Fire Classifications & Fire Test Methods for the European Railway Industry
(EN 455452; EN 17084; EN 16989)
European Regulations such as the Construction Products Regulations have led European regulators and industries to utilise harmonised testing methods and classification system for assessing the products used in the construction of buildings. The European Rail Industry is similarly developing harmonised procedures particularly to facilitate interoperability of railway rolling stock. Growth in European crossborder rail movements has further emphasized the need for European harmonisation both of these test methods and classification systems for the materials are used in vehicles.
The European Commission mandated CEN (CEN/TC 256/WG 1) to identify and standardise the fire test methods for use in the classification of products and materials employed in railway carriages throughout Europe. In 2013, CEN/TC 256 and CENELEC/ TC 9X published a 7 part standard EN 45545, “Fire Protection on Railway Vehicles” which includes:
- Part 1: General
- Part 2: Requirements for fire behaviour of materials and components
- Part 3: Fire resistance requirements for fire barriers
- Part 4: Fire safety requirements for railway rolling stock design
- Part 5: Fire safety requirements for electrical equipment including that of trolley buses, track guided buses and magnetic levitation vehicles
- Part 6: Fire control and management systems
- Part 7: Fire safety requirements for flammable liquid and flammable gas installations
Part 2 describes the reaction to fire test methods, test conditions and reaction to fire performance required for classification of structural products including flooring, seats, cables and non-listed items.
This standard specifies that:
- Railway vehicles are classified in accordance with the fire hazard level associated with their design and operation.
- Three hazard levels HL 1 to HL 3 are defined, HL 1 being the lowest requirement and HL 3 being the highest.
- The test methods used depend on the product under investigation.
The performance of all the products is determined with respect to ignitability, flame spread and the amounts of heat, smoke and toxic fumes produced. These reaction to fire tests aim to qualify and classify the products according to their final applications which are separated into groups, including: structural products, seats, cables and non-listed items. Each of these product groups are required to meet a specific set of performance requirement levels (listed R1 to R26). Each requirement has a corresponding series of test performance criteria imposed for each fire risk levels HL 1 to HL 3.
Heat Release Rate is the key measurement required to assess the fire hazard of products and materials, as it quantifies fire size, rate of fire growth and consequently the release of associated smoke and toxic gases. It is measured using a technique called oxygen consumption calorimetry.
A new Rate of Heat Emission parameter has been introduced in EN 455452.
This parameter is known as MARHE or Maximum Average Rate of Heat Emission. The heat release rate is determined using the oxygen consumption technique from which an Average Rate of Heat Emission (ARHE) is calculated. The maximum ARHE over the testing period is MARHE. The MARHE parameter was selected because it is not greatly affected by normal experimental variation or measurement noise. It has also proved to be a fairly robust measure of the propensity for fire development under real scale conditions.
Heat Release Rate is determined with the Cone Calorimeter according to ISO 56601. Thresholds concerning the potential heat release for almost all combustible materials and products used in the railway industry are required by EN 455452.
These requirements depend on the end use of the product and the Hazard Level of the carriage. The Cone Calorimeter is the most significant bench scale instrument in the field of fire testing because it measures important real fire properties of the material being tested, under a variety of preset conditions. These measurements can be used directly by researchers or can be used as data for input into correlation or mathematical models used to predict fire development.
The FTT Dual Cone Calorimeter has been the benchmark in this field for its ease of use, robustness, sophisticated software that guides users through the calibration, testing and report protocols.
Building on this expertise FTT has developed a new generation of the Cone Calorimeter called iCone that utilise state of the art technology to improve the efficiency and accuracy of the fire test process.
The iCone is an automatic and interactive system. Not only does it possess all the advantages of a conventional Cone Calorimeter, it also features an interactive and intuitive interface, flexible control options, and built in data acquisition technology and reporting with the user friendly ConeCalc software. It has been designed using FTT’s decades of experience in calorimetry and incorporates many new features, not seen by fire testing laboratories
up until now. It is perceived as the new benchmark in calorimetry. Directly measured properties include:
- Rate of Heat Release
- Time to Ignition
- Critical Ignition Flux
- Mass Loss Rates
- Smoke Release Rates
- Effective Heat of Combustion
- Rates of Toxic Gas Release (e.g. carbon oxides) According to EN 455452, the electrical heater within the Cone Calorimeter must impose two different irradiance levels: 25kW/m2 and 50kW/m2.
