Engineering Design Practice: Fire Investigation - Lab Report Example

Name Course Tutor Date FV1202 – engineering design practice Laboratory: Experiment 7a Fire investigation Aims of the experiment To determine the origin of the fire To examine closely the site of origin so as to determine the cause of fire at the location Hypothesis If combustible materials are present in a fire event, then the intensity of fire increases and extent faster If the fuel and oxygen are present, then the fire continues. Methodology This practical involved examination of the site of fire damage. It begins with trying to get an overall impression of the site and fire damage. This was followed by examination of material present and the condition of debris in the site. Indicator was used to test for the direction of travel, duration or intensity of heat, and the point of origin. Results The following results were obtained. The fire did not start in a location there was not normally a source of ignition, because the fire started through electrical fault. There were no previous fires There was no pile of fuel at the seat of fire There was a traceable line or spills patterns There was a glow under UV light source There were no odours noticed. Discussion The fire patterns formed after fire occurrence is mainly dependent on the characteristic of the environment and the proximity of the flammable material (Bengtsson et al., 2001). The convection forces cause the fire to move upwards and outwards creating a V shape pattern, unless it encounters a barrier. A V-shape pattern is a natural convection pattern resulting from buoyancy of heated gas, the gas tend to spread out as they rise, forming V shape (Chandler, 2009). The shape may point to the source of fire, especially on a vertical plane. The pattern may be contributed by thermal decomposition of the combustible materials. In the current case, the source of fire was an electrical fault in the socket. It had no start location, no previous fire, no debris, had traceable lines and there was a glow under UV light source. As part of investigation of fire scene, an investigator first looks for the general area of fire site. It is then followed by the search for the origin and an attempt to identify the specific point of origin. In some cases, it may not be possible to locate the exact source of ignition if the fire destroys the traces of evidence, such as the present case. In this case the source of fire can be classified as undetermined cause. The char depth, smoke residue and burn patterns can be used to determine the specific fire source but may not be conclusive evidence (Grau & Jacobson, 1981). Review The experiment worked as expected, as it was expected to point out the origin of fire. The source of fire was the socket and was caused by an electrical fault. The fire patterns produced is depends on the characteristic of the environment and the flammable material available. In some cases V-shape pattern may not be formed, but other factors like formation of char may be used to identify the origin of fire. Experiment 7b: FMVSS 302 – federal motor vehicle safety standard flammability of interior materials Aims To determine the burning resistance requirement for a material for occupant compartment of motor vehicles To find way s of reducing the death to the occupants of the vehicle due to fire originating from the interior of vehicle. Hypothesis If the fire occurs in the compartment with ventilation, then the fire propagates faster. Setup Cabinet Methodology The specimen was mounted such that two sides and one end of the specimen were clamped in the U-shaped frame, leaving the other end on the open end of the frame. The mounted specimen was then placed on the support rails in a horizontal position, and ensured that the distance between the centre of the bottom edge of the sample and the centre of the burner tip was 19mm. After exposing the flame on the specimen for 15 seconds, time taken for the flame to move along the specimen was recorded on a table. The burning rate was calculated from the following equation. Where B= burning rate in mm/min D = the length that the flame travel in mm T = the time that the flame travel through the distance D in seconds Results The table showing the results for the test for different samples Sample number Sample type/description Sample thickness, D (mm) Time to travel distance D, T (s) Burn rate (mm/min) 1 Cartoon or board 5 27 11.11 2 Carpet 6 76 4.74 3 Carpet 6 76 4.74 4 Board 5 27 11.11 Calculation Thus, for the cartoon and board as shown in the table above For the carpet, The burn rate for cartoon and board is higher than the burn rate for the carpet. All of the materials met the FMVS 302 standard as the flame spread rate for the samples did not exceed the recommended flame spread rate of 101.6 mm/min. Discussion A graph showing the burning rate for different samples. As shown in the graph above, all of the materials are combustible, but the burning rate for the carpet is 4.74 mm/min which is lower compared to the burning rate for cartoon and board whose burning rates are 11.11 mm/min each. For this reason, carpet is the preferred material to be used in the interior of the vehicle. Burn rate is the rate of propagation of heat energy along the material