Different Extinguishing Methods - Assignment Example

STUDENT NO: XXXXX NAME: XXXX TUTOR: XXXXX TITLE: XXXXX DATE: XXXXXX ©2016 In approximately 250 words discuss the different extinguishing methods of a water, a powder and a carbon dioxide fire extinguisher. Fire may be extinguished using dry chemicals, water or carbon dioxide. Dry chemicals are usually in powder form, and they are used for class A, B or C fires. Fires caused by ordinary materials such as burning paper and cardboard are Class A fires. Class B are those caused by flammable liquids like kerosene and gasoline. Class C fires include fires caused by electrical equipment that has been energized. Water, on the other hand, is used only for class A fires while carbon dioxide extinguishing gets used for class B and C fires but not class A since the materials tend to reignite. In a powder fire extinguisher, the central principle applied is that of decomposition and particle size. It is well known that smaller particle sizes tend to be more productive than their big counterparts. The surface area of powder particles hence is the key to extinguishing the fire. The powder causes some smothering action that helps decompose the flame producing carbon dioxide in the process (Voelkert, 2009, pp. 5, 11-18). After the production of carbon dioxide, though in small quantities, cooling takes place as the powder decomposes and water vapour is formed as a product. The solid particles then act as a barrier between the surface of the fuel and the heat created by the flames in the space of the vapour which is above the liquid fuel. The said barrier prevents reigniting (Toreki, 2015). Carbon dioxide extinguishers which have a mixture of pressurized liquid and gaseous carbon dioxide at room temperature work by the principle of expansion whereby upon release, the pressurized gas expands and cools making a huge jet which is white in colour. It, therefore, smothers oxygen and due to its cold nature, removes heat from the fire (Woodford, 2015) Water extinguishers only remove heat from the fire, and it is, for this reason, they are only suitable for class A fires (Woodford, 2015). In approximately 250 words explain what is meant by, and the differences between, prescriptive and performance based design. A prescriptive based design is a design methodology which outlines how a building is supposed to be built. It mainly focuses on the inputs of the construction regarding the quality of the materials to be used how it will be constructed and the workmanship (Spataro & Masteller, 2011, p. 6) A performance based design is a design methodology that depicts that a building or construction will be able to offer the intended services continually even after a disaster has occurred. The design method is mainly focused on the output of the building. Prescriptive and performance-based models differ in that; a prescriptive based design is based on the experience of the person constructing while a performance based design is based on scientific principles. A prescriptive based design may in that matter only the legally set standards while a [performance based one not only focuses on the legally set standards but also the goals of the stakeholder regarding safety (FEMA, 2014, p. 65) A prescriptive design is most suitable for simple structures, and this may lead to increased cost due to redundancy while a performance based design is suitable for complex structures and any other buildings and it also focuses on reducing the cost without lowering the safety. In conclusion, a prescriptive based design is said to look at solutions in a quantitative manner while a performance-based design looks at them in a qualitative manner. In that matter, a performance based design is the ideal design methodology to use because it incorporates in addition to other principles, the principles of a prescriptive based design (FEMA, 2014). In approximately 250 words explain the difference between complete and in-complete combustion. Combustion is the process in which oxygen combines with other compounds to result in water and carbon dioxide. This process may occur in two forms either as complete combustion or incomplete combustion. Complete combustion is the process by which elements in fuels react in the presence of plenty or excess amounts of oxygen to produce carbon dioxide and water. Incomplete combustion, on the other hand, occurs when there is a limited quantity of oxygen to produce water, carbon monoxide and soot (Waickamn, 2013, pp. 39-41). The main differences between these two types of combustion are that complete combustion takes place when there is enough amount of oxygen, and all components are completely burnt without leaving behind any products while incomplete combustion occurs when there is a little quantity of oxygen, and it leaves behind small particles of carbon compounds. For instance, in case a hydrocarbon undergoes complete combustion, it produces carbon dioxide and water only as opposed to when it undergoes incomplete combustion leading to the production of water, carbon monoxide and carbon particles that mainly float in the air causing environmental pollution. An easy way to distinguish between complete and incomplete combustion is by the nature of the flame produced. Complete combustion usually occurs in a blue flame while incomplete combustion occurs in a yellow flame. The flame produced by complete combustion usually has a lot of heat as compared to the one of incomplete combustion. The flame produced by incomplete combustion, however, produces more light as compared to that of complete combustion (Waickamn, 2013, p. 40). In approximately 250 words explain the difference between premixed and diffusion flames. Diffusion flames are the flames that occur when the fuel and air are not mixed initially. The fuel and air, in this case, may mix when leaving the burner. This type of flame is usually evident in a candle where the air and fuel meet at the front part of the flame. Premixed flames, on the other hand, are flames that arise when fuel and