Cable Testing Fire Resistant Cable

Cable Testing & Fire Resistant Cable

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Fire Performance Testing

At present, in cable industry, Fire Retardant, Low Smoke Halogen Free (LSOH) OR Low Smoke Fume (LSF), Fire Resistant cables are all described as Fire Retardant & Resistant Cables.

In cable industry, the most common are showed below,

1. IEC Flame Retardant Grade
2. UL Fire standard
3. IEC Fire Resistance Testing

         IEC Flame Retardant Grade

The European Electrical Committee categorized the fire performance of the cables into three classes, namely

IEC-1, IEC-2 & IEC-3. IEC -1 and IEC -2 are used to assess the flame propagation characteristics of a single wire. IEC -3 is used to assess the flame propagation characteristics of bundled cables. Comparatively speaking, IEC -3 for bundled cables is more demanding than IEC-1 for single wires.

             IEC -1/BS -1(Flame Test On Single VerticalInsulated Wires/Cables)

This test details a method of test for the assessment of the flame propagation characteristics of a single wire or cable. In this test, a 60cm cable sample is fixed vertically inside a metallic box and a 175mm long flame is applied at 45C from a gas burner placed at 450mm from the top at the upper portion. The specimen is deemed to have passed this test, of after burning has ceased, the charred or affected position does not reach within 50mm of the lower edge of the top clamp which is equivalent to 425mm above the point of flame application. The test method is not suitable for the testing of some small wires due to the melting of the conductors during the time of application of the flame.

             IEC -3/BS -3(Flame Test On Bunched Wires/Cables)

IEC-3C describes a method of type approval testing to define the ability of bunched cables to resist fire propagation. In this test, a cable specimen, consisting of number of 3.5m lengths of cables are fixed to a vertical ladder tray where they are applied with a flame from a gas burner for a specified times under controlled air flow. Four categories (A, B, C & D) are defined and distinguished by test duration and the volume of non metallic material of the sample under test. The cable specimen is deemed to have met the requirements of the standard 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.

UL Fire Standard

If a cable can pass a specified UL fire standard, an UL performance verification mark can be applied onto the cable jacket, illustrating both the UL class and the number. There are four primary fire testing standards as follows:

CMP (Plenum Flame Test/ Steiner Tunnel Test)

Plenum rated cables meet the NFPA -262 standard (formerly known as UL910) which provides the most stringent requirement of all the tests. Cable samples on a horizontal tray in a tunnel type of chamber are burned at 87.9KW ( BTU/Hr) for 20 minutes. To qualify for a plenum rating, the cables must have the flame spread of less than 5 feet or 1.5 meters, with a smoke density during the test of (a) 0.5 peak; and 0.15 maximum averages.
The CMP cable is usually installed in air ventilation duct and air return widely used in Canada and USA. The fire retardancy properties of CMP cable is much better than LSOH cable complying with IEC -1 and IEC -3.

CMR (Riser Flame Test)

Riser rated cables meets UL . Cable samples on a vertical shaft are burned at 154.5KW ( BTU/Hr) for 30 minutes. To qualify for a riser rating, the cables must have the flame spread of less than 12 feet beyond the ignition point. This test does not look at the smoke density or toxicity. Riser cable is suitable for vertical shafts not defined as an environmental air plenum.

CM (Vertical Tray Flame Test)

General purpose cables meet UL . Cable samples on a 8 feet vertical tray are burned at 20KW (70,000 BTU/Hr) for 20 minutes. The cable is deemed to pass the test if the flame spread will not extend to the upper portion and extinguish by itself. UL is similar to IEC -3C, except for that the number of testing samples is different. This test does not look at the smoke density or toxicity. The CMG cables are usually used in runs penetrating single floor. This cable cannot be installed in vertical pathways.

CMG (Vertical Tray Flame Test)

This general purpose cables also meets UL . CM and CMG are similar, both recognized in Canada and USA. This test does not look at the smoke density or toxicity. The CMG cables are usually used in runs penetrating single floor. This cable cannot be installed in vertical pathways

        CMX(Vertical Wire Flame Test)

The restricted cable meets UL , Limited-use. The test consists of 25 feet long ventilated tunnel. The cable is placed on a ladder inside the tunnel and the flame of 30,000 BTU/Hr is applied to the cable 15 seconds on and 15 seconds off five times for a total exposure to the flame of 1 minute and 15 seconds. To quality for this test, after the test flame is removed, the cable can flame for not more than 60 seconds and the charred portion will not exceed by 25%. UL , VW-1 is similar to IEC -1, except for the difference in the time for flame applied. This test does not look at the smoke density or toxicity. The CMG cable is suitable for use in. dwellings and for use in raceway. This cable cannot be installed in bundles and must be protected in metal conduit. This type of cable is the minimum requirement in commercial installations.

