How to Choose Mineral Insulated Cable?

Mineral insulated cable stands out for its impressive performance in extreme conditions. Often overshadowed by the more common PVC and rubber insulated cables, these rugged cables play an irreplaceable role. We will we’ll take a comprehensive look at their construction, applications, and manufacturing processes, as well as their advantages and disadvantages. Let us unravel the mystery of MI cables.

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What is mineral insulated cable?

Mineral insulated cable, also known as MI cable, MICC cable, or pyro cable, is an electrical cable using copper sheath to wrap the copper core and insulated with magnesium oxide powder; commonly used in high-temperature or harsh environments. Cable that adopts metal instead of copper sheath wrapped cores are known as mineral insulated metal sheathed cable (MIMS cable).

Mineral-insulated copper-clad cables are known for high-temperature resistance and durability and are commonly used in medium-voltage and high-voltage applications. Dense powdered magnesium oxide imparts MI cable excellent thermal endurance, enabling continuous operation above 250°C and resistance to corrosion and UV rays. The metal sheath of the cable can sometimes be used as a grounding circuit to simplify the wiring process. Compared to non metallic wire, MI wire is more robust and resistant to physical damage, making them durable even in harsh environments.

Next, Let’s take a look at the specific applications of mineral insulated cables.

What is mineral insulated copper cable used for？

Mineral insulated copper cables are used in a variety of applications due to their high fire resistance, superior electrical properties, and durability. Some of the main uses include:

1. Fire safety systems: Fire alarm systems, emergency lighting systems, and other safety systems that need to continue operating during a fire often utilize MI cables due to their ability to ensure that crucial communication remains intact in extreme temperatures. Cable with a red outer coating is usually used for fire alarms.
2. High-Temperature Environments: MI cables also find extensive use in high-temperature environments where conventional cables may fail, including furnaces, ovens, kilns, ceramic firing, iron and steel metallurgy, and even nuclear reactors where temperature resilience and nuclear radiation resistance are paramount. Furthermore, in construction and building services, MI cables are used for power supply circuits and heating systems.
3. Critical power supply: In places where power supply is critical, such as hospitals, data centers, and airports, MI cable is often used due to its durability and reliability.
4. High-rise buildings and public venues: MI cables are often used in high-rise buildings, theaters, schools, parking lots, and other public venues that require reliable emergency systems. In residential buildings, MI cable sometimes cab be used as service entrance cable.
5. Transportation Systems: MICC cables are used in transportation systems, such as tunnels, airports, and underground railways. In a famous example, during a fire in the Channel Tunnel connecting Britain and France in , installed mineral-insulated cables still provided emergency lighting for evacuating passengers even after the reinforced concrete and welded steel rails had been burned.
6. Chemically active or wet environments: The waterproof and corrosion resistance nature of MI cables also makes them suitable for applications where moisture or chemically corrosive is a concern, such as in underground systems, outdoor lighting installations, shipbuilding, and chemical processing plants.

Depending on the specific application, there are various mineral insulated cable sizes and specifications. And through the above typical applications of MI cables, we can summarize their key advantages and disadvantages.

Advantages and Disadvantages of Mineral Insulated Cable.

Just like everything has two sides, mineral insulated cables naturally have advantages and disadvantages, analyzed as follows:

Advantages:

• High Temperature Resistance: Mineral insulated cables comply with British BS fire safety standards, with a continuous operating temperature of 250 degrees Celsius, and can supply power for 3 hours at up to degrees Celsius.
• Electrical stability: Mineral insulated cable exhibits high insulation resistance and low capacitance to minimize capacitive coupling and charging currents, resulting in precise signal transmission and stable power delivery.
• Fire resistance: The mineral insulation utilized in MI cables is inherently noncombustible and will not propagate flames in the event of a fire. Additionally, it prevents the spread of harmful gases and chemicals produced when conductors or other components burn.
• Large carrying capacity: Mineral Insulated cables are capable of transmitting higher currents than ordinary cables of the same size, and can withstand high overload currents for short periods without causing serious damage.
• High Durability: Mi cable conductors are embedded in the mineral insulation, the cable is less susceptible to cracking and abrasion; and the metal sheath provides excellent mechanical protection, thus increasing the durability of MI cables in harsh environments.
• Electromagnetic Shielding: The metallic sheath of the cable acts as an electromagnetic shield to prevent interference in signal transmission, which is essential for critical applications requiring maintaining signal integrity, such as industrial automation and control systems.
• Long Service Life: The materials used in MI cables (copper and magnesium oxide) are naturally resistant to aging and have a service life of over 100 years.

