Application & Operating Conditions
BS 6708 Type FS4 is a 640/1100 V flat-profile flexible power and pilot supply cable designed specifically for overhead catenary suspension loops, monorail festoon trolleys, and compact cable carriers in deep underground coal mines and surface mineral plants where explosive methane or coal dust atmospheres can accumulate.
Overhead Catenary & Monorail Festoons
Parallel flat core arrangement without inter-core contact eliminates axial twisting (corkscrewing) during high-cycle folding on underground roadway monorails and stage-loader festoon tracks.
Tight Single-Plane Bending (100–120 mm)
Achieves a minimum bending radius of just 100 mm (4×2.5 mm²) to 120 mm (4×4 mm²) across the minor axis—allowing compact loop stacking on short trolley beams in low-seam headings.
Full 4-Core Earth-Fault Screening
Every core—both the three power phases and the pilot conductor—carries an individual tinned copper braided screen (7.40–8.48 Ω/km) encapsulated inside a thick 3.8 mm flame-retardant PCP sheath.
Catenary Trolley Clamping Note: Support flat BS 6708 Type FS4 loops using radiused elastomer-lined festoon saddles matched to the 20.1 × 14.4 mm (4×2.5) or 34.1 × 15.3 mm (4×4) profile, and maintain at least 100–120 mm bend radius at loop crowns.
Cable Construction (BS 6708 Type FS4 Flat Architecture)
All four screened cores are positioned parallel in a single plane without touching each other, moulded directly into the heavy-duty chloroprene elastomeric web so mechanical shear during trolley travel cannot abrade adjacent screens.
| Layer / Component | Material & BS 6708 Engineering Specification |
|---|---|
| 1. Conductors (4 Cores) | Electrolytic annealed flexible stranded tinned copper wire, IEC 60228 Class 5 (50/0.25 mm for 2.5 mm²; 50/0.30 mm for 4 mm²). |
| 2. Core Insulation | Extruded Ethylene Propylene Rubber (EPR) dielectric, 1.0 mm nominal radial wall thickness. |
| 3. Core Identification Separator | Coloured textile tape applied helically over the EPR insulation for unambiguous phase and pilot core identification. |
| 4. Individual Metallic Screens | Close-woven tinned copper wire braided screen applied individually over all phase cores and the pilot core. |
| 5. Parallel Flat Lay-Up | Four screened cores laid parallel in a flat configuration without contacting each other, separated by integral elastomeric web sections. |
| 6. Outer Sheath | Heavy-duty black polychloroprene (PCP / chloroprene) compound, 3.8 mm nominal radial thickness, oil-, abrasion-, and flame-resistant. |
BS 6708 Type FS4 Cross-Section: Four parallel Class 5 tinned copper cores with EPR insulation, coloured textile separator tapes, and individual tinned copper wire braids encapsulated in a non-contacting flat black PCP profile.
Technical Characteristics
Electrical test parameters, dimensional limits, and thermal ratings verified in accordance with British Standard BS 6708 for 640/1100 V flat catenary cables.
| Parameter | BS 6708 Rated Value |
|---|---|
| Reference Standard | BS 6708 (Flexible Flat Cables for Overhead Catenary Systems in Mines) |
| Rated Voltage (Uo/U) | 640 / 1100 V AC |
| Routine AC Test Voltage | 3 kV AC |
| Core Configuration | 4×2.5 mm² and 4×4 mm² (3 Screened Phase Cores + 1 Screened Pilot Core) |
| Minimum Bending Radius | 100 mm (4×2.5 mm²) / 120 mm (4×4 mm²) across flat plane |
| Continuous Current Rating (@ 25 °C) | 28 A (4×2.5 mm²) / 37 A (4×4 mm²) |
| Conductor / Screen Max. DC Resistance | 7.82 / 7.40 Ω/km (4×2.5 mm²); 4.85 / 8.48 Ω/km (4×4 mm²) at 20 °C |
| Outer Sheath Compound | Heavy-Duty Chloroprene (PCP), Black, Flame-Retardant & Mineral-Oil Resistant |
BS 6708 Type FS4 Complete Specification & Electrical Tables
Complete dimensional, mass, ampacity, and DC resistance parameters for BS 6708 Type FS4 flat catenary cables.
