Assessment of fire behaviour of high‐speed trains' interior materials: small‐scale and full‐scale fire tests

The development of fire‐safety measures for high‐speed passenger trains has been focused on preventing fire initiation or delaying fire growth and spread through small‐scale tests of the materials used in trains. However, new fire‐safety approaches for trains consider a systemic approach. This approach considers numerous global factors that influence fire dynamics, such as the influence of vehicle design, selection of materials, and active and passive protection systems installed. In the present paper, the results of small‐scale and full‐scale tests carried out on the new generation of high‐speed trains operating in Spain are presented. This rolling stock is classified as category B according to the Technical Specification for Interoperability and Operation Category 3 according to EN 45545–1. The results confirmed good fire behaviour using both approaches (small and full‐scale tests). Additionally, several analyses have been performed, including an analysis of the quality of materials used for making different components of the passenger compartment and the influence of ignition source position on fire development. Copyright © 2013 John Wiley & Sons, Ltd.     

Screening of plenum cables using a small‐scale fire test protocol

The extent of flame propagation of electric cables in the FM Global intermediate‐scale parallel panel test (PPT) using a 60 kW sand burner has been correlated with a dimensional fire propagation index (FPI,)[(m/s^1/2)/(kW/m)^2/3] derived from ignition and vertical propagation tests in small‐scale ASTM E‐2058 Fire Propagation Apparatus (FPA). Two distinct types of fire behavior were observed in the PPT. The cables that did not propagate beyond the vicinity of the ignition burner flames have a FPI equal to or less than 7 [(m/s^1/2)/(kW/m)^2/3], whereas cables that propagated to the top of the 4.9 m parallel panels had a FPI equal to or greater than 14 [(m/s^1/2)/(kW/m)^2/3]. All the plenum rated (Ul‐910 or NFPA 262 tested) cables tested in this study did not exhibit flame propagation in the PPT, had FPI values of 7 [(m/s^1/2)/(kW/m)^2/3] or less and generated considerably lower smoke than those cables that propagated in the PPT. Based on this study, it is suggested that FPI measured in ASTM E‐2058 FPA may be used for screening cables for UL‐910 or NFPA262 tests, thus requiring substantially less cable to be supplied for testing. Copyright © 2005 John Wiley & Sons, Ltd.     

Numerical simulations of a full‐scale cable tray fire using small‐scale test data

This paper presents a computational fluid dynamics (CFD)‐based modeling strategy for the prediction of cable tray fire development. The methodology is applied to a set of five horizontal trays (each 2.4‐m long and 0.45‐m wide) that are positioned with a 0.3‐m vertical spacing and set up against an insulated wall. Each tray contains 49 power PVC cables. Ignition is performed with an 80‐kW propane burner centrally positioned at 0.2 m below the lowest tray. A collection of four groups of cables per tray (made of one homogeneous material) is considered. These groups are separated by longitudinal slots of air to “mimic” their relatively “loose arrangement.” The thermal properties and surface ignition temperature are estimated from cone calorimetry (CC). When the ignition temperature is reached, the cables burn according to a prescribed heat release rate per unit area (HRRPUA) profile obtained from CC, as is or in a modified shape. A realistic flame pattern is predicted. Furthermore, using only data from CC, the peak HRR is underpredicted, and the time to reach the peak is overpredicted. The proposed “design” for the modified HRRPUA CC‐profile significantly improves the results.     