While MI cables offer numerous advantages, it’s essential to acknowledge their limitations.

Disadvantages:

• Cost: MI cables are typically more expensive than PVC cables, which can be a limiting factor for limited-cost projects.
• Installation complexity: MI cable installation and termination require special termination kits and training, which can add to the overall cost and time of the project.
• Limited Flexibility: MI cables are quite rigid due to their construction and therefore have limited flexibility, making it difficult to install in confined spaces or around corners.
• Quality Control: MI cables are difficult and costly to manufacture, and products from small factories may have quality problems. That’s why you should choose a reliable mineral insulated cable company, like ZW Cable.

In summary, MI cables offer unique advantages, particularly in high-temperature and critical applications, but their higher cost and limited flexibility may render them less ideal for specific applications. When cabling, the advantages and disadvantages of MI cables must be carefully weighed to make an informed decision.

How is mineral insulated cable made?

The manufacturing process for MI cables requires precise engineering due to their intricate construction. First, copper or alloy conductors are arranged in the desired configuration and enclosed within a seamless copper sheath (or stainless steel or alloy, depending on the application). The space between the conductors and sheath is then filled with highly compressed magnesium oxide powder which serves as the insulator. This powder undergoes vibrational compaction to achieve a dense, uniform insulation layer.

Once the cable assembly is completed, it goes through a process known as annealing, which involves heating the cable to remove residual stresses created during the processing of copper parts. Annealing also removes trace moisture from the magnesium oxide, optimizing its insulating properties.

After that, the cable undergoes a series of stretching and intermediate annealing cycles. The stretching reduces the cable diameter to a specified size. Intermediate annealing restores ductility and prevents conductor breakage. Toward the end of the manufacturing process, MI cable ends are usually sealed with casting compounds to prevent moisture ingress. And the outer sheath can be coated with LSZH for added protection.

Lastly, finished cables undergo rigorous testing to confirm the insulation resistance, dielectric strength, and other critical parameters of the cable meet the safety standards and industry standards. Stringent quality control is essential to ensure cables achieve performance expectations in demanding applications.

Bottom Line.

In summary, mineral insulated cables stand out as a remarkable solution for electrical installations requiring high performance. The unique properties of mineral insulated cables, including resistance to high temperatures and corrosion, give them a clear advantage in terms of safety, reliability, and operation under demanding conditions.

Mineral insulated cables are referred to as MICC cables, and when used as wiring, they are also customarily referred to as mineral cables or fireproof cables.

Mineral-insulated cables consist of inorganic materials such as copper conductors, mineral insulation, and copper or other metal sheaths.

In , the English Channel Tunnel connecting Britain and France had a serious fire, installed the tunnel mineral insulated cable system was even after the destruction of reinforced concrete and welded steel rails, but the evacuation of passengers to provide emergency lighting, and withstood the fire and high temperature of the severe test.

Because mineral insulated cables have the quality and performance of ordinary cables that can not be compared, it is also more and more widely used.

At present, the most commonly used mineral insulated cables in the cable market are mainly the following three kinds:

Copper core copper sheath magnesium oxide insulated cable

Without outer sheath for BTTZ, BTTQ models, with outer sheath BTTVZ, BTTVQ, WD-BTTYZ.

It consists of a solid copper rod, magnesium oxide insulation, and a seamless copper tube sheath.

Flexible Inorganic Mica Tape Mineral Insulated Cable

Without outer sheath YTTW, RTTZ, with outer sheath YTTWV, WD-YTTWY, RTTZV, WR-RTTZY, BTTW, BTTRZ models.

It consists of copper-stranded wire, fluorine mica tape insulation, and copper tape longitudinally wrapped with a continuous welded sheath.

Flexible isolated aluminum sheathed mineral insulated cable

Generally NG-A, BTLY models.