per unit time as a result of conversion of chemical energy of material fuel during combustion process. The heat in the compartment is propagated by heating through radiation and ventilation which is similar to ventilation from the windows of the vehicle. The heat radiated by the burning materials within the compartment significantly increases the rate at which fire spread in the compartment. Propagation of fire in a confined space is high due to the fact that the burning of materials is increased by the feedback from the surroundings (Bergman & Incropera, 2011; Steinberg et al., 2000). The standard for flammability for interior materials under consideration specifies the burning resistance requirements for materials in the occupant’s compartment of the vehicle. It does not apply to the exterior of the vehicle. It is meant to reduce injuries and death for the occupants of motor vehicle due to fire occurrence especially those that originate from the interior like a cigarette and a match (Chandler, 2009). The purpose of this standard is to evaluate the material’s capability to resist fire ignition and the spread of the flame in case of small ignition origin such as the cigarette or a match light. This standard does not represent fire circumstances whereby there has been a large source of ignition or when there is considerable preheating of the materials. In addition, the test apply to materials that are oriented horizontally, a test which is not so difficult compared to the test on vertical orientation (Steinberg et al., 2000). Review The experiment provides the fire resistant of material that can be used in the occupant’s compartment of motor vehicles. Materials like carpet have less burn rate compared to board or cartoon. This experiment has provide more understanding with regard to causes of fire as well as inserts on reduction of fire especially those originating from the interior of the vehicle. In future more material can be analyzed. The disadvantage for this experiment is that it may not be used to predict the behavior of large scale fires. Future experiment may require simulation so as to capture all aspects of fire. Experiment 7C: fire investigation- flame colours Aims To determine the flame colour produced by different salts Hypothesis If a material containing a salt is burn, then the flame burn with a unique colour. Methodology After lighting the burner, the spatula was cleaned using a glass paper to remove any residue before heating on the burner until no more colouring was observe. A small quantity of the substance under test was then placed on the spatula end. Finally, the sample was placed on the burner flames to observe the colour. This was also done on other samples. Results Metal ion Expected flame colour Potassium K+ Greenish Sodium Na+ Orange Lithium Li+ Red Calcium Ca+ Red Copper Cu+ Green Strontium Sr+ Pinky Discussion Flame test is a quick way for producing characteristic colours for metallic ions. In the current experiment, different colours were emitted when the samples were heated in a hot flame. The colours indicate the identity of unknown compounds samples (Tilley, 2005). Basically, metallic ions emit different colours when their respective metal salt is heated in a hot flame. This is because the electrons of the metal that are loosely held can easily be exited on the flame of the Bunsen burner. In essence, the color is produced when energy is emitted in the visible range of the spectrum, as the electrons return after being excited to lower levels. The colour is result of the combination of wavelengths different transition. This process is used to identify the ion present in a flame incident. The colour of the flame is usually observed at the initial stages of fire occurrence to identify the ions that are causing fire acceleration (NFPA, 2004; Bell, 2008). Review This experiment involved has been used to determine the flame colour for different salts. The flame produced from each of the sample had a unique that is characteristic to the colours for the respective metal ions. References Bell, S. (2008). Crime and circumstance: Investigating the history of forensic science. Westport, Conn: Praeger. Bengtsson, L.-G., & Statens räddningsverk (Sweden). (2001). Enclosure fires. Karlstad, Sweden: Swedish Rescue Services Agency. Bergman, T. L., & Incropera, F. P. (2011). Fundamentals of heat and mass transfer. Hoboken, NJ: Wiley. Chandler, R. K. (2009). Fire investigation. Australia: Delmar Cengage Learning. Grau, J. J., & Jacobson, B. (1981). Criminal and civil investigation handbook. New York: McGraw-Hill. International Association of Fire Chiefs., & National Fire Protection Association. (2004). Fundamentals of fire fighter skills: Rookie experiences. Sudbury, Mass: Jones and Bartlett. Steinberg, T. A., American Society for Testing and Materials, International Symposium on Flammability and Sensitivity of Materials in Oxygen Enriched Atmospheres, & International Symposium on Flammability and Sensitivity of Materials in Oxygen- Enriched Atmospheres. (2000). Flammability and sensitivity of materials in oxygen- enriched atmospheres: ninth volume. West Conshohocken, Pa: ASTM. Tilley, R. J. D. (2005). Understanding solids: The science of materials. Chichester [u.a.: Wiley. Read More