       IEC Fire Resistance Testing

Fire resistant cables are designed for maintaining circuit integrity during a fire. Both the IEC and the BEC adopted two different standards, namely the IEC and BS . Comparatively speaking, the fire performance requirement for BS is more demanding.
IEC Fire Performance Standard

A cable sample is placed over a gas burner and connected to an electrical supply at it&#;s rated voltage. Fire is applied for a period of 3 hours. The temperature on the cable is between 750&#; & 800&#;. After 3 hours, the fire and the power is switched off. 12 hours later, the cable sample is reenergized and must maintain its circuit integrity.

BS Fire Performance Standard
BS 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 rate voltage. Four survival categories are defined: Cat A (3hours 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 is exposed to

flame at 650C 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 surpassed the testing requirement. Resistance to fire with mechanical shock &#; the final requirement is mechanical shock damage. A fresh sample is mounted on a backing panel in an S bend and is exposed 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-rated cable has been a very popular product type in the cable industry, third-party testing of fire-rated cable performance verification has a crucial role, TSTCABLES share with you about fire-rated cable flame retardant classification and related standards.

Fire-resistant cable, that is, under the specified test conditions, the specimen is burned, after the withdrawal of the test fire source, the spread of the flame is only within the limits of the residual flame or residual burning in the limited time to extinguish the cable, in the event of a fire, there is a possibility of being burned and can not be operated, but the spread of the fire can be prevented. In layman&#;s terms, the wire in case of fire, the ability to limit the combustion to a localized range, does not produce the spread, save a variety of other equipment, to avoid causing greater losses. At present, the cable industry is accustomed to flame retardant (Fire Retardant), halogen-free low smoke (Low Smoke Halogen Free, LSOH) or low halogen low smoke (Low Smoke Fume, LSF), fire-resistant (Fire Resistant) and other cables with a certain degree of fire resistance collectively referred to as fire-resistant cables. So what is the difference between these four types of fire cables? Let&#;s take a brief look.

First, the classification of fire-resistant cable
Flame Retardant Cable (Flame Retardant)

Flame retardant cable is characterized by delaying the spread of flame along the cable so that the fire does not expand. Because of its low cost, it is a large number of fire-resistant cable cable varieties used. Whether it is a single cable or a bundle of laying conditions, the cable is burned when the spread of flame can be controlled within a certain range, so you can avoid major disasters caused by the cable fire retardant, thus improving the fire level of the cable line.

Halogen-free, low-smoke, flame-retardant cables (LSOH)

Halogen-free low-smoke cable is characterized not only by excellent flame retardant properties, and constitute a low-smoke halogen-free cable materials do not contain halogen, low corrosion and toxicity of combustion, resulting in a very small amount of smoke, which reduces the human body, equipment and instruments damage, and is conducive to the occurrence of a fire in a timely manner to the rescue. Although halogen-free low-smoke flame retardant cables have excellent flame retardancy, corrosion resistance and low smoke concentration, their mechanical and electrical properties are slightly worse than ordinary cables.

Low Halogen Low Smoke Flame Retardant Cable (LSF)

Low Halogen Low Smoke Flame Retardant Cable has hydrogen chloride release and smoke concentration indicators between flame retardant cables and halogen-free low smoke flame retardant cables. Low Halogen (Low Halogen) cables also contain halogens in the material, but the content is lower. This type of cable is characterized not only by flame retardant properties, but also in the combustion of the smoke released is less, the release of hydrogen chloride is lower. This low-halogen, low-smoke flame-retardant cable is generally made of polyvinyl chloride (PVC) as the base material, and then processed with high-efficiency flame retardants, HCL absorbers and smoke suppressants. Therefore, this flame retardant material significantly improves the burning performance of ordinary flame retardant PVC materials.

Fire Resistant Cables

Fire-resistant cable is in the flame burning situation can maintain normal operation for a certain period of time, can maintain the integrity of the line (Circuit Intergrity). Fire-resistant cable combustion produced by the amount of acid gas smoke is small, fire-resistant and flame retardant performance is greatly improved, especially in the combustion, accompanied by water spray and mechanical strike vibration, the cable can still keep the line running intact.

