— A Practical On‑Site Selection Guide

In industrial projects such as oil & gas, chemical, and power, instrumentation cables are critical for signal transmission. A common question is: Do I need armour?

Armour is a metallic protective layer (typically steel wire or steel tape) added inside the cable. This “metal exoskeleton” significantly enhances mechanical protection, but also increases cost, weight, and installation difficulty. This practical guide helps you make a quick, accurate decision based on field applications.

With nearly five decades of experience in instrumentation cable manufacturing, Anhui Tiankang (Group) Co., Ltd. offers a full range of armoured and unarmoured products, customizable to project requirements.

1. Structural Differences: Armoured vs Unarmoured

Key point: The primary value of armour is mechanical protection, not electrical shielding (though metal armour provides some auxiliary shielding).

2. When Must You Use Armoured Cables?

Based on engineering practice, the following scenarios strongly recommend or mandate armoured cables:

1. Direct burial
   Cables buried directly in soil must withstand backfill pressure, accidental digging, stone crushing, etc. Unarmoured cables are easily damaged.
   ✅ Recommendation: Steel tape armour (STA) + PE outer sheath (waterproof).

2. Exposed installation in hazardous areas (without conduit)
   In hazardous areas of chemical plants and oil & gas facilities, codes allow armoured cables to be installed exposed without additional metal conduit, saving significant material and labor.
   ✅ Recommendation: Steel tape or steel wire armour, with explosion‑proof cable glands.

3. Rodent/termite prone areas
   In remote oilfields, warehouses, tropical regions, rodents and termites chew through PVC sheaths, causing water ingress and short circuits. Steel tape armour provides effective protection.
   ✅ Recommendation: Steel tape armour (rodents cannot bite through).

4. High mechanical stress locations
   Such as vehicle traffic areas, cable trenches subject to foot traffic, or mountainous areas with falling rock risk.
   ✅ Recommendation: Steel tape armour or heavy‑duty steel wire armour.

5. Vertical high drops or tensile load requirements
   Such as shafts, tall towers, offshore platform vertical sections. Steel wire armour (SWA) can support self‑weight and additional tensile loads.
   ✅ Recommendation: Steel wire armour.

3. When Can You Use Unarmoured Cables?

In the following scenarios, unarmoured cables are sufficient, more economical, and easier to install:

1. Cable tray installation (indoor/outdoor)
   Trays provide inherent mechanical protection, and cables are arranged neatly without heavy crushing.
   ✅ Recommendation: Unarmoured, shielded, flame‑retardant sheath.

2. Metal conduit installation
   If the design requires full‑length metal conduit, the cable itself does not need armour.
   ✅ Recommendation: Unarmoured; ensure conduit and cable outer diameter match.

3. Indoor control rooms, equipment rooms
   No mechanical damage risk; flexibility and ease of termination are priorities.
   ✅ Recommendation: Unarmoured, low smoke zero halogen (LSZH), flame retardant.

4. Temporary or mobile equipment
   Frequent plugging, unplugging, and bending – unarmoured cables are lighter and more flexible.
   ✅ Recommendation: Unarmoured, rubber or highly flexible PVC sheath.

5. Buried duct banks with pre‑installed conduits
   Cables are pulled through pre‑buried pipes, so armour is not needed.
   ✅ Recommendation: Unarmoured, but water‑resistant sheath (PE) is advisable.

4. Choosing Armour Type: Steel Tape vs Steel Wire

Selection tip:

• General direct burial, exposed in hazardous areas → Steel tape armour (STA)

• Vertical, high drop, offshore platforms → Steel wire armour (SWA)

5. Grounding Requirements for Armoured Cables

The armour layer must be properly grounded; otherwise, hazardous voltages or electromagnetic interference may occur.

• Basic principle: The armour should be grounded at one end (typically at the field side or control room side, per design) to avoid ground loop currents.

• Hazardous area special requirement: For intrinsically safe circuits, armour grounding must comply with explosion protection codes, typically achieved via explosion‑proof cable glands.

• Tiankang note: Tiankang armoured cables are supplied with no electrical connection between the armour and the outer sheath. During field installation, the installer must ground the armour using dedicated grounding clamps or glands. Always follow the design drawings.

6. Cost and Schedule Trade‑offs

Economic analysis: For short distances and small quantities, the added cost of armour is limited. For long distances and large quantities, evaluate total cost of direct burial vs conduit. Sometimes armoured cable + direct burial is cheaper than unarmoured + conduit.

7. Quick Selection Reference Table

8. Tiankang Armoured and Unarmoured Instrumentation Cables

Anhui Tiankang Group offers a full range of instrumentation cables compliant with GB/T 9330, IEC 60332, IEC 60754, and other standards.

Unarmoured series:

• General instrumentation cable (PVC sheath)

• Computer cable (PE insulation, individual + overall shield)

• Intrinsically safe cable (low capacitance)

• Low smoke zero halogen (LSZH) cable

Armoured series:

• Steel tape armoured instrumentation cable (STA)

• Steel wire armoured instrumentation cable (SWA)

• Armoured intrinsically safe cable

• Armoured computer cable

Core advantages:

• CNAS‑accredited laboratory testing (flame retardance, capacitance, impedance, armour strength)

• Custom armour construction, sheath colour, and printing per customer drawings

• Explosion‑proof gland matching service

• Long‑term supplier to major projects of CNPC, Sinopec, CNOOC

9. Frequently Asked Questions

Q1: Can armoured cable replace shielding?
A: No. Armour is primarily for mechanical protection. It provides some auxiliary electromagnetic shielding but cannot replace copper braid or foil shielding. Instrumentation cables still require a dedicated shield.

Q2: Does armoured cable always need conduit?
A: Not necessarily. Armoured cable can be directly buried or exposed. However, certain special codes (e.g., extra‑high voltage environments) may still require additional protection. Follow the design drawings.

Q3: Can steel wire armour and steel tape armour be used interchangeably?
A: Not recommended. Steel wire armour is slightly more flexible and has better tensile strength, but costs more. Steel tape armour has better crush resistance but a larger bending radius. Choose by scenario.

Q4: How to bend armoured cable?
A: The minimum bending radius for armoured cable is typically 12–15 times the outer diameter (steel tape) or 10–12 times (steel wire). Refer to the product datasheet.

10. Conclusion

The core decision for selecting armoured vs unarmoured instrumentation cable is: Is there a risk of mechanical damage?

• Risk present (direct burial, exposed in hazardous areas, rodents, high stress) → Choose armoured

• No risk (trays, conduit, indoor) → Choose unarmoured

Balance safety, reliability, cost, and construction convenience. Anhui Tiankang provides professional selection support.

Contact Us

For project‑specific instrumentation cable selection advice or quotations, please contact:

Yin Shuangjie
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/

Anhui Tiankang (Group) Co., Ltd. – providing reliable, economical cable solutions for your industrial signal transmission.