In oil and gas plants, refineries, and offshore platforms, the presence of flammable gases, vapors, and combustible dusts makes cable selection a matter of safety, not just performance. A poorly selected cable in a hazardous area can become an ignition source, turning a minor fault into a catastrophic explosion.
Unlike standard industrial installations, cables in hazardous areas must meet stringent international standards—primarily IEC 60079-14—and carry certifications such as ATEX or IECEx-. This guide walks you through the key principles of selecting cables for hazardous areas in oil and gas facilities, helping engineers and procurement professionals make safe, code-compliant, and cost-effective decisions.
1. Understand Your Hazardous Area Classification
The first and most critical step is identifying the zone classification of the installation area. Zones are defined by the frequency and duration of explosive atmospheres-:
| Zone | Description | Typical Cable Requirement |
|---|---|---|
| Zone 0 | Explosive gas atmosphere present continuously or for long periods | Intrinsically safe (Ex ia) only- |
| Zone 1 | Explosive gas atmosphere likely to occur occasionally in normal operation | Intrinsically safe (Ex ia) or flameproof (Ex d)- |
| Zone 2 | Explosive gas atmosphere unlikely to occur, or only for short periods | Increased safety (Ex e) or intrinsically safe- |
For dust hazards, the equivalent zones are Zone 20, 21, and 22, with similar principles applying-.
Why this matters: The zone classification determines which protection technique (and therefore which cable type) is permissible. Zone 0 demands the highest level of protection—intrinsic safety—where the cable itself is designed to limit electrical energy to levels incapable of ignition-.
2. Choose the Right Cable Protection Technique
In hazardous areas, cables are selected based on the protection technique employed by the connected equipment and the cable itself:
Intrinsically Safe (Ex i / IS) Cables
An intrinsically safe cable is engineered to not generate or store enough electrical energy to cause ignition—even under fault conditions such as short circuits or ground faults-. Unlike flameproof methods that contain an explosion, intrinsic safety prevents the explosion from occurring in the first place-.
Key requirements for IS cables:
Low capacitance and inductance: Must match the parameters of the associated safety barrier-.
Light blue sheath (RAL 5015) : Per IEC 60079-14, cables used for intrinsically safe circuits must be identified by the colour light-blue-.
Ex-ia/Ex-ib marking: Indicates the level of intrinsic safety protection-.
Tiankang offering: Tiankang manufactures a full range of intrinsically safe instrumentation cables with low distributed capacitance and inductance, light-blue LSZH sheaths, and full Ex-ia certification—ensuring safe operation in Zone 0, 1, and 2 hazardous areas.
Flameproof (Ex d) Cables
Flameproof (Ex d) equipment contains any internal explosion within a heavy enclosure, preventing flame propagation to the external atmosphere-. For cables used with Ex d equipment:
The cable itself may be a standard cable entering via a flameproof cable gland-.
Armoured cables (steel tape or wire armour) are commonly used with Ex d installations for mechanical protection and to maintain the flameproof integrity at the cable entry-.
IEC 60079-14:2024 introduced fundamental changes in how cables and cable entry devices are selected for Ex d applications—requiring careful attention to gland selection-.
Tiankang offering: Tiankang supplies armoured instrumentation and control cables (steel tape and steel wire armour) compatible with Ex d installations, paired with certified flameproof cable glands for a complete, code-compliant solution.
Increased Safety (Ex e) Cables
Ex e is a protection technique that provides additional measures to prevent the possibility of excessive temperatures and arcs/sparks in normal operation. For Zone 2 applications, Ex e cables are often sufficient-.
3. Cable Construction Requirements for Hazardous Areas
Beyond protection technique, cables installed in hazardous areas must meet specific construction requirements:
Sheath Requirements
According to IEC requirements, cables installed in hazardous areas must have at least a non-metallic impervious overall sheath with braiding or other metallic covering for earth fault detection and mechanical protection-. For mineral insulated cables, a copper or stainless steel sheath is acceptable-.
