Hermetic cartridge heaters - Import export

Occasionally also these terms are used for cartridge heates: heating cartridge, insertion heaters, spiral cartridge heaters. As a rule cartridge heaters consist of a cylindrical stainless steel tube and thus provide a high corrosion prevention. There is a heating wire inside which is wound onto a ceramic core. The number of coils varies depending on the power. In order to avoid a short-circuit, the cartridge heater is filled with magnesium oxide and compressed afterwards. Highly compacted they reach a surface watt density of up to 50 W/cm² and withstand highest stress. In the plastics industry cartridge heaters are used in hot runners in order to temper thermoplasts during injection moulding processes. Other areas of applications for process heat are e. g. packaging, diecasting or continuous casting in which zinc or aluminium are processed. Further applications are to be found in mechanical as well as medical and laboratory engineering.

Square cartridge heaters are used where much power has to be installed near the surface of a tool, e.g. in cutting knives, sealing stations or hot plates. With a soft, malleable condition in stainless steel or nickel sheath square cartridge heaters can easily be pressed into common milled rectangular grooves. Apart from the advantageous heat transfer over ¾ of the sheath, it is not necessary to cement or cast in the heater which is imperative for round cartridge heaters. Unlike tubular heaters which are also available in square sections (see chapter Flexible Heating Pipes), the square cartridge heaters have the termination on one side and can be loaded with 16W/cm² (2.5W/in²) due to their special inside construction.