Troubleshooting Cap and Liner Sealing Issues

Understanding the interaction between the cap, induction liner (also referred to as induction wad) and container is critical for successful cap sealing. For a good hermetic seal, it's necessary for the foil innerseal (inside of the cap) to be in contact with the lip of the container and have consistent pressure around the container land area.

If you’re experiencing inconsistent sealing results use the tips below to identify potential sealing problems.

Application Torque

80% of all sealing failure is caused by inconsistent application torque. Containers that are capped by hand can be subject to great differences in application torque. Inconsistent torque from cappers may be a result of the cappers being out of adjustment or having worn tightening wheels. Poor bottle/closure tolerances resulting in caps and bottles not fitting properly together can also cause this problem. Sometimes these irregular fits can be solved with proper types of foil innerseals.

Container Lip/Liner Contact

Good contact between the liner material and the container lip is important. Even when cap application torque levels are sufficient, problems with the contact area can cause inconsistent seals. The land area of the container should be consistently wide enough and rigid enough to support the pressures and heating required for a good seal. A thin or weak land area can cause poor contact between the liner material and the container lip resulting in a poor seal.

Container Lip Deformations

Gaps between the land area and liner material can be the result of any number of problems, from mold imperfections to container material issues. Any gap between the liner and container land area may cause a failure to seal. Defects can be detected on the container land area before the container is capped.

Cocked Cap

A cocked cap results from a problem with the capping process. The gap created can cause overheating and the cap itself may actually jam the container under the sealing head. Cocked caps can be detected and ejected prior to passing under the induction sealer.