Armour
Armoured cables are commonly specified in hazardous areas for:
Mechanical protection: Protecting against impact, abrasion, and rodent attack in refineries and offshore platforms
Flameproof integrity: Maintaining the seal at cable entry points
Earth fault detection: Providing a continuous metallic path
Tiankang offering: Tiankang offers galvanised steel tape armour (STA) for crush resistance and steel wire armour (SWA) for tensile strength—both suitable for hazardous area installations.
Low Smoke Zero Halogen (LSZH)
In confined spaces such as offshore platforms, control rooms, and underground cable galleries, LSZH sheaths are often mandatory. They:
Reduce smoke emission during fire (IEC 61034, transmittance ≥60%)
Eliminate halogen acid gases (IEC 60754, pH ≥4.3)
Provide flame retardance (IEC 60332)
Tiankang offering: Tiankang LSZH instrumentation cables are available with IS, OS, or IS+OS shielding configurations, light-blue sheath for IS circuits, and full ATEX/IECEx certification.
Shielding
Instrumentation cables in hazardous areas must maintain signal integrity in high-EMI environments:
Overall Screen (OS): For general protection against external interference
Individual Screen (IS): For eliminating crosstalk between pairs in multi-pair cables
IS + OS: The gold standard for critical analogue signals and IS circuits
Tiankang offering: Tiankang provides all three shielding configurations—OS, IS, and IS+OS—with 100% aluminium/polyester foil coverage and tinned copper drain wires.
4. Cable Gland Selection
The cable gland is often the weakest link in hazardous area installations. Key requirements:
The gland must be certified for the same zone and protection technique as the installation (e.g., Ex d gland for Ex d equipment)-.
The gland must match the cable diameter precisely. The use of sealing tape, heat shrink tube, or other materials to make the cable fit is not permitted-.
For armoured cables, the gland must properly terminate and earth the armour.
Metal coverings of cables installed in hazardous zones must be effectively earthed at both ends, unless otherwise permitted by IEC 60079-14-.
Tiankang offering: Tiankang supplies a complete range of Ex d, Ex e, and Ex ia certified cable glands in brass nickel-plated and stainless steel, compatible with both armoured and unarmoured cables.
5. Installation Best Practices
Even the best cable will fail if installed incorrectly. For hazardous areas:
Cable runs should be uninterrupted where practicable-.
Bending radius should comply with the cable manufacturer's data or be at least 8 times the cable diameter-.
Cables must be protected against mechanical damage—extra important in hazardous areas-.
Separation from power cables: Control and instrumentation cables shall be separated from power cables to minimise interference-.
6. Common Mistakes to Avoid
| Mistake | Consequence |
|---|---|
| Using non-certified cable in Zone 1 | Loss of explosion protection, safety incident |
| IS cable without light-blue sheath | Field identification failure, possible mix-up with non-IS circuits- |
| Mismatched cable and gland diameters | Seal failure, gas ingress- |
| Armour not earthed | Electric shock risk, fault current path缺失 |
| Ignoring temperature rating | Insulation meltdown, short circuit- |
7. Why Choose Tiankang for Hazardous Area Cables?
With nearly five decades of experience in instrumentation and cable manufacturing, Anhui Tiankang (Group) Co., Ltd. is a trusted supplier to the oil and gas industry:
Full hazardous area product range: Intrinsically safe (Ex ia) cables, armoured cables (STA/SWA), LSZH cables, and Ex-certified cable glands
Complete certifications: CCC Ex, ATEX, IECEx, SIL, and China Classification Society (CCS)
CNAS-accredited laboratory: Full testing for capacitance, inductance, flame retardance, fire resistance, and smoke density
Proven track record: Long-term supplier to CNPC, Sinopec, CNOOC, and major international EPC projects
One-stop supply: From instrumentation to cables to glands—reducing vendor management for EPC contractors
Conclusion
Selecting cables for hazardous areas in oil and gas plants requires a systematic approach: identify the zone → choose the right protection technique → specify the correct cable construction → select compatible glands → install to code. Getting it wrong can have catastrophic consequences; getting it right ensures safe, reliable, and compliant plant operation.
Contact Us
For hazardous area cable selection advice, technical documentation, or project quotations, please contact:
Yin Shuangjie
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/
Anhui Tiankang – Your partner for safe, reliable hazardous area cable solutions.