air are mixed before getting into the burner (Sakar, 2009, p. 3). A premixed flame is usually shown by a Bunsen burner flame where gas enters the base of the burner through a valve, and as it flows upwards, air enters through the slots near the base of the burner. The two flames differ in that premixed flames have their oxidizer and fuel very well mixed before the fire can be produced, and the flame also burns at a strength that is fixed throughout, which is defined by an equivalence ratio while diffusion flames have their fuel and air separated and heat over a range of strength in terms of the air and fuel mixture. Also, premixed flames have a limit of flammability that is more defined as compared to the diffusion flames. The flame in a premixed flame also burns at a rate that can be mathematically proven using functions while the rate in a diffusion flame solely depends on the rate of supply of air and how well the air and fuel mix (Williams, 2011). The temperature in a premixed flame can also be said to vary in a constant way but in a diffusion flame, this temperature just like the other factors depends on the mixture of the fuel and air. In approximately 250 words discuss the objectives of fire safety and the five tactics available to the fire safety designers seeking to fulfill the fire safety objectives? Fires usually have very many fatal outcomes and when they occur may lead to so many losses. Fire safety is, therefore, a necessity for that matter. Fire safety mainly aims at preventing fire, safely fleeing from a fire, containing a fire and also intervening in the case of a fire by the emergency teams (Witloks, 2014, p. 199). These objectives can, however, be narrowed down to two main objectives that include ensuring the safety of life and protecting property (Abrahams, 1999, p. 14) To achieve the goals of fire safety, the designers have to follow certain criteria and the tactics available for fire safety. These tactics include prevention whereby the designers have to make sure they control ignition and combustion sources so that fires do not start. The second tactic is communication. This ensures that in case combustion occurs; the occupants are made aware, and the fire systems triggered. It then leads to the third tactic that escapes. Escape tactic in the design makes sure that the occupants can move to safety in good time Containment is also another tactic in fire security, and it involves ensuring that the fire does not spread but is rather contained in the smallest area possible to prevent losses of life or property. Lastly, the fire safety tactics should end with the tactic of extinguishment. The designer should make sure that in the case of a fire, it can be extinguished very fast before causing much damage to the building (Abrahams, 1999, pp. 14-15). Convert the following temperatures into Kelvin: The conversion formula below is used; a) 12°C b) -177°C c) 1233°C d) 392°C Balance the following equations: a) Ca(AlO2)2 + HCl → AlCl3 + CaCl2 + H2O Ca (AlO2)2 + 8HCl → 2AlCl3 + CaCl2 + 4H2O b) Fe + O2 + H2O → Fe(OH)2 2Fe + O2 + 2H2O → 2Fe (OH) 2 c) MgNH4PO4 → Mg2P2O7 + NH3 + H2O 4MgNH4PO4 → 2Mg2P2O7 + 4NH3 + 2H2O d) AlCl3 + Ca3N2 → AlN + CaCl2 4AlCl3 + 2Ca3N2 → 4AlN + 6CaCl2 e) C15H26 + O2→ CO2 + H2O 2C15H26 +28 O2→ 30CO2 + 26H2O Ammonia and oxygen react to form nitrogen and water: 4NH3 + 3O2 → 2N2 + 6H2O a) How many grams of O2 are needed to react with 6.0 moles of NH3? From the equation. The reaction ratio for O2 to NH3 is 3:4 This means that 3moles of O2 react with 4 moles of NH3 6 moles of NH3 therefore require: Converting this to grams……. 16g=1 mole Hence, 4.5*16= 72g b) How many grams of N2 can be produced when 5.45g of O2 react? The reaction ratio for N2 to O2 is 2:3 Hence 2moles of N2 are produced from a reaction involving 3 moles of O2 From the reaction ratio, 0.227 moles of N2 will be produced 1mole= 14g 0.227*14= 3.178g c) How many grams of water can be formed from the reaction of 43g of NH3? From the reaction ratio, 6moles of H2O are formed from a reaction involving 4 moles of NH3. The moles of oxygen produced in this case will be 1mole=16g Hence 3.7935 moles = 60.696g How many joules of heat are needed to raise the temperature of 43.0g of aluminium from 22°C to 55°C, if the specific heat of aluminium is 0.90J/g°C? 0.9J raises 1g of aluminium’s temperature by 1o c To raise 1g by 33o c….. Hence for 43g= Using the Ideal Gas Law solve the following problems: (use 0.08206 L atm mol¯1 K¯1 or 8.314kPaL/molK for the gas constant). a) If 4.7 moles of propane are at 28ºC and under 154.2kPa of pressure, what volume does the sample occupy? Where: P= pressure (atm, mmHg or kPa) V= volume (L) n= number of moles R= ideal gas constant T= temperature (K) =76.31L b) Determine the volume occupied by 3.34g of carbon dioxide gas at STP. At STP, pressure= 1atm Temperature=0o C= 273.15K Changing 3.34g to moles = V= 1.7L c) A sample of argon gas at STP occupies 46.2L. Determine the number of moles of argon and the mass in the sample. At STP, pressure= 1atm Temperature=0o C= 273.15K = 2.06 moles 1mole= 39.948g 2.06moles= 39.948*2.06 =82.29g d) At what temperature will 0.654 moles of neon gas occupy 12.30L at 1.95 atmospheres? =201.5o C e) A 30.6g sample of gas occupies 22.414L at STP. What is the molecular weight of this gas? At STP, pressure= 1atm Temperature=0o C= 273.15K A sample of carbon monoxide at 57ºC and under 0.67atm of pressure takes up 85.3L of space. What mass of carbon monoxide is present? A pan 200mm diameter pan is placed on a stove to boil some water (see figure 1 page 4). The thickness of the bottom of the pan is 7.5mm and the inner surface temperature of the bottom of the pan is 150°C. Determine the outer surface temperature of the pan if the pan was a) Aluminium, and b) Copper. Assume one-dimensional, steady state conduction through the bottom of the pan. Where: L= thickness q= heat transfer T1= inner surface temperature T2= outer surface temperature k= thermal conductivity For aluminium, =150.02o C For copper, =150.01o C References Read More