Induction Cap Sealing Best Practices
Packagers rely on hermetic induction seals to prevent containers from leaking, preserve freshness and to provide tamper evidence.
Packagers who Achieve a Perfect Seal understand the core principles of induction sealing (heat, pressure & time); ensure materials are compatible (caps, liners, bottles & products), and define the cap sealing operating window that is best for their application.
How Induction Sealing Works
Induction sealing creates a hermetic seal by passing a capped bottle under the induction sealer in a non-contact process. The system’s sealing head produces an electromagnetic field that heats up the foil liner inside the cap. The hot foil in turn melts the polymer coating on the inner-seal. The heat, coupled with the pressure of the cap, causes the inner-seal to bond to the lip of the container resulting in a hermetic seal.
Selecting the right liner for your application.
Induction seals prevent leaks and preserve product freshness. Packagers should specify whether the induction liner will peel away cleanly or leave indication of tamper evidence. Peelable liners can include tabs which make the liner easier to remove.
Some liners have a secondary function of resealing. These liners are referred to as two piece liners. They rely on a wax or mechanical bond between the foil liner and a foam or pulpboard backing piece which remains in the cap when it is removed.
Certain products containing oils and chemicals may require an additional barrier layer to protect the foil liner.
Caps, Caps and more Caps
Virtually any cap that can apply adequate downward pressure on the liner to the land area can be used in the induction sealing process. The geometry of the cap, size of the liner and other factors can impact its ability to be induction sealed. Most Continuous Thread (CT) caps and Child Resistant Caps (CRC) have a minimal distance between the liner and the top of the cap. However Dispensing Caps (yorker, disc or flip top) have a larger distance between the top of the cap and induction liner and these may require the use of specially designed sealing heads.
Sealing Head Design
Not all sealing heads are created equal. Enercon has engineered a variety of sealing heads to optimize the induction field for different applications as shown below.