Comparison of simulated wet bench fires with small‐ and intermediate‐scale fire tests

Fire hazard studies of clean room facilities indicated that significant losses due to fire may occur in the semiconductor industry. The present study reports the results of full‐scale wet bench fire tests conducted (1) to assess the fire hazards of existing wet bench materials not meeting the listing requirement of NFPA 318, (2) to assess the impact on wet bench fires of engineered materials with improved flammability characteristics, and (3) to compare the observed fire behavior with the results of simpler small‐ and intermediate‐scale fire tests using the same materials. The full‐scale wet bench fires were observed to be consistent in terms of chemical heat release rate, fire propagation, and smoke generation with the results of the small‐ and intermediate‐scale test results. The simpler fire tests are incorporated in FM Approvals 4910 certification for materials to be used in semiconductor fabrication facilities. The small‐scale test protocol is also standardized in NFPA 287. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental study of tenability during a full‐scale motorcoach tire fire

Full‐scale fire experiments were conducted at the National Institute of Standards and Technology (NIST) to investigate tire fire interactions with the passenger compartment of a motorcoach. A single full‐scale experiment with a partially furnished interior was conducted to investigate tire fire growth within the passenger compartment and the onset of untenable conditions. A tire fire was initiated using a burner designed to imitate the frictional heating of hub and wheel metal caused by failed axle bearings, locked brakes, or dragged blown tires. Measurements of interior and exterior temperatures, interior heat flux, heat release rate, toxic gases, and visibility were performed. Standard and infrared videos and still photographs were also recorded. The results of this single experiment showed that after fire penetration into the passenger compartment, the tenability limits were reached within 8 minutes near the fire and within 11 minutes throughout the passenger compartment.     

Modelling decomposition and fire behaviour of small samples of a glass‐fibre‐reinforced polyester/balsa‐cored sandwich material

This publication presents the experimental and numerical methods to model the devolatilization process of a glass‐fibre‐reinforced polyester/balsa‐cored sandwich material on small scale. The fundamental modelling of the source term in pyrolysis‐based fire simulations requires as input data the thermochemical properties of solid fuel and the kinetic parameters of the devolatilization process. First, the thermal decomposition of both elements composing the sandwich structure was studied by thermogravimetry coupled with gas analysis, in air and pure nitrogen atmospheres at several heating rates, in order to define a comprehensive multi‐step reaction pathway. A differential equation system is defined to model these decomposition processes. The kinetic parameters were then estimated by solving the system of equations by an inverse problem. Second, the fire behaviour of each element was studied separately and then combined in the sandwich structure on the cone calorimeter. In addition, numerical simulations with Fire Dynamics Simulator were performed to gradually assess the ability of the model(s) to reproduce each element composing the sandwich structure. Numerical and experimental results are compared and then discussed. Overall, the model provides a good agreement with the experimental data and encourages to model higher scales. Copyright © 2012 John Wiley & Sons, Ltd.     

A methodology for predicting and comparing the full‐scale fire performance of similar materials based on small‐scale testing

Reconstructive fire testing is an important tool used by fire investigators to determine the cause, origin, and progression of a particular fire. Accurate reconstruction of the fire requires the laboratory structure to be outfitted with materials that, in terms of contribution to fire growth, perform similarly to the original materials found at the fire scene. Therefore, a procedure was developed to enable fire investigators to select these replacement materials on the basis of a quantitative assessment of their relative fire performance. This procedure consists of gram‐scale and/or milligram‐scale standard testing accompanied by inverse numerical modeling of these tests, which is used to obtain relevant material properties. A numerical model composed of a detailed pyrolysis submodel and empirical flame heat feedback submodels, which were developed in this study, is subsequently employed to simulate the early stages of the Room Corner Test, which was selected to represent full‐scale material performance. The results of these simulations demonstrate that this procedure can successfully differentiate between fire growth propensities of several commercially available medium density fiberboards.     

