Flameproof vs. Flame Retardant Cables (FRLS-H): Fire Resistance Ratings for GIDC Heavy Engineering Units

In heavy industrial environments—such as metallurgical foundries, forging mills, chemical manufacturing plants, and heavy engineering factories in **Vatva, Naroda, Sanand, and Kalol GIDC**—electrical systems carry massive current loads. High-voltage machinery, high ambient operating temperatures, and abrasive airborne elements expose industrial power cables to continuous thermal stress. Crucially, during a building fire, standard PVC-insulated cables act as a dangerous fuel source, rapidly propagating flame along vertical cable shafts, while generating dense black smoke and highly toxic Hydrogen Chloride (HCl) acid gas. To prevent this, **DISH** (Directorate of Industrial Safety and Health) and **NBC 2016 Part 4** mandate the use of specialized **Flame Retardant (FRLS-H / LSZH)** or **Fire Survival (FS)** cabling systems under **IS 10810** and **IEC 60332** standards.

This technical guide details the molecular properties of FRLS, LSZH, and Fire Survival (FS) cables, explaining fire resistance tests, acid gas limits, and installation standards required to pass GIDC CFO audits.

The Critical Role of Specialized Industrial Cabling

Understanding the difference between **Flame Retardant** and **Fire Survival** cables is vital. Flame retardant cables are designed to self-extinguish when the external flame source is removed, preventing the cable path from acting as a fuse. In contrast, fire survival cables are designed to **continue operating** during a live fire, maintaining power to critical safety systems like fire pumps, ventilation fans, and alarms.

1. The Four Cable Classes Compared

Industrial power and control cables are classified into four distinct classes based on their molecular compound chemistry and fire performance:

1. Standard PVC Cables

Insulated with standard Polyvinyl Chloride (PVC). Standard PVC contains massive amounts of halogens (chlorine). When ignited, PVC cables burn rapidly, generating thick, black smoke and discharging up to **25% to 30%** of their weight as toxic, highly corrosive Hydrogen Chloride (HCl) gas. This HCl gas combines with atmospheric moisture to form hydrochloric acid, corroding delicate electronics throughout the facility.

2. FRLS-H (Flame Retardant Low Smoke & Halogen) Cables

Insulated with modified PVC compounds containing specialized fire-retardant additives (such as Antimony Trioxide or Alumina Trihydrate). FRLS-H cables significantly reduce flame propagation, limit smoke generation, and restrict HCl gas release to **less than 20%** of total weight under **IS 10810 Part 58** tests.

3. LSZH / LSHF (Low Smoke Zero Halogen) Cables

Insulated with thermoplastic compounds entirely free of halogens (fluorine, chlorine, bromine). When exposed to fire, LSZH cables generate very light, translucent white smoke, zero toxic acid gases, and restrict HCl release to **less than 0.5%** under **IS 10810 Part 59**. This makes them the absolute standard for enclosed high-density workspaces, clean rooms, and data centers in Gandhinagar and GIFT City.

4. FS (Fire Survival / Circuit Integrity) Cables

Designed with a specialized **Mica glass tape barrier** wrapped directly around the copper conductors, insulated with XLPE or LSZH compounds. During a fire, the plastic insulation burns away, but the mica tape fuses onto the copper core, maintaining complete electrical insulation. FS cables must maintain circuit integrity under direct **950°C flames** for a minimum of **180 minutes** under **IEC 60331** tests.

2. Fire Testing Parameters & Standards

To qualify as FRLS-H or LSZH under Indian Standard **IS 10810**, cables must pass three rigorous mechanical and chemical tests:

• Oxygen Index Test (Part 58): Measures the minimum concentration of oxygen required to support combustion. Normal air contains 21% oxygen. FRLS-H cables must maintain an Oxygen Index of at least **29%**, ensuring they cannot burn naturally in normal air without a massive external flame source.
• Temperature Index Test (Part 64): Measures the temperature at which the plastic compound will burn under normal air conditions. Compliant FRLS-H cables must maintain a Temperature Index exceeding **250°C**.
• Acid Gas Emission Test (Part 59): The insulation is burned in a tube furnace at 800°C, and the escaping gases are dissolved in water. The resulting acidity (pH) and conductivity are measured. LSZH cables must yield a pH exceeding 4.3 and a halogen content under 0.5% weight.

3. Mandatory Cabling Installation & Routing Standards

To obtain a valid CFO Fire NOC, cabling paths must be engineered to prevent fires from leaping between structural zones:

Segregation of Power & Control Lines

High-voltage power lines generate significant electromagnetic fields and heat. They must never share conduits or cable trays with low-voltage fire alarm loop cables to prevent heat induction and false alarms. Cable trays require continuous grounding and must maintain a minimum **300mm physical separation gap**.

Horizontal and Vertical Intumescent Barriers

Where cable trays pass horizontally through compartment walls or vertically through floor slabs, the opening must be completely sealed. Safety codes mandate **intumescent firestops (IS 12458)**. During a fire, the intumescent compound expands up to 40 times its original volume, completely sealing any gaps around the cables to stop fire propagation.

4. Regulatory Liaison: Passing the CFO Electrical Audit

To successfully pass the CFO and electrical inspector audits for new GIDC installations, developers must supply:

1. Cable Manufacturer Test Certificates: Authentic documents showing compliance with IS 10810 and IEC 60332 for the specific cable batches installed.
2. Mica Tape FS Verification Plans: Blueprints showing that all critical emergency lines (fire pumps, elevator power, exit signs) utilize certified Fire Survival (FS) cables.
3. Firestop Compliance Sign-off: Certified completion reports showing that all floor and wall penetrations have been professionally sealed using certified intumescent barriers by a licensed partner like **JSNM Engineers**.

Frequently Asked Questions