Second, the difference between flame retardant cables and fire-resistant cables

The general public is very easy to confuse the concept of flame retardant cables and fire-resistant cables, although flame retardant cables have many advantages that are more applicable to the chemical industry, such as low-halogen, low-smoke fire-retardant, etc., but in general, fire-retardant cables can be used to replace the flame retardant cables, while flame retardant cables can not be replaced by fire-retardant cables.

The two principles are different, halogenated cable flame retardant principle is to rely on the halogen flame retardant effect, halogen-free cable flame retardant principle is to rely on the precipitation of water to reduce the temperature to extinguish the fire roasting. Fire-resistant cables rely on the fire-resistant layer of mica materials in the fire-resistant, heat-resistant properties to ensure that the cable in the fire also work properly.

The two structures and materials are different, the basic structure of fire-retardant cable is: insulation layer using fire-retardant materials; sheath and outer jacket using fire-retardant materials; wrapping and filling with fire-retardant materials.

The fire-resistant cable is usually between the conductor and insulation layer and then add a fire-resistant layer, so theoretically you can add a fire-resistant layer in the structure of the fire-retardant cable, the formation of both fire-retardant and fire-resistant cables, but in practice there is no need for this. Because the fire-resistant cable fire-resistant layer, usually using multi-layer mica tape directly wrapped around the wire. It can withstand prolonged combustion, even if the polymer is burned at the applied flame, but also to ensure the normal operation of the line.

The fire-resistant cable is usually between the conductor and insulation layer plus a fire-resistant layer, so theoretically you can add a fire-resistant layer in the structure of the flame-retardant cable, the formation of both flame-retardant and fire-resistant cables, but in practice there is no need for this. Because the fire-resistant cable fire-resistant layer, usually using multi-layer mica tape directly wrapped around the wire. It can withstand prolonged combustion, even if the polymer is burned at the applied flame, but also to ensure the normal operation of the line.

The main technical indicators of fire safety for cables are the flame resistance of CO 2 cables, the density of smoke and the toxicity of gases. Based on the above factors to develop the cable flame retardant standard system includes IEC standards, UL standards, etc., we come together to understand what are the important provisions of the level contained therein.

Third, the fire cable standards

1, fire cable IEC standards

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In order to assess the cable&#;s flame retardant performance, the International Electrotechnical Commission formulated IEC-1, IEC-2 and IEC-3 three IEC standards, IEC-1 and IEC-2 were used to assess the single cable according to the tilt and vertical deployment of flame retardant capacity (the domestic counterpart of GB.3 and GB.4). IEC-1 and IEC-2 are used to assess the flame retardancy of single cables when they are arranged in an inclined and vertical position respectively (GB.3 and GB.4 in China). In contrast, the requirements for vertical burning of bundled cables are much higher in terms of flame retardancy.

IEC-1/BS-1 Flame Retardant Rating (Flame Test On Single Vertical Insulated Wires/Cables)

This is a standard for the flame retardancy of single cables. Test provisions, a 60cm long specimen fixed vertically in the front wall of the opening of the metal box, flame length of 175mm propane burner from the upper part of the specimen from the fixed end of the position of 450mm on the flame cone and the cable at an angle of 45 degrees in contact with the specimen if the specimen burns damaged part of the distance from the fixed end of the lower part of the test is not more than 50mm, the test passes.

IEC-3/BS-3 Flame Retardant Rating (Flame Test On BunchedWires/Cables)

This is a flame retardant standard for bundled cables. The test specifies that a bundle of 3.5m long cable specimens are fixed with wire in a trapezoidal test frame, and the number of specimens is determined by the non-metallic materials required for different classifications. The specimens are hung vertically on the back wall of the combustion furnace, and air is introduced into the combustion furnace through the air inlet on the bottom plate. Propane plane burner to 750 &#; flame and specimen contact, the specimen in the mandatory blowing (air emissions 5m3 / min, wind speed 0.9m / s), must be in the vertical combustion within 20 minutes of combustion does not come up, the cable in the flame spread 2.5 meters within the self-extinguishing. iec has a class A, B, C and D class points to assess the merits of flame retardant properties.

2&#;Fire-resistant cable UL standard

UL listed any cable after testing and verification if it meets a certain fire rating, can be printed on the cable UL identification word, fire rating and approval number.

