An Effective Manager of Home Depot Essay

As indicated by Robbins and Coulter (2005), viable directors everywhere throughout the world recognize the job that key administration plays in their organization’s execution. Besides, Drucker (2004) said that the measure of a compelling chief or official is the capacity to complete the correct things. This commonly involves doing what others have overlooked notwithstanding maintaining a strategic distance from what is ineffective. Creative mind, insight, and information may all be squandered in an official activity without the achieved propensities for mind that structure them into results. I accept that Bob Nardelli is displaying these attributes and the executives style of a compelling chief as he drives Home Depot to turn out to be constantly fruitful in its tasks. As he triumphed over different issues in dealing with the organization and a s an outcome gracious his administrative procedure, Home Depot is presently has now expanded deals by 60 percent and profit for each offer by 105 percent (Business Week Online, 2006). During his first day as CEO at Home Depot in the year 2000, the organization has different issues to manage, some of which, were as per the following: it did not have the fundamental framework to send even a companywide electronic mail, Home Depot stores were at that point run-down and was being known as a store with poor client care, the stores’ shipments were logged utilizing pencil and clipboard, and Home Depot stores didn't have robotized stock frameworks (Sellers, 2001). Being a visionary head that he is, Nardelli accepted that better procedures must prompt better quality promotion higher benefits for Home Depot. He utilized vital administration in intending to improve the organization. As declared by Robbins and Coulter (2005), the predominant confidence in the executives hypothesis and society in general is that chiefs are totally capable or responsible for an organization’s achievement or disappointment. Nonetheless, Nardelli showed that beside the way that quite a bit of an organization’s achievement or disappointment is a direct result of outer powers outside of the manager’s control, the supervisor has a major duty in settling on choices for the accomplishment of the association. A significant segment of Nardelli’s broad move to change Home Depot, which is viewed as the world’s third-biggest retailer, into a progressively brought together organization, incorporate bringing in individuals, thoughts, and maxims from the military (Business Week Online, 2006). This may be an unwanted idea in the executives circles; in any case, Nardelli couldn’t care less. He accepts that it is a crucial part of his methodology to lead in a lumbering 2,048-store chain and prepare for its next leg of development (Business Week Online, 2006). In a questionable and dynamic condition, genuine associations utilize vital dynamic when settling on choices offers administrators with an exhaustive and orderly methods for mulling over the outer condition, focusing on an organization’s quality, diminishing shortcomings, and perceiving openings in which an association can have a serious edge (Shafritz and Hyde, 2004). As kept up by Holstein (2004), the Nardelli dynamic model may help make an example for different CEOs who have been amazingly disappointed and baffled by their absence of accomplishment in tackling innovation. In changing Home Depot to what it is presently, Nardelli expanded data innovation spending by right around 20 percent (Sellers, 2001). At that point in year 2003 Nardelli spent a sum of $400 million on stock transportation and following frameworks (Sellers, 2001). Beside these, Nardelli likewise spent around $250 million restoring Home Depot stores (Pellet, 2001). This remembered the establishment of self-checkout frameworks for 800 stores to diminish client lines and back off sales reps. This likewise incorporated the foundation of two-way cordless scanners, which empowered items to be cost checked in the shopping basket, as such shortening lines. Being a successful chief, he additionally focused on persuading the organization’s laborers. Armstrong (2002) said that in giving compensations to workers, directors and administrators ought to distinguish what prizes will prevail for explicit representatives at some random time. Despite the fact that directors and chiefs probably won't have the option to have control over specific prizes like advantages or wages, they have the freedom to give out remunerations like acknowledgment and applause. In Home Depot, Nardelli initiated developments in giving prizes and in human asset the board. To start with, he subbed 157 distinctive worker assessment structures with two (Pellet, 2001). Furthermore, collaborators, above and underneath them, evaluated aalaried work force starting from the ceo and pay rates were gotten from the scores. At that point during a period when Home Depot was wanting to enlist roughly 100,000 new workers, Nardelli didn't naturally terminate those representatives with poor scores (Pellet, 2001). Nardelli first mentioned for the exhortation of others and educated underperformers accurately what they were fouling up. Thusly, Nardelli demonstrated that it is significant for a chief to enthusiastically look for restricting conclusions and ask with respect to the reason for those assessments before choosing a strategy is being worried, rather than following up based on implied or pre-organized understanding. Fundamentally, this needs continually tuning in with genuine interest in order to advance improvement of various suppositions and supporting reasons, rather than simply presenting proposals and attempting to settle on understanding around them (Drucker, 2004). Moreover, Nardelli appeared to follow stage two in Peter Drucker’s model (204) that administrators require both themselves and their staff or subordinates what they contribute directly to the association and what they could add to the association later on. In Home Depot, Nardelli stated that regardless of whether a person’s conviction of what he/she presently contributes, or could contribute, rises to his/her manager’s conviction, accentuating and drawing out the significance of everybody’s job as a supporter is important to the organization’s general adequacy. In starting change in Home Depot, Nardelli indicated that everyone in the association decides; in any case, dynamic is explicitly imperative in a manager’s work. I feel that he followed what Robbins and Coulter (2005) said that dynamic is a piece of every one of the four administrative capacities †arranging, sorting out, driving, controlling, and that dynamic is equivalent with overseeing. Holstein (2004) has composed that when Nardelli joined Home Depot, the test of improving the company’s flexibly chain and coordinations became evident on the grounds that the organization is route behind different stores in these regions. Henceforth, he set up a model called â€Å"full truckload to the store,† which implies that the more you brought, the more it would oblige you to sell, since you get sort of stuck (Holstein, 2004). Regarding data innovation, at Home Depot, Nardelli has built up an arrangement of governing rules (Sellers, 2001). The way is which Nardelli is dealing with the innovative change is standing out and enthusiasm from different administrators and supervisors. Venders (2001) said that Nardelli has acquired from the CE playbook to set up an arrangement of governing rules on how innovation is overseen, and Nardelli has similarly consolidated innovation choices profoundly into his business procedure in runring and overseeing Home Depot. Moreover, Nardelli similarly utilized structure further associations with less sellers. As expressed before, the Nardelli dynamic model may potentially help make an example for different CEOs who have been exceedingly baffled and frustrated by their absence of achievement in using innovation. Taking everything into account, in changing Home Depot to turn into the winning organization that it is presently, I accept that Nardelli showed that initiative is the capacity to impact individuals or gatherings toward the achievement of objectives. As a procedure, Nardelli demonstrated that authority shapes the objectives of an association or gathering, motivates conduct toward the accomplishment of those objectives, and describes authoritative or bunch culture; henceforth, it is in a general sense a procedure of impact. # References Armstrong, M. (2002). Worker Reward (third Edition), CIPD: London. Drucker, Peter. â€Å"What Makes an Effective Executive,† Harvard Business Review, Vol. 82, No. 6, June 2004. Holstein, W. (2004). â€Å"The Depot goes advanced: how CEO Bob Nardelli is dealing with a $2 billion innovation transformation,† The Chief Executive. Pellet, J. (2001). â€Å"Mr. Fix-It Steps In,† Chief Executive. â€Å"Renovating Home Depot. † (2006). Business Week Online. Robbins, S. , and M. Coulter. (2005). The board, (eighth ed. ). Prentice Hall. Venders, P. (2001). â€Å"Exit the Builder, Enter the Repairman: Home Depot’s Arthur Blank Is Out. New CEO Bob Nardelli Is In. His Job: To Tackle the Company’s Renovation following Two Decades of Nonstop Expansion,† Fortune. Shafritz, J. M. and A. Hyde. (2004). Works of art of Public Administration, fifth ed. Belmont , CA : Wadsworth/Thompson

Process Design Matrix and Summary Essay

We’ll start by characterizing forms advancement. As indicated by (Chase and Jacobs) process is characterized as basic fabricated items that depict the vital basic strides for the plan of an item. These strategies speak to a fundamental succession of steps or exercises that an association uses to make or alter an item. A significant number of these undertakings include more learned information than physical movement. A few organizations characterize and follow an exact and nitty gritty advancement process, while others may not have the option to depict their procedures. Each organization utilizes an alternate procedure from some other organization; truth be told, a similar association may follow an alternate procedure for every one of its items or markets. The motivation behind this methodology procedure is to plan a procedure that meets the clients needs and to item subtleties inside the expense and other authoritative limitations. Note that the chose procedure will have a dra wn out impact on rivalry and the adaptability of the creation, just as on the expense and nature of merchandise delivered. In this manner, a great part of the methods procedure is given at the hour of the dynamic. I work at Humana Healthcare Insurer Company. It is a Kentucky based Company with 45 years in the market, an innovator in buyer driven medical advantages and a Fortune 100 organization with incomes of more than $ 30 billion, positioning 79 in our developing way to deal with prosperity. To assist individuals with accomplishing long lasting prosperity, the components of direction, having a place, security and wellbeing all work together to deliver genuine prosperity and we make our commitment to greater than balance through center quality of our wellbeing. Taking into considering the administration offered, which is a medical coverage plan, Humana has a call community that utilizes a trend setting innovation stage that permits access to different stages simultaneously to concentrate on tackling the goals of the call. Calls are replied by exceptionally prepared work force to fulfill the most noteworthy guidelines of value and customerâ satisfaction. We answer brings in a period of 20-80 seconds permitting each call to be a decent encounter for our clients. This will permit streams and procedures intended to meet and conform to operational prerequisites and client needs. To arrive at the most elevated levels of fulfillment our Call Center Workforce Management zone nee ds to estimate calls volume, operator necessity computation, think about outcomes and assemble plan workforce. Our consequences of the overview led to our clients surpass the measures of 98 percent fulfillment. Another help that Humana offers are programs coordinated to social insurance. Avoidance is one of the principle approaches for ideal wellbeing. Humana includes esteem advancing projects, for example, Humana Beginning for pregnant ladies, asthma counteraction program and sustenance programs where our nutritionists facilitate wellbeing projects to control and advance an ideal wellbeing that would bring about more advantageous representatives and lower usage costs. With this vision a 30 percent decrease of your bill for clinical cases is normal. The innovation utilized for the call dissemination it’s an ACD which permits evenhanded appropriation. Humana gives a devoted unit called SBU/VIP Area which is a committed zone of incorporated administrations for our clients. The goal of this territory is to oversee VIP client calls through this committed region, offering them a select and one of a kind help. Our item is elusive, where every one of our programming techniques is coordinated to the contact with the client, the reaction time is short, and our business sectors are neighborhood and universal. Another of our highlights is the concurrent creation and utilization with reaction; obligation cycles that are shut after each call and frameworks innovation for call log requests to archive the call goals. The primary target is to improve quality, partners efficiency and auspicious reaction. References Boothroyd, G.,P. Dewhurst and W. Knight. Item Design for Manufacture and Assembly. second ed New York Marcel Dekker 2002 Cooper, R. G Winning at New Products: Accelerating the Process from Idea to Launch Reading MA Perseus Books. 2001 Morgan James M., and Jeffrey K. Liker: The Toyota Product Development System: Integratimg People, Process, and Technology. New York Productivity Press, 2006 Ulrich, Karl T., and Steven D Eppinger. Item Design a Development third ed. New York: McGraw-Hill/Irwin, 2004 Un diagrama de flujo estã ¡ diseã ±ado para representar un proceso, ya ocean en negocios o en lo individual, para mostrar la forma mã ¡s eficaz de completar un proceso. Un diagrama de flujo puede ayudar a visualizar lo que estã ¡ pasando y ayudar a la persona o personas que estã ¡n buscando en ellas para entender el proceso que se depict, y si es necesario, la forma de mejorarlo. Cada dã ­a, las personas realizan diferentes tareas que consumen una gran parte de su rutina diaria. En el siguiente artã ­culo, de un proceso especã ­fico ha sido identificado y, a continuaciã ³n un diagrama de flujo ha sido diseã ±ado para mostrar los diferentes factores que pueden afectar el proceso, asã ­ como la mã ©trica especã ­fica que identifica el proceso. En el diseã ±o de un diagrama de flujo, los resultados muestran cã ³mo la cantidad de tiempo podrã ­a ser minimizado y que hacer para que el proceso ocean mã ¡s eficiente. Roughage diferentes tipos de diag ramas de flujo, y cada uno tiene diferentes cuadros que representan distintas etapas en el proceso que se discute. Tambiã ©n pueden incluir distintos niveles de detalle, segã ºn ocean necesario y se muestra la estructura general del sistema. Diagramas de flujo suelen utilizar sã ­mbolos especiales, como los diamantes o rectã ¡ngulos. Un rectã ¡ngulo de bordes redondos representa las actividades de inicio y finalizaciã ³n. Un rectã ¡ngulo normal representa una actividad o un solo paso. Un diamante representa el punto de decisiã ³n. Las lã ­neas de flujo muestran la progresiã ³n de una etapa a la siguiente. Los factores que afectan el proceso de diseã ±o de tiempo dedicado a prepararse para el dã ­a serã ¡n los siguientes: 1.  ¿Por quã © me levanto de inmediato o no oprimã ­ el botã ³n de la alarma? 2.  ¿Està ¡ mi ropa planchada para el dã ­a o tienen que ser planchada? 3.  ¿Mis hijos preparan sus bultos para sus prã ¡cticas de volleyball en la noche o lo hace n en la maã ±ana? 4.  ¿Mi hijo de 11 aã ±os tienen practica o va a quedarse en casa? Si tiene prã ¡ctica, el tiempo debe ser aã ±adido en vestirse, lavarse la cara, cepillarse los dientes, desayunar. Todos y cada uno de estos factores puede afectar el tiempo de proceso, ya que potencialmente pueden afectar la cantidad de tiempo dedicado a cada tarea. Algunas otras medidas que podrã ­an incluirse en la rutina de la maã ±ana child los siguientes: 1) Lavarse los dientes 2) Ducha 3) Secarse el cabello 4) Aplicar el maquillaje La mã ©trica que se ha identificado para medir este proceso serã ¡ el tiempo. Estoy buscando una manera mã ¡s eficiente para agilizar el trã ¡fico de la maã ±ana con mis hijos a partir del tercer grado en dos semanas y un bebã © reciã ©n nacido en casa. El diagrama de flujo incorporarã ¡ la mã ©trica del tiempo para cada dã ­a de la semana que se estã ¡ estudiando, en un plazo de cinco dã ­as. El tiempo es un componente crã ­tico en la maã ±ana si me les pido a mis hijos preparar los bultos para las prã ¡cticas de volleyball a tiempo o salir por la puerta para el nombramiento de un mã ©dico u otra actividad programada. Los tiempos que se enumeran an incluir la colecta de datos durante cinco dã ­as de la semana del 3 de octubre de 2011. Lunes, 10/03/11 tiempo de preparaciã ³n: 32 minutos Martes, 10/04/11 tiempo de preparaciã ³n: 20 minutos Miã ©rcoles, 10//05/11 tiempos para prepararse: 33 minutos Jueves, 10/06/11 tiempo para prepararse: 15 minutos Viernes, 10/07/11 tiempo de preparaciã ³n: 19 minutos El tiempo all out gastado en el transcurso de cinco dã ­as: 119 minutos Un diagrama de flujo puede ayudar an una persona a decidir quã © medidas tomar para agilizar un proceso en el trabajo o en su vida individual. El diagrama de flujo que dise㠱ã © muestra claramente que el balance de agilizar la rutina de la maã ±ana, es necesario cuidar al mã ¡ximo la noche foremost. Esto incluye el planchado de la ropa, preparar los bultos, y tener a mi hijo ducha. El diseã ±o del diagrama de flujo muestra el tiempo additional que serã ¡ necesaria si cada paso que no se toma el cuidado de la noche foremost, o AM si me decido a golpear el botã ³n del despertador a las 6:00 a.m. Authentication OF ORIGINALITY I confirm that the appended paper is my unique work. I know about, and recognize my duties which are a piece of, the University of Phoenix Student Code of Academic Integrity. I assert that any segment of the paper which has been submitted already is credited and refered to all things considered, and that this paper has not been put together by any other person. I have distinguished the wellsprings of all data whether cited verbatim or summarized, all pictures, and all citations with references and reference postings. Along withâ citations and reference postings, I have utilized quotes to recognize citations of less than 40 words and have utilized square space for citations of at least 40 words. Nothing in this task damages copyright, trademark, or other licensed innovation laws. I further concur that my name composed on the line beneath is expected to have, and will have, a similar legitimacy as my written by hand signature

Analysis of The Darling, by Anton Chekhov Essay -- The Darling Essays

The story â€Å"The Darling† by Anton Chekhov, represents a lady that is forlorn, unreliable, and lacking completeness of oneself without a man in her life. This lady, Olenka, nicknamed â€Å"Darling† is caring, delicate and wistful. Olenka is depicted for being traditional, a lady who is dependent, tireless, and thought less. Despite the fact that, this story depicts that this lady, known as the Darling needs a male to be genuinely dependant upon, it seems as though she is a dark widow, she can win warmth, however without regard. Just ready to discover joy through the refection of the convictions of her sweethearts, she never develops inside the story. This story, â€Å"The Darling† presents how a lady, named Olenka, the principle character, who is additionally, in this story, known as the dear, has a dependence on others, and for the most carries on with an unfilled life. Olenka doesn't groups any character of her own; in this way, she just discovers joy in mirroring the conviction of her spouses/darlings. Olenka wants to be partial to somebody, and she as often as possible, fills her unfilled life through others, however simply in the wake of having time of lacking completeness in her self. Before all else apparently Olenka is sitting tight for Mr. Right, however it is actually thus, that Olenka, is dependant and requirements to adore and have the affection for other people. She discovers this adoration, this genuine love that most search for, in individuals, for example, her auntie, the school’s French ace, and even her dad. Afterward, Olenka winds up wedded to a man, by the name of, Kukin, and Kukin being her first spouse. Kukin is somebody whom Olenka feels she can't be without. Olenka sitting forlorn on her back yard, after a long time after night, and out to lunch, tuned in, one night, to Kukin, the chief of an outside theater, called the Tivoli, says, â€Å"Again!†. â€Å"It’s going to rain again!† significance there will be no work. She again on the next night, tunes in to him, as he, with a snicker of panic, says, â€Å"Well, downpour away, at that point! Flood the nursery, suffocate me!.....† Olenka attempting to turn out to be a piece of something and feel as though she has a reason, would tune in to Kukin with quiet gravity, and now and again there would be tears that would fill her eyes. Kukin proposed to Olenka. A while later damaging and getting a closer perspective on Olenka, he surrenders and says, â€Å"You darling!† After observing her neck and her full, fine s... ...end demonstrates to this peruser that Olenka has always been unable to satisfy this need she is searching for, this need to adore and to be cherished. Voloditchka and Sasha do return to this spot where Olenka is, yet with his significant other and the mother of his child, to accommodate. In Conclusion, this story depicts a lady who is uncertain, forlorn, and hoping to adore and to be cherished. This affection is something which Olenka looks for in guys, the two grown-ups, and young men, she thinks she discovers this adoration, in her spouses and, darling. She what she thinks to be love, in her first spouse, and afterward her second, yet the third male in her life, her sweetheart, known as Voldichka is there just for his fulfillment. Olenka gets the satisfaction of affection required y Voldichka. Olenka than attempts through a kid named Sasha, Voldichka’s child. It is consistent with this peruser that despite the fact that Olenka encountered these associations with these men and the kid, Sasha, she still never found a total satisfaction throughout everyday life. Olenka didn't encounter regard as a lady, yet somebody who might be there varying. Olenka never earned regard as most ladies do, she to this peruser just was a filler for other people, others of the sex known as male.

The Importance of Mobile Database Research Papers

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Research Paper on the Tudors Essay Topics

<h1>Research Paper on the Tudors Essay Topics</h1><p>If you're attempting to get that ideal article for your British history class, at that point you may be keen on exploring a few assets on the Tudors. Perhaps you've just perused a smidgen about them, or possibly you're searching for new points of view to your authentic study.</p><p></p><p>If this is the situation, at that point it's a smart thought to get an examination paper on the Tudors article subjects on your rundown. These are going to prove to be useful regarding helping you center your contemplations and lessen your nervousness about what you'll write.</p><p></p><p>The research paper on the Tudors will likewise assist you with figuring out how to improve your composing aptitudes and make your expositions all the more intriguing. A decent one will give you bits of knowledge into the characters of the time, data on the wars that were battled, and data on the ti mespan itself.</p><p></p><p>Some individuals figure they needn't bother with an examination paper on the Tudors since they don't think a lot about them. This isn't totally obvious, however. While you probably won't have a deep understanding of the Tudors, you can get a smart thought from an exploration paper on the Tudors exposition themes, which will give you the foundation you need.</p><p></p><p>A research paper on the Tudors article subjects can likewise assist you with increasing a superior comprehension of the timespan. Regardless of whether you're a history buff or not, you'll see you can gain so much from perusing a couple of articles, blog entries, and statements about the period. Regardless of whether you're not a history buff, you may in any case discover these sources helpful in increasing a comprehension of the timeframe and a portion of the individuals involved.</p><p></p><p>One of the best things a bout the paper themes is that it doesn't expect you to dig too profoundly into the history. Rather, it lets you get the nuts and bolts, yet keeps it brief and simple to understand.</p><p></p><p>There are such a significant number of assets out there on the Internet, you don't need to stress over perusing papers on the Tudors article points. In case you're simply beginning on your paper composing vocation, this is an incredible spot to begin, particularly in case you're stressed over having a ton of things to compose about.</p>