The fire patterns produced is depends on the characteristic of the environment and the flammable material available. In some cases V-shape pattern may not be formed, but other factors like formation of char may be used to identify the origin of fire. Experiment 7b: FMVSS 302 – federal motor vehicle safety standard flammability of interior materials Aims To determine the burning resistance requirement for a material for occupant compartment of motor vehicles To find way s of reducing the death to the occupants of the vehicle due to fire originating from the interior of vehicle.

Hypothesis If the fire occurs in the compartment with ventilation, then the fire propagates faster. Setup Cabinet Methodology The specimen was mounted such that two sides and one end of the specimen were clamped in the U-shaped frame, leaving the other end on the open end of the frame. The mounted specimen was then placed on the support rails in a horizontal position, and ensured that the distance between the centre of the bottom edge of the sample and the centre of the burner tip was 19mm.

After exposing the flame on the specimen for 15 seconds, time taken for the flame to move along the specimen was recorded on a table. The burning rate was calculated from the following equation. Where B= burning rate in mm/min D = the length that the flame travel in mm T = the time that the flame travel through the distance D in seconds Results The table showing the results for the test for different samples Sample number Sample type/description Sample thickness, D (mm) Time to travel distance D, T (s) Burn rate (mm/min) 1 Cartoon or board 5 27 11.

11 2 Carpet 6 76 4.74 3 Carpet 6 76 4.74 4 Board 5 27 11.11 Calculation Thus, for the cartoon and board as shown in the table above For the carpet, The burn rate for cartoon and board is higher than the burn rate for the carpet. All of the materials met the FMVS 302 standard as the flame spread rate for the samples did not exceed the recommended flame spread rate of 101.6 mm/min. Discussion A graph showing the burning rate for different samples. As shown in the graph above, all of the materials are combustible, but the burning rate for the carpet is 4.

74 mm/min which is lower compared to the burning rate for cartoon and board whose burning rates are 11.11 mm/min each. For this reason, carpet is the preferred material to be used in the interior of the vehicle. Burn rate is the rate of propagation of heat energy along the material per unit time as a result of conversion of chemical energy of material fuel during combustion process. The heat in the compartment is propagated by heating through radiation and ventilation which is similar to ventilation from the windows of the vehicle.

The heat radiated by the burning materials within the compartment significantly increases the rate at which fire spread in the compartment. Propagation of fire in a confined space is high due to the fact that the burning of materials is increased by the feedback from the surroundings (Bergman & Incropera, 2011; Steinberg et al., 2000). The standard for flammability for interior materials under consideration specifies the burning resistance requirements for materials in the occupant’s compartment of the vehicle.

It does not apply to the exterior of the vehicle. It is meant to reduce injuries and death for the occupants of motor vehicle due to fire occurrence especially those that originate from the interior like a cigarette and a match (Chandler, 2009). The purpose of this standard is to evaluate the material’s capability to resist fire ignition and the spread of the flame in case of small ignition origin such as the cigarette or a match light. This standard does not represent fire circumstances whereby there has been a large source of ignition or when there is considerable preheating of the materials.

In addition, the test apply to materials that are oriented horizontally, a test which is not so difficult compared to the test on vertical orientation (Steinberg et al., 2000).

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