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Mineral Insulated Cable

What is MI Cable?

Mineral Insulated cables, or simply MI cables, are cables in which conductors or wires are enclosed by a metal jacket and insulated with hard-packed Magnesium Oxide (MgO). When subjected to harsh environments, this basic construction provides high-temperature capability, exceptional electrical isolation, and physical protection for the conductors especially.

Mineral insulated cable consists of copper or thermocouple wires inside a copper, stainless steel, or Inconel ® sheath, 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 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 identification and to add an additional layer of protection from corrosion.

An MI cable may contain any number of wires, but the most common configurations include 1, 2 or 3 pairs of conductors. Specialized MI cables may include additional thermocouples in customized configurations. MI cable is available in a variety of diameters and lengths, relying on the specific requirements. Many MI cables are calibrated using sensitive, highly accurate and fast dry block probe calibrators.

Temperature sensors manufactured from MI cable, such as some RTDs or thermocouples, are used extensively in heat treating metals, solid waste incinerators, sintering powdered metals, firing ceramic materials, gas or oil fired furnaces, fuel fired heat exchangers, box furnaces, and nuclear or hydrocarbon-based energy plants.
Mineral Insulated cables

What is the Structure of MI Cable?

Metal Sheath:
Metal sheaths can consist of a number of different metals including 304, 310, 316, 321 Stainless Steel (SS) as well as Inconel ® 600. In the most extreme cases, a customized sheath can be manufactured to withstand temperatures up to 1150 ° C( 2102 ° F).
Conductor Wire:
Conductors can be made from a variety of materials, the most common include thermocouple alloys, copper, nickel, nickel-plated copper, constantan and others. The number of conductors will vary from 1 to 6 or more, relying on the application where it will be used.
Magnesium Oxide (MgO):
MgO is used to isolate the conductors from the external sheath and from each other. This is a great material to use due to its dielectric constant, rounded grain structure, high-temperature capability, and its chemical inertness.

What is the Spec of MI Cable?

Type Rated Voltage Model Name Core Section (mm²)
Lightweight 500V BTTQ Lightweight copper core copper sheathed mineral insulated cable 1 / 2 / 3 / 4 / 7 / 12 / 19 1.0~4.0


Lightweight copper core copper sheath LSZH outer sheathed mineral insulated cable
BTTVQ lightweight copper core copper sheathed PVC outer sheathed mineral insulated cable
Heavy-duty 750V BTTZ Heavy-duty copper core copper sheathed mineral insulated cable 1 1~400
2 / 3 / 4 1~25
WD-BTTTZ Heavy-duty copper core copper sheathed LSZH outer sheathed mineral insulated cable 1 1~400

2 / 3 / 4

BTTVZ Heavy-duty copper core copper sjeathed PVC outer sheathed mineral insulated cable 1 1~400
2 / 3 / 4 1~25

What is the Key Features of MI Cable?

Strong Fire Resistance.
Mineral insulated cables are all composed of inorganic substances (copper and magnesium oxide). It does not ignite on its own, nor does it cause a source of ignition. Mineral insulated cables works well even with an external source of ignition.

High Temperature Resistance.
Because the melting point temperature of magnesium oxide in the insulating layer is much higher than that of copper, the maximum normal temperature of mineral insulated magnesium oxide cable can reach 250 ℃, and it can continue to run at 1083 ° C, which is close to the melting point of copper, in a short time.

Large Current Carrying Capacity.
The mineral insulated cable has great current-carrying capacity because of the special insulating material and structure of magnesium oxide cable. Compared with traditional plastic cables, the same amount of current can be reduced by 1 to 2 cross-section levels.

Resistance To Radiation.
Because the MI cable is composed of inorganic materials. Therefore, after undergoing nuclear radiation, the electrical and mechanical properties of the Mineral insulated cables will not change in any way.

Waterproof And Explosion-Proof Performance.
Mineral insulated cables use copper tubes as sheaths. The highly compacted insulating materials in the cables and the cable terminations installed with special sealing sleeves can organize the water gas, flame and vapor to be immersed in the electrical equipment connected to the MI cable. It is suitable for the connection of various explosion-proof equipment and equipment in places with explosion hazard.

Safety And Environmental Performance.
The MI cable's constituent materials are all inorganic materials and do not contain any organic materials. Therefore, even if the cable is placed in a fire above 1000 ° C or in a flame that is destructive to copper, it will not produce the slightest amount of smoke, halogen and toxic gases. This cable is a product that can truly achieve green, environmental protection and safety.

High Mechanical Strength.
The Mineral Insulated cable has the characteristics of high strength and high toughness, and can withstand bending, flattening, twisting and other conditions. When the cable is flattened to 1/3 ~ 2/3 of the original cable outer diameter, it can still operate normally.

Good Bending Performance.
After the Mineral Insulated cable is fully annealed, it can be bent repeatedly and many times, and has a bendability that ordinary plastic cables can not compare.

Excellent Shielding Performance.
The Mineral Insulated cable copper sheath is the most excellent shielding protection layer, which can prevent the MI cable itself from interfering with other cables, and it can also prevent the external magnetic field from interfering with itself.

Good Grounding Performance.
The copper sheath of the mineral copper-clad cable can function as a grounding wire, and has a very low grounding resistance, without the need for a separate grounding wire.

What is the application of MI Cable?

RTD and Thermocouple Sensors Constructed Using MI Cable are Used Extensively in Various Applications such as:.
  • Solid waste incinerators.
  • Sintering powdered metals.
  • Firing ceramic materials.
  • Gas or oil fired furnaces.
  • Fuel fired heat exchangers.
  • Box furnaces.
  • Nuclear or hydrocarbon based energy plant.

Can You Direct Bury MI Cable?

As an experienced engineer or contractor, you might be wondering if it is possible to direct bury the MI cable. By now, you probably know the advantages of the fire-rated MI cable.

So, the organic construction of the MI cable gives it excellent capabilities to resist heat and fire. The cable can easily sustain heavy current overloads and high temperatures. Neither does it emit toxic substances, smoke nor allow flame propagation. A unique feature about the MI cable is that it never deteriorates at low temperatures. It is never affected by extreme changes in temperature because the cable is moisture and solid resistant. It is designed with an extruded metal sheath made of copper to make it impervious to liquids. You can rely on the cable in any environment because neither corrosive solutions, water, or process liquids can affect it.

Go ahead and make your move to direct bury the MI wire because it is extremely safe.

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