Cone Calorimeter to Determine Material Reaction to Fire - Essay Example

Page Use of a Cone Calorimeter to Determine Material Reaction to Fire Contents 3 Introduction 4 Aims & Objectives 4 Method & Materials 4 Test Procedure 5 Results 6 Discussion 9 Conclusions 10 References 10 Abstract A cone calorimeter was used to test the inflammability of three different materials -green carpet, blue carpet and underlay to evaluate the differences if any between their properties by subjecting them to different levels of heat fluxes and measuring end parameters like the cumulative heat release, the rate of heat release per unit area, time to ignition, effective heat combustion, total mass loss, mass loss rate, smoke obstruction and yields of gases like carbon monoxide and carbon dioxide with the aid of specifically designed apparatus and uniform measurement protocols. Although conclusive comparison data was not obtained, it was discovered that the blue carpet samples produced the maximum damage. Introduction Fire hazards are a stark reality in the modern world due to the use of multifarious natural and synthetic construction materials. Evaluation of such materials is therefore of utmost importance to design a fire safety protocol for a prospective new construction as well as for the evaluation of preexisting buildings and materials. The flammability of a material depends upon its chemical composition and the availability of oxygen. Post-fire investigations also need some analytical tool for the forensic investigation to evaluate the extent as well as the cause of damage due to fire. Cone calorimeter is presently considered the best technological tool available for the evaluation and assessment of any material’s reaction to fire. In any physical or chemical reaction if the elements being used up and the products obtained if measured can yield pertinent data about the properties of the substance under study. Cone calorimetry similarly employs the principle of oxygen consumption to determine the net heat of combustion of any organic material. In this experiment, a Cone calorimeter was used to determine the net heat of combustion of three experimental materials – ‘Blue Carpet, Green Carpet and Underlay2’ Aims and Objectives Based upon the above principle, three materials, a piece of Blue carpet, Green carpet and an Underlay were selected for evaluation of various parameters like the heat of combustion, ignition time and the amounts of carbon dioxide, carbon monoxide and smoke produced. The heat released during combustion of a measured weight piece of any of the above three materials was determined by measuring the amount of oxygen consumed in burning the product in a specified period of time. Methods and Materials (or Equipment) The Cone Calorimeter is a specialized apparatus which consists of a radiant heater in the shape of a cone. The specimen to be tested is set on fire using an ignition mechanism protected by a radiation screen. There is a weighing device for the measurement of the mass of specimen which is then put into a specimen holder. There is an exhaust system for collection and measurement of the effluents and an oxygen analyzer which measures the amount of oxygen consumed. Other inbuilt devices are a heat flux meter, a calibration burner and a gas sampling apparatus. The output data is recorded and analyzed by means of specialized software. Cone Calorimeter (Picture Courtesy: www.sintef.no) Test Procedure Before initiating an experiment, the carbon dioxide and the final moisture trap are examined and accumulated water, if any, is drained off. The power supply to the cone heater and the exhaust is then turned on until the exhaust flow rate is set at a value of 0.024 ± 0.002m3/s. Calibration procedures are then run on the heater, oxygen analyzer, heat release and the mass measuring system. The actual test procedure on the experimental material is then