YTTW flexible fire-resistant cable is made of copper conductor and is heat-resistant, belonging to the industrial category.
Performance Comparison between YTTW Flexible Fire-Resistant Cable and BTLY Mineral Insulated Cable
I. Product Structure:
1. BTLY New Aluminum-Sheathed Continuously Extruded Mineral Insulated Cable Structure:
① Copper Conductor ② Phlogopite Mica Tape Insulation ③ Aluminum Metal Sheath ④ Cross-Linked Isolation Jacket ⑤ Mg(OH)2+ or Al(OH)2+ Fire-Resistant Layer ⑥ Halogen-Free Low-Smoke Polyolefin Outer Sheath
2. YTTW Flexible Fire-Resistant Cable Structure:
① Copper Conductor ② Inorganic (Mineral) Insulation Tape that Resists High Temperatures (1375°C) and Does Not Burn ③ Outer Copper Sheath
II. Mica Tape Classification:
1. Inorganic (Mineral) Insulation Tape is commonly known as synthetic mica tape. Mica tape is also known as fire-resistant mica tape and is a fire-resistant insulating material.
2. Mica Tape by Application: Mica Tape for Motors and Mica Tape for Cables.
Mica Tape by Structure: Double-Sided Tape, Single-Sided Tape, Three-in-One Tape, Double-Film Tape, Single-Film Tape, etc. Mica tape can be categorized by type: synthetic mica tape, phlogopite tape, and muscovite tape.
3. Room Temperature Performance: Synthetic mica tape performs best, muscovite tape is second, and phlogopite tape is inferior.
High-Temperature Insulation Performance: Synthetic mica tape performs best, phlogopite tape is second, and muscovite tape is inferior.
High-Temperature Resistance: Synthetic mica tape (fluorophlogopite tape) contains no water of crystalline solids, has a melting point of 1375°C, offers a wide safety margin, and offers the best high-temperature resistance. Phlogopite mica releases water of crystalline solids above 800°C, offering second-best high-temperature resistance, while muscovite releases water of crystalline solids at 600°C, offering inferior high-temperature resistance.
4. Synthetic Mica Tape
Synthetic mica is an artificial mica with large, well-defined crystal structures synthesized under normal pressure using fluoride ions instead of hydroxyl groups. Synthetic mica tape is made from mica paper made from synthetic mica, with glass cloth attached to one or both sides with an adhesive. Glass cloth bonded to one side of mica paper is called "single-sided tape," while glass cloth bonded to both sides is called "double-sided tape." During the manufacturing process, the layers are bonded together, then oven-dried, rolled, and slit into tapes of varying sizes.
Synthetic mica tape not only shares the characteristics of natural mica tape—low expansion coefficient, high dielectric strength, high resistivity, and uniform dielectric constant—but also boasts high heat resistance, reaching Class A fire resistance (950-1000°C). Synthetic mica tape has a temperature resistance exceeding 1000°C, and thicknesses range from 0.08 to 0.15 mm, with a maximum width of 920 mm.
5. Phlogopite Mica Tape
Phlogopite mica tapes offer excellent electrical insulation and heat resistance, as well as strong resistance to acids, alkalis, compression, peeling, and radiation. They also possess excellent flexibility, bendability, and tensile strength, making them suitable for high-speed winding. Fire resistance tests show that wires and cables wrapped with phlogopite mica tape can withstand 90 minutes of fire resistance at 840°C and 1000V.
Phlogopite fiberglass fire-resistant tape is widely used in high-rise buildings, subways, large power stations, and key industrial and mining enterprises, where fire safety and firefighting are crucial. For example, it serves as the power supply and control lines for emergency equipment like firefighting equipment and emergency guidance lights. Due to its low price, it is the preferred material for fire-resistant cables.
6. Synthetic Mica Tape Information
Application of Synthetic Mica Tape in Class A Fire-Resistant Cables
①Overview
The application of Class A fire-resistant cables is gradually expanding, from offshore oil platforms to aviation, aerospace, shipping, subways, tunnels, shopping malls, hospitals, dance halls, metallurgy, chemical industry, and power plants, all requiring high fire resistance. In recent years, with the maturity of manufacturing technology for Class A fire-resistant synthetic mica tape, the use of Class A fire-resistant cables has continued to increase. As we all know, fire-resistant mica tapes are divided into two categories: Grade A (950-1000°C) and Grade B (750-800°C). The most popular types in the market are phlogopite and synthetic mica tapes.
