IEC 60331 & BS 6387: Critical Fire-Safety Standards
Cable manufacturers must comply with fire-resistance regulations to safeguard buildings, industrial plants, and transit systems. IEC 60331 and BS 6387 are international tests that ensure cables maintain circuit integrity during a fire. IEC 60331 subjects powered cables (up to 1.0 kV) to a high-temperature flame (~830°C) with mechanical shock, while BS 6387 applies a hotter flame (~950°C) plus water spray and impacts to verify that the cable still conducts. These rigorous tests simulate worst-case fire scenarios, verifying that emergency lighting, alarms, ventilation, and other critical circuits stay powered during a blaze.
Fire-resistant cables incorporate a multi-layer mica-tape insulation around each conductor. For example, after the copper core and primary insulation are applied, one or more wraps of mica tape (often glass-fiber-reinforced phlogopite or synthetic mica) are bonded with high-temperature silicone. This inorganic tape has excellent dielectric strength and thermal stability, resisting flame temperatures above ~1000 °C while emitting no halogen or toxic smoke. In practice, each live conductor is spiral-wrapped with mica tape (often in multiple layers) so that even if the outer jacket burns away, the circuit remains insulated. Mica tape thus enables cables to meet IEC 60331/B /B/B and IEC 6387 fire tests (including flame, water spray, and shock) by keeping the conductors alive under fire conditions.
Phlogopite vs Synthetic Mica Tape: Performance Trade-Offs
Cable designers balance cost and performance by choosing phlogopite or synthetic mica. Phlogopite mica tape offers good fire resistance and is flexible with high tensile strength (ideal for high-speed wrapping). In endurance tests, cables wrapped with phlogopite tape “guarantee no breakdown for 90 min” at 840 °C (1 kV). Its lower cost makes phlogopite tape the standard choice for most building, industrial, and transit cables. By contrast, synthetic mica (a fluorophlogopite) has no bound water and a melting point around 1375 °C, so it retains insulation above ~1000 °C. This superior heat tolerance means synthetic mica tapes are reserved for mission-critical or high-performance cables. Manufacturers select synthetic mica when a maximum fire-safety margin is required, and phlogopite mica when budget or flexibility is the priority.
Mica Tape Formats: Spool vs Pad
Mica tape is offered in spool or pad formats. Suppliers often label products as “mica tape in spool” (long reels) or “mica tape pad” (short rolls) to denote these options. Spools (large reels) contain kilometers of tape, allowing high-speed taping lines to run continuously without stopping. For example, some systems use tower trays that hold up to 50,000 m of tape on 400 mm reels (standard cores are 52–120 mm). In contrast, mica tape pads are shorter rolls (hundreds to a few thousand meters) intended for vertical, single-layer wrapping machines. Manufacturers choose the spool format for uninterrupted, large-volume production, and the pad format for compact or specialized taping equipment.
By selecting the right mica-tape type and format, cable makers can reliably meet IEC 60331 and BS 6387 fire-resistance requirements. Properly wrapped mica layers maintain cable circuits' integrity under severe flame, water, or mechanical stress, thereby preserving power to vital safety systems in buildings, industrial plants, and transit installations, while meeting fire-safety certification requirements.
Sources: IEC 60331/BS 6387 test descriptions; mica-tape properties and applications.