started and the material’s behavior when it is subjected to variations of heat fluxes is noted. Results The samples tested were as follows: Cone Sample Details 2009 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 Table 1: Results of Experiment with Green Carpet Samples Parameters tested 1st Green carpet 2nd Green carpet 3rd Green carpet 4th Green Carpet Mass of Sample 13.68 g 12.95 g 12.65 g 12.17 g Surface Area 100cm2 100 cm2 100 cm2 100 cm2 Thickness 5.5 mm 5.5 mm 5.5 mm 5.5 mm Heat Flux of the Experiment 25 kW/m2 35 kW/m2 45 kW/m2 50 kW/m2 Time of Test 495 seconds 281 seconds 265 seconds 460 seconds Total Heat Evolved 25.9 MJ/m2 - 309.7 MJ/m2 28.2 MJ/m2 Total Amount of Oxygen Consumed 18.6 g - -1174.7 g 20 g Smoke Released 393.9 m2/m2 - 486.2 m2/m2 517.9 m2/m2 Mass lost during the Experiment 9 g - 8.1 g 9.6 g Specific Mass Loss Rate 2.45 g/m2s - 3.25 g/m2s 2.11 g/m2s Average Heat Release Rate 57.53 kW/m2 - 1237.36 kW/m2 62.3 kW/m2 Effective Heat of Combustion 23.10 MJ/Kg - 380.66 MJ/Kg 29.21 MJ/Kg Mass Loss Rate 0.025 g/sec - 0.033 g/sec 0.021 g/sec Specific Extinction Area 131.71 m2/Kg - 549.70 m2/Kg 423.16 m2/Kg Carbon monoxide Yield 0.0140 Kg/Kg - 0.0239 Kg/Kg 0.0239 Kg/Kg Carbon dioxide Yield 1.52 Kg/Kg - 1.90 Kg/Kg 1.68 Kg/Kg Table 2: Results of Experiment with Blue Carpet Samples Parameters tested 1st Blue carpet 2nd Blue carpet 3rd Blue carpet 4th Blue Carpet Mass of Sample 21.96 g 17.63 g 24.9 g 27.6 g Surface Area 100 cm2 100 cm2 100 cm2 100 cm2 Thickness 8.00 mm 8 mm 8 mm 8 mm Heat Flux of the Experiment 25 kW/m2 35 kW/m2 45 kW/m2 55 kW/m2 Time of Test 481 seconds 378 seconds 715 seconds 458 seconds Total Heat Evolved 45.5 MJ/m2 34.9 MJ/m2 39.4 MJ/m2 38.8 MJ/m2 Total Amount of Oxygen Consumed 31.8 g 24.7 g 27.5 g 27.4 g Smoke Released 651.0 m2/m2 474 m2/m2 449.4 m2/m2 736.3 m2/m2 Mass lost during the Experiment 12.1 g 13.2 g 12.4 g 13.2 g Specific Mass Loss Rate 2.79 g/m2s 5.09 g/m2s 1.82 g/m2s 3 g/m2s Average Heat Release Rate 108.79 kW/m2 103.45 kW/m2 57.32 kW/m2 87.95 kW/m2 Effective Heat of Combustion 38.66 MJ/Kg 20.88 MJ/Kg 31.41 MJ/Kg 28.83 MJ/Kg Mass Loss Rate 0.028 g/sec 0.051 g/sec 0.018 g/sec 0.030 g/sec Specific Extinction Area 494.81 m2/Kg 204.47 m2/Kg 180.12 m2/Kg 506.11 m2/Kg Carbon monoxide Yield 0.0194 Kg/Kg 0.0149 Kg/Kg 0.0126 Kg/Kg 0.0170 Kg/Kg Carbon dioxide Yield 2.04 Kg/Kg 1.21 Kg/Kg 1.68 Kg/Kg 1.65 Kg/Kg Table 3: Results of Experiments with Underlay Samples Parameters tested 1st Underlay Sample 2nd Underlay Sample 3rd Underlay Sample 4th Underlay Sample Mass of Sample 10.46 g 11.68 g 12.12 g 16.05 g Surface Area 100 cm2 100 cm2 100 cm2 100 cm2 Thickness 10 mm 10 mm 10 mm 10 Mm Heat Flux of the Experiment 45 kW/m2 25 kW/m2 35 kW/m2 55 kW/m2 Time of Test 139 seconds 225 seconds 303 seconds 240 seconds Total Heat Evolved 16.2 MJ/m2 16.3 MJ/m2 18.3 MJ/m2 23.6 MJ/m2 Total Amount of Oxygen Consumed 12 g 11.9 g 13.4 g 17.4 g Smoke Released 416.6 m2/m2 291 m2/m2 305.7 m2/m2 553.6 m2/m2 Mass lost during the Experiment 12 g 12.4 g 9.3 g 58.4 g Specific Mass Loss Rate 8.63 g/m2s 6.85 g/m2s 3.15 g/m2s 21.93 g/m2s Average Heat Release Rate 118.71 kW/m2 74.94 kW/m2 61.44 kW/m2 99.55 kW/m2 Effective Heat of Combustion 13.66 MJ/Kg 10.69 MJ/Kg 19.49 MJ/Kg 4.48 MJ/Kg Mass Loss Rate 0.086 g/sec 0.069 g/sec 0.031 g/sec 0.219 g/sec Specific Extinction Area 338.71 m2/Kg 154.9 m2/Kg 221.93 m2/Kg 102.46 m2/Kg Carbon monoxide Yield 0.0291 Kg/Kg 0.0125 Kg/Kg 0.0269 Kg/Kg 0.0093 Kg/Kg Carbon dioxide Yield 1.04 Kg/Kg 0.79 Kg/Kg 1.40 Kg/Kg 0.33 Kg/Kg Discussion/ Analysis In the experiment with green carpet samples no results were obtained at 35 kW/m2 and at 45 kW/m2 too erroneous values were obtained which were not consistent with the expected results. There was an exceptionally higher amount of smoke released at 50 kW/m2. With the exception of the average specific mass loss, all the rest values were high when compared to the value obtained at 25 kW/m2. The specific extinction rate in the experiment was almost quadrupled when compared to the value obtained at 25 kW/m2. The mass loss rate was lesser by a small margin at 50 kW/m2 than at 25 kW/m2, but still the average values of effective heat of combustion, heat release rate, specific extinction area, carbon monoxide and carbon dioxide were high. The first blue carpet sample had an initial weight of 21.96 g and a surface area of 100 cm2 which was common for all the samples, as was the thickness of 8 mm each. The total time of the test for the first sample was 481 seconds which resulted in the total heat evolution of 45.5 MJ/m2 with a heat flux of 25 kW/m2.The total oxygen consumed was comparable in all samples despite the variations in heat flux used. The amount of the sample mass lost was independent of the rate of heat flux. The heat release recorded had a low value of 45 kW/m2, which could be attributed to the increased duration of the test. The carbon monoxide and carbon dioxide yields at 35 kW/m2 increased from ignition to ignition plus. The yield of both these gases was higher at 25 kW/m2 and 55 kW/m2 than at 35 kW/m2 and 45 kW/m2. Identical values for the rest of parameters were obtained until the exhaustion of the total heat flux. In the experiment with underlay samples all values at 45 kW/m2 flux were reduced to zero within four minutes and reliable data could be obtained only at 35 kW/m2 flux. Similarly at 25 kW/m2 and 55 kW/m2 flux values all dependent values were reduced to zero in 5 minutes and 6 minutes respectively. However the total mass lost, the specific mass loss rate and the amount of smoke released were in accordance with the proportions of the heat fluxes used. The maximum values of the mass lost and average specific mass loss rate at 55 kW/m2 in comparison to other fluxes. At this value the effective heat of combustion was very low. At all time intervals the carbon monoxide and carbon dioxide yields from ignition to ignition plus were steady at 35 kW/m2. Conclusion and Recommendations From the data obtained in these experiments conducted on three different materials no conclusive comparison could be made as regards their properties as expressed by the variation in values obtained. However it was clear that the total oxygen consumed, total heat evolved as well as smoke released were highest for the blue carpet. The lowest mass lost was seen in the green carpet material. The highest average specific mass loss rate was recorded for the underlay. Nevertheless the heat release rate and effective heat of combustion were highest for the blue carpet samples. The blue carpet samples also had a very high specific extinction area as compared to the other two. The blue carpet also had the highest yield of carbon monoxide and carbon dioxide with a value of 0.0194 kg/kg and 2.04 kg/kg respectively at 25 kW/m2. Cone calorimetry can therefore yield some important data to compare the inflammability of materials and such data can be analyzed for selecting the most appropriate material to be used for construction purposes to reduce the incidents as well as damage caused due to fire. The blue carpet material in the above experiment appears to be the most damaging during a fire due to the high levels of carbon monoxide and carbon dioxide production as well as a higher value of heat release rate. If substances which display the least level of inflammability, radiation as well as smoke production are used they can enhance the safety level in an incidence of fire. The method can help evaluate the most fire retardant material which can then be recommended for use. References ISO 5660-1:1993: THE CONE CALORIMETER TEST, Illustration and information available at: http://www.sintef.no/Home/Building-and-Infrastructure/SINTEF-NBL-as/Key-projects-and-topics/Fire-testing-of-railway-seats/ISO-5660-11993-THE-CONE-CALORIMETER-TEST/ Read More