Cable Heater Makes Tamper Proof Packaging Possible


A manufacturer of equipment for applying tamper-resistant seals to various containers, bottles and plastic cups. Unfortunately, many were wide mouthed and made standard heating methods difficult.

Inserting a cartridge heater into a drilled hole did not produce an even temperature around the sealing head's circumference. A tubular heater was also considered, but dropped when the watt density exceeded the recommended maximum.


The problem was solved with a Watlow cable heater. A 1.6 mm (0.062 in.) diameter cable, 130 cm (50 in.) long was wound to a 4.7 mm (0.187 in.) inside diameter by 100 mm (4 in.) long coil. This coil was fitted into a round sealing head with a slot milled along the circumference. Installing the heater in this fashion made a ring-shaped sealing head possible. This configuration drastically reduced the sealing head's mass and provided rapid heat-up and recovery times. Teflon® leads and seals protected the heater against moisture from the frequent washdowns.

Teflon® is a registered trademark of E.I. Du Pont de Nemours & Company.