Why choose mineral insulated (MI) heaters?

(MI) heaters versus other forms of electrical heating assemblies

To explain this, we first need to explaint the several main forms of electrical heating assemblies:

  • MI heater cable (metal sheath – ceramic insulation – metal wire straight)
  • MI Cartridge heater (metal sheath – ceramic insulation – metal wire wound)
  • Polymer incased heater wire (polymer insulation – metal wire wound or straight)
    1. Polymer coated wires
    2. Wires set in melted polymer which solidifies
  • Ceramic incased heater wire (ceramic insulation; metal wire wound or straight)
    1. Fiberglass wrapped wires
    2. Wires set in a ceramic slurry which solidifies
  • Bare heater wire (metal wire wound; straight or bar)

The main benefits of MI heaters is that it has a protective metal sheath and can handle relatively high temperatures.

What is relatively high temperatures?

  1. Tantalum; <1600C in vacuum or inert gas
  2. Inconel 600; <1100C in vacuum or inert gas, <1000C in air
  3. Stainless Steel; <900C

With MI Heaters it is also possible to make a seamless transition internally to a less resistive wire material (cold/hot/cold), which can be helpful in almost any application.

What does a protective metal sheath do?

Depending on the sheath material used;

  1. Moisture resistant (not always – depends on sheath material)
  2. Chemical resistant (not always – depends on sheath material)
  3. Small formed intricate geometries (no fear of shorting to surroundings)
  4. User friendly installation (no fear of shorting to surroundings)
  5. Easy to solder/braze onto complex geometry (good conductive heat spread)