Fire Retardant Cables

Fire Retardant Cables

The fire properties of cables are of great importance from a fire safety perspective. To ensure that cable performs up to the mark on fire safety standards is critical to both manufacturers and end users.

Cables are used for transmission of electricity. Hence, efficient transmission of electricity is the basic value proposition that we offer to the customer. However, mere transmission is not enough. Safety and especially human safety is of prime importance. Cables, therefore, have to be shock proof as well as short circuit proof.

Fires have been a major cause of losses of both human life as well as property, and hence, safety from fire is one of the major areas of focus for us. 90 percent of the fires are electrical fires, mainly caused by a Defective Electric Circuit (DEC). DEC can be caused by overloading, short circuit, faulty installation, or due to poor quality of products used, which again could be poor quality of raw materials, or poor quality of manufacture, or both. The sufferer is mainly the common man, who has to bear the brunt of mistakes or cost cutting measures of someone else. We are acutely conscious of this fact and we have been the first Company in India who offered FR (Flame Retardant) cables as a standard feature on all our XLPE cables.

Since, cost becomes a major factor in almost all purchase decisions, especially for Industrial products, we constantly look to manufacture products that are less prone to catch and propagate fires without adding to costs. Hence, Research & Develop-ment is a constantly ongoing process for making safe cables without added costs.

There are different types of safety norms used for cables as per applications, all are important from safety, technical & commercial point of view. Few of those are:

•      For standard installation conditions – cables with standard flame retardancy are used.
•       For installations in non-hazardous industries and open conditions–Cables with improved oxygen index are used, popularly known as ‘FR’ cables.

For installations with human surroundings and chemical or refineries, or hazardous plants etc – Cables with improved oxygen index and low smoke properties are used, popularly known as ‘FRLS’ cables.

•        Further, cables with ‘Low smoke & Zero halogen (LSZH)’ are used in Hospitals, Railways and metros, high rise buildings, shopping malls, theaters, airports, i.e. basically areas of high population in closed circumstances.
•        Fire survival cables are mandatory to use where circuit integrity is of prime importance in case of fire.Those are used mainly along with fire alarm systems, elevators, lighting systems at Metro railways, airports, high rises, mines, etc.

The fire properties of cables are of great importance from a fire safety perspective. About those properties of cable which ensure safety from fire.

Fire retarding properties in cable are of great importance. To make it simpler to understand, will take example of ‘Fire triangle’. It has got three sides ‘Oxygen (Air), Fuel (Flammable material) & Heat (Source of fire)’. If anyone of the component is missing, flame or fire will not propagate itself nor will it spread.

For making the cable safe from fire, we improve the properties of cable jacket and try and ensure self-extinguishing compounds, which even if there is external fire, they will not propagate the flames.

Technically it is narrated as below:

• Outer jacket of the cables are of flame retardant material only, which doesn’t allow fire propagation. It is measured as per IS 10810 Part 53 or IEC 60332 Part 1.
• In the atmosphere normal Oxygen percentage is 21 percent, we improve the cables Oxygen index to a level of 30 to 35 percent. Means in the standard atmospheric condition till the percentage of oxygen reaches 30 to 35 percent; cable will not act as fuel. It is measured as per IS 10810 Part 58 or ASTM D 2863.
• This condition can be also looked from different angle i.e. if source of fire (heat) is more than at 21 percent also cable can act as fuel. For such condition temperature index is measured, which is maintained in the range of 250 to 350 °C. Therefore till such high temperatures cables don’t act as fuel. It is measured as per IS 10810 Part 64 or ASTM D 2863.

It is reported that 80 percent deaths which occurs due to fire are not caused by burns; they are actually caused by the inhalation of these toxic gases. We can therefore realize that smoke generated from these conventional polymers under fire is the most important issue that a cable manufacturer has to consider. Considering this issue FR, FRLS, LSZH & FS cables have evolved.

Fire Survival cables which maintain circuit integrity for minimum 3 hrs up to 950 deg Celsius under fire, water and shock conditions to ensure transmission of signals and communication.

PE vs PVC usages in cable insulation for fire safety?

