Yesterday, 03:34 PM
When you use bubble leak testing to check product seals, the presence of bubbles often indicates that the product has failed. But is it really defective?
In actual testing, another situation can also cause bubbles: trapped air. Air tends to become trapped in the folds of packaging. When a sample is placed in a vacuum chamber filled with liquid—and provided no other actions are taken on the sample—the air adhering to the packaging surface will expand as the equipment begins to evacuate the chamber, forming bubbles that escape from the sample’s surface. This can lead to “false positive” results, causing the product to be incorrectly deemed defective. This not only results in product loss but also impacts production decisions.
How can you distinguish between a true leak and trapped air?
1. Continuous stream of bubbles
A true leak produces a continuous stream of bubbles. Trapped air, on the other hand, typically produces sporadic bubbles.
2. Observation time
If bubbles appear as the vacuum level rises but cease to form once the pressure stabilizes, the issue is trapped air rather than a leak. A true leak often produces a continuous stream of bubbles even under stable vacuum conditions.
3. Observe the Location of the Bubbles
True leak points are usually located at the seal line or perforations, while bubbles caused by trapped air often roll down from the surface of the package.
4. Shake the Sample
Gently shake the package before evacuating to expel residual air.
Use the methods described above to verify whether the bubble leak test has detected a genuine leak, thereby avoiding misjudgments of product seal integrity, improving production efficiency, and ensuring product quality.
Want to optimize your quality inspection workflow? Please refer to our Basic Guide to Leak Testing.