fire suppression technology - Free Essay Example

CHAPTER ONE: 1.1: Introduction Choosing the best fire suppression technology is not an easy task. It even involves discussing risks and operations with insurance companies. The most relevant concern of a fire safety engineer is the protection of life which entails the safe evacuation of personnel. The starting point of a suppression system is a risk analysis to reduce the potential occurrence of a fire. This is followed by the control of the damage and the recovery effort or emergency response associated with the means of fire suppression adopted. The quality of installation, efficiency and maintenance of the suppression system adopted cannot be over-emphasised. The phase out of halons, due to environmental concerns, has lead to forceful development of new fire prevention strategies and technologies that are efficient, as well as environmentally friendly technologies. Fire protection halons were phased out of production in developing countries due to the quest to regulate the use of ozone depleting substances(ODS) as reflected in the Montreal Protocol,1987(London Amendment 1990, and Copenhagen amendment1992). Fire suppression agents have two (2) toxicological aspects to them: The toxicity of the agent The toxicity of combustion products of the agent. Several new fire suppression systems have been developed such as inert and halocarbon gaseous systems, water mist systems, gas and aerosol generators. Fire has been extinguished with water since ancient times. Water in the normal form is not a suitable suppression medium of all classes of fire. The efficiency of water in suppression is enhanced by its use of water in form of mists. Survey by Mawhinney and Richardson in 1996 showed that about 50 agencies worldwide are involved in the research and development of water fire mist and suppression systems. Water mist in fire suppression does not behave like true gaseous agents and is affected by fire size, the degree of obstruction, ceiling and the ventilation conditions of the compartment. To effectively suppress a fire, a water mist system must generate and deliver optimum sized droplets with an adequate. 1.2: Objectives and Structure of Dissertation This project aims at studying the water mist as a replacement for halons systems in the extinguishment of fires. This replacement is a direct consequence of the phase out of halons due to environmental issues and the need to find a drop-in replacement or a suitable alternative in areas where high level of fire safety is required and the cost of fatalities is too high. Chapter 2 2.1: Overview of Fire Suppression To suppress fires, the type of fire needs to be identified. The class of the fire to be extinguished also determines the type of extinguisher that can be used. There are six (6) types of fires: Class A FIRES: These involve flammable or combustible solids such as wood, rubber, fabric, paper and some plastics. Class B FIRES: These are fires involving flammable and combustible liquids or liquefiable solids such as oil, alcohol, petrol, paint and liquefiable waxes.[9] Class C FIRES: These are fires involving flammable gases such as natural gas, hydrogen, propane, butane.[9] Class D FIRES: These are fires involving combustible metals, such as sodium and potassium.[9] Class E FIRES: These are fires involving any of the materials found in Class A and B fires, but including electrical appliances, wiring, or other electrically energized objects in the vicinity of the fire, with a resultant electrical shock risk if a conductive agent is used to control the fire.[9] https://www.sqa.org.uk/e-learning/FirstLineO2CD/page_06.htm Class F FIRES: These fires involve cooking fats and oils, especially in industrial kitchens. The temperature of these fats and oil on fire is much greater than that of other flammable liquids. 2.2: Means of Fire Suppression The aim of fire suppression is to provide cooling, control the spread of the fire as well as extinguish the fire. The behaviour of a fire is charcterised by the fire triangle which has fuel, oxygen and heat as its three sides. Combustion process is represented by: Fuel + O2 HEAT H2O + CO2 à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦.eqn2.1 The combustion process is an exothermic reaction, involving a fuel and oxygen. The ratio of fuel to air must be within the flammability limits of the fuel for combustion to occur. The Lower Flammability Limit (LFL) is the minimum concentration of fuel vapour in air, below which a flame cannot be supported in the presence of an ignition source. The Upper Flammability Level (UFL) is the maximum concentration of fuel vapour in air, above which a flame cannot be supported. Stoichiometric Mixture is the ratio of fuel in oxygen that requires minimal energy to support a flame. A branch of the triangle must be removed for the fire to be extinguished. Fires can either be smoldering or flaming combustion. Smoldering occurs when solids such as wood or plastics burn at or on the surface. It usually involves the release of toxic gases and can be difficult to extinguish. Flaming combustion is a gas phase phenomenon that involves the release of visible and infrared radiation. This type of fire generates much more heat. The extinguishing of a fire involves either chemical or physical mechanisms. Physical mechanism: Involves the removal of one side of the fire triangle. This can be done by either blanketing the fire (causing the fuel and air to be separated) or by removing the heat source using an agent with a high heat capacity/ latent heat of vaporization (this will cool the flame by absorbing the heat). Physical mechanism could be thermal or dilution. Thermal physical effect involves adding non-reactive gas to a fire plume leading to a reduction in the flame temperature. This is achieved by the distribution of the heat generated to a larger heat area. The heat capacity of the introduced agent determines the efficiency of the process. On the other hand, for dilution physical effect, the collision frequency of oxygen molecules with the fuel is lowered when the additional gas is introduced into the fuel-air mixture. This effect is quite minimal and negligible. Chemical mechanism: This is the use of an extinguishing agent or its degradation product to disrupt the chain reaction for sustaining combustion. This entails inhibition by halogen atoms. Most good suppressants apply both the physical and the chemical mechanisms. The type of hazard associated with an area determines the fire protection system that will be put in place. Halons have been used in a wide range of applications. Other alternatives include: Water Sprinkler Systems: This is a very common type of fixed protection that offers safe protection to limit structural damage. The cost of installing water sprinkler systems into existing structures is quite expensive. They are better at protecting structures than its contents [11]. The reliability of water sprinkler system has encouraged its wide use. Accidental discharge is uncommon with water sprinkler systems. Water sprinklers have a much slower response than other systems. They also cause a considerable secondary damage. They cannot be used on live electrical equipment and flammable liquids, but they are used widely in computer and control rooms as well as storage rooms in the USA. Detectors: This involves the use of high sensitive smoke detection. This is not exactly an active fire protection approach but it serves as an initiator to other fire protection systems [2]. Carbon dioxide: Carbon dioxide is widely used in gaseous based fire extinguishing systems. There are two types of carbon dioxide system depending on the manner by which they are stored. These are high pressure and low pressure carbon dioxide systems. It is a clean agent and has a good penetrating ability. This makes it safe for use on live electrical equipment. They are also used in unoccupied spaces such as computer and control rooms. Carbon dioxide causes very minimal direct or secondary damage and allows the installation being put back to immediate use after a fire. It is however toxic and cannot be used in total flooding situations. Carbon dioxide cannot also be used in situations where weight and space are important. High concentrations of carbon dioxide are required for extinguishment and as such they are bulky and heavy. They cannot be used in manned areas because they reduce the oxygen concentration to levels below life support and thus cannot be set in automatic mode. Carbon dioxide systems are generally fast acting and cost effective. Carbon dioxide has also found use in record storage, flammable liquid fires, chemical processing equipment, turbine generators, marine applications, computer rooms and shipboard machinery. Inert Gases: inert gases in use for fire suppression are majorly argon and nitrogen mixtures. These are electrically non-conductive fire suppressants. The mechanism behind their use is the lowering of the oxygen concentration of air to that below the lower flammability point (LFL). They are not liquefied gases and they are bulky because they are stored at high pressure. The concentration of inert gases released in the hazardous area is high because they have densities that are similar to that of air. Their response time is not very fast and so they are not efficient in situations where the rate of fire spread is high. Inert gases do not decompose thermally and thus they form no breakdown products [2]. Inert gases can cause an extreme decrease in the composition of oxygen in the body accompanied by an increase in the concentration of carbon dioxide leading to loss of consciousness or death and as such health and safety issues have to be considered in its use. Inert gases have found wi de acceptance because they pose no environmental problems. They are not ozone depleting substances neither do they contribute to global warming. They are employed in computer and control rooms, record storage, flammable liquid fires and shipboard machinery [2]. Halocarbon Gases: These are hydrofluorocarbons and perfluorocarbons with zero ozone depleting potentials. They are however greenhouse gases and are governed by the Kyoto protocol and hence its release counts towards the national emissions inventory of global warming gases. Halocarbons are electrically non-conductive, are clean agents and are not bulky in terms of space and weight. Foam Systems: Foam systems could be low, medium or high expansion systems. Foam systems are efficient for extinguishing liquid pool fires and large cable fires. In this case, the foam acts as a barrier between the fire and the supply of oxygen. The use of chemical dispersants to clean up after its use has limited the wide use of foam systems. Furthermore the use of smoke detectors for its activation limits its speed of response. They cannot be used to protect any substance that reacts violently with water. Foams systems are often used with water sprinklers. This increases the efficiency of the systems. Foam systems have found use in the extinguishment of flammable liquid fires, engine compartments and shipboard machinery. Dry Powder: Powders have very high response time for extinguishing fires but have no cooling effect. They thus become ineffective as soon as it settles [2]. They are limited in application to extinguishing flammable liquid fires as well as engine spaces. Fine Solid Particulates: This system is used in combination with halocarbon gases and inert gases [2]. They have the advantage of reduced wall and surface losses relative to water mist and particle size is easier to control[2]. They however pose problems to sensitive equipment and cannot be used for explosion suppression applications because they are generated at high temperatures. Fine solid particulates can only be used in unmanned areas because of the problems associated with inhalation of particulate substances. Water Mist: This employs the use of fine water sprays, usually less than 100 microns in diameter. Water mists can be used on flammable liquid fires, as well as electrical equipment. They are not as effective on small or slow burning fires. Water mist installations pose problems in their design and fabrication. Hybrid Systems: Hybrid systems combine one or more of the above fire protection system. A common example of this is the combination of water mist systems and carbon dioxide. There are two methods of applying fire extinguishing agents-Total Flooding and Local Application. Total Flooding: They are operated automatically and manually. It entails applying an