Controlled-atmosphere Cone Calorimeter Research Articles

Effects of Oxygen Concentration on the Reaction to Fire of Cross-Laminated Timber in a Controlled-Atmosphere Cone Calorimeter

Effects of Oxygen Concentration on the Reaction to Fire of Cross-Laminated Timber in a Controlled-Atmosphere Cone Calorimeter

Reaction to fire of polymethylmethacrylate and polyvinylchloride under reduced oxygen concentrations in a controlled-atmospherecone calorimeter

Electrical cable sheaths are the most abundant fire load in nuclear power plants, mainly in rooms that are kept in under slight pressure. This configuration leads fires to grow in under-ventilated and vitiated conditions. Assessing fire threat involves characterizing the heat released, responsible for fire growth, and the smoke evolved, which may interact with sensitive components in the area. For that purpose, a revisited controlled-atmosphere cone calorimeter has been designed, set up, and coupled to a Fourier transformed infrared spectrometer and an electrical low-pressure impactor to measure simultaneously the evolved gases and aerosols, respectively. This bench-scale apparatus has been first qualified with polymethylmethacrylate. It has second been used to characterize polyvinylchloride cable sheath representative material reaction to fire in under-ventilated and vitiated conditions. It appeared that vitiation in under-ventilated fires lowers the heat release rate and the fuel mass loss rate.

Use of the modified controlled atmosphere cone calorimeter for the assessment of fire effluents generated by burning wood under different ventilation conditions

SummaryThe ISO 5660‐1 cone calorimeter is an affordable, practical, and commonly used solution for the measurement of main fire properties of products and materials. Among its chief drawbacks is its limited ability to reproduce combustion conditions found in real fires. This deficiency is mainly due to its inability to control oxygen availability in order to simulate an underventilated fire. As several toxic or potentially toxic species are formed primarily in oxygen‐poor conditions, the controlled atmosphere cone calorimeter (CACC), now defined in ISO 5660‐5, is a major improvement when trying to study the toxicity of fire effluents. A proposed additional modification of the CACC via the introduction of chimney sampling ports and oxygen sensors improves the reproducibility and veracity of effluent sampling. This approach allows the implementation of various techniques to sample, collect, and analyze the generated fire effluents. In this study, the experimental set‐up was used to capture fire effluents generated by burning wood under different ventilation conditions. A gas chromatograph coupled with mass spectrometer was used to assess and compare the chemical composition of the collected samples. The results obtained with the new experimental set‐up proved the ability of the system to reproducibly generate fire effluents under various controlled burning circumstances. It could prove useful as a tool in characterizing the toxicity of fire effluents from various materials on a benchtop scale and ultimately contribute data for the numerical modeling of toxicity of fire effluents in real buildings.

Experimental and numerical study on the evaporation rates of liquid fuels using a controlled atmosphere cone calorimeter

The work described in this paper presents a set of experimental tests carried out in a Controlled Atmosphere Cone Calorimeter (CACC) in order to study the evaporation rate of a 250 ml-‘batch’ of n-heptane and methanol poured into an insulated 0.10 × 0.10 × 0.04 m3 steel pan and exposed to two ‘nominal’ irradiation levels of 25 and 50 kW/m2. A low oxygen concentration is imposed during the CACC tests. The intent is to provide experimental data for the assessment and validation of the numerical modelling of liquid heat-up and evaporation in pool fires, without the need to model combustion and the subsequent associated complex phenomena. The analysis of the mass loss rate profiles shows that the evaporation rate of n-heptane increases with time due to the preheating of the liquid, whereas for methanol, a quasi-steady-state is reached. This is due to differences in specific heat, boiling point and latent heat of vaporization. Numerical simulations of the liquid phase using the Fire Dynamics Simulator (version 6.7.0) point out the importance to account for increased heat transfer due to the convective motion of the liquid by increasing the thermal conductivity of the liquid by 10–20 times. Other limitations and uncertainties in the modeling are also highlighted.

Experimental determination of the evolution of the incident heat flux received by a combustible during a cone calorimeter test: Influence of the flame irradiance

The decomposition kinetic of polymeric materials in a cone calorimeter strongly depends on the irradiance level imposed at the sample’s surface. Indeed, even if the irradiance level is supposed to be kept constant during cone calorimeter test, the amount of heat flux which is emitted by the flame can greatly increase the total heat flux received by the material. Analytical treatment on recently obtained results of an acrylonitrile-butadiene-styrene’s mass loss rate with controlled atmosphere cone calorimeter has shown that the differences observed between well-ventilated and inert environments can be attributed to the impact of the flame. This observation has brought the necessity to determine the impact of the flaming process on the material thermal decomposition. To do so, series of experiments have been devised, based on the insertion of a heat fluxmeter within the matrix of an acrylonitrile butadiene styrene material, during cone calorimeter tests in order to measure the flame heat flux as a function of the decomposition and the combustion processes.

