Mineral Insulated Cable

Mineral-insulated cable (MI cable) is a special type of cable whose conductor is embedded in an inorganic mineral insulation layer (magnesium oxide) and encased in a seamless metal sheath, providing superior fire resistance, heat resistance, and mechanical protection.

MI cables are used in applications requiring extremely high fire safety, heat resistance, and circuit integrity, such as fire alarm systems, emergency lighting, fire pumps, smoke extraction systems, industrial furnaces, nuclear facilities, and critical power/control circuits.

Mineral-insulated cables use an inorganic mineral insulation layer (MgO) and a metal sheath, giving them superior fire resistance, high-temperature resistance, and mechanical properties; while ordinary insulated cables use organic polymers (such as PVC/XLPE), which have lower fire resistance and heat resistance.

MI cables should be used in fire-resistant, high-temperature, or hazardous environments, such as high-rise buildings, tunnels, petrochemical plants, and emergency systems, where ordinary cables may fail under extreme conditions.

"MI" cable refers to mineral-insulated (MI) cable, sometimes also called mineral-insulated metal-sheathed (MIMS) cable. Its conductor is insulated with compacted mineral powder and protected by a metal sheath.

Compared to traditional cables, MI cables offer superior fire resistance, high-temperature resistance, long service life, corrosion resistance, extremely low smoke/toxic substance emissions, and strong mechanical protection.

Cable insulation can be broadly classified into organic polymer insulation (PVC, PE, XLPE), inorganic mineral insulation (MgO in MI cables), and rubber/elastomer insulation—each insulation material has different heat resistance, fire resistance, and environmental performance. (General classification of cable insulation)

MI cables typically consist of copper or alloy conductors, a magnesium oxide (MgO) mineral insulation layer, and a metallic outer sheath (copper or stainless steel), providing heat resistance, fire resistance, and mechanical resistance.

MI cables are not suitable for applications involving repeated bending or vibration, such as connections to moving machinery, as their rigid structure may crack or break under repeated movement. (Based on installation practices—e.g., the flexibility requirements versus the characteristics of rigid MI cables)

Cables are generally classified into power cables, control cables, communication/data cables, and special/insulated cables (e.g., MI cables, fire-resistant cables, armored cables)—each type is designed for its electrical or environmental function. (Based on industry-standard cable classification)