extinguishing agent to an enclosed space to achieve a concentration of the extinguisher that is capable of putting out the fire. This method is the most common system of application Local Application: The agent is applied directly onto the fire plume or the affected enclosure. Portable fire extinguishers are the most common forms of this approach. This method is also known as streaming application. There is an increase in the need for the phasing out of halons and this has brought the search for the perfect or drop-in replacement. The department of trade and industry in 1995 listed checklists for the selection of alternatives to halons in critical uses situations as: Fire fighting effectiveness: This involves the speed of fire suppression, the post fire hold time, the ability of the alternative to permeate, the elimination of the risk of reignition, the suitability of the alternative to the fire hazard. Ease of Installation: Ease of maintenance, pipe work, and cost of installation, cost of refill, floor space and weight, system re-instate time, and availability of the extinguisher. Hazards to occupants: Toxicity, noise levels, pressurisation, inhalation, visibility, safety as regards electrical work, thermal decomposition products [2]. Discharge effect on equipment: water damage, clean up, corrosion, thermal shock. Environmental acceptability: Ozone depletion potential, atmospheric lifetime, and global warming potential. Discharge damage: This entails clean up of the agent after use, water damage, thermal shock and corrosion. Esso Australia, while looking for alternatives to halons on their installations considered the following issues [14]: Effectiveness at extinguishing fires Environmental effects (a zero ozone depleting and global warming potential) of the agent before use and after thermal decomposition. Toxicity level and a safety margin between its No Observed Adverse Effects Level (NOAEL value) and the extinguishing concentration required Third party approval from regulatory bodies and safety partners such as International Maritime Organisation (IMO), NFPA, and EPA or Underwriters laboratory Organisations. Level of engineering required to modify an existing halon protected installations. Availability as regards to installation and maintenance at a reasonable cost. 2.2: Health and Safety Issues Considering the health and safety in the UK, there is no specific regulation as regards choice of fire extinguishing systems. Otherwise fire risks and risk from the use of extinguishment can be categorised under risks at work. The Management of Health and Safety at Work Regulations 1992 stipulates all risks at work are to be assessed and prevented where ever it is reasonably practicable, controlled. In cases where fire extinguishing systems contain toxic substances then the Control of Substances Hazardous to Health Regulations 1988 (COSHH regs) will also apply. The basis of the two regulations is the prevention rather than control of the risk. 2.3: Environmental regulations The International Maritime Organisation (IMO) has prohibited the use of new halon systems from 1994, but accepts the use of existing ones. The EU has banned its use onboard vessels by the end of 2003. The following are regulations that are put in place to phase out the use of halons. The Montreal protocol on Substances that Deplete the Ozone layer- the Montreal protocol, signed by 25 countries on the 16th of September, 1987 is an international treaty for the control of the production and use of ozone depleting substances. It involves the restriction and eventual prohibition of the production, distribution and use of Ozone Depleting Substances. A copy of this document is attached in Appendix 1. The EC regulations: This European legislation was put in place to further tighten the restriction on the ban of ozone depleting substances. EC Regulation 3093/94 came into force on the 23rd of December 1994. EC Regulation 3093/94 is directly binding in all EU Member States and does not require any national implementing legislation. The new Regulation EC 2037/2000 came into force on 1 October 2000, replacing the Regulation 3093/94. The enforcement requires the use of bodies such as the HM Customs and Excise concerning import of controlled substances. The Department of the Environment proposes to implement these arrangements through enforcement regulations made under both the Environmental Protection Act 1990 s.140 and the European Communities Act 1972.(EC REGULATION) The new requirements are applicable to the production, distribution, use and recovery, and control of hazardous substances. The regulations also require the recovery of used controlled substances from certain equipment, s uch as fire protection systems, for disposal or recycling, during servicing and maintenance procedures of equipment. A copy of the regulation is attached to Appendix 2. The Victorian Environment Protection Legislation for the Control of Ozone Depleting substances (Victorian Government Gazette No.S57, 1990) this piece of legislation depicts the Australian governments compliance, reliance and advocacy to the implementation of the Montreal protocol on the phasing out of halon use [14]. Environmental Protection agency: Under the Clean Air Amendment, the United States Environmental Protection agency, EPA analysed various substances that could substitute fire extinguishing agents that destroy the ozone layer. These substances also have low global warming potential and low Atmospheric lifetime. The SNAP program (Significant New Alternatives Policy) is used by the EPA to replace the use of halons with environmentally friendly systems in the United States. The Clean Air Act was signed into law in 1990. With this Act, the US banned the production and import of new halons 1211, 1301 and 2402 from the 1st of January 1994 in compliance with the Montreal Protocol. The US government also imposed excise tax on halons through specialized training and proper recycling and disposal. Chapter Three: Halon Systems Halon is the generic name for bromine contained halogenated hydrocarbons. Halons systems were first installed in the late 1960s and early 1970s. In the gaseous form, halons are excellent fire extinguishers. Halons are mostly employed in situations where fire safety standards are high. Halons are identified by a four digit number. The numbering system is assigned by the number of carbon, number of fluorine, chlorine and bromine atoms respectively. Halon 1301, containing carbon, fluorine and bromine is used in total flooding applications while halon 1211, containing carbon, fluorine, chlorine and bromine is used as hand held portable extinguishers. The two common halon types described are effective in extinguishing classes A, B and C fires. These halons are preferred because they exhibited: high efficiency in suffocating combustion, availability in volume at reasonable cost, high storage stability, low electrical conductivity, as well as acceptable toxic properties. 3.1: Characteristics of Halons Halons interfere with the chemical reactions which take place during a fire. The properties of halons allow for its use in most situations and thus most of its applications are linked to particular characteristics. These principal applications include: Clean fire fighting agent: Halons leave no residue after use. This eliminates secondary damages and keeping loss caused by the fire to a minimum [12]. Electrically non-conductive: This property makes it suitable for safe application on fires involving electrical equipment. It will prevent exposure of fire fighters to electric shock. Low toxicity: This property makes halons acceptable and in most cases halon flooding systems are set in automatic mode by default. They can also be used to extinguish fires while people are present in the protected room. Halon flooding systems do not displace so much oxygen which can lead to suffocation[12] Rapid response: Halons are effective for rapid knockdown of flames. This property is mostly essential for class B fires involving liquid and liquefiable solids. Low concentration requirement: This means low quantity or amount of halons are required for extinguishment. It minimizes weight and space allowance [12]. Gaseous state: This allows for good penetration and effective extinguishment in confined spaces. Boiling point: The boiling point of about -4 allows it to be discharged (in the case of hand-held extinguishers) as a liquid for a while before it vaporises. This is a key requirement in some manual fire fighting applications.[12] Low heat of vaporisation: Halons will not condense to form water or ice in halon flooding systems. The most important advantage of halons is in its cost effectiveness. Halon fixed systems are the most cost effective of all extinguishing systems. 3.2: Extinguishing Mechanisms of Halons Halons extinguish fires both chemically and physically. Chemically they interfere with the chemical reactions that take place during the fire. This characterises halons as inhibitors. Radicals released during combustion to keep the fire burning are suppressed chemically by halons. This reaction is anti-catalytic. When halons are heated during combustion, they produce free radicals which compete with those produced by the original combustion process [2]. Halon 1301 produces bromine radicals which react with hydrogen free radicals to produce hydrogen bromide. The hydrogen bromide then reacts with hydroxyl radical to form water and bromide. The bromide released reacts with the combustion fire again and the whole cycle is repeated. The hydrogen and hydroxyl free radicals produced by combustion are greatly reduced in concentration by combining with the halogen free radicals produced by halons [3]. Where RH is the combustible fuel, XBr is a halon agent RH + O2 ENERGY OH + R à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦.eqn3.1 XBr ENERGY Br + Xà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.2 RH + Br HBr + Rà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.3 HBr + OH H2O + Brà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.4 RH ENERGY R + Hà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.5 H + Br HBrà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.6 The combination of bromine and hydroxyl radical is also an ozone destructive reaction: HOBr UV Br + OHà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦..eqn3.7 OH + O3 HO2 + O2..eqn3.8 Br + O3 BrO + O2à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.9 BrO + HO2 HOBr + O2 à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦..eqn3.10 3.3: HALONS AND THE OZONE 3.3.1: The ozone layer The earth is enclosed by the atmosphere. This atmosphere is made up of a mixture of numerous gases in varying proportions. The atmosphere is further subdivided into three regions depending on temperature. These regions are: Mesosphere, Stratosphere and Troposphere. The word ozone is from a Greek word, ozein, for to smell. It is an allotropic form of oxygen having three atoms in each molecule. It is a pale blue, highly poisonous gas with a strong odour. [10] In its thickest part in the stratosphere, it is only a trace gas.. Ozone is highest in concentration, about 97%, in the stratosphere (15-60 kilometers above the Earths surface) where it absorbs the ultraviolet radiation from the sun. Ozone is also highly concentrated at the Earths surface in and around cities. The buildup of ozone on the earths surface in and around cities is a result of industrial activities and is toxic to organisms living at the Earths surface. Table 3.1 shows the percentage volume composition of the constituents of atmospheric air Gas Name Chemical Formula Percent Volume Nitrogen N2 78.08% Oxygen O2 20.95% *Water H2O 0 to 4% Argon Ar 0.93% *Carbon Dioxide CO2 0.0360% Neon Ne 0.0018% Helium He 0.0005% *Methane CH4 0.00017% Hydrogen H2 0.00005% *Nitrous Oxide N2o 0.00003% *Ozone O3 0.000004% *variable gases https://www.physicalgeography.net/fundamentals/7a.html Ozone is very reactive and a stronger oxidising agent than oxygen. It is used in purifying water, sterilising air, and bleaching certain foods. Ozone is formed when an electric spark is passed through oxygen. Ozone is prepared commercially by passing cold, dry oxygen through a silent electrical discharge [7]. Ozone formed in the atmosphere is from nitrogen oxides and organic gases emitted by automobiles and industrial sources [7]. This is achieved by short wavelength ultraviolet. This is actually a health hazard, and it may cause crop damage in some regions. Ultraviolet wavelengths less than 200 nanometer reacts with oxygen molecules to make ozone. O2 UV O + Oà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn3.11 O + O2 O3 + Heatà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦.eqn3.12 The heat released here is absorbed by the atmosphere and results in a rise in temperature of the atmosphere. The structure of ozone has 3 oxygen atoms, but steric hindrance prevents it from forming a triangular structure, with each O atom forming the expected 2 bonds. Instead each atom of oxygen forms only 1 bond, with the remaining negative charge being spread throughout the molecule.