Canning and Fish Packaging Technology

Unit 11 - Heat Sealing

11.1.2.Type of heat seals

• Lap seal: In a lap seal, opposite surface of a sheet film are sealed together. Therefore for this type of seal, both the surfaces need thermoplastic coatings. The tubular film with the lap seal is heat sealed, channel may be formed at the seal junctions and atmospheric exchange may take place.
• Fin seal: In this type the same surface of the sheet is sealed together, therefore such seals can be made using one side coated material. Since fin seals protrude from the pack, no pressure is exerted on the contents during sealing. The fin seal may be crimped or corrugated along the seal for better strength.
• Bead seal: At the end of the pack, the edges are melted together to form a narrow weld. Bead seal can only be made using homogeneous thermo plastic film.