Fire Performance Testing

IEC 60332 Part 1:Flame Propagation Test (Single Cables)

This tese defines the flame propagation characteristics of single vertical insulated

wire or cable. The specimen is deemed to have passed this test,if after burning

has ceased,the charred or affected postion does not reach within 50mm of the

lower edge of the top clamp.

IEC 60332 Part 3:Flame Propagation Test (Bunched Cables)

This test defines vertical flame propagation characteristics of bunched cables.The

test comprises of 3 categories each defined by the amount of combustible material

in a 1 metre sample,as shown as below.

The cable samples are placed vertically next to one another on a vertical ladder

tray where they are exposed to fire from a gas burner for the above mentioned

times.

The specimen consisting of 3.5m,is deemed to have met the requirements,if after

burning has ceased,the extent of charred or affected portion does not reach a

height exceeding 2.5m above the bottom edge of the burner.

IEC 60331: Circuit Integrity Test

A cable sample of 1200mm in length is placed over a gas burner and connected to

an electrical supply at it’s rated voltage.Fire is applied for a period of 90min or

120min according to different specified standards.

The temperature on the cable is 750℃ or 830℃

BS 6387:Circuit Integrity Test

BS 6387 specifies the performance requirements for cables required to maintain

circuit integrity under fire conditions It details the following methods to categorize

the cables according to cable withstand capacities.

Resistance to fire alone –the cables is tested by gas burner flame while passing a

current at its rated voltage.Four survival categories are defined :Cat A(3 hours at

650℃);Cat B(3 hours at 750℃); Cat C(3 hours at 950℃)& Cat S(20 minutes at

950℃).

Resistance to fire with water spray-A new sample of cable if exposed to flame at

650℃ for 15 minutes while passing a current at its rated voltage and then the

spray is turned on to give exposure to both fire and water for a further 15

minutes .A single survival category W is defined if the cables surpasses the

testing requirement .

Resistance to fire with mechanical shock –the final requirement is mechanical

shock damage.A fresh sample if mounted on a backing panel in a S bend and is

exposed to flames while the backing panel is stuck with a steel bar with same

diameter as the cable under test every 30 seconds for 15 minutes.The cables will

be tested under the following temperatures:X(650℃).Y(750℃)and Z(950℃).

Fire Performance Testing

IEC 60754-1 or BS 6425 Part 1: Determination of The Amount of Halogen

Acid Gas

This specifies a test for determination of the amount of halogen acid gas,other

than the hydrofluoric acid evolved during combustion of compound. When tested

in accordance with IEC 60754-1,the hydrochloric acid yield should be less than

0.5% (5mg/g) for LSHF compound. For LSF compound,the hydrochloric acid yield

should be between 5% to 15%.

IEC 60754-2 :Determination of Degree of Acidity of Gases.

This test specifies a method for determination of acidity of gas evolved during

combustion of cables by measuring pH and conductivity .The specimen is deemed

to pass this test if the pH value is less than 4.3 when related to 1 litre of water

and conductivity is less than 10 us/min.

IEC 61034: Smoke Density Test

The ″3 metre cube test ″measures the generation of smoke from electric cables

during fire. A light beam emitted from a window is projected across the enclosure

to a photo cell connected to a recorder at the opposite window .The recorder is

adjusted to register from 0% for complete obscuration to 100% luminous

transmission.

A 1 metre cable sample is placed in the centre of the enclosure and then

subjected to fire. The minimum light transmission if recorded. The result is

expressed ad percentage of light transmitted. The specimen is deemed to pass

this Test (IEC 61034-2) if the value is greater than 60%. A similar test BS 6724

also defines the density of smoke emitted from armoured cables during fire. The

amount is expressed as the standard absorbance Ao,Ao value is usually less than

0.8 for a cable with overall diameter of 15mm to 25mm.

ISO4589-2 or BS 2863 :Minimum Oxygen Concentration to Support Candle

like Combustion of Plastics (Oxygen Index)

This test gives a measure of the cable sheath flammability characteristics under a

specific set of conditions . Oxygen index is defined as the minimum concentration

of oxygen,expressed as volume per cent,in a mixture of oxygen and nitrogen that

will just support flaming combustion of the material initially at room temperature

under the test condition.

ISO 4589-3 or BS 2782 Part 1 Method 143A &143B :Temperature Index of

Materials

This is similar to the oxygen index test. Whereas in the oxygen index test,the

oxygen content is varied at room temperature,in the test the oxygen

concentration is kept constant at 21% and the test temperature is varied

until,again,combustion is just sustained.this test is more complex but gives a more

realistic measure of a material’s performance in a real fire.