PVC (Polyvinyl chloride) is a flame retardant material; it has this plus point over PE (Polyethylene). However, it is applicable for outer jacket only. As mentioned above depending on application one has to choose material for outer sheath.

As far as insulation is concerned, PE or XLPE (cross-linked polyethylene) has got more advantage over PVC. PE is not used in insulation of energy cables, and is only used in lower voltages of telecommunication cables.

XLPE is used in insulation world over, and it does not propagate flame, nor does it emit smoke or toxic gases and world over; XLPE is insulation and PVC or LSZH is used in sheathing, which is a safe proposition from the point of flame resistance.

There are developments going on to improve the property of Polyethylene to make it flame retardant, and we will see better standards implemented, which is now imperative especially after the few large fires where lots of valuable human lives have been lost.

What standards and certifications are the most prevalent in India, and globally to ensure fire properties of cables? Are your products able to meet those standards’ requirements?

Indian standards for cables e.g. IS 1554 (for PVC insulated Cables), IS 7098 (for XLPE insulated cables, or IS- 694 for wires and flexibles) covers the requirements for cables for safety against fire.On the cable or wire outer jacket additional properties against fire are mentioned by marking word ‘FR’ or ‘FRLS’. By this user understands the cable type.

Internationally also, similar practices are followed and there are tests to monitor the performance of the cable under fire condition.

a) Smoke emission from cable during fire is monitored as under:

•        For ‘FRLS’ cables during fire, visibility maintained is at least 40% or smoke density of 60% maximum. It is measured as per IS 10810 Part 63 or ASTM D 2843.
•            For ‘LSZH’ cables during fire, visibility maintained is at least 80% or smoke density of 20%. It is measured as per IS 10810 Part 63 or ASTM D 2843.

b) Halogen Acid gas emission from cable during fire is monitored.

•       For ‘FRLS’ cables during fire, maximum halogen gas emitted should be 20% by weight. It is measured as per IS 10810 Part 59 or IEC 60754 Part 1.
•       For ‘LSZH’ cables during fire, maximum halogen gas emitted should be 0.5% by weight. It is measured as per IS 10810 Part 59 or IEC 60754 Part 1.

c) Flame retardant tests for cables installed in group

•        Condition of fire for group of cable is simulated & extend of fire propagation is measured. It is measured as per IS 10810 part 62 or IEC 60332-3.

Depending on the specifications and end usage chosen, we have capabilities to manufacture and test all these products in house.

For fire safe cables, a combination of Standards are being followed:

• Test for Oxygen Index – ASTM D 2863

• Test for Temperature Index – ASTM D 2863

• Test for Smoke Density – ASTM D 2843

• Test for Acid Gas evolution- IEC 60754

• Flammability Tests – Category A, B, C as per IEC 60332-3

• 3 m Cube Test – IEC 61034/BS 7622

• Fire Resistance Test – BS 7846 & BS 6387

STANDARDS FOR FIRE RESISTANT CABLES:

