Bubble leak test equipment is widely used in the packaging industry to check for whole package integrity. Also known as visual vacuum bubble leak testing or underwater immersion leak test, the process involves submerging the package in a water bath and observing for a stream of air bubbles escaping from a defect in the sealer or sterile barrier system. This type of quality assurance testing method is relatively simple and cheap but does not provide the high accuracy demanded in many applications.
In fact, this type of bubble emission test cannot even detect leaks down to the size of a human hair. The reason why bubbles are emitted is because of the pressure difference between the inside and outside the test specimen. This causes the trapped air in the defective seal to be forced through minute holes in the package and into the surrounding water.
These tiny air bubbles can be seen by the inspector and are used to locate a leak in the package seal. Disadvantages of this testing method include a long test time, low sensitivity and the use of water in the test which can clog the hole in the food package or cause the test to be overloaded by viscous food materials during testing. In addition, parts are wet and can’t be reused or distributed due to the fear of contamination.
Compared to the more costly air pressure decay and dye penetration testing methods, bubble testing offers a lower accuracy of detection. For example, a molded plastic soda bottle requires a 1x10-7 or lower leak rate for a desired shelf life. A bubble test would require 11 hours to accomplish this and is too time consuming for some applications. In comparison, a high vacuum leak tester that incorporates Clippard EV valves can accomplish the same test in 13 minutes or less.