Investigation of smoke gases and temperatures during car fire – large‐scale and small‐scale tests and numerical investigations

The hazards for passengers during vehicle fires result from the increasing temperature and the emitted smoke gases. A fire was set on a car to investigate the development of temperature and of gaseous fire products in the passenger compartment. The study was based on a full‐scale test with a reconstructed scene of a serious car fire. The aim of this work was to identify the conditions for self‐rescuing of passengers during a car fire. A dummy, equipped with several thermocouples, was placed on the driver's seat. Also, the smoke gases were continuously collected through a removable probe sensor corresponding to the nose of the dummy in the passenger compartment and analyzed using Fourier transform infrared spectroscopy. Additionally, several car components were investigated in the smoke density chamber (smoke emission and smoke gas composition). It was found that the toxic gases already reached hazardous levels by 5 min, while the temperatures at the dummy were at that time less than 80 °C. The toxicity of smoke gases was assessed using the fractional effective dose concept. The various experimentally parameters (temperature and smoke gas composition) were implemented into numerical simulations with fire dynamics simulator. Both the experimental data and the numerical simulations are presented and discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental study of the burning behavior of n‐heptane pool fires at high altitude

The same configured calorimeters were built in Hefei (99.8 kPa) and Lhasa (66.5 kPa), respectively. Four sizes of round pans with diameters of 10, 15, 20, and 25 cm were adopted to study the effect of high altitude on the burning behavior of liquid pool fires. Analysis on the burning rate obtained in this study and in the literature at different altitudes indicates that pressure fire modeling performs better than radiation fire modeling in correlating the burning intensity (burning rate per unit area) with pressure and pool diameter for cases under low ambient pressure. The study also shows that heat release rate and combustion efficiency decrease at higher altitude. For medium pool fires, the burning intensity and heat release rate are proportional to D^5/2, thus the combustion efficiency being independent on pool sizes but decreases at higher altitude by a factor approximate to the pressure ratio. Copyright © 2014 John Wiley & Sons, Ltd.     

Influences of specimen size and heating mode on the ignitability of polymeric materials in typical small‐scale fire test conditions

Small‐scale fire tests including the Underwriters Laboratories 94 (UL94) vertical burning test and the cone calorimeter test are widely used. In this paper, the ignition times of materials heated by the conical heater of a cone calorimeter and the UL94 flame were measured. It was found that for polymer bars heated by the UL94 flame, the ignition time is relatively short and increases with the specimen thickness. But the contribution of the specimen thickness to the delay of the ignition time is limited. The intrinsic properties of materials play a more important role in the ignition time than the specimen thickness. In addition, respectively corresponding to one‐dimensional, two‐dimensional, and three‐dimensional heat transfer, three heating modes of the UL94 flame were presented and compared with the conical heater. It was found that whether the heat source is the conical heater or the UL94 flame, the ignition time depends on the heat flux and the multidimensional heat transfer. The ignition time decreases with the increasing heat flux, and the magnitude order of the ignition time might drop when the heating mode changes from one‐dimensional to multidimensional heat transfer. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental study on fire properties of interior materials used in low‐floor light‐rail trains

In this work, cone calorimeter tests were conducted to investigate fire properties of interior materials (floor covering [FC], aluminum plate covered with paint [APCP], light diffuser [LD], and gel coat [GC]) used in low‐floor light‐rail trains. Ignition time (t_ig) of each material decreases with the increase of radiative heat flux. The decreasing order of the four samples by ignition time under the same radiative heat flux is LD > APCP > FC > GC. The heat release rate (HRR), peak value of HRR (PHRR), time from ignition to PHRR (t_p), fire growth rate index (FIGRA), and fire growth index (FGI) rise with the increasing radiative heat flux. For the FC, LD, and GC, single HRR peak is observed in the HRR history while three peaks are observed for APCP. For PHRR, LD > FC > APCP > GC, while for t_p, GC < FC < APCP < LD. Under most conditions, the FIGRA and FGI of the FC is the highest among the four materials. Results of this work are beneficial to evaluate fire hazard of low‐floor light‐rail train and determine the emphasis of fire prevention.     

