Application & Operating Conditions
BS 6708 Type 11 is a compact 640/1100 V 4-core individually screened trailing cable (3×16+16 mm², 85 A continuous) designed for mobile auxiliary mining machines, stage loaders, hydraulic power packs, and smaller coalcutters where tight bending (264 mm radius) and lightweight handling (2,000 kg/km) are critical.
Cradle-Supported High Flexibility
Replacing the central metallic earth wire with a profiled elastomeric cradle cushions the four 16 mm² screened cores under sharp bending (264 mm min. radius).
4-Screen Earth Continuity
All three phase cores and the 16 mm² pilot core carry composite copper/nylon braided screens laid in mutual electrical contact (1.05 Ω/km combined resistance).
Compact 30.9–33.0 mm Envelope
Achieves a 5.6 mm smaller outside diameter and 20% lower weight than Type 7M 3×16+16+16 for portable underground pumps, drills, and auxiliary face equipment.
Type 11 vs. Type 7M Distinction: Unlike Type 7M (which includes a central bare copper earth core), BS 6708 Type 11 uses a non-metallic elastomeric centre cradle and utilizes the four mutually contacting composite copper/nylon screens as the collective protective earth conductor.
Cable Construction (BS 6708 Type 11)
Constructed to BS 6708, Type 11 lays four identical composite-screened 16 mm² EPR cores in mutual screen contact around a shock-absorbing elastomeric rubber cradle.
| Layer / Component | Material & BS 6708 Engineering Specification |
|---|---|
| 1. Conductors | Electrolytic stranded tinned copper wire, IEC 60228 Class 5 (126/0.40 mm stranding, 5.50 mm diameter on all 4 cores) |
| 2. Core Insulation | Thermosetting EPR insulation (8.60 mm diameter over insulation) |
| 3. Core Separator | Coloured textile tape for core identification (Red, Yellow, Brown phases; Blue pilot) |
| 4. Composite Screens | Tinned copper and nylon braided screen over all three phase cores and the pilot core (10.90 mm screen OD) |
| 5. Core Lay-Up | Four screened cores laid up around a central elastomeric rubber cradle and in direct screen-to-screen contact |
| 6. Bedding & Outer Sheath | Rubber-based inner bedding compound and heavy-duty flame-retardant chloroprene (PCP) outer sheath |
BS 6708 Type 11 Cross-Section: Three composite-screened phase cores and one composite-screened pilot core laid in mutual contact around a central elastomeric cradle.
Technical Characteristics
Tested at 3 kV AC under BS 6708, Type 11 combines 85 A continuous / 96 A intermittent current capacity with compact geometry.
| Parameter | BS 6708 Rated Value |
|---|---|
| Manufacturing Standard | BS 6708 (Flexible cables for use at mines and quarries) |
| Rated / Test Voltage | 640/1100 V AC (Routine AC Test: 3 kV) |
| Nominal Size & Stranding | 3×16 + 1×16 mm² (126/0.40 mm Class 5 tinned copper) |
| Overall Diameter (Min – Max) | 30.9 mm – 33.0 mm |
| Minimum Bending Radius | 264 mm |
| Maximum Pulling Tension | 384 kgf |
| Current Rating (@ 25 °C) | 85 A continuous | 96 A intermittent |
| Combined 4-Screen Earth Resistance | 1.05 Ω/km at 20 °C |
Complete Dimensional & Electrical Data (BS 6708 Type 11)
Full nominal dimensional, mechanical, and electrical parameters for BS 6708 Type 11 (3×16+16 mm²).
