVVI (semi-automatic, vacuum, venturi, immersion) vacuum chamber with PI (internal pressurization) option. Therefore, it can be tested in accordance with D3078 and F2096.
We have published some videos on Youtube showing how to carry out a leak test on the bags: