Laboratory Analysis: Cone Calorimeters - Lab Report Example

LABORATORY REPORT: CONE CALORIMETERS By [Client’s Name] To [Professor’s Name] [University Details] Table of Contents Introduction ……………………………………….. Aims and Objectives ……………………… Methodology and Equipments ………………….. Results …………………………………………….. Discussion and Analysis …………………………. Conclusion and Recommendations …………….. References ………………………………………… Appendix …………………………………………… Abstract A better understanding of how fires behave lies in one’s ability to understand the properties of the elements that produce, maintain, and propagate fires and flames. This knowledge can lead policy-makers to place regulatory requirements for the manufacture and use of certain materials that can easily produce and propagate fire. This knowledge can also aid building engineers in their inspection and implementation of certain policies to save hundreds of lives during fire emergencies Introduction Fires have specific attributes and these attributes depend on the types and volume of combustible fuel, the availability of oxygen, and the path of propagation (Drysdale 1998). An effective method of fighting fire is to understand the nature of fire, gain deeper knowledge of the elements that aid in the generation and propagation of fire, and to do something about the information that were obtained. In most cases, fires leave imprints in the damage they cause. These signature marks were then used by fire forensics to analyze and decipher what factors were involved in the fire, leading to the understanding of the cause of fire, the size and intensity of their flames, the amount of smoke produced during the fire, and the potential health hazards the fires may cause (Quintere 1997). Some of the most common variables measured to gain better understanding of fires are: heat of combustion, the amount of gases emitted particularly the amount of carbon monoxide and carbon dioxide present in the smoke, the ignition time, and size and thickness of the smoke, mass loss rates, and heat release rates. These elements make up the fire parameter since they are inter-related which implies that if one aspect is determined, the other aspects can be too. One of the most important fire parameter is heat release rate – the driving force behind every fire (Babrauskas 1995b). The importance of HRR as a fire parameter can be seen in the following: as fires produce heat which in turn produces more heat, the whole process facilitates the propagation and the germination of fires. This process does not show in other fire elements. For example, the generation of carbon monoxide does not ensure that more carbon monoxide is produced. But the HRR could indicate and predict how much smoke, heat, and gases are produced in the process, making HRR a very important fire perimeter. In effect, it tells people how dangerous the fires are. HRR can be measured using calorimeters. With calorimeters, understanding HRR and the related fire parameters like heat flux, mass loss rate, ignition time, smoke production, carbon dioxide and carbon monoxide levels, and effective heat of combustion became relatively easier to determine. Aims and Objective The main goal of this experiment is to determine the relationship between HRR and heat flux, mass loss rate, ignition time, smoke production, carbon dioxide and carbon monoxide levels. In order to establish these relationships, a test specimen is subjected to varied heat flux and is observed using a cone calorimeter. All changes in the specimen were noted, segregated, and measured using various measuring equipments integrated with the cone calorimeter. Methodology and Equipments By principle, the amount of heat released during combustion is determined by the amount of oxygen the combustion consumes. For most materials, the relationship between the heat release rate and the amount of oxygen consumed is 13.1MJ of heat with very small variation (ISO 1995). Hence, the heat release rate can be determined by measuring the oxygen concentration of the combustion chamber (the cone calorimeter) and the flow rate of the exhaust gas. From this, the other fire parameters are also obtained. This is the main principle involved in the methodology of this experiment. A test sample is burned in ambient air conditions while being subjected to external irradiance ranging from 0kW/m2 to about 100kW/m2 while the oxygen and exhaust gas flow rates are closely observed. Cone Calorimeter System A cone calorimeter system is composed of nine independent systems integrated into one. Generally, every cone calorimeter has: (a) cone-shaped radiant electrical heater that is capable of delivering 5000W of heat at an operating voltage of 240V. The electrical heater also allows vertical and horizontal orientation of samples. The heat flux coming from the heater is held at pre-set levels which can be varied using a temperature controller, producing a uniform heat flux in a 50mm x 50mm area; (b) An ignition device powered by a 10kW transformer. The ignition device is also capable of recording ignition intervals; (c) A radiation screen that protects the specimen from unwanted heat fluxes, particularly those that are present before the test occurs. This also allows the load cell to stabilize first before the heat flux is allowed to penetrate the specimen; (d) A weighing device for measuring specimen mass is integrated in the cone calorimeter system. This device has an accuracy of ±0.1g and can be used to measure specimen weighing 500g; (e) An exhaust system that is composed of high temperature rated centrifugal exhaust fan, a hood, an orifice plate flow meter, and intake and exhaust ducts for the fan. The exhaust system is closely integrated with other measuring systems such as that used to sample gases, the temperature of the gas stream, and its own gas flow rate. The system is capable of producing gas flows from 0.012m3/s to 0.035m3/s, at standard conditions of temperature and pressure. (f) An oxygen analyzer that is able to detect ± 50 parts per million of oxygen for over a period of 30 minutes. The oxygen analyzer requires special settings since the equipment is very sensitive to slight fluctuations of pressures and vibrations. (g) Specimen holders that can be oriented on any axis. These holders have an opening of 106 ± 0.5 mm x 106 ±0.5 mm at the top and a depth of 25 ±0.5mm to allow proper alignment and ensure central location of the specimen. When in horizontal orientation, the distance of the cone heater to the top of specimen is adjustable to 25 ± 0.5mm. (h) Both the calibration burner and heat flux meter calibrate the apparatus. The heat flux meter is used to calibrate the heater with a range of 100 ± 10kW/m2 whereas the calibrated flow meter is used to calibrate the whole apparatus, particularly the readouts pertaining to the heat release rate. Methane gas of 99.5% purity is used in calibration burner. (i) The gas sampling apparatus is a measuring system integrated to the cone calorimeter. It if composed of a pump, a soot filter, a cold trap, and a bypass system that diverts all gas flows except the flows that are needed by the gas analyzers. (j) The data collection and analysis system is the complete system that measures the fire parameters. It retrieves and process data and information pertaining to the parameters of interest, particularly the HRR, the oxygen levels, and the presence of gas. It is generally calibrated to at least 50 parts per million of oxygen channel, 0.50C for the temperature measuring channels, and 0.01% of full-scale instrument output for all other instrument channels. After calibrating the cone calorimeter system, the initial set-up is made and is recorded. Three samples were chosen and were subjected to four different amounts of heat fluxes. The thickness for each type of samples is varied as well. The initial weights of the samples were taken and were recorded. The pertinent details of the samples were given in Appendix B. Results The samples react differently when introduced to various heat fluxes although most of the results indicate similar graphical relationships for all three samples. This means that the results were somehow expected: decline in the heat release rate as time increases, increase in effective heat of combustion over time, decrease in mass loss rate over time, faster time to ignition of samples as the heat flux applied increases, and material dependence of gas emissions. There are numerous readings though for each type of sample that does not have a linear correspondence with the other samples and the initial condition they were in, like the flameout period, total heat evolved, and total oxygen consumed. The difference is attributed to the property of the materials rather than on the parameters of the experiment. The similarities of the result are more of the behavior of the graphical representation of the reaction over time. Each sample, whether from the same kind or not, exhibit different reactions towards the initial heat flux applied. Some samples react very fast to the heat flux applied by igniting in less than 20 seconds while other samples took more than 30 seconds to ignite. Once on fire, the samples took more than 200 seconds to flame out. The amount of oxygen consumed by each sample relates directly to the type and the properties of the sample. One erratic result that was observed is the reaction of the underlay towards the heat flux that was introduced to it. For the underlay at 25kW/m2 and at 45kW/m2, the sample is totally consumed before the 5th minute whereas the sample is consumed before the 6th minute for the underlay at 55kW/m2. The underlay sample was not consumed when subjected to heat flux with at 35kW/m2. There is also no definite pattern that can be established for the flameout of the underlay. The time to ignition of the samples is inversely proportional to the heat flux applied as expected. The other parameters are linearly dependent with the period of exposure to the heat flux; that is, significant increase or decrease is noted as the period of exposure increased. Discussion and Analysis There are three elements that must be present for fires to start and propagate. These are the source of ignition, the source of fuel, and oxygen supply (Quintiere 1997). In the experiment conducted, the source of ignition and the oxygen supply are regulated and the source of fuel is observed in order to explain the