Fire Safety and Engineering Design - Essay Example

August 20, 2009 Engineering Design Give a definition of Combustion. Answer: Combustion is a chemical reaction of chemicals that occur between a fuel and oxidizing agents that are usually in the form of heat and light. 2. Fire safety in building is concerned in achieving two fundamental objectives, name them. Answer: The two fundamental objectives in fire safety in buildings are: 1) getting the building occupants out safely, 2) minimizing loss of structure and contents and minimizing interruption of operations. 3. What are the 5 functional requirement of Approved Document B Answer: The 5 functional requirements of the Approved Document B are: B1 means of Escape - the purpose of which is to ensure the people to be able to escape from a building. There should be sufficient number of escape routes which are being protected from fire and the requirements are in the Approved Document. B2 Internal Fire Spread(lining) - the internal lining of the building can considerably contribute to fire growth as a result of the spread of flames across the surface, or by the amount of heat that is released during combustion. B3 Internal Fire Spread(structure) - this is intended to ensure that fire is contained within the room or space of origin, and that the spread of smoke and fire is inhibited by fire resisting compartmentation so that the structural integrity is maintained for a reasonable period. B4 External Fire Spread - this specifies that the external walls and roof of a building shall resist the spread of fire over the surfaces, and from one building to another. B5 Access and Facilities for the Fire Service - This defines the requirements which ensure Adequate access to, and within , the building in order to fight fire. This makes no specific requirements relating to glazing, although it does refer to B5 5588. 4. Give a definition of the term "Means of escape from fire". Answer: the definition of 'means of escape from fire' is a safe route or routes is provided based Largely on the construction and layout of a building to achieve a degree of protection. 5. What information do you need to know when design means of escape Answer: The information needed to design means of escape are: Assessment of use - decide on the purpose into which the building falls affects the calculation occupant capacity, especially where the actual population density is not known, an has implications for allowable travel distances and width of escape stairs. Calculation of occupant capacity - it is necessary to assess the number of people who are likely to be present in the different parts of the building. Assessment of escape routes and travel distances - check maximum travel distances from scaled floor plans. Assessment of number and widths of storey/room exits - Check that assumed numbers and widths of exits can cater for expected occupant numbers at each level. Access the need for protection and/or separation of escape routes - Establishment of the identified horizontal escape route need to be fire protected or separated form other parts of the building. 6. Why is it important to perform fire tests Answer: A fire test is a means to determine if a fire protection product would meet the minimum performance as set out by the building code. The consideration of fire testing is very important for the applicable intentions for product specification and product certification. It is also a prudent act to test products to ensure ease of use and the broad, economical applications with regards to its listing and approval use and the compliance. Fire test is also a means to gather data and information in order to understand a specific Hazard such as construction or storage configuration. 7. Why is it important to carry out more than one experiment to test the same parameter Answer: It is very important to carry out more that one experiment to test the same parameter In order to make sure that the object being tested will perform well. It something like perfecting a certain procedure in order to avoid accidents and it is another way of testing the resistance of certain products. 8. Explain the term "trench effect". Answer: Trench Effect is a combination of two well understood but separate ideas. The trench effect occurs when a fire burns next to a steepy-inclined surface. The flames are down along the surface, and it heats up the material farther going up. These will emit gases, reach the auto ignition temperature, then start burning. The flames from these area are subject to the Coanda effect and blow a jet of flame up to the end of the inclined surface. The jet is sustained until the fuel is exhausted. 9. Define the terms "upper and lower flammability limits". Answer: Upper flammability limit is the mixture of substance and air is too rich in fuel(deficient in oxygen) to burn. Lower flammability limit is the mixture of substance and air lacks sufficient fuel(substance) to burn. 10. There are five main factors which affect the development of fire growth within a compartment. They can be divided into two categories; those that are concerned with the compartment itself and those which are concerned with the fuel. Please name four of these factors. Answer a) Fuel supply - it is the control of fuel supply as one method used to reduce fire growth and spread potential. b) ventilation factor - the fuel load and its distribution throughout the compartment is a major determining factor in the growth of fire. c) burning regime - as the fire grows, the oxygen in the air in the compartment is consumed, unless sufficient supply of air is available for combustion. d) fire location and room geometry - the size and shape of the room and the openings, influence fire growth. As the fire grows, flames eventually reach the ceiling height, and would spread out under the ceiling. 