Cable Types for Installation in Flammable and Explosive Environments
Working in flammable or explosive environments such as petroleum plants, chemical manufacturing facilities, and mining operations requires strict compliance with safety regulations. Electrical cables in these areas are not just about carrying current, they are part of the safety system, preventing ignition sources and ensuring the integrity of the installation.
This guide explains the types of cables used, relevant standards, and installation requirements for hazardous areas.
1. Understanding Hazardous Areas and Flash-Point
In hazardous areas, flammable liquids or gases can mix with air to form explosive atmospheres. This risk is most dangerous between the lower explosive limit (LEL) and upper explosive limit (UEL).
- Flash-point: The lowest temperature at which a liquid produces enough vapor to form an ignitable mixture.
- Liquids safe at room temperature can become dangerous when heated to their flash-point.
Key Standard: BS 5345 and IEC 60079 classify hazardous zones and define flameproof equipment requirements.
2. Cable Requirements in Explosive Atmospheres
Electrical cables in hazardous areas must:
- Prevent ignition by containing any spark or hot gas.
- Maintain integrity under fire and mechanical stress.
- Be installed with flameproof glands to ensure a sealed system.
3. Approved Cable Types for Hazardous Areas
3.1 Mineral Insulated Copper Cables (MICC)
- Features:
- Non-combustible copper sheath.
- High temperature resistance.
- Excellent mechanical protection.
- Installation:
- Terminate with approved flameproof glands.
- For underground installation, use PVC sheath and bury at least 500 mm deep.
Applications:
- Control circuits in refineries.
- Fire detection and alarm systems.
3.2 PVC Armoured Cables
- Features:
- Steel wire armouring (SWA) for mechanical protection.
- PVC insulation resistant to oil, water, and sunlight.
- Installation:
- Must use Ex-certified flameproof glands.
Applications:
- Power distribution to motors and pumps in hazardous zones.
3.3 Enhanced Performance Cables (BS 5467 / BS 6724)
- Features:
- Low Smoke Zero Halogen (LSZH) for fire safety.
- High tensile strength and abrasion resistance.
- Installation:
- Suitable for fixed installation in cable trays or underground ducts.
4. Certification & Marking
Cables and accessories for hazardous areas must have proper markings:
- Ex: Certified for explosive atmospheres.
- EEx: Compliant with harmonized European Standard (EN).
- Group II: For surface industries (petroleum, chemical plants).
- Group I: For mining.
5. Installation Best Practices
| Step | Best Practice | Reason |
|---|---|---|
| Use Ex-certified glands | Prevents gas ingress into cable terminations | Maintains flameproof rating |
| Follow burial depth (≥ 500 mm) | Protects from mechanical damage | Long-term reliability |
| Avoid sharp bends | Prevents stress on insulation | Extends cable life |
| Separate from non-Ex circuits | Reduces interference & risk | Compliance with IEC/BS standards |
6. Real-World Example: Chemical Plant Hazardous Area Installation
In a new greenfield chemical plant project, the engineering team selected:
- 33 kV PVC armoured cables for main feeders to explosion-proof switchgear.
- MICC cables for emergency lighting circuits inside hazardous zones.
- All terminations used EEx d flameproof glands with double sealing.
This ensured compliance with BS 5345, IEC 60079, and local petroleum regulations.
7. Key Standards to Follow
- BS 5345 – Code of Practice for Installation in Hazardous Areas.
- IEC 60079 – Explosive Atmospheres Electrical Equipment.
- NEC Article 500 – National Electrical Code for hazardous locations.
- ATEX Directive – European Union certification for equipment in explosive atmospheres.
Final Thoughts
Selecting the right cable for hazardous areas is not just about power delivery, it’s about fire prevention, explosion protection, and compliance. Using MICC or armoured PVC cables with certified flameproof accessories ensures both safety and reliability in these critical environments.