The construction of cartridge heaters positions a nickel-chrome resistance wire precision wound around a magnesium oxide core. It is inserted into a stainless or Incoloy tube locating the resistance wire close to the sheath.

The core is centrally positioned within the tube and filled with magnesium oxide powder. Nickel pins pass through the centre of the core making contact with the resistance wire at both ends.

The whole is assembly is highly compacted by a swaging operation and thus ensuring excellent heat transfer to the external sheath. This allows for operating temperatures to 1600oF and high watt densities.

One end of the heater is closed with a welded metal end-disc and wire leads exit at the opposite end which is typically closed with a lava seal. A variety of wire leads and lead protection options are available.

Heaters can be supplied with internal thermocouples, mounting fittings and many other options.