Effects of oxygen availability on the combustion behaviour of materials in a controlled atmosphere cone calorimeter

The reaction-to-fire of materials is commonly studied with bench scale experiments conducted under controlled test conditions. Two bench-scale instruments commonly used for this purpose are the cone calorimeter and the fire propagation apparatus. Research performed with these test apparatuses on the burning behaviour of polymeric materials has demonstrated the significant effect on the results of test variables such as pressure, irradiance, flow velocity, etc. In spite of the fairly large number of studies, little is known concerning the effect of oxygen vitiation and reduced ventilation on the burning behaviour of polymeric materials. Recent work in a controlled oxygen environment raises the question of interpretation and accuracy of the results. This paper reports the results of a study to evaluate the effect of oxygen vitiation and reduced ventilation on the burning behaviour of materials in a controlled atmosphere cone calorimeter. The study was performed on a typical thermoplastic material, i.e., a black poly(methyl)methacrylate. The dependence of the results on the experimental fire conditions is presented and discussed. The experiments show that the inlet airflow rate is a major factor to consider when studying the burning behaviour of polymeric materials in an enclosure. It strongly affects the available amount of oxygen that can react and may lead to a misinterpretation of the results when the effects of oxygen are studied.

Fire Toxicity Assessment: Comparison of Asphyxiant Yields from Laboratory and Large Scale Flaming Fires

In a fire, normally non-hazardous thermoplastic materials can produce lethal concentrations of toxic effluents in the smoke. The toxic product yields of the asphyxiants carbon monoxide (CO) and hydrogen cyanide (HCN) from developed fires are typically 10 times greater than those generated in small-scale laboratory fire test apparatuses. Since most fire deaths, and most fire injuries, result from inhalation of toxic effluents, accurate replication is important for both fire hazard assessment and forensic fire investigation. The stoichiometric equivalence ratio allows the ventilation condition of flaming fires to be compared across different scales. The yields of CO and HCN from five laboratory-scale methods have been compared to large-scale data under the range of flaming fire conditions. Toxic product yield data from the smoke density chamber (SDC) (ISO 5659-2), the controlled atmosphere cone calorimeter (CACC) (based on ISO 5660), the fire propagation apparatus (FPA) (ASTM E 2058), the French railway test (NFX) (NF X 70100), and the steady state tube furnace (SSTF) (ISO/DIS 19700) are compared to published large-scale enclosure fire data (from a standard ISO 9705 room) for two polymers, polypropylene (PP) and polyamide 6.6 (PA 6.6). The results from the SSTF and FPA show the best agreement with those from the full and ⅓ scale ISO room for both materials under a range of fire conditions. The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. The NFX generates data intermediate between the well-ventilated and under-ventilated fire conditions.

Evaluation of a Headspace Solid‐Phase Microextraction Method for the Analysis of Ignitable Liquids in Fire Debris

The chemical analysis of fire debris represents a crucial part in fire investigations to determine the cause of a fire. A headspace solid-phase microextraction (HS-SPME) procedure for the detection of ignitable liquids in fire debris using a fiber coated with a mixture of three different sorbent materials (Divinylbenzene/Carboxen/Polydimethylsiloxane, DVB/CAR/PDMS) is described. Gasoline and diesel fuel were spiked upon a preburnt matrix (wood charcoal), extracted and concentrated with HS-SPME and then analyzed with gas chromatography/mass spectrometry (GC/MS). The experimental conditions--extraction temperature, incubation and exposure time--were optimized. To assess the applicability of the method, fire debris samples were prepared in the smoke density chamber (SDC) and a controlled-atmosphere cone calorimeter. The developed methods were successfully applied to burnt particleboard and carpet samples. The results demonstrate that the procedure that has been developed here is suitable for detecting these ignitable liquids in highly burnt debris.

Accuracy (Trueness and Precision) of Cone Calorimeter Tests with and Without a Vitiated Air Enclosure

Over the last few years, new many laboratory fire tests have been developed. One such test is the controlled atmosphere cone calorimeter (CACC). Until now this bench-scale test has not been standardized and the device design differs from one laboratory to another. These differences can affect measurement accuracyaaAccuracy: The closeness of agreement between a test result and the accepted reference value. (truenessbbTrueness: The closeness of agreement between the average value obtained from a large series of test results and an accepted reference value. and precisionccPrecision: The closeness of agreement between independent test results obtained under stipulated conditions.) and direct comparison of literature results is difficult. No studies have been conducted to understand the effect of the design on the fire behaviour of materials and measurement accuracy in the CACC. The present publication focuses on these effects under ambient and non-ambient oxygen conditions. Several designs were investigated using Poly(methyl)methacrylate (PMMA) as the test material. Statistical analyses were performed in some cases to assess the data. The results are presented and discussed.