1. Core, Flat Profile & Mechanical Data (4×2.5 mm² & 4×4 mm²)
| Nominal Size (mm²) | Conductors | Stranding (No./mm) | Cond. Dia. (mm) | Insul. Thick. (mm) | Outer Sheath (mm) | Min. Overall W×H (mm) | Max. Overall W×H (mm) | Min. Bend Radius (mm) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|---|
| 4×2.5 | 4×2.5 | 50/0.25 | 2.10 | 1.0 | 3.8 | 18.1 × 12.4 | 20.1 × 14.4 | 100 | 450 | 160 |
| 4×4 | 4×4 | 50/0.30 | 2.70 | 1.0 | 3.8 | 32.2 × 13.3 | 34.1 × 15.3 | 120 | 550 | 230 |
2. Continuous Current Ratings & DC Resistance Values
| Nominal Size (mm²) | Continuous Current @ 25 °C (A) | Conductor Max. DC Res. @ 20 °C (Ω/km) | Each Screen Max. DC Res. @ 20 °C (Ω/km) |
|---|---|---|---|
| 4×2.5 | 28 | 7.82 | 7.40 |
| 4×4 | 37 | 4.85 | 8.48 |
Selection Guide: BS 6708 Auxiliary, Catenary, Drill & Control Cables
Match your underground auxiliary circuit—catenary festoon, 125 V face drill, 550 V lighting feeder, or multi-core machine control—to the dedicated BS 6708 construction.
| BS 6708 Model | Core & Pilot Architecture, Earth Design & Primary Duty |
|---|---|
| BS 6708 Type FS4 (640/1100V Flat) (This Product) | Flat parallel 4-core geometry (4×2.5 & 4×4 mm²) with tinned copper braided screens on all phase and pilot cores for monorail festoon and overhead catenary loops (100–120 mm bend radius). |
| BS 6708 Type 44 (125/72V Screened Drill) | BS 6708 Type 44 (125/72V Screened Drill): 5×6 mm² handheld drilling machine cable with composite copper/nylon braided screens on 3 phase cores + unscreened pilot & earth cores around an elastomeric cradle. |
| BS 6708 Type 43 (125/72V Conducting Rubber Drill) | BS 6708 Type 43 (125/72V Conducting Rubber Drill): 5×6 mm² metal-braid-free drilling cable with cores separated around a semiconducting elastomeric cradle and 1.5 mm conducting rubber inner sheath for non-fraying flex fatigue resistance. |
| BS 6708 Type 70 & Type 71 (320/550V Armoured) | BS 6708 Type 70 & Type 71 (320/550V Armoured): 4-core (Type 70, 4×4 mm²) and 5-core (Type 71, 5×4 mm²) unscreened EPR power & coalface lighting cables protected by 7/0.45 mm galvanized steel pliable wire armour. |
| BS 6708 Type 506 / 512 / 518 / 524 (320/550V Control) | BS 6708 Type 506 / 512 / 518 / 524 (320/550V Control): 6-, 12-, 18-core (1.34 mm²) and 24-core (0.93 mm²) individually composite-screened & pliable wire armoured control cables for inter-segment mining machine telemetry and pilot interlocks. |
| BS 6708 Type 7 (640/1100V Trailing) | BS 6708 Type 7 (640/1100V Trailing): Primary 640/1100 V unarmoured coalcutter trailing feeder (16–150 mm²) with 3 composite-screened phase cores, 1 unscreened pilot core, and central bare earth. |
Frequently Asked Questions (FAQ)
Engineering answers regarding BS 6708 Type FS4 earth continuity, flat trolley clamping, and core screening.
How is protective earth continuity achieved in a 4-core BS 6708 Type FS4 flat cable?
In BS 6708 Type FS4, each of the four cores (three phases plus one pilot) carries a low-resistance tinned copper wire braided screen (7.40 Ω/km per screen on 4×2.5 mm² and 8.48 Ω/km on 4×4 mm²). When bonded together at the flameproof gland or catenary junction box, the four parallel metallic braids form both a radial fault-interception shield and the collective earth-continuity path.
Why are the four screened cores separated inside the PCP sheath rather than touching?
Unlike circular trailing cables where contacting screens share earth-fault current directly, flat catenary cables flex repeatedly over small 100–120 mm trolley saddles. Moulding an elastomeric chloroprene bridge between adjacent braided screens prevents wire-on-wire fretting fatigue while preserving single-plane flexibility.
Can TEBAOFLEX supply BS 6708 Type FS4 pre-cut for monorail festoon kits?
Yes. We manufacture BS 6708 Type FS4 in continuous drum lengths or pre-measured catenary assembly lengths with full 3 kV AC routine dielectric test certificates and conductor/screen DC resistance reports.
Need BS 6708 Type FS4 Flat Catenary Cable Pricing?
Share your required cross-section (4×2.5 mm² or 4×4 mm²), monorail travel length, and destination port. Our engineering team provides factory quotations and BS 6708 compliance data within 12 hours.
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