Furniture Calorimeter Vandalised Seat
According to EN 455452, the burning behaviour of passenger seats should be tested on the complete seat, including upholstery, head rest, seat shell and
arm rest. In addition, the seat shell and any vertical faces of the arm rests should also be tested in relation to fire integrity.
In order to determine MARHE, a complete seat assembly should be tested using the ISO 97052 as a furniture calorimeter.
FTT builds and supplies the ISO 97052, complete with the appropriate instrumentation package or supply instrumentation to clients wishing to upgrade
existing facilities or with a wish to build their own apparatus. In the latter cases we supply a Gas Analysis Console and an Instrumented Duct Insert section. The console is housed in a 19″ instrument rack and it contains all the necessary instrumentation to measure Heat Release Rates and other associated parameters. The Gas Analysis Console contains:
- A Paramagnetic Oxygen Analyser supplied with temperature and pressure compensation for primary heat release measurement.
- An Infrared Carbon Dioxide Analyser for use in heat release measurement.
- A Dual Stage Soot Filter, Refrigerant Cold Trap, Drying Column, Pump and Waste Regulators for conditioning the sample gases prior to analysis.
- Controls for the smoke measurement system.
- Data logger.
The specification of this instrumentation is the same for both large and small scale calorimeters and can therefore also be conveniently used with the FTT Dual Cone Calorimeter.
The duct section houses all the sampling, temperature and mass flow probes required for gas sampling and air velocity measurement along with smoke measurement equipment (white light or laser). Most dynamic fire testing apparatuses can be instrumented with this equipment to measure heat released and smoke produced from products burnt in them. The requirement sets in relation to passenger seats are:
- R6: Passenger seat shell – Base and Back
- R18: Complete passenger seats
- R19: Seats in staff areas
- R21: Upholstery for passenger seats and head rest
Lateral Flame Spread Apparatus
Flame spread of structural products including floorings and insulation materials is determined according to ISO 56582.
The requirements specified in EN 455452 depend on the end use of the product and the Hazard Level of the carriage.
The Lateral Flame Spread Apparatus measures the lateral spread of flame on vertically oriented specimens using a rectangular radiant panel and an
additional gas burner flame as the ignition source.
It provides data suitable for comparing the performance of essentially flat materials, composites or assemblies, which are primarily used as the exposed surfaces of walls.
Following ignition, any flame front which develops is noted, and the progression of the flame front horizontally along the length of the specimen in terms of the time it takes to travel various distances is recorded.
The results are expressed in terms of the flame spread distance/time history, the flame front velocity versus heat flux, the critical heat flux at extinguishment and the average heat for sustained burning.
Single Flame Source Test Apparatus
Flame spread of light diffusers and air filters are determined according to EN ISO 119252.
This test is also required as part of the European construction products regulation for assessing and qualifying reaction to fire performance of all types of construction products to classes B, C, D and E.
EN ISO 119252 is based on the Kleinbrenner method for determining ignitability of materials in the vertical orientation by direct small flame impingement under zero impressed irradiance. It is supplied as a complete easy to use system incorporating safety features. The combustion chamber is made from corrosion resistant stainless steel, to maximise operating life. It has large front and side doors which are glazed with toughened glass for full view of the specimen during a test and easy access.
Flooring Radiant Panel
The burning behavior of floorings, including any substrates if used, is tested according to EN ISO 92391 in a closed chamber using a radiant panel heat source.
The FTT Flooring Radiant Panel (FRP) evaluates the critical radiant flux below which flames no longer spread over a horizontal surface.
This test method is used to measure the critical radiant flux of floor covering systems exposed to a flaming ignition source in a graded radiant heat environment, within a test chamber.
A smoke measuring system according to DIN 50055 is mounted on a separate frame at the exhaust stack. It can also be used to measure this same critical radiant flux for exposed attic floor cellulose insulation.
The FTT Flooring Radiant Panel can also comply with ASTM E648, ASTM E970, NFPA 253 and DIN 4102 Part 14.
