A mineral insulated cable is a specialized type of cable used in high temperatures or harsh environmental conditions because it has low flammability, even when operating at high temperatures. It resists oxidation and enables precise measurement.
Mineral Insulated Cables are considered to be one of the ultimate fire survival solutions. They are known for their versatility and ultimate fire survival performance.
With a basic inorganic construction of a copper sheath and conductors, together with a mineral insulant, the cable provides a unique combination of dependability, versatility, and permanence. This construction, with the melting points of 1083°C and 2800°C for the copper and the insulant respectively, provides the unsurpassed Fire Survival properties which enable the cable to continue to carry current at temperatures in excess of 1000°C.
This cable consists of copper wires inside a copper or stainless steel insulated by packed minerals such as magnesium oxide (MgO). Magnesium oxide makes an excellent electrical insulation material because it resists oxidation and ionizing radiation, and it is both chemically and physically stable at high temperatures. After the MI cable has been packed with MgO insulation, it may be rolled under pressure to achieve the desired diameter. The outer sheath protects the internal thermocouple wire from heat, chemical or other environmental damage. The metal sheath may be covered with an additional colored plastic sheath to add in the identification and to add an additional layer of protection from corrosion.
The metal sheath that clad MI cable helps to protect the thermocouple wires from oxidation when used in chemically active or wet environments. Corrosion resistance makes mineral insulated cable ideal for use in areas where failure and replacement could be dangerous or even impossible. These cables are used in nuclear plants to monitor core temperatures. It would be extremely dangerous if the temperature controllers were not receiving accurate readings, and it would be difficult to repair or replace cables in that environment.
The mineral fillings in MI cables provide excellent non-reactive insulation, preventing the thermocouple wires from contact with each other or with caustic substances such as oils, solvents or water. This helps to ensure that the thermocouple probes remain accurate, critical in applications such as heat-treating or sintering where the quality of the product could be adversely affected by temperature fluctuations.
The insulation in Mineral insulated cables does not burn, which makes it ideal for applications where a fire could be catastrophic.