Booster level &#; CMP level (air supply combustion test / Steiner sodium duct test Plenum FlameTest / Steiner TunnelTest)

This is the highest requirement of UL fire safety standards in the cable (Plenum Cable), the applicable safety standards for UL910, the test provides for the laying of a number of specimens in the device on the horizontal duct, with 87.9KW gas Bunsen burner (300,000 BTU / Hr) for 20 minutes. The qualifying criterion is that the flame must not extend more than 5 feet beyond the front of the Gas Bunsen burner flame. Optical density has a maximum peak value of 0.5 and a maximum average density value of 0.15. These CMP cables are typically installed in air return pressurization systems used in ventilation ducts or air handling equipment and are approved for use in Canada and the United States. FEP/PLENUM materials conforming to UL910 have better flame retardancy and lower smoke concentrations than low-smoke, halogen-free materials conforming to IEC-1 and IEC-3.

Trunk grade &#; CMR grade (Riser Flame Test)

Trunking Class-CMR (Riser Flame Test)

This is a UL standard for commercial grade cable (Riser Cable), applicable safety standard UL, the test specifies that multiple specimens are laid on a simulated upright shaft with a prescribed 154.5KW gas Bunsen burner (527, 500 BTU/Hr) for 30 minutes. The qualifying criterion is that the flame must not spread to the upper portion of a room 12 feet high. Trunking grade cable has no smoke concentration specification and is typically used for vertical and horizontal wiring use on floors.

Commercial Grade &#; Class CM (Vertical Tray Flame Test)

This is UL&#;s standard for Commercial Grade Cable (General Purpose Cable), which is governed by safety standard UL. The test involves laying multiple specimens on a vertical 8-foot-high support and burning them for 20 minutes with a prescribed 20KW strip torch (70,000 BTU/Hr). The passing standard is that the flame must not spread to the upper end of the cable and extinguish itself.UL is similar to IEC-3C, except that the number of cables laid is different. Commercial grade cables do not have a smoke concentration specification and are generally only used for horizontal routing on the same floor, not for vertical routing on the floor.

General Purpose Class &#; CMG Class (Vertical Tray Flame Test)

This is the UL standard for General Purpose Cable (General Purpose Cable), and the applicable safety standard is UL. Commercial grade and General Purpose Cable have similar test conditions, and are recognized for use in both Canada and the United States. General Purpose Cable does not have a smoke concentration specification and is generally only used for horizontal wiring on the same floor, not vertical wiring on the floor.

Household Class &#; CMX Class (Vertical Wire Flame Test)

This is the UL standard for household grade cable (Restricted Cable), the applicable safety standards for UL, VW-1. The test specimen is required to be kept vertical and burned (30,000 TU/Hr) for 15 seconds with the test torch, then stopped for 15 seconds and repeated 5 times. Passing criteria are that the residual flame must not exceed 60 seconds, the specimen must not be burned more than 25%, and the surgical cotton padded on the bottom must not be ignited by falling objects.UL-VW-1 is similar to IEC-1, except that the burning time is different. This rating also has no smoke or toxicity specification and is intended for use only in home or small office systems where a single cable is laid. These cables should not be used in bundles and must be sleeved. Smoke density, halogen content and toxicity levels.

3&#;Fire-proof cable other standards

IEC-1/BS-1 Determination of halogen gas content (Emission Of Halogens)

This is the IEC and BS standards for hydrogen chloride (HCL) release concentration specification. Halogens contain fluorine, chlorine, bromine, iodine and the radioactive volatile element astatine, which are highly toxic. Experimental provisions, combustion furnace preheated to 800 &#;, a built-in 1.0 g sample pushed into the furnace, the use of air emission rate so that HCL dissolved in water, and then determine the halogen acid content of the aqueous solution. If the cable material combustion halogen acid (HCL) release less than 5mg / g, can be called halogen-free cable (LSOH), if the halogen acid (HCL) release more than 5mg / g but less than 15mg / g, can be called low-halogen cable (LSF). It is worth noting that the IEC-1 method can not be used to determine the HCL content of less than 5 mg / g of material, that is, can not determine whether the &#;halogen-free&#;. If you need to determine whether it is completely halogen-free, you can use IEC-2 method to determine.