Experimental study of the ignition behaviour of an adiabatic SRC-II coal liquefaction reactor

Experimental data are presented which describe the thermal behaviour of a bench-scale adiabatic coal liquefaction reactor operating in an open loop. The reactor employed external feedback control for maintaining adiabaticity. Conditions for both ignition and quench have been found for coal liquefaction at SRC-II operating conditions where repeated ignition/quench behaviour was demonstrated. No stable steady states were found between 450 °C and 475 °C for SRC-II operation. Ignition occurred at a feed temperature of ≈415 °C. The low steady states occurred at conditions of essentially no heat generation; at a very low extent of reaction. Some unexpected evidence of a preheater effect on reactor ignition was observed; however, the effect of preheater temperature profiles on reactor performance was not systematically studied.     

Experimental study of the combustion characteristics of methanol‐gasoline blends pool fires in a full‐scale tunnel

The combustion characteristics of methanol‐gasoline blends pool fires were studied in a series of full‐scale tunnel experiments conducted with different methanol and gasoline blends. The parameters were measured including the mass loss rate, the pool surface temperature, the fire plume centerline temperature, the ceiling temperature, the smoke layer temperature profile, the flame height, and the smoke layer interface height. The gasoline components were analyzed by GC‐MS. The effects of azeotropism on the combustion characteristics of the different blends were discussed. On the basis of the results of the fire plume centerline temperature, the ceiling temperature, and the flame height, it shows that the tunnel fire regime gradually switches from fuel controlled to ventilation controlled with increasing gasoline fractions in the blends. The fire plume can be divided into 3 regions by the fire plume centerline temperature for the different blends. The N‐percentage rule to determine the smoke layer interface height is found to be applicable for tunnel fires with different blends for N = 26.     

Experimental fire analysis of steel‐to‐timber connections using dowels and nails

The paper describes and discusses the results of an extensive testing programme on the structural behaviour of timber connections under ISO‐fire. The results of reference tests performed at normal temperature are also presented. From the variety of timber connections multiple shear steel‐to‐timber connections with dowels and slotted‐in steel plates and connections with steel side plates and annular ringed shank nails were experimentally studied. Particular attention was given to the analysis of the efficiency of different strategies in order to increase the fire resistance of the timber connections. The test results showed that unprotected multiple shear steel‐to‐timber connections with dowels designed for normal temperature reached a fire resistance of about 30 min. A reduction of the load level applied during the fire did not lead to a significant increase of the fire resistance. By increasing the side timber members as well as the end distance of the dowels by 40 mm the connections reached a fire resistance of more than 70 min. Connections protected by timber boards or gypsum plasterboards showed a fire resistance of around 60 min. Thus, from a fire design point of view these strategies were favourable in order to increase the fire resistance of the connections significantly. Unprotected connections with steel side plates and annular ringed shank nails failed already after about 12 min due to large deformations of the nails and the steel side plates directly exposed to fire. By protecting the steel side plates using an intumescent paint the fire resistance of the connections was increased to around 30 min. The test results enlarged the experimental background of timber connections in fire significantly. Copyright © 2009 John Wiley & Sons, Ltd.     

Numerical simulation of the fire behaviour of facade equipped with aluminium composite material‐based claddings‐Model validation at large scale

The recent fire events in buildings involving combustible cladding systems have raised concerns regarding the risk that these systems can pose. Understanding such facade fires is complex as they involve a combination of various products and system. Facade fire propagation tests at ISO 13785‐1 intermediate scale were performed on different combinations of aluminium composite material (ACM) claddings and insulants. Simulations were addressed to reproduce these tests and were validated in terms of thermal conditions in the system. This allowed additional investigation and understanding of fire propagation on the facade and more accurate determination of the fire behaviour of the overall system. In this paper, the scaling influence on the fire behaviour of ACM clad systems is investigated with simulations performed to reproduce fire tests at the BS8414‐1 larger scale on three different combinations of ACM and insulants. The contributions of the cladding and insulant were numerically investigated. The fire behaviour of each component and of the overall system is validated by comparison with experiments. Simulations and tests show that the ACM cladding is the most important element driving the global fire behaviour of the systems. In particular, ACM‐PE‐based cladding systems, whatever the insulant, show extensive fire propagation while its degradation affects the integrity of the cavity.     