BS 6708 Type 11 (3×16+16 mm²) — Core & Mechanical Dimensions
| Nominal Size (mm²) | Phase / Pilot Strand. (mm) | Cond. Dia. (mm) | Insul. Dia. (mm) | Screen Dia. (mm) | Min. OD (mm) | Max. OD (mm) | Min. Bend Radius (mm) | Max Pulling Tension (kgf) | Approx. Weight (kg/km) | Copper Weight (kg/km) |
|---|---|---|---|---|---|---|---|---|---|---|
| 3×16+16 | 126/0.40 | 5.50 | 8.60 | 10.90 | 30.9 | 33.0 | 264 | 384 | 2000 | 1100 |
BS 6708 Type 11 (3×16+16 mm²) — Current Rating & Electrical Characteristics
| Nominal Size (mm²) | Cont. Current @ 25°C (A) | Interm. Current @ 25°C (A) | Phase DC Res. 20°C (Ω/km) | Pilot DC Res. 20°C (Ω/km) | Screens+Earth Res. (Ω/km) | Reactance 50Hz (Ω/km) | Reactance 60Hz (Ω/km) | Min. Insul. Res. (MΩ·km) | Volt Drop (mV/A/m) |
|---|---|---|---|---|---|---|---|---|---|
| 3×16+16 | 85 | 96 | 1.24 | 1.24 | 1.05 | 0.109 | 0.131 | 435 | 2.62 |
Selection Guide: BS 6708 Type 11 vs. Type 7, Type 14 & Type 16
Compare BS 6708 640/1100 V trailing cable designs when sizing 16 mm² auxiliary feeds vs. larger 25–150 mm² face machinery cables.
| BS 6708 Model | Core & Pilot Architecture, Earth Design & Primary Duty |
|---|---|
| BS 6708 Type 7 | BS 6708 Type 7: 3 composite-screened phase cores + 1 unscreened single pilot core + central bare tinned-copper earth (16–150 mm², 8 sizes) for standard 640/1100 V coalcutters and face shearers. |
| BS 6708 Type 7M | BS 6708 Type 7M: 3 composite-screened phase cores + 1 individually screened pilot core (equal phase/pilot size up to 150 mm²) + central bare earth for enhanced pilot earth-fault segregation. |
| BS 6708 Type 7S | BS 6708 Type 7S: 3 composite-screened phase cores + 1 unscreened 3-core pilot sub-unit (3×4 to 3×10 mm²) + central bare earth (50–150 mm²) for multi-channel interlock/telemetry control. |
| BS 6708 Type 11 (This Product) | 3 composite-screened phase cores + 1 composite-screened pilot core (3×16+16 mm²) laid up around an elastomeric rubber cradle (earth continuity via contacting screens). |
| BS 6708 Type 14 | BS 6708 Type 14: 5-core cradle layout: 3 composite-screened phase cores + 1 unscreened pilot core + 1 unscreened insulated earth core (25–95 mm²) around an elastomeric centre. |
| BS 6708 Type 16 | BS 6708 Type 16: Compact trefoil layout: 3 composite-screened phase cores + 2 unscreened interstitial earth cores + 1 unscreened pilot core tucked into outer valleys (25–95 mm²) for reduced overall diameter. |
Frequently Asked Questions (FAQ)
Engineering answers on Type 11 screen-earth fault capacity and larger cross-section alternatives.
How is protective earthing achieved in BS 6708 Type 11 without a separate earth core?
All four cores (3 phases + 1 pilot) feature heavy tinned-copper and nylon composite braided screens laid in continuous physical contact around the elastomeric cradle, yielding a low parallel earth resistance of 1.05 Ω/km.
Which BS 6708 cable should I select if my equipment requires cross-sections above 16 mm²?
Type 11 is standardized specifically at 3×16+16 mm². For 25 mm² to 95 mm² cradle-core trailing cables with dedicated earth cores, select Type 14 or Type 16; for 16–150 mm² central-earth cables, select Type 7 or Type 7M.
Is BS 6708 Type 11 suitable for explosive underground coal atmospheres?
Yes. Its heavy-duty flame-retardant polychloroprene (PCP) outer sheath and individual metallic core screening are specifically engineered for Group I deep coal mines and dusty surface quarries.
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