cable fire behaviour [compatibility mode]

BU Industrial Projects

The Quality Connection

Fire Behaviour of Cables

(Detlef Uerlings)

LEONI Kerpen GmbH, September 2014 2


Contents

- Introduction

- Classification

- Tests

- Cable Types with CI-Properties



Introduction

• In recent years we had various fire disasters worldwide withhuman victims and high amount of damages.

• We could find fires in the industry (e.g. Refineries, petro-chemical plants, power plants, offshore platforms), publicbuildings (e.g. airports, subways, tunnels) and vehicles (e.g.ships, trains, coaches, planes).

• The reasons for these fire disasters were different. Theaccidents were caused by natural disasters, human failureor technical defects.

• Summarising we can say that precautions must be taken to avoid fire catastrophes. But we must note too that blasts are notpreventable in all cases.



Introduction

In consequence of this recognition, we have to do all efforts toprotect human lives and material assets in case of fire.

What does it mean for cables

?



Introduction

Cables, if they are installed professionally, are under normalcircumstances never the source of a fire!

But cables are very often involved in fires.

Due to this fact we have more and more requirements for cables concerning the fire behaviour.



“Classification“

FR Flame Retardant (IEC 60332-1)

RP Reduced Flame Propagation (IEC 60332-3-…)

FRLS Flame Retardant Low Smoke (…+ ASTM D 2843)

HCL Halogen Content (…+ IEC 60754-1)

FRNC Flame Retardant Non Corrosive (… + IEC 60754-2)

LSZH Low Smoke Zero Halogen (…+ IEC 61034-1 & -2)

CI Circuit Integrity (Fire Resistant) (…+ IEC 60331-…)

CI Circuit Integrity (Fire Resistant) (…+ DIN 4102-12)



We must differentiate into:

- Material Tests

- Cable Tests



Material Tests

� Halogen Acid Gas (HCL-Emission)

� Degree of Acidity of Gases (Zero Halogen)

� Toxicity

� Limiting Oxygen Index (LOI)

� Flammability Temperature (FT)

� Flame Retardant Low Smoke (FRLS)



Cable Tests

� Flame Retardancy

� Reduced Flame Propagation

� Smoke Density

� Circuit Integrity (Fire Resistance)



Material Tests



IEC 60754-1

Synth. air

Furnace

Combustion boat containing sample

Thermo Couple

Gas Washing Bottles

• Halogen acid gas contains mainly following elements:Fluorine, Chlorine, Bromine, Iodine, Astatine

• 0.5 – 1.0 g of a material is burnt at a test temperature of800 °C for 40 minutes (min. 20 minutes at max. temperature)

• Not suitable for defining compounds described aszero-halogen.

Halogens

Comparable tests:

• EN 50267-2-1

• DIN VDE 0472-267-2-1

Determination of the Amount of Halogen Acid Gas (HCL-Emission)

• Evaluation: Measured HCL-Emission in percentage



IEC 60754-2

Synth. air

Furnace

Combustion boat containing sample

Thermo Couple

Gas Washing Bottles

• Halogen acid gas contains mainly following elements:Fluorine, Chlorine, Bromine, Iodine, Astatine

• 1.0 g of a material is burnt at a test temperature of935 °C for 30 minutes.

Halogens

Comparable tests:

• EN 50267-2-3

• DIN VDE 0482-267-2-3

Determination of Degree of acidity of gases (Zero Halogen)

• Limit values: pH-value ≥ 4.3 / Conductivity ≤10 µS/mm



Defence Standard 02-713 (NES 713)

• Analytical data of certain small molecular gaseous species arising when thematerial is completely burnt at a flame temperature of 1150 °C for 5 minutes,are mathematically computed, using the exposure level (in ppm) of each gasto produce fatality in 30 minutes as a base, to derive a combined toxicityindex. The concentration of gas considered fatal to man for a 30 minute exposuretime.

• Typical limit values for the Toxicity Index (T.I.) are for e.g.- marine applications: 5 – 8- railway applications: < 5

That means the smaller the value the better

Comparable tests:

• NF C 20-454

Determination of Toxicity Index of Materials



ASTM D 2863 / ISO 4589

• The oxygen index describes the minimum concentration of oxygen,expressed as volume percentage, in a mixture of oxygen and nitrogen that will just support combustion of a material / plastic / compound.

For information: LOI ≤ 23 combustible24….28 conditional flame retardant29….35 flame retardant

≥ 36 extra flame retardant

Limiting Oxygen Index (LOI)



ISO 4589-3 annex A

• The flammability temperature (F.T.) is the temperature at which combustionof a material / plastic / compound is just supported in air under specified testconditions.

For information:

F.T. of compounds are e.g. 200°C up to 300°C

Flammability Temperature (F.T.)



ASTM D 2843

• This test covers a laboratory procedure for measuring the relative amountsof smoke obscuration produced by the burning of plastics.The measurements are made in terms of the loss of light transmittancethrough a collected volume of smoke produced under standardizedconditions.

Typical value is a Smoke Density of max. 60%

Max. Smoke Density Rating (Flame Retardant Low Smoke (FRLS))



Cable Tests



IEC 60332-1-2

Comparable tests:

• EN 60332-1-2

• DIN VDE 0482-332-1-2

Test on a single core or a single cable (Flame Retardancy)

• The wire or cable shall pass the test, if the distance between the loweredge of the top support and the onset of charring is greater than 50 mm.