② Regarding the Toxicity of Synthetic Mica Tape
Synthetic mica tape is made from fluorphlogopite. The structural formula of phlogopite is Kmg3(AISi3O10)(OH)2, while the structural formula of fluorophlogopite is Kmg3(AISi3O10)(OH)F2. Molecularly, the difference between the two is that the former contains OH ions, while the latter contains F ions. Their fluorine content is 8.89%. It is precisely because of the F ions in synthetic mica that its heat resistance is significantly improved. The fluorine content in synthetic mica is a pretext used by foreign film-reinforced phlogopite tape manufacturers to compete. In reality, the presence of fluorine is not the key factor for fire-resistant cables; the key is how much fluorine is released when the cable burns, and whether the released fluorine reaches a lethal level. One foreign manufacturer simply states that its film-reinforced phlogopite tape uses a "polymer film," but makes no mention of whether this polymer contains fluorine, a puzzling statement. The product manual only recommends wearing gloves when handling the film and washing hands with detergent afterward. This suggests that film-reinforced phlogopite tape contains toxic components.
III. Disadvantages of YTTW Flexible Fire-Resistant Cable
1. YTTW cable utilizes a copper sheath, significantly increasing production costs due to the increased copper usage.
2. Cables with larger cross-sections are still relatively rigid and lack flexibility. Therefore, larger cross-sections (greater than 630 mm²) cannot be produced, and cannot meet the high current requirements of the system.
3. According to the testing requirements specified by the British Metro, during testing, YTTW cable samples were subjected to two stages of combustion and spray testing. When bent 180° at the impact point, the copper sheath of the inorganic mineral insulated cable (YTTW) cracked along the weld at the bend. The crack length exceeded 10 cm, and the mica tape was observed to have burned into a black powder. Subsequently, the bend point was subjected to further impact testing at 30-second intervals for 15 minutes. The crack in the YTTW copper sheath at the bend was even larger, and the mica at the crack had severely fallen off. The insulation test showed 0 MΩ. After the impact, the sample was immersed in water and a voltage of 750V was applied. The YTTW sample failed the test due to surface cracking and a short circuit in the sheath.
Observations of the samples during the test and the final test results indicate that, under sustained high-temperature combustion conditions, the mica used for insulation and fire resistance in inorganic mineral insulated cables (i.e., flexible fire-resistant cables) will shed as powder, and the glass fiber cloth will become hard and brittle. Due to its structural characteristics, there are considerable gaps between the sheath and insulation, creating space for the shed mica powder, which can easily cause an electrical short circuit under external impact. Furthermore, the insulation layer of this type of cable lacks the dense magnesium oxide insulation of BTT cables, resulting in poor explosion-proof performance. Combustible gases, gasoline, and steam can spread through the gaps between the cable sheath and insulation layer to connected electrical equipment or other areas requiring explosion-proof protection. Therefore, caution should be exercised in selecting this cable for use in critical locations, such as fire protection systems.
4. According to cable withstand voltage test regulations, a voltage increase of 150V/s to 2500V for 15 minutes should not result in a breakdown. Some YTTW cables experienced breakdown when the voltage was increased to 1300V. Three hours later, when the voltage was reapplied, the cables broke down again at 2000V. This test shows that YTTW cables cannot recover their electrical performance after breakdown. BTT cables experienced no breakdown after the voltage was increased to 2500V at a rate of 150V/s for 15 minutes. To test their withstand voltage, the cables experienced breakdown when the voltage was further increased to 3500V. Three hours later, when the voltage was reapplied at a rate of 150V/s to 2500V, the voltage remained intact for 15 minutes. This demonstrates that traditional mineral insulated cables can recover their original performance after breakdown. This also means that if an overvoltage is accidentally generated during cable use and the cable breaks down, the insulation layer of the BTT cable is damaged due to the partial melting of the magnesium oxide caused by air ionization at the breakdown site. However, the composition of the magnesium oxide remains unchanged after melting, and the cable can recover its original electrical performance. Once a YTTW cable is punctured, its electrical performance cannot be restored and it must be scrapped.
The experimental results show that under the same current and ambient temperature conditions, the conductor and sheath temperatures of the BTT cable in free air are approximately 6°C lower than those of the YTTW cable. Regarding the cable itself, the type of insulation material and its heat resistance and heat dissipation properties significantly affect the cable's current carrying capacity. Mica tape clearly has poorer heat dissipation than magnesium oxide. According to GB/T 16895, for bare mineral insulated cables not intended for human contact with flammable materials, the current carrying capacity is 140A at a metal sheath temperature of 105°C and an ambient temperature of 30°C. However, the above experiments were conducted at an ambient temperature of 20°C. If the ambient temperature reaches 30°C, the cable sheath surface temperature will be even higher.
IV. BTLY and BTTLY Continuously Extruded Aluminum-Sheathed Mineral Insulated Cables
Based on the traditional BTT mineral-insulated cable, we have independently developed the new BTLV, BTTLV, BTLY, and BTTLY aluminum-sheathed continuously extruded mineral-insulated cables.
