BS 6708 Type 20 & Type 21 640/1100V Armoured Heavy-Duty Mining Power Cable for Excavating and Crushing Equipment (EPR Insulation, Steel Wire Armour, Chloroprene Sheath)
APPLICATION:
Used for supplying excavating, crushing machines and equipment.
Cable Structure:
CONDUCTOR : Electrolytic, stranded, tinned copper wire IEC 60228 Class 5
INSULATION : EPR
LAYUP : Cores are laid up over a cradle without contacting each other.
BEDDING : Rubber based bedding compound.
ARMOUR : Galvanized steel pliable armour.
OUTER SHEATH : Heavy duty chloroprene outer sheath.
Cable Properties:
RELATED STANDARDS : BS 6708
RATED VOLTAGE : 640/1100 V
TEST VOLTAGE : 3 kV
Technical Specifications:
BS 6708 TYPE 20 | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Cross Section | 3×2,5 | 3×4 | 3×6 | 3×10 | 3×16 | 3×25 | 3×35 | 3×50 | 3×70 | 3×95 | 3×120 | 3×150 | |
Phase and Earth Conductors | |||||||||||||
Conductor diameter | Nom. mm | 2.10 | 2.70 | 3.30 | 4.40 | 5.50 | 7.10 | 8.40 | 10.10 | 11.90 | 13.90 | 15.80 | 17.00 |
Insulation thickness | mm | 1.4 | 1.4 | 1.5 | 1.5 | 1.5 | 1.6 | 1.6 | 1.7 | 1.8 | 2.0 | 2.2 | 2.3 |
Cable details | |||||||||||||
Radial thickness of inner sheath | mm | 2.0 | 2.0 | 2.5 | 2.5 | 2.5 | 2.5 | 2.5 | 2.5 | 2.5 | 3.8 | 3.8 | 5.0 |
Size of armour | mm | 7/0,45 | 7/0,45 | 7/0,71 | 7/0,71 | 7/0,71 | 7/0,90 | 7/0,90 | 7/0,90 | 7/0,90 | 7/0,90 | 7/0,90 | 7/1,25 |
Outer sheath thickness | mm | 2.5 | 2.5 | 3.8 | 3.8 | 3.8 | 4.0 | 4.3 | 4.7 | 5.2 | 5.8 | 6.2 | 6.6 |
Max. overall diameter | mm | 26.9 | 28.2 | 36.5 | 38.4 | 40.8 | 47.0 | 50.6 | 56.7 | 62.7 | 72.1 | 77.0 | 87.3 |
Min. bending radius | mm | 243 | 254 | 329 | 346 | 368 | 423 | 456 | 511 | 565 | 649 | 693 | 786 |
Appx. cable weight | kg/km | 990 | 1.15 | 2 | 2.35 | 2.75 | 3.35 | 4.3 | 5.32 | 6.75 | 8.75 | 10.65 | 12.5 |
Copper weight | kg/km | 72 | 115 | 173 | 288 | 461 | 720 | 1.008 | 1.44 | 2.016 | 2.736 | 3.456 | 4.32 |
Electrical details | |||||||||||||
“Continuous current | A | 28 | 37 | 46 | 63 | 85 | 110 | 135 | 170 | 205 | 250 | 295 | 320 |
Max. DC resistance at 20°C | |||||||||||||
Phase and earth conductors | Ω /km | 8.21 | 5.09 | 3.39 | 1.95 | 1.24 | 0.795 | 0.565 | 0.393 | 0.277 | 0.210 | 0.164 | 0.132 |
Armour | Ω /km | 4.6 | 4.2 | 2.2 | 2.0 | 1.9 | 1.3 | 1.2 | 1.1 | 0.94 | 0.80 | 0.74 | 0.45 |
What Is BS 6708 and Why Is It Important for Mining Power Cables?