It consists of copper-stranded wire, gold mica tape insulation, seamless aluminum tube sheath, oxygen barrier filling, isolation fire-resistant layer, and low-smoke halogen-free sheath.

Characteristics of MICC cables

Above 3 types of cables, the best fire resistance is the BTTZ series, which is the only recognized high-standard mineral insulated cable in the international market.

It adopts a high conductivity solid copper conductor, highly compressed powdered magnesium oxide as insulation, and a seamless copper tube as sheath.

It is also made by a special process of modern building wiring cable and special industries, such as metallurgy, chemical industry, petroleum, and other cables.

Due to the special nature of its materials and structure, the product has electrical properties, mechanical properties, environmental performance, and environmental performance that cannot be compared with organic cables.

This unique structure makes the melting point of the conductor and insulation materials °C and °C respectively.

This enables the cable to be used in fire conditions while the equipment can continue to operate safely under load even at temperatures over °C.

Advantages of Mineral Fire-Resistant Cables

● Service life of up to 100 years.

● Does not burn, does not support combustion, does not release toxic gases, zero combustion energy.

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● Continuous operating temperatures up to 250°C and short-term operating temperatures up to °C.

● Excellent fire resistance.

● Excellent fire resistance, cable can be reused after fire.

● Cable terminations and intermediate couplings are supplied with the cable for enhanced fire resistance reliability.

● The cable can withstand extremely high temperatures, falling objects, and fire water spraying during a fire.

● The cable can be used in high-temperature applications.

● Water, moisture, oil, and corrosion resistance.

● No aging, extremely stable cable performance.

● The metal sheath of the cable can be used as a grounding circuit.

● Excellent mechanical strength, good bending performance, can be used in complex structures and tight space installation environments.

● High current-carrying capacity due to the special characteristics of the cable structure.

● Small cable outer diameter, easy installation, low overall cost, no need to protect the cable through the pipe.

● Good explosion-proof performance and excellent resistance to nuclear radiation.

● Excellent electromagnetic shielding performance and electromagnetic compatibility.

● Can prevent animals from biting.

Mineral Insulated Cable Price Market

Mineral insulated cables can be used 1 to 2 sizes lower and save a ground wire core.

Most people think that mineral-insulated cables are expensive and do not use them.

Through the continuous efforts of manufacturers and material suppliers in recent years, the price of mineral-insulated cables is constantly approaching the price of ordinary cables.

Mineral insulated cable cross-sections of 25 mm2 or more are single-core cables, and thus the cable's current-carrying capacity than ordinary cables to be larger.

At the same time, the copper sheath of mineral insulated cable can be used directly for the grounding line so that the selection of mineral insulated cable can reduce a cable core.

For example, in China's National People's Congress Hall auditorium lighting system renovation project, the original plan was to use fire-resistant cable through the tube then decided to switch to mineral-insulated cable.

The two programs proposed to select the same cable specifications are small-size cables.

However, according to the total cost of the final project, with mineral insulated cable and fire-resistant cable price ratio of 97.59:100.

Installation of Mineral Insulated Cable

With the expansion of the scope of application of mineral insulated cables, many installation or construction units began to contact mineral insulated cables. 

Some project units do not understand the construction method of the product and do not know how to install it, resulting in many project installation problems, and some construction units resist the use of mineral insulated cable.

The cable is a simple way to put the line and does not need special tools and auxiliary facilities.

Laying can either go to the bridge, bracket or open laying.

In the cable accessories terminal and coupler installation, the manufacturer will send professional and technical personnel to the site to guide and support the supply of special construction tools.

Now the use of cable accessories is pressure-mounted, and the accessory connection is simple, and easy to operate, for the first contact, with less than two hours can master the installation and laying technology.

In addition, the mineral-insulated cables purchased from ZMS can be provided with a detailed explanation of the cable installation method, giving guidance on installation.

Installers can install and lay the cables without the guidance of the manufacturer's technicians as long as they follow this procedure.

Due to the many excellent characteristics of mineral insulated cables, and the manufacturing plant's vigorous promotion, the mineral mineral-insulated cable market gradually springs. 

In recent years, it has been adopted by many electrical design codes or standards at home and abroad, and also used in many projects in different industries.

It can be expected that in the next decade, the use of mineral insulated cables will continue to rise significantly.