[7] Ozone is very unstable. It is decomposed either by collision with monoatomic oxygen or by ultraviolet radiation on it. The decomposition causes ozone to form oxygen molecules. Heat is also released to the atmosphere by this reaction O + O3 O2 + O2à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦.eqn3.13 O3 UV O2 + O + Heatà ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦.eqn3.14 Ozone is decomposed in the stratosphere to prevent highly energetic ultraviolet radiation from reaching the surface of the earth. 3.3.2: Halons and ozone depletion The ozone layer is mainly depleted by compounds containing chlorine and bromine. Halogens are a chemical family containing fluorine, chlorine, bromine and iodine; any carbon compound containing them is known as a halocarbon. While all halogens have the ability to catalyze ozone breakdown, they have an unequal impact on the ozone layer. The quantity of halons released into the atmosphere is small relative to the number of gases present in the atmosphere. Yet they are more active in destroying the ozone or disrupting the ozone balance for two reasons: Ozone is in a constant state of imbalance, as it is destroyed and produced by natural processes. This process is controlled by solar input that does not undergo significant fluctuations. The stability of halons makes it transportable from the troposphere to the stratosphere where halogens are made active and broken down very fast, destroying ozone in the stratosphere. . The impact is described as depletion potential of the halocarbon. The OZONE DEPLETING POTENTIAL (ODP) is a simple measure of its ability to destroy stratospheric ozone. The ODP of compounds are calculated with reference to the ODP of CFC-11, which is defined to be 1. Thus ODP is a relative measure. A compound withan ODP of 0.2 is, roughly speaking, one-fifth as bad as CFC-11. The ODP of a compound x is expressed mathematically as the ratio of the total amount of ozone destroyed by a fixed amount of compound x to the amount of ozone destroyed by the same mass of CFC-11[8]: Global loss of Ozone due to x ODP(x) == à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦..eqn3.15[8] Global loss of ozone due to CFC-11. The above expression depicts that the ODP of CFC-11 is 1.0 by definition. The uncertainties experienced in evaluating the global loss of ozone due to a compound are eliminated here since the mathematical expression is a ratio. Evaluating the ODP of a compound is affected by the following: The quantity of chlorine or bromine atoms in a molecule. The nature of the halogen, as bromine is a more ozone- destructive catalyst than chlorine. Atmospheric lifetime of the substance: The atmospheric lifetime of the halon is the time it takes for the global amount of the gas to decay to 36.8% of its original concentration after initial emission. Compounds with low atmospheric lifetimes have lower ODP because it is destroyed in the troposphere. Molecular mass of the substance: This is because ODP is evaluated by comparing equal masses and not number of moles. Table3.2 gives time-dependent and steady-state ODPs for some halocarbon in wide use. Compound Formula Ozone Depletion Potential 10yr 30yr 100yr Steady State CFC-113 CF2ClFCl2 0.56 0.62 0.78 1.10 Carbon tetrachloride CCl4 1.25 1.22 1.14 1.08 Methyl Chloroform CH3CCl3 0.75 0.32 0.15 0.12 HCFC-22 CHF2Cl 0.17 0.12 0.07 0.05 Halon-1301 CF3Br 10.4 10.7 11.5 12.5 https://stason.org/TULARC/science-engineering/ozone-depletion-intro/18-What-is-an-Ozone-Depletion-Potential.html Halons as catalysts alter the rate of the combustion reaction without permanently being altered by the process, and so can react over and over again. This way, a molecule of chlorine or bromine can degrade over 100000 molecules of ozone before the end of its life. The inactive compounds formed by halogens afterwards are known as reservoirs. These reservoirs can release active halogens when attacked by sunlight. The stability of the reservoir compounds determines the potency of halons in ozone depletion. Hydrogen fluoride, HF, is so very stable that fluorocarbons have relatively no known impact on ozone. Bromine reservoirs, such as HBr and BrONO2, are much more easily broken up by sunlight; making bromine up to 100 times more effective at destroying ozone than chlorine. Most bromocarbons released to the atmosphere are man-made (methyl bromide fumigants and halon fire extinguishers). 3.3.3: IMPACT OF OZONE DEPLETION The basic impacts of ozone depletion are majorly environmental. Exposure to higher amounts of UV radiation could have serious impacts on human beings, animals and plants [4]. UV radiation is harmful because it causes premature ageing of the human skin. One of the major health dangers of ozone depletion is skin cancer since UV-B radiation is known to cause certain types of the disease and white-skinned people are at greatest risk [5]. Similarly, the exposure of the eyes to UV radiation can lead to eye diseases such as cataracts. Research by the Environment, Canada in 1993 showed that 10% thinning of the ozone layer is expected to result in almost two million new cases of cataracts per year, globally [4]. Research has also shown that very high levels of UV radiation can have an adverse effect on the human immune system. This invariably means that UV radiation will reduce the human bodys resistance to diseases such as cancer and increase autoimmune problems and allergies. The World Health Organisation is concerned that if the bodys immune system is suppressed by solar radiation, it wont be able to fight off common infections and diseases. This means that people could even die from illnesses that would not normally have proved fatal.[5] https://www.ozonedepletion.co.uk/health-effects-ozone-depletion.html Crops are affected by increased UV, resulting in reduced growth, flowering and photosynthesis. Planktons are threatened by increased UV radiation. Since planktons are basically the first in aquatic food chain and decrease in the planktons will disrupt the food chains and result in a shift in species. Most construction materials including wood, plastic are degraded by UV radiation. Replacing or protecting such materials has a negative economic impact. 3.4: Halons and Global Warming Chemical Name Atmospheric Lifetime ODP GWP Halon1211(CF2ClBr)Bromochlorodifluoromethane 16 3 1860 Halon 1301 (CF3Br) Bromotrifluoromethane 65 10 7030 Halon 2402 (C2F4Br2) Dibromotetrafluoroethane 20 6 1620 ODP-Ozone Depleting Potential GWP- Global warming Potential Though the total emissions of halons are relatively small globally, their Global Warming Potential (GWP) cannot be overlooked. 3.5: Phasing Out and recovery of Halon systems. The use of halons is not illegal. To continue use of halons, the requirements of the EC regulation 3093/94 concerning the recovery and prevention of leakages must be observed. The EC regulation 3093/94 requires that ozone depleting substances must be recovered if practicable for recycling or destruction during the service and maintenance of equipment. Section 33 of the EPA 1990 states that it is illegal to treat, keep or dispose-off controlled waste in a manner likely to cause pollution to the environment or harm to human health. Section 34 states the duty of care that imposes a responsibility on persons who has control of waste at any stage from production to disposal. This duty of care involves ensuring that their waste is safely and legally disposed off and well documented. Disposing it off entails transfer to properly authorized persons along legitimate routes towards proper recycling or disposal. Halons can be sold to critical users who still need them through fire equipment suppliers or as advised by the Halon Users National Consortium (HUNC)[2]. The HUNC Ltd was formed by a number of halon users with Government support to advice on disposal of halons as well as helps find halons to keep critical systems running. Its long term purpose is to put an end to the use of halons in a responsible way. CHAPTER FOUR: WATER MIST The National Fire Protection Association 750, Standard on Water Mist Fire Protection Systems, 2006 edition defines water mist as a water spray whose diameter, Dv0.99 as measured at the coarsest part of the spray in a plane about one metre from the nozzle at its minimum design pressure is less than 1000microns. The recent economic and industrial interest in water mist technology is driven by two (2) circumstances: The rise in need for low-weight-impact replacement sprinkler systems on commercial ships driven by International Maritime Organization (IMO) regulations requiring a modification of most commercial marine vessels. This encouraged the search and development of low-water-demand, high-efficiency mist systems. The phase-out of halons and the search for alternative agents that possess most or all of the qualities of a clean total flooding agent. 4.1: GENERATION OF WATER MIST Water mist generation is categorised based on the mechanism used in producing the droplets. These are: Impingement Nozzles: these are used in generating droplets required for extinguishing class A fires where large droplets are required. Mists produced by impingement nozzles are also effective for suppressing hydrocarbon pool and jet fires. Twin-fluid Nozzles: this employs the use of compressed air and water. This is used widely in industrial spray systems. It operates on a low pressure range and is disadvantaged cause of its cost and low discharge pressure. Pressure Jet Nozzles: It produces fine droplets with wide spray angles for wider projection. The applied pressure determines the size and distribution of the water droplets formed. This increased pressure results in finer sizes. It is widely used to generate mist for suppression of class A and B fires. It can also be used effectively on some class C fires involving electrical equipment. This method is expensive cause of the cost of operating at a high pressure. Flashing of Superheated Liquid: When superheated liquid is released suddenly under pressure, ultra fine water droplets of water are produced. Mists generated this way are effective at suppressing dust explosions. It is disadvantaged because it is difficult to control the direction of projection of water mist generated. Combination of Pressure and Improvement Nozzles and Pressure Jet Nozzle with nitrogen gas inserted in the water line. 4.2: Characteristics of water mist systems Water mist is a fine spray of water droplets usually with a diameter of less than one millimetre. Thus, water mist systems work by using smaller quantities of water than normal sprinkler systems. The water droplets from water mists possess a high surface area to volume ratio which invariably increases their ability to absorb more heat. The smaller the droplet sizes, the more efficient the system is. This is so because a larger surface area is provided by small droplet sizes for evaporation and heat extraction. The National Fire Protection Association 750, Standard on Water Mist Fire Protection Systems, 2006 edition defines the following classes of water mist according to the droplet sizes as: Class I mist- 90% of the volume of the spray =200microns Class II mist- 90% of the volume of the spray =400microns Class III mist- 90% of the volume of the spray =400microns Mist sprays are formed from nozzles by three (3) different mechanisms [15]: Colliding water jets Creating a swirl in the spray Direct droplet formation from a turbulent jet of water The most common mechanism is the direct droplet formation from a turbulent water jet. The jet speed and the diameter of the nozzle determine how the droplets are formed. There are four ways by which droplets are formed from a turbulent water jet. These are: Rayleigh break up Regime: The diameter of droplets formed is bigger than the nozzle diameter because the droplets are formed far away from the nozzle [15]. Atomisation: the droplets are formed just outside the nozzle. This produces droplets that are much smaller in diameter than the nozzle [15]. First wind-induced break up: The droplet diameter is almost the same as the diameter of the nozzle hole. Formation of droplet occurs at a considerable distance away from the nozzle outlet [15]. Second wind-induced break up: The droplet is formed a short distance from the nozzle and this result in droplet sizes that are smaller in diameter than the nozzle hole [15]. The variables Reynolds number and Ohnersorge number are determining factors for the formation of droplet sizes. The Ohnersorge number, Oh is a relationship between viscous forces and surface tension while the Reynolds number, Re is a relationship between inertia forces and viscous forces [15]. These numbers are defined by the following equations: Re =à ¢Ã¢â€š ¬Ã‚ ¦eqn 4.1 Oh = à ¢Ã¢â€š ¬Ã‚ ¦eqn 4.2 Where, ? = density of the fluid ? = velocity of flow of the fluid d = diameter of nozzle  µ = dynamic viscosity of the fluid s = surface tension The energy required to produce smaller diameter sizes is more than large diameter droplets as well as carry them to the fire, due to drag and hydrodynamic effect of the fire. Larger droplets penetrate better than small ones. Large droplets can splash the fuels in pool fires while small droplets with low momentum would not penetrate the fire [17]. There is no one-size droplet distribution for all fire scenarios. Water mist system with mixed droplet size distribution is more effective than uniform droplet sized distribution. The size of the water mist droplet depends on the nozzles orifice design and pressure. All three pressure systemsà ¢Ã¢â€š ¬Ã¢â‚¬ low, intermediate, and highà ¢Ã¢â€š ¬Ã¢â‚¬ can be used for fixed (total flooding) and local (streaming) applications.[1] Low-pressure systems are used in large open-room areas and enclosures. They operate at pressures 175psi or below. They are usually used as where fire fighting nozzles need to be embedded in the floor. Examples include airplane hangars and fuel truck garages for putting out fire below planes and vehicles. Intermediate systems use pressure in the 175- to 500-psi range. Total flooding systems using intermediate pressure generate water droplets that provide good circulation and prolonged hang time throughout the protected space, demonstrating enhanced flame-cooling and high oxygen-deleting characteristics.[1] High pressure systems can withstand pressures greater than 500 psi. In general, this type of system requires fewer nozzles and less water to achieve successful fire suppression results than low- and intermediate-pressure systems. The high pressure generates substantially smaller water droplets at the nozzle than the other two systems, enhancing the surface area and heat-absorbing capacity of the droplets.[1] Water mist flooding systems efficiency is generally determined by spray momentum, droplet size, and flux density. The enclosure effects, dynamic mixing, additives and location of the system also aid the efficiency of the system. The spray momentum is the mass, velocity and direction of spray relative to the fire plume. It affects the rate at which the surrounding air is encroached into the fire as well as the depth of penetration of the droplets. This spray momentum is determined by the droplet size, the discharge pressure, cone angle, and the ventilation conditions of the compartment as well as the geometry of the compartment. The spray momentum of the mist has to be equal in strength and opposite in direction to the momentum of the plume for water mist not to be carried away by the fire plume. The flux density is the quantity of water spray in a unit volume applied to a unit area. This flux density of the water mist must be high enough for the fuel to cool below its flammability limit. The enclosure effect is the ability of a compartment to capture heat and restrict the movement of combustion products. This effect aids the suppression of shielded areas fires in heavily obstructed compartment. Dynamic mixing is achieved in the course of operation of a water mist extinguisher. This reduces the oxygen level in regions closer to the fuel surface. And hence increases the convective mixing of water vapour, fuel gases and the water mist, resulting in increased effectiveness of the mist system. This dynamic mixing is further influenced by ventilation conditions of the compartment, spacing and characteristics of the nozzles, as well as the spray characteristics. The dynamic mixing created The National Fire Protection Association 750, Standard on Water Mist Fire Protection Systems, 2006 edition defines the following as types of water mist extinguishers: Engineered water mist systems: systems that require individual design and calculations for the determination of flow rates, pipings, area covered by each nozzle, number and types of nozzles and nozzle placement. Wet pipe water mist systems: the automatic nozzles attached to the piping system containing water discharges immediately from nozzles operated by heat from a fire. Local application water mist system: this is the only non total flooding system. It is usually in form of hand-held extinguishers. It discharges directly on the subject in enclosed and or outdoor situations. Preaction water mist systems: the automatic nozzles attached to the piping system contain air, usually under pressure, with additional detection system installed in the same zones as the mist nozzles. The detection system acts to open a valve allowing water to flow into the piping system and discharges through all opened nozzles in the system.[1] Dry pipe water mist systems: the automatic nozzles are attached to the piping system containing air, nitrogen and inert gases under pressure. The release of the air, allows the water pressure to open a dry pipe valve. The water then flows into the piping system and out through any open nozzle. The types of water mist systems listed above are all total flooding systems except the local application system. There are two types of water mist total flooding systems : Single Fluid/ High pressure system-uses lone pipe to supply water mist nozzles[1] Twin fluid System (Low pressure)-uses dual piping to supply water and compressed air or inert gas separately to water mist nozzles[1] Single fluid systems are more difficult to fabricate because a specific droplet size, spray momentum must be maintained; but this is compensated for since only a high pressure water source is required. Twin fluid water mist systems are disadvantaged because there is need for a sufficient quantity of compressed air as well as higher cost since two supply lines are required for air and water. Water mist hand-held extinguishers are perfect for class A fires, and situations where class C fire hazards exist [13]. Components of water mist systems The components of a water mist system include: Water source Additive source(foam) Compressed gas source Piping Nozzles Pumps Detection device Water supply for 30minutes is necessary for a water mist system. Water is usually stored in pressurized containers. Foam concentrates added to the water supply improves the efficiency of the water mist system by repressing buried ordinary combustibles and liquid fuel spill fires. The resulting thin layer of foam solution blanketing the fuel spill reduces the amount of vaporization and inhibits the amount of radiant heat energy absorbed by the fuel.[1] Water mist nozzles can be automatic, nonautomatic or hybrid type nozzles (edition). The different types of nozzles used in water mist systems are: Air-atomisation nozzles, High-pressure single orifice nozzles and Low-pressure single fluid nozzles. The type of the nozzle determines the diameter of fine spray generated. They are thermally activated, using quick-response glass bulbs or opened by valves either manually or automatically by an electrical, hydraulic, or pneumatic signal. They consist of an assortment of nozzles of different sizes, depending on the fire hazard. Nozzles have total flooding and local applications.[1] The pipings required for water mist extinguishing systems are usually small-diameter, stainless-steel or copper/copper alloy pipings. [1] Pumps or high pressure accumulators, containing air or nitrogen, supply the pressure necessary for the system. Fire pumps for water mist extinguishing systems are designed to exceed flow rate and pressure demands by a minimum of 10 percent[1]. Two types of pumps are used depending on the pressure of the water mist system. Low and intermediate pressure water systems use centrifugal pimps while positive displacement pumps are used in high pressure systems. Automatic smoke or fire detection systems are usually used with water mist systems. 4.3: EXTINGUISHING MECHANISMS OF THE WATER MIST SYSTEM Water mists do not act like a complete gaseous agent in the course of extinguishing fires. The distance between the flame and the nozzle as well as the water spray rate influence the effectiveness of the water mist system in extinguishing fires. Some water droplets do not reach the fire; some penetrate the fire plume while others cool the fuel or burning surfaces. Other droplets wet adjacent areas and prevent the spread of fires. It has been observed that fire extinguishment with water mist in an open environment has a direct impact, cooling the fuel surfaces rather than cooling the fire plume itself.[17] Braidech et al identified two mechanisms by which water mists extinguish fires[17]: Displacement or dilution of oxygen and fuel vapour: this displacement depends on the fire size, the volume of the compartment and the ventilation conditions of the surrounding area. When the fire size is increased, more oxygen is consumed by the fire and also the formation of water vapour is increased thus effecting the extinguishment. The properties of the fuel determine the efficacy of oxygen dilution in fire extinguishment [17]. Heat extraction: this involves gas-phase cooling of the fire plume and wetting of the fuel surface. This cooling is achieved by the conversion of water into steam. As the water droplets vaporise to steam, the radiation from the fire and burning substance is absorbed. As the water droplets vaporise to steam, the radiation from the fire and burning substance is absorbed. The vaporization of the water droplets is determined by the surrounding temperature, the surface area of the droplets, the velocity of the droplets and the heat transfer coefficient of the mist system. The fire is extinguished when the adiabatic flame temperature is equal to or below the flammability limit of the fuel [17]. The brain behind this extinguishment is the Fire point theory which involves making an energy balance for the flames. This thermal quenching theory is based on energy balance at stochiometry in the flame. This can be represented as [15]: Xw [L + gw dT] =XF?HC- SXPgp dT XN2gN2 dT SXdi ?Hdi à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦eqn 4.3 where 1550 is the adiabatic flame temperature of hydrocarbon flame, ?Hdi = heat of dissociation ?HC = heat of combustion L = latent heat of vaporisation of water Cgp = molar heat capacity of combustion products Clw = molar heat capacity of liquid water CN2 = molar heat capacity of nitrogen XN2 = mole fraction of nitrogen Xp = mole fraction of combustion products Xf = mole fraction of fuel Xw = mole fraction of water Wetting of the fuel surface reduces the rate of combustion of the fuel and prevents re ignition when the fuel is cooled. Fuel wetting is the main mechanism for extinguishment of fuels that do not produce combustible mixtures of vapour above the fuel surface[17]. Secondary mechanisms of fire extinguishment by water mist systems include Kinetic effects, that is, dynamic mixing and radiation attenuation. Water acts as a thermal barrier when water mist reaches the surface of the burning fuel. It also acts to absorb radiant energy from the fire and re-radiates it at a minimized intensity. This action prevents the spread of fire to unignited zones. Generally speaking, the process of the extinguishment can be summarized as- water droplets absorb the heat from the fire and evaporate. This evaporation causes the flame to cool. Oxygen is displaced by the expansion of the water vapour while heat is extracted by the reduction of heat transfer around the fire plume due to suspended water droplets in the air. The mechanisms are basically independent of each other but only the combination of these mechanisms result in fire suppression. Small diameter mist droplets behave like gases, and thus have airflow patterns of movement. This movement is exhibited around obstructions just like gaseous fire extinguishers. The main fire extinguishing mechanisms of the smaller water particles are radiant heat attenuation and oxygen displacement. Droplets over 50  µm diameter are projected into the fire zone because of their greater momentum [6]. Mists are directed to the flame zone by entrainment. This produces local dilution of the concentration of oxygen as well as slows down the reaction kinetics, cooling the liquid fuels below flashpoint temperatures. 4.4: Water mists, its uses and limitations. Water mist systems and extinguishers have no ozone depleting potential nor do they contribute to global warming. Their atmospheric lifetime presents no environmental concerns. Water mist fire suppression systems have shown effective applications in combating Class A, B, C, and F fires with effective cooling, much less water requirement and damage than conventional water sprinklers, and less clean-up time than most other extinguishing agents. Fine water mists do not conduct electricity as normal streams of water. This favours its use on electrical equipment and makes it a good alternative to halons in this sense. Very small amounts of water are required to achieve suppression and control. Water mist systems extinguish and cool rapidly preventing re-ignition as well as protecting life and property. Water Mist also removes toxins, corrosive gases and smoke from the atmosphere, this mechanism is known as Smoke-scrubbing. They can be used on flammable liquids but not on reactive metals. The following are areas where water mist extinguishment can be put into use as replacement for halons: Telecommunications and control rooms Archive storage Flammable liquid hazards Shipboard machinery Protection for Electric Transformers and industrial hazards. Protection for Combustion and Gas Turbines Printing presses Protection for Baking Ovens, Fat Fryers and Industrial Cookers Water mist cannot be applied in all situations to replace halons. They are usually used in combination with other inert gases extinguishing agents to improve the efficiency of the suppression of hydrocarbon pool fires. It can also be used with chemical additives but this increases the operating cost and equipment as well as corrosivity and toxicity of the mist. Examples of such situations are in switchgear and control rooms, as well as flare snuffing on oil platforms. Unlike most other gaseous agents, water mists do not require enclosure doors and windows to be closed. Water mist can extinguish fires where there were possible cases of a cross draught- this is considered as a distinct advantage. Water mists also extinguished fires within 45 seconds depending on the fire size and type. Water mist is effective at suppressing backdrafts in compartment fires. A backdraft occurs when a fire is starved of oxygen and when oxygen is allowed in by the action of opening the door or a window, th e result is an explosive and violent combustion. This is because the fuel gas which was at a high temperature heats up and expands. Water mists system act by diluting the fuel gas in the compartment and reducing the total hydrocarbon mass fraction. Water mist systems are more expensive than other gaseous alternatives to halons, especially in equipment costs. Water mists systems are also favoured cause of the ease in obtaining water as well as recharging the systems. The implementation of water mist systems is quite challenging because it a rapidly evolving technology, thus it involves continual research by industries to catch up with the technology. Water mist is well suited for large space application. It becomes more expensive when applied to small spaces because of redundancy as regards piping and pumps. Water mists systems are generally more expensive to install cause of its high maintenance cost and expensive stainless steel pipework. 4.4.1: Water mist and Shipboard Machinery Water mists have made tremendous entry into three (3) main applications: Protection of turbine and diesel powered machinery; Protection of passenger cabins aboard ships ; and Protection of machinery spaces aboard ships. Ships are exposed to a wide range of risks, thus adequate fire safety measures must be put in place. This is very essential since external emergency responses are limited at sea. Water mist systems have been adopted for use on some ship to protect passenger, storage as well as machinery spaces. The system uses filtered sea water automatically fed from the ship and is usually combined with a foaming agent for use in machinery spaces. In the event of a fire, an alarm signal is displayed in the engine control room through a fire detector and the value for the affected space is opened either automatically or manually. The pressure before the valve then drops to activate the sprinkler pumps and the affected space is engulfed with high pressure water mist. 4.4.2: Water Mist and the Civil Aviation. Water mist systems could be used in aircraft whether in the passenger cabin, the cargo space or engine space. Water mist systems to be used on an aircraft have to be designed specifically for its use. In cabin areas, the water mist will be used to prevent the spread of fire from an external pool fire, cool the fuel gases and provide extended time for the evacuation of passengers. The weight problem as regards water mist systems is compensated for by partitioning the cabin into different water spray zones. Water mist discharged within each zone was triggered by a sensor within the zone. Zoned water mist systems are directed to the hazard and it invariably improves the quality of fire suppression achieved. This zoning system also improves visibility within the cabin, reduced the production of toxic gases and maintained high oxygen concentration in the cabin. In engine nacelle, class B fires, involving highly flammable liquids and highly explosive fires are the major concerns. Weight restrictions and the efficiency of water mist systems under cold operating temperatures are two major concerns for the use of water mist systems in aircraft engine nacelles. (pro3) The use of additives, such as antifreeze, in water mist systems allows for their use at temperatures below ambient. The level of obstruction in the engine nacelle prevents its use as total flooding system in this area. The performance of water mist in these spaces was dependent on the nozzle location, water mass flow, spray characteristics and temperature (pro3) A cargo fire is usually deep seated and so a high pressure water mist system will be required to reduce the spread of the fire till the airplane gets to safe landing. In this scenario, water mists systems tend not to be effective in extinguishment. 4.4.3: Water mist and Electronic equipment Fires involving electronic equipment are usually slow growing and smoky. The electrical conductivity of water limits the use of water mists systems in the extinguishment of electrical rooms and situations. Water mists systems have exhibited some cogent uses in extinguishing electrical equipment. Water sprays are better at extinguishing fires involving hot cable fires due to its efficient cooling, while other methods, failed to conductors and temperatures exceeded the auto-ignition temperature of the plastics [80]. In addition, evacuation of the compartment may not be necessary and the electronic equipment can continuously be operated during discharge of the water mist system, especially if a zoned water mist system is used. On the contrary, when halocarbon gaseous agents are used, the compartment has to be evacuated completely due to high concentrations of corrosive gases generated by the agent in fire suppression, thus disabling the operation suppress a flaming cable fire once the h eat of combustion had penetrated to the copper of the room [83]. In order to enhance the effectiveness of water mist as a halon alternative to protect facilities with substantial amounts of electronic equipment, the National Research Council of Canada (NRC) has initiated the IntelMistà ¢Ã¢â‚¬Å¾Ã‚ ¢ project. The basic principle of the IntelMistà ¢Ã¢â‚¬Å¾Ã‚ ¢ system is the use of state-of-the-art fire detection technology to control a zoned water-mist fire suppression system, so that water can be applied to the smallest possible area directly associated with a fire. The design parameters of a zoned water-mist fire suppression system examined in the IntelMistà ¢Ã¢â‚¬Å¾Ã‚ ¢ project included the water droplet size, spray angle, spray momentum, nozzle location as well as flow rate.(pro3) 4.4.4: Water mist and Standards There is no UK standard or UK approved land based water mist system standard. The standards available are guidelines for installation of water mists systems. These standards include: National Fire Protection Association 750, Standard on Water Mist Fire Protection Systems (NFPA 750). This is an American standard that provides details of the design requirement. The document nevertheless states in its scope that, This standard does not provide definitive fire performance criteria nor does it offer specific guidance on how to design a system to control, suppress or extinguish a fire. FM global, FM5560 Approval Standard for Water. FM Global, a leading commercial insurance company in the UK that helps clients to support risk management including fire risks. This standard also shows overriding requirement of testing. In its scope, the standard also says, Approval standards are intended to verify that the product described will meet stated conditions of performance, safety and qualify useful to the ends of property conservation. BSI DD8489 and DD8458. British standard institute is due to publish these standard. This is a code of practice for design and installation of fixed fire protection systems-commercial and industrial water mist systems. This code specify test requirements against which a system is tested against successfully before its design and installation. The document also states in its scope that, This draft for development gives recommendations for the design, installation, commissioning and maintenance of water mist system and gives performance criteria for fixed water mist system for specific commercial and industrial hazards. These three (3) documents show that water mist is seen by all standards as risk and fire test specific and thus users or designers are at their own risk. The potential limitations of the design of a water mist system are: Each risk requires its own specific design. Systems designed to protect a particular hazard are not necessarily applicable to other hazards. The systems are designed to meet fire tests and are not generic protection. Changes in surrounding area can negate the design and thus lower the efficiency of the protection. This will require a review and redesign of the installed system. Equipment is not interchangeable. The replacements of parts of the system have to be the same specification or a complete re-design may be necessary. It requires rigid maintenance procedures and cleaning of the nozzles. CHAPTER FIVE: It must be recognised that there are some special applications where there are no alternatives to halon based fixed systems. These are manned spaces where the fire protection system needs to be in an automatic mode of operation. These include military defence installations and special control rooms. This is also true for transport systems where low space and weight requirements are critical. These include the civil aviation industry and shipboard machinery. Furthermore the European Commission has issued proposals to remove the critical use exemption for halon based aviation safety applications Further development of a cabinwater mist system, however,was discontinued after an industry-wide cost benefit study concluded that the cost of outfitting a fleet of aircraft with passenger-compartment water mist systems would be too high, compared to the benefits [70]. Good progress on improving water mist effectiveness in fire suppression has been made over the last decade. New methods include the combination of both total flooding and local applications, cycling water mist discharge mode, hybrid water mist systems, as well as the intelligent water mist system that combines zoned water mist application with intelligent detection. In order to further apply these new technologies in fire suppression, however, more research efforts are needed, including studies on optimum cycling frequency in the cycling discharge mode; reliable and cost-effective intelligent water mist systems, as well as the performance of hybrid water mist systems in the practical applications.(pro3)

Best College Writing and Essay Topics

<h1>Best College Writing and Essay Topics</h1><p>There are numerous interesting points while picking the best school composing and exposition subjects for school. One of the most troublesome difficulties is that your exposition must incorporate a specific scholastic subject and you need to remember that point for request to get acknowledged into the school. The themes are recorded underneath, and there are numerous different kinds of points and recommendations that can be used.</p><p></p><p>Writing a reaction to a test will be one of the simplest to achieve. This is particularly obvious if the inquiry that has been posed was very explicit. It could be a related random data question. On the off chance that it has a general thought that can be expounded on, it tends to be useful to consolidate that data into the exposition. For instance, if it somehow happened to state, 'How would you cook a chicken?'</p><p></p><p>You ca n take the general diagram of how to make a chicken and compose an article about the various kinds of chicken bosoms, and afterward you can name them and their specific parts. This would be an incredible method to concoct thoughts for challenges paper points that don't expect you to truly buckle down. In any case, there is nothing amiss with buckling down. It is simply going to expect you to use a greater amount of your cerebrums than your composing skills.</p><p></p><p>Another extraordinary test for composing an article is one that is to some degree general thought related. It doesn't need to be a convoluted thought; it tends to be something as straightforward as asking yourself an inquiry that you can reply in a couple of sentences. For instance, if the inquiry that was posed was, 'What is a raccoon?'</p><p></p><p>The reason this is a good thought is that it gives you a lot of room to think. It is a typical practice to utilize senten ces that are three or four words in length. Your concern is that when you think for longer than three or four words, your cerebrum rests. The utilization of short sentences will really assist your cerebrum with staying alert and will build your review of the thoughts that you came up with.</p><p></p><p>A testing difficulties paper themes will likewise need to manage difficulties and changes. The fundamental issue with any school paper is that it is likely going to change in any event once in the center of the procedure. Difficulties can be unreasonably confounded for certain understudies, so they don't work.</p><p></p><p>One simple methodology is to expound on the hardest pieces of the progressions that you needed to experience in your life. This could be the passing of a friend or family member, a mishap, or a significant clash with a relative. It doesn't need to be anything excessively troublesome, however it has to be personal.</ p><p></p><p>Very troublesome expositions typically expect issues to illuminate in the article itself. It will likewise expect you to make sense of an answer or strategies to an issue. The best kinds of issues are questions that are straightforwardly associated with the course of study that you are taking. These kinds of issues don't need to be intricate; they simply must be sufficiently general to address your school composing and exposition topics.</p>

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Research Essay Topics For Class

<h1>Research Essay Topics For Class</h1><p>When understudies finish expositions, they are not really the points that they need to keep dealing with; a significant number of them would prefer to concentrate on schoolwork or finish their different assignments before they consider composing another paper. You must be imaginative when composing the paper themes for class.</p><p></p><p>When I showed math, one reason understudies didn't care for composing articles was a result of how exhausting the point was. They needed to concentrate on getting their work done and taking care of issues and not composing an article. In any case, so, you despite everything need to compose a theme for every understudy in light of the fact that your goal is to ensure that they comprehend the ideas you talked about in class.</p><p></p><p>In my showing vocation, I recollect a few understudies who would not like to compose a research paper since they would not like to compose another exposition. This is a typical issue. Most understudies are excessively bustling attempting to finish their different assignments or simply need to keep their evaluations up. Along these lines, in the event that you have sufficient opportunity, it is a smart thought to make up some exposition points for class so understudies can proceed with their learning while additionally writing.</p><p></p><p>However, there are sure subjects that understudies despise composing. These incorporate things, for example, governmental issues, wellbeing, and religion. As you may know, these are themes that have just been shrouded in class by your colleagues. So you won't have the option to disclose to them how these ideas apply to your particular situation.</p><p></p><p>Of course, it is reasonable that understudies would prefer not to compose a paper subject on religion since they definitely realize what to compose. A ll things considered, we get the chance to discuss it in class all the time. In any case, I had an understudy who needed to compose an exploration paper on Christianity however had never perused any books on Christianity. Along these lines, they picked a theme that they thought may intrigue the individual; and this subject was legislative issues and social issues.</p><p></p><p>This understudy didn't get that on the off chance that they were going to concentrate on these kinds of points, they would need to expound on something beyond religion and policy driven issues. For instance, they would need to expound on instruction, war, and worldwide warming.</p><p></p><p>This understudy saw nothing about these subjects and expected to utilize their political and social issues to assist them with expounding on it. Whenever this understudy needs to compose an examination paper, they should consider picking a point that they know something about. </p><p></p><p>Of course, when an understudy has figured out how to compose an exploration paper and exposition themes for class, it won't be important to keep making up these subjects for the remainder of the year. You can depend on understudies to have the option to finish the subject that you doled out and afterward have them turn in their essays.</p>

Tips to Prepare For College Essay Tests

<h1>Tips to Prepare For College Essay Tests</h1><p>Preparing an individual exposition school test is hard for any understudy. You will be required to show a far reaching comprehension of different subjects, which requires thinking and basic thinking. You need to comprehend the material before giving a test that would be a benchmark in your scholastic profession. There are approaches to get ready for such tests and you can discover them in the accompanying paragraphs.</p><p></p><p>The first thing you have to know is what number of tests you will be facing. There will be numerous understudies in your group and you will rival a significant number of them for similar spots in the class. You ought to set yourself up for a higher number of tests. You will likely need to do a ton of readiness and not simply concentrating on a couple subjects.</p><p></p><p>Take a gander at your group burden and set the quantity of tests you an ticipate that yourself should need to get ready for your school paper test. Remember that there will be numerous tests that you need to take. This implies it is significant that you work on doing the training test until you can respond to each address confidently.</p><p></p><p>The next thing you have to think about your paper school test is the principles of the test. You will be given numerous subjects in each area of the article test and you have to choose if you will decide to consider a specific subject or stick to one primary theme. Remember that you should give a response to the paper test question, which implies that you should have the option to think and settle on the privilege response.</p><p></p><p>You additionally need to set yourself up for the way that there will be numerous interruptions in the room. You have to glance around to locate a tranquil territory where you can work without being upset by other students.</p&g t;<p></p><p>Another thing you have to consider is the organization of the article school test. You have to know ifyou will be given the test in an open zone or in the event that it will be in a homeroom or library setting.</p><p></p><p>The rules of the exposition school test can likewise be totally different for various understudies. You have to know the standards of the test in the event that you will be permitted to utilize the test for your end of the year test. There are likewise sure zones where you will be approached to turn in answers and this may imply that you should turn in an inquiry paper rather than a test.</p><p></p><p>There are a ton of things you have to remember when you get ready for your school exposition test. You ought to consider every one of these variables to assist you with composing an article that will win you the ideal grade.</p>

Questbridge Writing A Good Supplemental Essay

<h1>Questbridge Writing A Good Supplemental Essay</h1><p>The most concerning issue for understudies when they begin recorded as a hard copy is that they will in general compose excessively. On the off chance that you resemble most understudies, you likely started by composing a ton of your expositions and tests. This difficult will keep on appearing as you get more established and begin attempting to accomplish more research and other work around the house. The significant thing for you to recollect is that despite the fact that you don't have the entire story at the present time, by improving your composing ability you can truly eliminate the measure of things you need to compose about.</p><p></p><p>Before you start composing a decent supplemental article you should ensure that you know about Questbridge. One reason why this sort of composing appears to be so troublesome is on the grounds that understudies don't have the foggiest idea how to appropriately structure their articles. By finding out about how to do this it will make it simpler for you to get past most of the more troublesome segments of your essays.</p><p></p><p>There are a couple of tips that will help you recorded as a hard copy a decent supplemental article. As a matter of first importance, attempt and make it simpler on yourself by utilizing an article starter control that will give you the structure you have to move your paper along. You will likewise need to ensure that you plot the piece of the paper you have to cover and what precisely you are going to discuss.</p><p></p><p>Another extraordinary tip that will help you recorded as a hard copy a decent supplemental article is to have a center point. This can be something as straightforward as depicting an individual, for example, a 'Jim's mom'Jim's grandmother'. It doesn't need to be in any way similar to this however it can have a gigantic effect in ho w your article looks.</p><p></p><p>You ought to consistently take as much time as is needed when composing a supplemental paper since it will require some investment to finish. One of the most widely recognized errors understudies make is over-focusing on themselves. You ought to likewise abstain from getting enveloped with attempting to locate the 'great' word to depict your point. The main explanation that you need to utilize a particular word or expression is so you can enable the peruser to comprehend your topic.</p><p></p><p>You ought to likewise ensure that you abstain from utilizing such a large number of fillers in your supplemental paper. Individuals will in general skirt past filler words and this makes you lose focuses. For instance, in the event that you are talking about a carpool path, you should utilize fillers, for example, 'ride share' 'carpool' 'taxi', or 'ride sharing' rather than 'carpool.' By doing this you will en sure that you aren't bringing down your points.</p><p></p><p>Many individuals have said that the most ideal approach to figure out how to compose a decent supplemental exposition is to peruse a great deal of work by Questbridge. Questbridge is an asset that will show you how to structure your papers. You will likewise find that their exercise manual will assist you with your editing abilities. By perusing these materials you will have the option to see how to adequately utilize Questbridge to assist you with the composing process.</p><p></p><p>Even however Questbridge has some great items you would prefer not to simply depend on them for your composed work. In the event that you need to make a quality exposition, at that point you will need to take your own recommendation and search for approaches to improve your composing skills.</p>

Essay about The Revolutionary War - 1417 Words

The Revolutionary War The Revolutionary War started on April 19, 1775 at Lexington and Concord. America was very much unprepared with no central government or army. The congress stepped up as the government and began to organize an army. The Revolutionary War did not end until September 3, 1783 with the signing of the final peace treaty between America and Great Britain. The victory in the Revolution War led to the birth of a new independent nation. After the Revolution it was a time of cooperation. People in the nation were focusing on building a government, migrating west and their new found freedom. Military actions were more in surrounding areas mainly France, Mexico and Britain. In 1798 was the XYZ affair, an event that†¦show more content†¦After the first battle of the Civil War the Upper states in the South also seceded. Abraham Lincoln was able to persuade Maryland, Delaware, Kentucky, and Missouri to stay in the Union. By doing this Lincoln gained access to the river systems in Kentucky and Missouri that led into the heart of the South. This control effected the 1862 invasions of the south, which provided the North with most of its early military successes. The Civil War was total trench warfare. Technology was the main event that influenced total trench warfare. Technology led to ideas such as strategy, weapons, and transportation. It wasnt until 1865 the Civil War ended with the surrender of the Souths army. The Civil War was an event that impacted the United States greatly economically, politically and socially. This impact called for great reconstruction after the Civil War. *Political Constitutional Developments After the American Revolution ended there was a debate on if all ties should be broken with Britain. Support for American Independence rode strong up into 1776. Thomas Paine wrote a pamphlet, Common Sense. This pamphlet rebelled against King George III and argues for complete Independence of the American colonies. On July 4, 1776, a Declaration of Independence was adopted stating the colonies freedom from Britain. The time after the Revolution was a period of political reconstruction. A time were State franchises were developed andShow MoreRelatedThe Revolutionary War787 Words   |  4 PagesRunning head: Paine Thomas Paine’s Role in the Revolutionary War Dallin Hodgkin Mountain View High School Paine What sparks a revolution? What motivates the average man to rise up against everything he’s ever known? There have been many revolutions that have taken place in the past and each one has had different elements that powered them. The revolutionary war is an example of one such revolution. But what gave it power? There are two main ideas that start revolutionsRead MoreThe Revolutionary War957 Words   |  4 Pagestimes leading up to the Revolutionary War. These times include: Navigation Act, French and Indian War, Sugar Act, The stamp Act, Boston Massacre, Townsend Act, The Boston Tea Party, and the Intolerable Acts. All of these events are important in leading to the Revolutionary War. This essay will go into detail about the events leading up to the Revolutionary War. Starting with, the Navigation Act. The Navigation Act was the first event leading up to the Revolutionary War. The Navigation Act is whereRead MoreThe War Of The Revolutionary War1182 Words   |   5 PagesIn battling the British in the Revolutionary War, the American rebels did just as the great French military and political leader, Napoleon Bonaparte advised, â€Å"Never interrupt your enemy when he is making a mistake†. Though there were a great deal of missed opportunities and misguided actions taken by both sides of this war, none were as great as those by the ministers in London and British Generals Howe and Burgoyne. However, of these three, one held a great deal of responsibility for Britain’s failureRead MoreRevolutionary War1150 Words   |  5 PagesRevolutionary War Taylor Hunter ENG/101 October 26, 2014 The battle of Trenton and Princeton began to erupt in the same year of the Revolutionary War. The Revolutionary War had started because the Americans wanted the same rights the as the British citizens had. The British refused to give Americans the same rights because they (British) didn’t think the Americans shouldn’t be represented as a part of the British Parliament, instead their (British) minds were more focused on buildingRead MoreThe War Of The Revolutionary War1078 Words   |  5 Pagessubject to learn about in History is spies. With the ideas of secret ink and leaving important documents at Dead Drops would be someone’s dream to live. That does not mean that every story of a spy ended up that way. Several spies during the Revolutionary war were hanged if caught. Though, one major traitor in the United States did not get hanged. He escaped to England. The life of spies is quite different then what people imagine. Even the founding fathers of th e United States of America played suchRead MoreRevolutionary Artillery in the Revolutionary War Essay870 Words   |  4 Pagesovercome adversity and hardship. But with courage and dedication the artillery and its leadership were able to play a vital role in the success on the battlefields, and ultimately the victory resulting in America earning its freedom. During the Revolutionary War, the Artillery assets that were available were a combination of cannons, mortars and howitzers. There were two types of cannons used at this time. The Field Guns, which were lightweight and easier to move, and the Siege Guns, which were muchRead MoreThe American Revolutionary War796 Words   |  3 PagesThe American Revolutionary War was a long hard fought war that lasted about 8 years. Many Countries were involved in the war, such as The United States, France, Great Britain, Spain, and The Dutch Republic. Not all countries actually fought but they provided either side with weapons and supplies to help them have a greater chance of winning the war. More than 70,000 people were killed during the great American Revolutionary War. The Americans were tired of the loyalist British taking advantage ofRead MoreThe Revolutionary War And The War Of Independence1191 Words   |  5 PagesThe Revolutionary war another name for the war of independence and lasted f rom 1775 and ended 1783. There was a lot of tension between the 13 colonies and the British Monarchy. Smaller battles between British troops and smaller militias near Lexington and Concord kicked off the war. And by 1777 the rebels began a full scale war on Great Britain. The war turned into an international conflict when France joined the war and sided with the American colonists in 1778. 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The militiamen returned the volley which devastated the Redcoats. Eight officers were wounded and one British soldier lay dead and another mortally wounded. The Redcoats returned the volley

Essay on Writing Process - Do You Need a Sample to Help You Learn How to Write?

Essay on Writing Process - Do You Need a Sample to Help You Learn How to Write?Are you curious about writing samples, or you've just been studying for your essay on writing process? Do you need a sample essay to help you learn how to write, or to help improve your skills? You have several choices, and I will discuss some of them here.There are two kinds of essays that people write in school, those that are submitted to a teacher, and those that are written for assignments online. These two types of essays are actually quite different and require completely different resources. It's much easier to get an assignment online than it is to send a paper to your teacher, which is why you have to make sure that you know the difference between the two before you get started. I'll discuss both types of essay on writing process, because they can be very similar.Before you pick up a textbook or even an essay samples online, you should think about what kind of essay you're going to write. If you' re writing for an assignment, you can skip the sample essay, because you already know how to write from prior experience. But if you're trying to work on improving your skills, you may want to take a little time to see if there are any sample essays on the internet that you can use.How do you find a site that offers online essay writing samples? It's not hard to find them, and there are plenty of places that offer them for free. Some are paid sites, while others offer only basic materials. You'll want to consider the type of essay that you're interested in writing, so that you can find a site that is right for you.After you decide which type of essay you're interested in writing, there are two simple steps that you should take. First, you should read through the sample essay to figure out if it has the right information for you. Second, you should read through the writing that you read and consider ways that you can add or change it to make it more appropriate for your situation. If you do this, you should be able to write an essay on writing process that will help you improve your writing.This essay on writing process should not be overly complicated. It should take you a few minutes to complete, and you should be able to finish it within the deadline given by the teacher. There are no rules, and you don't have to follow anything in particular. Just find something that you like, and then work on it until you feel comfortable with it. If you do this, you should be able to write an essay on writing process that will help you improve your writing.It is possible to find a lot of essays on writing process on the internet, and these can help you learn how to write, or to help you improve your skills. It's easy to find essay samples, and if you take the time to learn how to do it properly, you should be able to find many samples on the internet. You might find a site that offers two different kinds of essays, or one of each, and you might find another site that offe rs very similar essays.It's important to take your time to find the right essay samples for you, because there are a lot of great ones available online. The best way to find the perfect essay for you is to start out simple, and work your way up. Just take your time, and you should be able to find a good essay on writing process that will help you improve your writing.

Understanding Research Paper Topics for Teens

<h1> Understanding Research Paper Topics for Teens </h1> <h2> Research Paper Topics for Teens Can Be Fun for Everyone </h2> <p>You ought to see totally that you're not composing an illustrative article. You should consistently look for scholastically demonstrated and dependable sources that you can refer to in your exposition. Papers are edited to ensure appropriate English use and sentence structure and to ensure they are unique. Composing phenomenal research papers shouldn't be hard. </p> <h2>The Rise of Research Paper Topics for Teens </h2> <p>Now you have a good thought of the best approach to chase for school examine paper themes, you are set up for certain recommendations. Understudies can't choose the absolute first thought they see on the web or in the print media it's tied in with picking generally excellent research paper subjects on the important difficulties. </p> <p>Writing an interesting article about popular themes is a chance to uncover your insight into earth. You should be sure to comprehend everything obviously once you select a paper subject. You should ensure you've picked a sufficient theme with the goal that you may present a top notch paper. Inquiring about the subject will allow you to discover increasingly about what entrances you, and should you pick something you truly like, composing the article will be more enjoyable.</p> <p>Depending on the point one needs to assemble information to make a significant base and contention in the exposition. Thus, it's constantly essential to find a point that intrigues you. Hence, the subject should be easy to refute! On the off chance that it is excessively tight, you may think that its elusive the applicable writing. </p> <p>The previously mentioned theme choice may give you a perfectly clear perception of what things to expound on. It is a unimaginable errand to create a theoretical research paper since this sort of article consistently addresses a specific theme and supplies a genuine quest for ideal techniques for unraveling a particular issue. For certain understudies, an assortment of point is the simplest part. Frequently, the perfect theme is one which you genuinely care about, yet you likewise should get solid and steady to investigate it.</p> <p>There are only a couple of things that characterize whether an exposition you're dealing with will be a decent one. You may likewise rehash the thoughts which you have talked about in the body sections so as to come to your meaningful conclusion legitimate. The theme must be intriguing, the point must be fundamental lastly the subject must be useful. At the point when you're picking your subject, recollect that it's a lot less complex to expound on something which you at present have intrigue ineven on the off chance that you don't have the foggiest idea about a decent arrangement about it. </p> <h2>The Fundamentals of Research Paper Topics for Teens Revealed </h2> <p>If you're mistaken for various intriguing subjects to inquire about on the web, it's greatly improved to figure out what intrigues you the most. In the current age, it's trying to keep young people from getting to sexual substance on the net or through different channels Therefore, most of them are sharpened on the benefit of utilizing contraceptives. The expansion and access to the web accomplishes more harm than great to adolescents. The ascent and access to the web accomplish more harm than great to youngsters. </p> <p>If you're composing a downturn investigate paper and you don't feel very certain where to start, coming up next are a couple of themes that you may decide to take a gander at. Before presenting your task, you need to guarantee that it's faultless and mistake free. The two alternatives aren't sufficient in light of the fact that it'll be hard to choose the correct writing. </p>