If the Cap Looks Fine, but the Bottle Still Leaks

A cork is correctly placed on a bottle as it leaves the filling line. The tamper band looks like it is still in place, and there doesn't seem to be anything unusual in the visual inspection. However, later, some bottles exhibit leaks around the neck.

The issue is annoying, as the closure was okay when it was still in production.

This is the type of problem that a Secure Seal Tester can help you resolve. The equipment tests the bottle and closure system together to determine if the closure will seal the bottle under specific test conditions, not based on the appearance of the seal.

There Are More Components to the Seal Than a Cap

The bottle neck finish can be used with a plastic closure. The cap must be made properly, and both surfaces must comply with the design requirements.

Several details can influence sealing:

• Neck finish: Damage, contamination, or dimensional variation may prohibit the intended contact.

• Closure: A defect or dimensional deficiency can lead to a loss of sealing.

• When applying, attempt to put the cap on with the wrong pressure settings, which can result in an improper or insufficient cap seal.

• Sealing features: Liners or linerless sealing surfaces should function as intended for that closure.

• Handling: Damage following capping can impact performance even though the first application was good.

The list is important, as it is not a rule that a leak will always be from a faulty cap. May include the bottle, the application process or the interaction between them.

Only replacing one component without checking the others can leave the actual cause unresolved.

What Will Be Checked by ASecure Seal Tester?

The general method of pressure-based closure integrity testing is that the sealed container is subjected to controlled conditions, and the operator waits until the pressure drops or another indication of leakage is detected, as specified in the test procedure.

Pressure, duration, specimen preparation, and pass criteria should be selected based on the type of bottle and closure and intended use. There isn't a single test pressure suitable for all containers.

The result addresses a specific question: Was the bottle-and-cap assembly able to keep the seal during the test?

Does not, in itself, detect all causes of failure. A leak identified in testing requires follow-up inspection.

Similarly, equipment developed for bottle closures cannot necessarily be referred to as suitable for heat-sealed pouches or other types of packages. Those might need different methods and fixtures.

Why Visual Checks Are Insufficient.

Capping torque can be valuable process data, but it cannot be used directly as a replacement for SIT.

The same application measurement can be seen on two closures, and the closure behavior will vary due to bottle-finish variation, cap geometry, or sealing surfaces. Even perfectly straight caps that feel tight can leak.

Quality teams may compare the following for a thorough investigation:

• Application settings and how they change.

• Finish and size of bottle necks.

• Closure condition and the sealing system used.

• Results of the specified pressure-leak test.

• Line/mould or batch failure repetition.

These checks are helpful in determining if the damage is isolated or if it is a repeat occurrence of a process problem.

The sequence of investigation may vary based on the information known by the plant. What is important is that there is sufficient traceability to link failed samples to the production conditions.

If There Is a Recurring Leak, You Need to Take a Targeted Action.

Suppose a theoretical line that makes several bottle sizes. One size has intermittent leaks following a changeover, and the others are within the agreed acceptance limits.

It would be too soon to say this day that all the caps provided were faulty.

The team could review changeover settings, the type of closure used, and the size of the bottle closure. It would then be able to rerun the test on appropriately chosen samples following a deliberate change.

A Secure Seal Tester is most useful not as a machine that's supposed to automatically diagnose the entire production line, but within that larger quality process.

Frequent and consistent records help to identify a genuine improvement from the normal sample variation.

Don't Confuse Seal Integrity With Bottle Strength.

Bottle burst testing involves testing a container's ability to withstand internal pressure, sometimes as far as failure. Secure seal testing is a test in which the closure assembly's performance to prevent leakage is assessed within a defined testing protocol.

Even a body with sufficient strength can leak at the cap. The opposite can occur, too: the closure may seal properly, but the bottle body fails to pass a separate pressure test.

Both results are important, but should be considered separately.

The practical aim is the same for a bottling plant, namely, to determine the point at which the seal has been broken, to check whether the fault recurs, and to check any corrective measure. One good way to start is to see if the cap is “visually acceptable”. It is not definitive proof that a bottle will seal.