Reduced‐scale test to assess the effect of fire barriers on the flaming combustion of cored composites: An upholstery‐material case study

Herein, we describe a reduced‐scale test (“Cube” test), measuring the fire performance of specimens including a fire barrier (FB) and a flammable core material, which acts as the main fuel load. The specimen is intended to reproduce a cross‐section of a composite product where heat/mass transfer occurs primarily in a direction perpendicular to the FB. The Cube test procedure and benefits are discussed in this work by adopting residential upholstery furniture as an exemplary study. One flexible polyurethane foam, one polypropylene cover fabric, and 10 commercially available FBs were selected. They were used to compare the fire performance of FBs, measured in terms of peak of heat release rate, in the ASTM E1474‐14 standard test and the newly developed Cube test. Edge effects severely affected the performance of FBs in the ASTM E1474‐14 standard test but not in the Cube test. Furthermore, appropriate test conditions were determined in the Cube test to measure the so‐called “wetting point,” that is, the time and value of heat release rate measured when flammable liquid products were first observed on the bottom of the specimen. The relevance of the “wetting point” in terms of full‐scale fire performance and failure mechanism of FBs is discussed.     

Multi‐scale experimental investigations of the thermal degradation of pine needles

In this work, the thermal degradation of pine needles (from a Mediterranean species) was studied using a thermogravimetric analysis and cone calorimeter that were coupled to Fourier transform infrared spectrometer. The thermogravimetric analyses were carried out at four heating rates, in both air and nitrogen atmospheres. The evolution of gaseous components, mass loss and mass loss rate were recorded as a function of time and temperature. In order to account for the observed behaviours of the materials, we have also proposed a mechanism for the thermal degradation of pine needles, by primarily analysing the evolutions of both mass loss rate and gaseous components under nitrogen and air atmospheres. The kinetic parameters were subsequently estimated by using a genetic algorithm method. The cone calorimetric measurements were mainly conducted with a view to investigating the influence of thermal transfer processes, occurring in a porous bed of pine needles with regard to its thermal degradation. The experiments were conducted at five external heat fluxes under a well‐ventilated atmosphere. Measurements consisted of the mass loss, mass loss rate and the amount of gaseous emissions. The main gases emitted during the thermal degradation and the combustion of the pine needles were found to be CH₄, CO, CO₂, NO and water vapour. In addition, the evolution of the temperature was measured by using a set of five thermocouples, placed in a vertical position at the centreline of the sample. The results obtained showed that the bed of pine needles behaved as a thermally thick fuel. On the contrary, at higher external heat fluxes, the sample behaved as a thermally thin sample. Copyright © 2016 John Wiley & Sons, Ltd.     

Full‐scale study on combustion characteristics of an upholstered chair under different boundary conditions—Part 2: Ignition at the backrest top

The objective of this work is to investigate the effects of both boundary conditions and ignition positions on the combustion characteristic of a combustible item in a room. A series of full‐scale experiments were carried out in an ISO 9705 fire test room with an upholstered chair at three typical locations, i.e. the middle of side wall, room center and room corner. Here, ignition was achieved through a BS No. 7 wooden crib at the top of the backrest. The results show there were two peak heat release rates (HRRs) when the chair is at the room corner. However, when the chair was placed at the room center, only one peak HRR was observed. In addition, the peak HRR for the chair at the room center, about 800 kW, was much higher than that of the chair at the room corner, about 600 kW. Taken together with earlier work, in which the igniting crib was placed on the chair seat, the results show that the ignition positions, as well as the boundary conditions, influence the combustion behavior of upholstered furniture in a room. Finally, it is suggested that the chair burning would develop more slowly when it is ignited at the backrest than at the seat. Copyright © 2011 John Wiley & Sons, Ltd.