BS	British Standard Institution
BS 5266-1	Emergency lighting. Code of practice for the emergency lighting of premises
BS 5839-1	Fire detection and fire alarm systems for buildings. Code of practice for system design, installation, commissioning and maintenance
BS 5839-6	Fire detection and fire alarm systems for buildings. Code of practice for the design, installation and maintenance of fire detection and fire alarm systems in dwellings
BS 5839-8	Fire detection and fire alarm systems for buildings. Code of practice for the design, installation, commissioning and maintenance of voice alarm systems
BS 5839-9	Fire detection and alarm systems for buildings. Code of practice for the design, installation, commissioning and maintenance of emergency voice communication systems
BS 6387	Specification for performance requirements for cables required to maintain circuit integrity under fire conditions
BS 7211	Electric cables. Thermosetting insulated, non-armoured cables for voltages up to and including 450/750 V, for electric power, lighting and internal wiring, and having low emission of smoke and corrosive gases when affected by fire
BS 7346-6	Components for smoke and heat control systems. Specifications for cable systems
BS 7629-1	Electric cables. Specification for 300/500 V fire resistant screened cables having low emission of smoke and corrosive gases when affected by fire. Multicore and multipair cables
BS 7846	Electric cables. Thermosetting insulated, armoured, fire-resistant cables of rated voltage 600/1000 V, having low emission of smoke and corrosive gases when affected by fire. Specification
BS 8434-2	Methods of test for assessment of the fire integrity of electric cables. Test for unprotected small cables for use in emergency circuits. BS EN 50200 with a 930° flame and with water spray
BS 8491	Method for assessment of fire integrity of large diameter power cables for use as components for smoke and heat control systems and certain other active fire safety systems
BS 8519	Selection and installation of fire-resistant power and control cable systems for life safety and fire-fighting applications. Code of practice.
CEI	Comitato Elettrotecnico Italiano
CEI 20-11 / EN 50363	Insulating, sheathing and covering materials for low voltage energy cables
CEI 20-36/2-1	Tests for electric cables under fire conditions - Circuit integrity - Part 21: Procedures and requirements - Cables of rated voltage up to and including 0,6/1,0 kV
CEI 20-45	Fire resistant elastomeric insulated cables, halogen free (LSOH) with rated voltage Uo/U 0.6/1 kV
DIN	Deutsches Institut fur Normung
DIN 4102	Fire behaviour of building materials and building components - Part 12: Circuit integrity maintenance of electric cable systems; requirements and testing
EN	European Norm
EN 50200	Methods of test for resistance to fire of unprotected small cables for use in emergency circuit
EN 50266	Test for vertical flame spread of vertically-mounted bunched wires and cables
EN 50267/2-1	Method of determination of amount of halogen acid gas evolved during combustion of polymeric materials taken from cables
EN 50267/2-2	Determination of degree of acidity (corrosivity) of gases by measuring PH and conductivity
EN 50288-7	Sectional specification for instrumentation and control cables
EN 50362	Method of test for resistance to fire of larger unprotected power and control cables for use in emergency circuits
EN 50363	Insulating, sheathing and covering materials for low voltage energy cables
EN 60228	Conductors of insulated cables
EN 60332-1	Test for vertical flame propagation for a single insulated wire or cable
EN 60332-2	Test for vertical flame propagation for a single small insulated wire or cable
EN 60332-3	Test for vertical flame spread of vertically-mounted bunched wires or cables
EN 61034	Measurement of smoke density of cables burning under defined conditions
IEC	International Electrotechnical Commission
IEC 60228	Conductors of insulated cables - Guide to the dimensional limits of circular connectors
IEC 60331	Test for electrical cables under fire conditions. Circuit integrity.
IEC 60332-1	Tests on electric and optical fibre cables under fire conditions -Test for vertical flame propagation for a single insulated wire or cable
IEC 60332-3	Test on electric cables under fire conditions - Test for vertical flame spread of vertically-mounted bunched wires or cables
IEC 60502-1	Power cables with extruded insulation and their accessories for rated voltages from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) - Part 1: Cables for rated voltages of 1 kV (Um = 1,2 kV) and 3 kV (Um = 3,6 kV)IEC 60754-1Method for determination of amount of halogen acid gas evolved during combustion of polymeric materials taken from cables
IEC 60754-2	Determination of degree of acidity (corrosivity) of gases by measuring pH and conducivity
IEC 60793-1	Optical fibres
IEC 60794-1	Optical fibre cables
IEC 61034-2	Measurement of smoke density of electric cables burning under defined conditions (LT)
NBN	Norme Belge
NBN C 30-004	Fire resistance of electical cables - Classification and test methods
NBN 713-020	Fire resistance of building materials
NF	Norme Française
NF-C-32-070	Insulated cables and flexible cords for installations - Classification tests on cables and cords with respect to their behaviour to fire
SS	Singapore Standard
SS 299 part 1	Fire resistant cables - Performance requirements for cables required to maintain circuit integrity under fire conditions
VDE	Verband der Elektrotechnik Elektronik Informationstechnik
VDE 0815	Wiring cables for telecommunication and data processing systems part 814 - Testing of cables, wires and flexible cords Continuance of insulation effect under fire conditions part 814 - Testing of cables, wires and flexible cords Continuance of insulation effect under fire conditions
VDE 0482	part 267 - Common test methods for cables under fire conditions - Test on gases evolved during combustion of materials from cables part 1034 - Measurement of smoke density of cables burning under defined conditions