BS 6708 is a British Standard specifically developed for flexible and armoured power cables used in mining and heavy industrial environments. Unlike general industrial cable standards, BS 6708 focuses on mechanical robustness, electrical safety, and durability under extreme operating conditions, such as vibration, impact, abrasion, and exposure to oils or moisture.
For mines using excavators, crushers, and mobile heavy equipment, compliance with BS 6708 ensures:
Safe operation under harsh mechanical stress
Reliable power delivery at medium voltage levels
Long service life with reduced downtime
BS 6708 Type 20 and Type 21 cables are among the most commonly specified solutions when armoured protection and high flexibility are both required.
What Are BS 6708 Type 20 and Type 21 Mining Cables Used For?
Both cable types are designed for supplying power to excavating, crushing, and heavy mining machinery, but they differ mainly in core configuration:
Type 20: 3-core construction (typically three phase + earth via armour)
Type 21: 4-core construction (three phase + dedicated earth conductor)
Typical Applications Include:
Mobile crushers and screening plants
Excavators and bucket wheel machines
Portable mining substations
Heavy conveyor drives
Open-cast and surface mining equipment
Their 640/1100 V rated voltage makes them ideal for medium-voltage mining distribution systems.
How Do Type 20 and Type 21 Cables Compare?
BS 6708 Type 20 vs Type 21 – Key Differences
Feature | Type 20 | Type 21 |
|---|---|---|
Core configuration | 3 cores | 4 cores |
Typical use | Three-phase systems using armour as earth | Systems requiring dedicated earth conductor |
Flexibility | High | Slightly lower due to extra core |
Overall diameter | Smaller | Larger |
Weight | Lighter | Heavier |
Safety redundancy | Standard | Higher (separate earth) |
Selection Tip:
Choose Type 20 where system design allows armour as earth.
Choose Type 21 when regulations or safety philosophy require a separate earth conductor.
What Are the Installation Recommendations for BS 6708 Type 20 & 21 Cables?
How Should Bending Radius Be Managed?
Always respect the minimum bending radius listed in the technical table
Avoid sharp bends near cable entry points on machinery
How Should Armour Be Terminated?
Use proper armoured glands
Ensure electrical continuity of armour where used as earth
What About Cable Routing?
Avoid dragging cables over sharp rocks
Use rollers or cable trays where possible
Regularly inspect outer sheath integrity
Proper installation directly impacts service life and operational safety.
Frequently Asked Questions (FAQ)
Are BS 6708 Type 20 and Type 21 cables suitable for underground mining?
Yes. Their armoured construction, EPR insulation, and chloroprene sheath make them suitable for both surface and underground mining when installed correctly.
Can these cables withstand continuous movement?
They are designed for moderate mobility. For highly dynamic reeling or trailing applications, specialized reeling cables may be more appropriate.
Why not use standard industrial SWA cables instead?
Mining cables under BS 6708 offer:
Higher flexibility
Superior mechanical protection
Better resistance to harsh mining conditions
Standard SWA cables often fail prematurely in mining environments.
How do I select the correct conductor size?
Selection should consider:
Continuous current demand
Ambient temperature
Voltage drop
Installation method
Consulting technical tables and engineering calculations is strongly recommended.
Why Choose BS 6708 Type 20 & Type 21 for Heavy-Duty Mining Equipment?
In demanding mining operations, power cable failure is not just a maintenance issue—it is a safety and productivity risk. BS 6708 Type 20 and Type 21 mining cables provide a proven balance of:
Electrical reliability
Mechanical strength
Operational safety
Long-term cost efficiency
Call to Action (CTA)
If you are designing, upgrading, or maintaining mining power systems for excavators or crushing equipment, selecting the right BS 6708 Type 20 or Type 21 cable is critical.
👉 Contact a professional mining cable supplier or technical engineer to:
Confirm correct sizing
Ensure compliance with local mining regulations
Optimize cable life and operational safety
The right cable choice today prevents downtime and hazards tomorrow.