The Critical Heat Flux at extinguishment value (CHFvalue) is the incident heat flux at the
specimen surface, at the point where the flame ceases to advance and may subsequently go out.
Vertical Flame Propagation Test Apparatuses
According to EN 455452, the fire behaviour and the flame impingement duration of cables should be tested and evaluated in respect to the diameter of the cables in question. In addition, these cables are separated into two groups:
I. Cables for Interior (Requirement category R15)
II. Cables for Exterior (Requirement category R16)
Smoke production & toxicity
There are two test methods detailed in EN 455452 that can be used for determining the toxic composition of gases and fumes generated by the combustion of specified railway products. These two methods, EN ISO 56592 and NF X 701001 are described as follows:
Smoke Density Chamber with FTIR Toxicity Test Apparatus
This method consists of a smoke density chamber as described in EN ISO 56592 and an FTIR toxicity test and sampling system. The two instruments dedicated respectively to the analysis of the opacity of the smoke and to the qualitative and quantitative analysis of gases emitted during the test, are capable of operating simultaneously as well as independently using two specific procedures for the acquisition of FTIR spectra and smoke opacity.
The NBS Smoke Density Chamber (SDC) has been established for many years and is used widely in all industrial sectors for the determination of smoke generated by solid materials and assemblies mounted in the vertical position with a closed chamber. It measures the specific optical density of smoke generated by materials, when an essentially flat specimen, approximately 25mm thick, is exposed vertically to a heat source of 25kW/m2, in a closed chamber, with or without the use of a pilot flame. The FTT smoke density chamber has been designed specifically to incorporate the ISO 5659 Conical Radiant Furnace. This extends the potential of the SDC by allowing testing at heat fluxes up to 50kW/m2, horizontal orientation of the specimen and the measurement of mass loss rate of the specimen.
Features of the FTT NBS Smoke Density chamber include:
- Test chamber with full width opening door, allowing easy access for sample loading and chamber cleaning.
- Photomultiplier control unit with all manual controls and digital display of optical density and relative intensity. Computer setting for use with FTT software to perform automatic control of the test procedure on the SDC.
- Controls are mounted beside chamber for convenient operation. They are not obstructed when the door is open.
- Smoke density and temperature are on digital displays, for easier use and greater accuracy.
- Chamber walls are preheated for easier startup and convenient equipment operation.
- Safety blowout panel, easily replaceable, allows for safe operation of test method.
- Gas measurement ports are provided, for optional measurements of toxic gases.
- Cabinet designed with a standard 19″ rack, for simple addition of gas analysers, chart recorder and other control units.
- Air cooled radiometer for furnace flux calibration.
The FTT SDC is supplied with a software package called SmokeBox, which is designed as a data acquisition and presentation package allowing either manual or automatic control. This enables a more efficient use of the instrument, leading to larger daily throughput of testing and enhanced quality graphical data presentation.
‘SmokeBox’ is a Microsoft Windows based package which collects test data and assists with all calibration routines.
According to EN 455452, the optical density of flat products, i.e. interior walls, floor coverings, seat backs and seat coverings should be determined using the closed chamber according to EN ISO 56592.
The smoke opacity during the combustion of the material is determined measuring the attenuation of a white light beam by the effluents.
The obscuration produced from the smoke is measured as a fraction of the light intensity reaching the photometric detector in the presence of smoke to the value corresponding to the luminous transmission in the absence of smoke before the start of the test.
Two different levels of irradiance have been standardised, depending on the application of the product:
- 50kW/m2 with no additional gas ignition source.
- 25kW/m2 with an additional gas ignition source.
The exposure conditions of the test specimen in the smoke chamber are radiant heat with or without application of a pilot flame. For large area products such as walls and ceilings, the test specimens shall be exposed to radiant heat flux conditions that simulate a developed stage of a fire; that is a heat flux of 50 kW/m2 without a pilot flame.
For floor coverings that generally receive lower levels of radiant heat during a fire, the test specimens shall be exposed to a radiant heat flux of 25 kW/m2 with a pilot flame.