Experience plan for controlled-atmosphere cone calorimeter by Doehlert method

Controlled-atmosphere cone calorimeter is an interesting test method to study at the same time the effect of oxygen concentration and radiant heat flux on materials' fire behaviour and gas release. However, measurements in an extended range for these two variables can be tedious. To optimize the experimental measurement, this paper proposes a methodology based on the Doehlert design. The Doehlert method allows significant optimization of the number of tests. The optimization of measurement response is then accomplished using polynomial approximations to establish fire behaviour constitutive. Copyright © 2012 John Wiley & Sons, Ltd.

Note: measuring the effective heats of combustion of transformer‐insulating fluids using a controlled‐atmosphere cone calorimeter

AbstractThe effective heats of combustion of two commonly used transformer‐insulating fluids, a high molecular weight hydrocarbon fluid and a 50 cS silicone fluid, have been measured using a controlled‐atmosphere cone calorimeter. The study shows that the cone calorimeter is a good tool to measure the effective heats of combustion of transformer‐insulating fluids. Copyright © 2002 John Wiley & Sons, Ltd.

Development of a controlled-atmosphere cone calorimeter

A controlled-atmosphere cone calorimeter has been developed that overcomes many of the shortcomings of previously developed units. The new apparatus is a fully sealed 'blow-through' system, which provides a full-size chamber in which the combustion process can occur. Oxygen concentrations from 0%-20.95% are achieved while maintaining the required configuration and flow rates to meet standard cone calorimeter testing requirements. The apparatus was developed in order to obtain data on the burning of materials at reduced oxygen levels for modelling purposes, It is now being used in pyrolysis studies assisting in the determination of fundamental material flammability properties.

Burning characteristics of selected substances: influence of suppression with water

The influence of suppression with water spray on the burning characteristics and composition of fire effluents of nylon, polypropylene and two industrial chemicals was investigated. The experiments were performed using a controlled-atmosphere cone calorimeter in which the ventilation conditions could be altered. The water spray was applied with a single horizontally positioned nozzle. In the experiments time to ignition, rate of heat release, sample weight and smoke production as well as the composition of the fire effluents were measured; the chemical analysis techniques employed were Fourier-transform infrared spectroscopy and gas chromatography/mass spectroscopy. The results give quantified information on the effects that water application may have on the burning and the properties of the exhaust gases. A comparison with results of similar experiments with no water application reveal notable changes, e.g. in the production of the toxic fire effluents. Copyright © 1999 John Wiley & Sons, Ltd.

Burning characteristics of selected substances: influence of suppression with water

The influence of suppression with water spray on the burning characteristics and composition of fire effluents of nylon, polypropylene and two industrial chemicals was investigated The experiments were performed using a controlled-atmosphere cone calorimeter in which the ventilation conditions could be altered. The water spray was applied with a single horizontally positioned nozzle. In the experiments time to ignition, rate of heat release, sample weight and smoke production as well: as the composition of the fire effluents were measured; the chemical analysis techniques employed were Fourier-transform infrared spectroscopy and gas chromatography/mass spectroscopy. The results give quantified information on the effects that water application may have on the burning and the properties of the exhaust gases. A comparison with results of similar experiments with no water application reveal notable changes, e.g. in the production of the toxic fire effluents.

Controlled-atmosphere cone calorimeter studies of silicones

A controlled-atmosphere cone calorimeter was used to investigate the burning of a silicone fluid and two silicone elastomers. The silicone materials were tested at 50 kW/m2 incident heat flux in environments containing 15–30% oxygen. The test results were compared with a high molecular weight hydrocarbon fluid and an ethylene propylene rubber in terms of time to ignition, peak heat release rate and total heat released, carbon monoxide yield and carbon monoxide production rate, and smoke production and smoke production rate. The data from this study show that when materials burn in oxygen-enriched, normal, and vitiated atmospheres, silicone-based materials have a comparatively low peak heat release rate, total heat released, average CO production rate, and average smoke production rate as compared with organic-based materials. The smoke production and smoke production rate of silicone elastomers can be significantly reduced by adding appropriate smoke suppressants and additives. © 1997 John Wiley & Sons, Ltd.

Flammability Testing of Flame-retarded Epoxy Composites and Phenolic Composites

Flame-retarded epoxy composites and phenolic composites containing fiberglass, aramid (Kevlar® 49), and graphite fiber-reinforcements were tested using the NASA upward flame propagation test, the controlled-atmosphere cone calorimeter test, and the liquid oxygen (LOX) mechanical impact test. The upward flame propagation test showed that phenolic/graphite had the highest flame resistance and epoxy/graphite had the lowest flame resistance. The controlled-atmosphere cone calorimeter was used to investigate the effect of oxygen concentration and fiber reinforcement on the burning behavior of composites. The LOX mechanical impact test showed that epoxy/fiberglass had the lowest ignition resistance and phenolic/aramid had the highest ignition resistance in LOX. The composites containing epoxy resin and/or aramid fiber reinforcement reacted very violently in LOX upon mechanical impact. © 1997 by John Wiley & Sons, Ltd.