Heat induction sealing is used on a wide variety of packaging throughout the industry. There are five major items that affect the functionality of the induction seal to a bottle. First is the land, or top surface of the finish of the bottle. This area needs to flat, smooth and free of nicks and grooves. An induction seal can adhere to a relatively small flat surface, but if there are deformities in that surface, the seal is often rendered useless.

Secondly, the closure liner must be sized correctly to fit into the closure and not fall out during the course of its run on a filling line. In some cases there is a liner well for the seal to sit in, while in other closures this is not the case and the liner must be held in by the thread of the closure. Knowing the closure type, (stripper or unscrewing tool) can go a long way in knowing how the liner needs to be sized.

The third, fourth and fifth items are the parameters that govern the seal being applied to the bottle after filling.

• Power. This is the setting on the induction seal machine that determines that amount of energy the electric field applies to the package. This is a setup issue in the filling plant that the supplier of the equipment can determine based on line speed, package size, liner type, etc.
• Time. This is the amount of time the bottle spends under the induction seal head as it travels down the conveyor. If the package passes by the sealer to quickly, the seal may never be made properly.
• Pressure. This is created by the application torque of applying the closure to the bottle. It is also one of the most common parameters to cause an ineffective seal. If the application torque for a certain size neck finish is not met, the pressure applied by the closure and liner in it is not high enough to properly adhere the liner to the liner to the land of the finish. The Society of the Plastics Industry (SPI) http://www.plasticsindustry.org publishes a general guideline of neck finish sizes and application torques to be used as a default. It should be noted that typically the closure supplier will publish a recommended application torque for their closure, and that would supersede the general guidelines.

These five major items determine the success or failure of the induction seal.

Achieving a Perfect Seal White Paper and Webinar:
http://enerconind.com/sealing/library/webinars/achieving-a-perfect-seal-every-time.aspx

Floratine - Customer Case Study
http://enerconind.com/sealing/library/application-articles/packaging-foursome-team-up-for-a-hole-in-one.aspx