11. Discuss and explain the stages of fire development. Answer: The stages of fire developments are: a) the growth stage - the average temperature in the compartment is low, even if the temperatures around the burning zone are high, and the fire is localized in the vicinity of the point of origin. Fire in this stage may last up to several hours or just a number of minutes. b) the fully developed fire - is the stage of the fire wherein the rate at which heat is released from the fill will reach a maximum. The temperature will continue to rise within the compartment. There is also a subsequent threat of further internal or external fire spread to the other sections of the building. c) the decay stage - by this time, most of the combustible contents of the room will have been depleted of their volatiles gases released from materials which burns. The fire will either have been manually suppressed by the fire brigade, or will have become depleted of oxygen or fuel. 12. Combustible and flammable fuels involved in fires have been broken down into five categories, identify them. Answer: The five categories are 1. Class A Fires - are fires involving organic solids like paper, wood. 2. Class B fires - are fires involving flammable liquids. 3. Class C fires - are fires involving flammable gasses. 4. Class D fires - are fires involving metals. 5. Class F fires - are fires involving cooking oils. 13. Name four parameters you can determine using the cone calorimeter. Answer: The four parameters determined using the cone calorimeter are: 1. Rate of heat release 2. Time to ignition 3. Smoke production rate 4. Carbon monoxide production rate 14. Explain what is meant by "ignitability" of a material. Answer: Ignitability of a material is the capability of any material of being ignited., it is one of the first properties to be manifested and should figure largely in any assessment of fire hazard. 15. Explain what is meant by "positive pressure ventilation". Answer: Positive pressure ventilation is used in fire fighting to blow smoke out of a room or structure. It is also the process of forcing air into the lungs of a patient usually using a bag valve mask or mechanical ventilator. 16. Explain the difference between heat and temperature. Answer: Temperature is defined as the number that is related to the average kinetic energy of a molecule of a substance, heat is the measurement of the total energy in a substance. The total energy is made up of not only the kinetic energies of the molecules of the substance, but total energy is also made up of the potential energies of the molecules. 17. Why is it important to investigate the cause of fires Answer: It is very important to investigate the causes of fire because of the following reasons. 1. To determine the liability for an insurance claims. 2. To Examine the possibilities for subrogation 3. To prevent further fires 4. To establish the extent of the fire damage 5. To have knowledge of the remaining unburned stock 18. Explain the difference between a diffusion flame and a premixed flame. Answer: Diffusion flame is the flame in which the oxidizer would combine with the fuel by diffusion flame burns slower and produces more soot than premixed flames due to the fact that there may not be sufficient oxidizer for the reaction to be completed. Premixed flame is a flame in which the oxidizer had been mixed with the fuel before it reached the flame front. A thin flame front is created as all the reactants are readily available. If the mixture is rich or thick, a diffusion flame will be found at the downstream. 19. Explain what the flashpoint of a fuel is. Answer: Flashpoint of a fuel is the lowest temperature at which it can form an ignitable mixture in air. At this temperature range, the vapour may cease to burn when the source of ignition is removed. 20. Why are vapours important to the burning process Answer: Vapours are important to the burning process because: a. They are present only at cold temperatures b. They are constantly dangerous. c. The applied heat releases the vapour and they are what actually burn. d. It has a bad smell and you will always notice their presence. 21. Explain the limiting oxygen index test. Answer: The limiting oxygen index test is a used research and quality control tool for the determination of the relative flammability of polymeric materials. A numerical index, the "LOI" id the minimum concentration of oxygen in an oxygen-nitrogen mixture, required to support the downward burning of a vertically mounted test specimen. 22. What are the limitations of the limiting oxygen test Answer: One limitation of the limiting oxygen test is that it does not characterise the burning behaviour of the polymer. Another one is that its high accuracy only pertains to testing plastic products. Its accuracy is reduced when it's done on rubbers, textiles, papers, and other materials. 23. Explain the terms "piloted-ignition" and "auto-ignition". Answer: Piloted ignition is the process of initiation and flame propagation in premixed fuel system. The minimum condition for piloted ignition occurs at the lower flammable limits. Auto ignition occurs without any spark or flame source. The fuel is still within specific concentration range and chemical kinetic processes must exceed the ability of the mixture to lose heat. 24 Presented below are 10 heat release rates for a piece of laminated wood at 25.00kW/m2. Calculate the range, the mean, the standard deviation and then the uncertainty in the mean And the uncertainty in the standard deviation. Test 1 2 3 4 5 6 7 8 9 10 Heat release at 25.00kW/m2 44.80 42.15 42.97 43.60 43.88 44.80 42.79 45.10 41.62 43.74 Answer: Computations: Range=Max-Min =45.10-41.62 =3.48 (Mean) = = = 43.545 (SD) = = 1.1678 Uncertainty in = = 0.645 Uncertainty in = = 0.49439 25. In the table below there is a set of results obtained from the "Bang Box" experiment. Plot a Graph which will best show your results and state what the results show. fuel acetone Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Number of drops 2 6 10 12 14 16 18 20 Height attained by lid (cm) 0 20 40 80 120 150 110 90 Answer: From the experiment of the Bang Box, a line graph was plotted. The rate of change in height attained by the lid is quite constant while that of the number of drops is not. Though, there are a few intervals where we can see a constant rate in the change of number of drops. After the sixth test, started a drop in the rate of change in height of the lid. This is because of he decreasing pressure inside the box, thus affecting the energy ratio. References 1. http://isotc.iso.org/livelink/livelink/6578018/presentation_Charter.pdffunc=doc.Fetch& nodeid=6578018 2. NFPA 13 Standard for the Installation of Sprinkler System 2007 Edition, Annex C Explanation of Test Data and procedures for Rack Storage. 3. http://www.lwf.co.uk/documents/Arc%202.pdf 4 http://pojokasuransi.com/content/view/154/41/ 5. http://www.geocities.com/havliceks/Fire_Safety050.html Read More