The occurrence of leaks is divided into two categories, the first being leaks that occur randomly during a normal packing run and are a measure of the overall capability of the process. These leaks cannot normally be attributed to any fault conditions and occur at random intervals during the production run.
The other type of leaks are caused by a fault condition and are more recognized as a group of leaks or a staggering increase in the appearance of leaking packages. You can also buy equipment for package leak testing via online sites.
Examples of random leaks would be products falling into the seal area, slight changes in process conditions due to inconsistent line operation, or a large wrinkle that forms in the packaging material and then disappears again. Variation in film quality will also cause random leaks throughout a run.
Clusters or staggered increases in leakage occurrence may be the result of heater element failure, thermocouple failure, or component failure, although these will require intervention to correct the problem. Contamination that builds up on sealing tools and belt tension problems will create clumps of leaks that can come and go during a production run.
Off-line sampling: In an off-line sampling regime, the total production capacity can be measured. On an average line operating at a throughput of 80 packages per minute, a well-managed sampling regimen could sample 1% of the product, which in an eight hour shift could produce a sample size of 300 packages per shift.
This will give a pretty good indication of the capability of the process and will be useful as a benchmark from one change to the next.
As the sampling regime is more comprehensive than offline testing, any change in the appearance of the leaking packages could be used to trigger alarms. Small clusters of leaking packages may once again go unnoticed.