Time of flame application:cable diameter ≤ 25 mm: 60 scable diameter 25 < D ≤ 50 mm: 120 scable diameter 50 < D ≤ 75 mm: 240 scable diameter > 75 mm: 480 s



Test on bunched cables (Reduced Flame Propagation)

• The cable shall pass the test, if the created flames are self-extinguishing and the maximum extent of the charred portionmeasured on the sample shall not have reached a heightexceeding 2.5 m above the bottom edge of the burner.

Samples / Time for flame application:No. of the samples (each 3.5 m long) iscalculated as follows:

• -22 (cat. A): 7 l / m, Time > 40 Min.• -23 (cat. B): 3.5 l / m, Time > 40 Min.• -24 (cat. C): 1.5 l / m, Time > 20 Min.(Total volume of non-metal material in ...litre / meter)

IEC 60332-3-…

Comparable tests:• VDE 0482-332-3-…• EN 60332-3-…• ANSI/IEEE 1202 (IEEE 383)



Test diagram of an unsuccessfull flame test IEC 60332-3-24 (cat. C)

max. height of the charred portion

Burnerswitched off

Burnerswitched on

NOTE: The tested sample will pass IEC 60332-1 only


Test diagram of a successfull flame test

max. height of the charred portion

Burnerswitched on

Burnerswitched off

IEC 60332-3-24 (cat. C)




Measurement of Smoke Density of Cables

• 1 litre of alcohol will be ignited in a closed test chamber. The light intensity willbe measured between the light source and the photocell. The test isconsidered as ended when there is no decrease in light transmittance for 5minutes after the fire source has extinguished or whenthe test duration reaches 40 minutes. The test will bepassed, if the recorded light transmittance is min. 60%(IEC recommendation).

IEC 61034-2

Comparable tests:• VDE 0482-1034-2• EN 61034-2



Tests for electric cables under fire conditions - Circuit integrity CI

• Conductors are connected to a separatephase of a transformer output with a 2 Afuse with the nominal voltage Uo/U.After the test duration of 90 minutes(flame temperature 750 °C) the burner willbe switched off, but the cable sample shallremain energised for further 15 min. Thetotal test duration shall be the flameapplication time together with the 15 mincooling period. The test will be passed, if during the course of the test no fusefails and a conductor does not rupture, i.e. the lamp is not extinguished.

IEC 60331-21 (Uo/U ≤ 0.6/1 kV)

Comparable tests:• BS 6387 B (750 °C / 3 hours)



Tests for electric cables under fire conditions - Circuit integrity CI(with mechanical shock)

• Conductors are connected to a separate phase of a transformer output with a2 A fuse with the nominal voltage Uo/U.

• Flame temperature min. 830 °C.• Flame application time 30 min, 60 min, 90 min or 120 min.(pH 30, pH 60, pH 90 or pH 120 – Cables)

• The shock-producing device shall impact the wall after 5 min from activationand subsequently at 5 min intervals.

• The cable possesses circuit integrity characteristics, if the voltage is maintainedand a conductor does notrupture.

IEC 60331-1 and -2 (Uo/U ≤ 0.6/1 kV)

Comparable tests:• BS 6387 C Z (950 °C / 3 hours)• EN 50 200• IEC 60331-1 (Ø > 20 mm)• IEC 60331-2 (Ø ≤ 20 mm)• IEC 60331-3 (met. enclosure)



Tests for electric cables under fire conditions - Circuit integrity CI(complete cable system with installation material)

DIN VDE 4102 part 12

Comparable tests:---

• Cables will be tested together withfitting accessories like cable clamps andcable tray from a defined supplier.

• Test chamber temperature of950 -1000 °C following a temperaturecurve.

• Test duration 30 / 60 / 90 min. (E30 / E60 / E90 – Cables)

• The cable possesses circuit integritycharacteristics, if the voltage is maintainedand a conductor does not rupture.

• Test voltage Uo/U, e.g. 400 V for LV-cables, 110 V for Telecommunication-Cables



Cable Types with CI-Properties



� All circuit integrity tests have one common ground:

Cables have to be checked for their electrical functionality!

� All efforts concerning the cable construction have one common target:


… to avoid a short circuit between the different cable elements.



� What are the methods to avoid these short circuits?


1.) Mineral insulated conductors in so-called MICC-Cables.Mineral insulated cables are manufactured from completely inorganicmaterials. Solid copper conductors are inside of a sealed coppertube packed with magnesium oxide as fireproofinsulator.

These kind of cables are very expensive andonly used for very special applications.





2.) Mineral tapes, so-called MICA-tapes, which arewrapped around the copper conductor under halogen-free insulatingmaterial.

The use of cables with MICA-Tapewrapping is established sincemany years in the market.





3.) Silicone-rubber insulated conductors.

The special silicone-rubber does notmelt and forms a ceramic layer aroundthe conductor during fire.

This kind of insulating of CI-cables is thelatest compared to MICC-cables andMICA-wrapped cables and can be calledas state-of-the-art.



…for common applications we find nowadays the cable versions withMICA-Tape and with silicone-rubber.

In the overall view the CI-cable with silicone-rubber has the better„standing“ compared to a cable with MICA-wrapped conductors:


- silicone-rubber is suitable for +180 °C- thinner core diameter- thinner cable diameter- no additional wrapping of glass tape or similar over the twisted elementsnecessary

- better performance profile in case of challenging fire tests- better handling performance for installation- lower smoke emission compared to standard PE and XLPE- more economic than MICA-constructions (LEONI Kerpen)



Thank you very much for your attention!

Any further questions

?

cable fire behaviour [compatibility mode]

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