1. Product Structure: 1. Conductor: Round stranded copper wire (softer than the solid copper rod of BTT); 2. Insulation: Pure gold mica tape (no longer composited with the extruded insulation, thus eliminating carbon particles and improving electrical stability); 3. Metal sheath: Continuously extruded aluminum tube (significantly simplifying the BTT copper tube drawing process); 4. Isolation sleeve (cross-linked insulation); 5. Fire-resistant layer (coated with an inorganic material—Mg(OH)2 or Al(OH)2—that is flame-insoluble, non-combustible, and expandable—fire-retardant); 6. Outer sheath: Plastic (polyolefin or polyvinyl chloride). Using aluminum as the primary material, extruded metal tubes instead of drawn copper tubes not only simplifies the process and improves efficiency, but also significantly reduces product costs (aluminum costs only 1/10 of copper). The reason aluminum tubes can replace copper tubes and remain resistant to high-temperature flames is due to the intumescent refractory layer extruded over the tubes. Under the attack of flames, the intumescent layer foams and solidifies, forming a thick barrier that blocks the flames from directly impacting the tubes. This not only preserves the integrity of the tubes but also reduces the heating temperature of the mica tape to below 600°C, undoubtedly improving the insulation stability of the mica tape (the insulation resistance of mica tape increases with decreasing temperature).
2. Features:
① Fire resistance meets the three tests of BS6387: no breakdown under 950°C flame for 3 hours, no damage after 30 minutes at 650°C and then 15 minutes of water spray (direct immersion is also acceptable), and no damage after 15 minutes of impact and vibration at 950°C flame, thus fully meeting the BTT fire resistance standards.
② This product is available in sizes from 1.5 to 6 square meters for 1 to 37 cores, 10 to 240 square meters for 1 to 5 cores, and 300 to 630 square meters for single cores. Lengths can be customized, and the cable is delivered in whole, jointless reels.
③ No additional conduit is required for installation, and it offers the same waterproof and impact-resistant properties as BTT cables.
④ Excellent rodent, ant, and radiation resistance ensures cable stability, long life, and durability.
⑤ With low operating temperature, low line loss, strong overload resistance, long service life, and high safety, it is particularly suitable for projects with environmentally friendly requirements.
⑥ Explosion-proof (The highly compacted insulation material in the cable and the cable terminals with specially sealed sleeves prevent steam, gas, and flame from entering the electrical equipment connected to the cable, making it suitable for use in explosion-hazardous areas and for connecting various explosion-proof equipment and devices.)
⑦ Corrosion-resistant (The metal sheath of the BTT(L) series mineral insulated cable is highly corrosion-resistant, eliminating the need for additional protective measures for most installations. Even in locations where the cable's metal sheath is susceptible to chemical corrosion or industrial pollution, the cable remains safe due to the protection of the outer plastic sheath.)
⑧ High mechanical strength (BTT(L) series mineral insulated cables are highly corrosion-resistant and require no additional protective measures for most installations.) The L series mineral insulated cables are rugged and durable, remaining operational even when deformed by one-third of their diameter. Even withstanding severe mechanical damage, their electrical performance remains intact.
3. BTLY new mineral insulated cables have been adopted in many key projects nationwide, including the Shanghai World Expo, China's tallest building, the Shanghai Tower, the Bank of China Headquarters in Beijing, and the Industrial and Commercial Bank of China Head Office Building Phase II (Business Operations Center) in Beijing. They are widely used in fire-resistant cable systems. Furthermore, this product has passed the following tests:
1. Passed testing by the National Fireproof Building Materials Quality Supervision and Inspection Center. Testing is based on the following:
① BS 6387:1994 "Performance Requirements for Maintaining Circuit Integrity of Cables Under Fire Conditions," including the simple fire resistance test (Category C) specified in Annex D2 of BS 6387:1994 (950°C, 180 min). When the sample is subjected to the rated voltage, a 3A fuse does not blow.
② Fire resistance test with water spray according to BS 6387:1994 Annex D3 (Category W): Fire at 650°C with water spray for 15 minutes. Under the rated voltage, a 3A fuse does not melt.
③ Fire resistance test with impact according to BS 6387:1994 Annex D4 (Category Z): Fire at 950°C with mechanical impact for 15 minutes. Under the rated voltage, a 3A fuse does not melt.
2. Tested in a real-life fire test conducted by the Sichuan Fire Research Institute of the Ministry of Public Security. Multiple parameters were tested during the real-life fire test, including smoke concentration, chemical composition, illumination, thermal radiation intensity, self-extinguishing time, and degree of combustion.
3. Certifications have been obtained from relevant departments and institutions.
V. Melting Point and Decomposition Parameters
1. Ordinary Mica Tape (Pure Mica Tape) 430°C 2. Muscovite Mica Tape 450°C
3. Phlogopite Mica Tape 820°C 4. Synthetic Mica Tape (Fluoromica Tape) 1020°C
5. Aluminum 660.4°C 6. Silver 960°C
7. Gold 1063°C 8. Copper 1083°C
9. Iron 1535°C