IEC-2 Gas Acidity Measurement (Corrosivity)
This is a specification in the IEC standard for the corrosivity of combustion gases. The test measures the acidity of the halogenated acid gases produced by the material during combustion. It is determined by the pH value and electrical conductivity of an aqueous solution. The test specifies that the combustion furnace is preheated to 800°C, a quartz tube with a built-in specimen is pushed into the furnace, and a time clock is started. The PH value and electrical conductivity are measured every 1 minute for the first 5 minutes of combustion, and every 5 minutes for the next 25 minutes. Generally, the PH value of halogen-free cable materials will be greater than 4.3, and the electrical conductivity is less than 10μs; the lower the PH value, that is, the higher the acidity of the material&#;s halogenated acid gas. It is worth noting that when the HCL content is greater than 2mg/g and less than 5mg/g (i.e., in line with the requirements of IEC-1), the PH value of its aqueous solution is also less than 4.3, that is, it does not meet the requirements of IEC-2.

IEC -1/ASTM E662 Emission of Smoke

This is the specification for smoke density in the IEC and ASTM standards. The experiment consists of a 3 m3 cube and a photometric system with a light source, the rectangle containing alcohol as a combustion source. A blower with a power of 10-15 m3/min ensures that the smoke is uniformly distributed over a windshield to prevent flame eddies on the trough, and a recorder connected to the light source notes the amount of light attenuation as the alcohol burns. Smoke density is measured in terms of light transmittance and if a light transmittance value of 60% can be achieved the cable material meets the low smoke standard, the higher the light transmittance the less smoke is released when the material burns.

ISO-2/BS Oxygen Index (Oxygen Index LOI)

This is the specification for the Oxygen Index in the ISO and BS standards. It means that at room temperature, when the oxygen content of the air is greater than this oxygen index, the material will burn immediately. The higher the Oxygen Index value, the more flame retardant the material is. If the oxygen index of a material is 21%, it means that the material will burn automatically at normal room temperature. At normal room temperature, the oxygen content of the air is 21%, and the oxygen index of general flame retardant cables is more than 33%.

ISO-3/BS.1 Temperature Index (Temperature Index TI)

This is the ISO and BS standard for the temperature index of the specification, the oxygen index of the material will fall with the temperature, when the temperature rises and the oxygen index of the material falls to 21%, the material will automatically burn, the temperature is known as the temperature index. For example, the oxygen index of coal at room temperature is 50%, but when the temperature rises to 150&#;, the oxygen index will drop to 21%, and the material will burn immediately, and the temperature index of the material is 150&#;. The temperature index of the material is 150&#;. Generally, the temperature index of flame retardant cables is more than 250&#;.

NES713 Toxicity Index (Toxicity Index)

This is the British naval engineering NES standard for cable materials for the combustion of gas toxicity specifications, toxicity is the structure of the organism caused by the destruction or dysfunction of a nature, toxicity index refers to the material combustion of all the gases produced by the toxicity of the total sum performance. The experiment stipulates that the combustion furnace is preheated to 800 &#;, the toxic substances contained in the cable material will be burned separately, and then use the airflow emission rate to collect each toxic gas, and then through chemical analysis to calculate the content of each toxic substance, this index is expressed in number of its toxicity. The greater the toxicity index, the higher the toxicity of the gases released by the material. Generally, the toxicity index of halogen-free cable materials are less than 5. It is worth noting that low-smoke halogen-free materials will also produce toxic CO when burned, if the material contains P, N, S, the generation of toxic gases is more, so halogen-free cables can not be called non-toxic cables, it should be called low-toxicity cables CM, CMR and CMP cables need to be through the stringent UL fire safety standards, the use of the cable material contains more halogen CM, CMR and CMP cables need to pass the strict UL fire safety standards, the cable materials used mostly contain halogens, CM and CMR cables are generally based on polyvinyl chloride (PVC), which contains chlorine; CMP cables are generally based on Teflon polytetrafluoroethylene (FEP), which contains fluorine. The toxicity of the gas produced by such halogen-containing cables is several times greater than that of halogen-free cables, which poses a great risk to fire safety and may lead to the death of most casualties at the fire scene, who are not burned to death but asphyxiated by the poisonous gas.

With China&#;s electric power industry, data communications industry, urban rail transportation industry, automotive industry and shipbuilding and other industries continue to expand the scale of the demand for wire and cable will continue to grow rapidly, the future of the wire and cable industry has great potential for development, and a full understanding of the wire and cable fire retardant standards and ratings for the relevant industry has become increasingly important.If you need high quality fire retardant cables, please feel free to contact us by .

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