dependence of flame propagation with the types of fuel materials present. The properties of the materials present in the flame path will be the determining factors for the deterrence or the success of fire propagation. Based on the experiment, there are at least two major components of the source of fuels (or combustible materials) that needs to be understood in order to prevent the spread of fire. These components are (a) combustibility of the materials, and (b) the thickness of the materials. Materials that are thick but porous easily catch fire whereas materials whose composition is not easily combustible would take longer periods before they catch fire. This is seen in the underlay samples that are thicker than the other two samples but is easily combustible. As was noted, the underlay samples ignited easily when exposed to the heat flux compared to the other two samples which took longer time to ignite. Conversely, materials that are thin but are not easily combustible do not catch fire easily as was seen in the results of the other two samples. Materials that took longer time to flameout allow fires to produce more heat, hence burning more materials in its wake. Materials that have high emission rates for carbon monoxide and carbon dioxide are the materials that produce more smoke and health hazard. Knowing which types of materials produce which hazard is an important factor as well in fighting the spread and propagation of fires. Conclusion and Recommendation A better understanding of how fires behave lies in one’s ability to understand the properties of the elements that produce, maintain, and propagate fires and flames. This knowledge can lead policy-makers to place regulatory requirements for the manufacture and use of certain materials that can easily produce and propagate fire. This knowledge can also aid building engineers in their inspection and implementation of certain policies to save hundreds of lives during fire emergencies. The cone calorimeter is one of the most excellent equipment for determining the reaction of certain materials to heat flux as well as in determining the ability of these materials to release heat when on fire. Even though the equipment has its limitations, the possible areas of application are numerous that it is hard to ignore its usability. References Babrauskas, V., (1990) ‘The Cone Calorimeter – A New Tool for Fire Safety Engineering’, American Society for Testing and Materials, ASTM Standardisation News, USA Babrauskas, V., (1995a) ‘The Cone Calorimeter’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA Babrauskas, V., (1995b) ‘Burning Rates’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA Brehob, E.G. and Kulkarni, A.K. (1993) ‘Time-dependent Mass Loss Rate Behavior of Wall Materials Under External Radiation’, Fire and Materials, Volume 17, pp. 249-254 Drysdale, D. (1998) ‘An introduction to fire dynamics’ Second Edition, Wiley Fire Safety Journal, Official Journal of the International Association for Fire Safety Science [available in the library and online] http://www.sciencedirect.com Foley, M. and Drysdale, D., (1994) ‘Smoke Measurement and the Cone Calorimeter’, Fire and Materials, Volume 18, pp.385-387 NFPA 264A, (1990) ‘Standard Method of Test for Heat Release Rate for Upholstered Furniture Components or Composites and Mattresses Using an Oxygen Consumption Calorimeter’, Technical Committee on Fire Tests, National Fire Protection Association (NFPA), USA International Standard ISO 5660-1 (1995) ‘Fire Test – Reaction to Fire Part 1: Heat Release Rate from Building Products (Cone Calorimeter Method)’, International Standard Organisation for Standardisation Janssens, M., (1995) ‘Calorimetry’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA Johansson, P. & Reich, P. (2005). Population Size and Fire Intensity Determine Post-fire Abundance in Grassland Lichens. Applied Vegetation Science. Vol 8. 193-198. Quintiere, J.G., and Rhodes, B., (1994) ‘Fire Growth Models for Materials’, National Institute of Standards and Technology (NIST), NIST-GCR-94-647, USA Quintiere, J. Q (1997) ‘Principles of fire behaviour’ Delmar Publishers, USA Tewarson, A., (1995) ‘Generation of Heat and Chemical Compounds in Fires’, The SFPE Handbook of Fire Protection Engineering, (2nd Edition), Ed: DiNenno, P.J., Society of Fire Protection Engineers, Boston, Massachusetts, USA Walton, W.D., and Twilley, W.H., (1984) ‘Heat Release and Mass Loss Rate Measurements for Selected Materials’, National Bureau of Standards, NBSIR 84-2960, Gaithersburg, USA Appendix A: Schematic view of the Cone Calorimeter System B. Cone Sample Details Blue Carpet Sample Weight before test (g) Weight After test (g) Dimensions (mm) Thickness (mm) 1 21.96 6.68 100 x 100 8 2 17.63 4.64 100 x 100 8 3 24.90 7.5 100 x 100 8 4 27.6 6.49 100 x 100 8 Underlay Sample Weight before test (g) Weight After test (g) Dimensions (mm) Thickness (mm) 1 16.05 3.84 100 x 100 10 2 10.46 1.62 100 x 100 10 3 12.12 2.93 100 x 100 10 4 11.68 3.23 100 x 100 10 Green Carpet Sample Weight before test (g) Weight After test (g) Dimensions (mm) Thickness (mm) 1 13.68 2.56 100 x 100 5 2 12.95 2.33 100 x 100 5 3 12.65 1.39 100 x 100 5 4 12.17 - 100 x 100 5 Read More