The optical density of the smoke produced is measured continuously by an optical system. Toxic effluents are analysed using FTIR Spectroscopy. For assessment of toxic gases from railway products the Conventional Index of Toxicity (CIT) is used which is always calculated from test data and is dimensionless. The analysis of the spectrum collected during the test determines the concentration of gases.
According to EN 455452 the analysis is carried out using the equipment and the procedures for testing and calibration described in ISO 19702.
The 8 gas components need to be analysed and their reference concentrations.
FTT FTIR is a modular construction that typically comprises of a FTIR gas analyser, heated sampling unit and an industrial PC which are mounted in a 19″ cabin. The FTIR gas analyser is an integral part of the system which allows simultaneous measurement of
multiple gas compounds. Typically concentrations of H2O, CO2, CO, SO2, NO, NO2, HCl, HF, HBr, HCN, NH3, etc. are continuously measured. The FTIR gas analyser has a multipass sample cell which
is heated to 180°C and features gold plated mirrors with protective MgF2 coating which ensures high performance even in high water
vapour concentrations or corrosive gases.
Toxicity Test Apparatus
This method is based on the exposure of 1g of test specimen. The test apparatus and conditions for this method are described in
NF X 701002 with additional gas analysis information provided in EN 455452.
The exposure conditions of the test specimen in the tube furnace are generally set at 600°C, a fixed ventilation condition which represents a developing fire condition for railway products.
When the CIT for a product on a railway vehicle is required, only one method is used for the testing, gas analysis & calculation of CIT.
The test conditions specified for use when performing EN ISO 56592 or NF X 701002 depend upon the application and position of the product on the railway vehicle.
The conditions selected are representative of fires that may impact on the railway product, during either the developing stages or the developed stage of a fire inside or outside the railway vehicle.
3 Metre Cube Smoke Test Apparatus
The 3 Metre Cube is used for measuring smoke emission when electric cables are burned under defined conditions, for example, a few cables burned horizontally. These units are produced to meet the specification used in many electric cable tests. The unit can be supplied in a self assembly kit form or can be fully installed by
The equipment comprises of:
- A 3 metre cubic chamber assembly
- Photometric system, stands, fans and sample mounting frames
- Extraction fan and ducting
- Chart recorder or Windows based operation software.
Oxygen Index Test
The Oxygen Index test is specified in EN 455452 for testing ignitability of listed and nonlisted plastic products, e.g. internal and external seals, isolators, and PCBs. It is also one of the most economical and precise quality control tests for combustible materials. Its ease of use together with high levels of precision has made this technique a primary characterising quality control tool to the plastic and electric cable industries and it has been specified by several military and transport groups.
The technique measures the minimum percentage of oxygen in the test atmosphere that is required to marginally support combustion.
The FTT Oxygen Index (OI) and Temperature Oxygen Index (TOI) offer many improvements such as the latest oxygen analyser technology for high accuracy, reliability and long operating life.
Vertical Flame Test
The EN 455452 specifies the EN 606951110 for testing small electrotechnical products, e.g. lower power circuit breakers, overload relays, contactors, etc.
The FTT EN 606951110 Vertical Flame Test Apparatus features digital test duration timers, high precision gas control system and a bench mounted draft free stainless steel combustion chamber having a large inside volume.
The chamber is fitted with an interior light and exhaust fan to enable simple evacuation of combustion products from the tests. The apparatus can also comply with UL 94 and several FAR Bunsen burner tests with addition of the dedicated accessories.
The EN ISO 1182 Non Combustibility Test and
EN ISO 1716 Bomb Calorimeter are specified in the EN 135011 to classify A1 and A2 class construction products.
Brake resistors used in rolling stock, e.g. casing and any heat shields, are tested to this Euroclass criteria. The EN ISO 1182 test identifies products that will not, or significantly not, contribute to a fire, regardless of their end use. The FTT system has been designed with significant new
Rather than the traditional variac control, where it is possible to supply too high a current to the heater element during the heating cycle, FTT has automated the process by using modern electronics which considerably extend the life of the furnace.
Although EN 455452 is published and operable in April 2013, CEN/TC 256 WG 1 is still working to improve the test methods used for both seating and toxic gas measurement.
Please contact us for the latest changes and development of this standard..