What Everybody Dislikes About All Night Essay Writing and Why

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With whatever you compose, be that as it may, you're think that its significantly more straightforward on the off chance that you prepare and I accept this is especially valid for expositions, which by and large require a solid structure that underpins you in making a particular contention. One staggering approach to do it is to sever your paper composing process into different stages (which will most likely compare to these periods of the creative cycle). </p>

Easy Process Analysis Essay Topics

<h1>Easy Process Analysis Essay Topics</h1><p>Easy process investigation article subjects are those that don't have an excessive number of capabilities. They can be utilized for a composed composition, for example, an examination paper, proposition, report, etc. In the event that you need to compose a straightforward paper, you can discover a lot of simple procedure examination exposition themes accessible online.</p><p></p><p>Some simple procedure investigation article points don't have such a large number of prerequisites, since they just require almost no in the method of composing abilities. You may very well need to figure out how to sort out your contemplations and your words so that you can introduce them in the most ideal manner to your peruser. Normally, these basic papers are for use in instructive classes, or for understudies who are at a beginning period in their scholastic career.</p><p></p><p>Some simple procedure investigation exposition points, in any case, request a lot from the author. These may be more confounded than a portion of the simple ones, however they are additionally all the more fascinating to peruse. Such expositions are helpful for individuals who are going for propelled instruction in their field. These are those for which you are required to place some idea into your article before the last draft is completed.</p><p></p><p>Some of the most effortless of the straightforward papers are those that just expect you to make the presentation and body of the exposition. The body of the paper is generally the more included part, since you should make a decent and persuading contention to the peruser. You may even need to compose a few sections, in light of your own judgment and realities, so you can unmistakably clarify how you come to the end results that you have shown up at.</p><p></p><p>There are additionally some simple procedure investigation paper themes that will expect you to compose a presentation that will diagram the extent of the exposition and the fundamental reason for the article. This presentation is the most significant piece of the paper, since it will be the main thing that your peruser will see and read.</p><p></p><p>Essays on points that include a great deal of detail may even expect you to compose more than one article. This is the place your capacity to sort out and orchestrate your considerations will come in handy.</p><p></p><p>These are only a portion of the simple procedure examination exposition themes that you can look into on the web. Much the same as numerous different things, there are bunches of different papers that can be composed on these points. Be that as it may, you can generally evaluate a couple of various papers, so you can discover something that interests to you.</p>

The Advantages of 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide

<h1> The Advantages of 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide </h1> <h2> The Appeal of 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide</h2> <p>It's a touch of confounding, yet we'll lead you through the methodology! It is the chief part of your work. It speaks with the judicious area of the psyche. Many individuals laud the capacity of such innovations to flexibly simple availability to data and encourage research and learning. In any territory, having solid composing aptitudes is very gainful. Space investigation isn't a special case. </p> <h2> The Meaning of 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide </h2> <p>Then we'll discuss the similitudes between the 2 courses, and afterward the distinctions. AP teachers get a score sheet demonstrating the individual score for all of their understudies, together with some score data and national midpoints. By and large, AP English Language and Composition test questions tend to fall into only a few classifications. The composite score is just a technique for consolidating the 2 scores such they are weighted effectively (for instance, for AP English, different decision is worth 45% and absolutely free reaction is 55%). </p> <h2> The Hidden Truth on 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide </h2> <p>Revision is among the most huge parts of composing a scholarly article. AP Language is likewise an extraordinary alternative on the off chance that you need to find out about characteristic science or building, since figuring out how to separate contentions and read genuine writings will presumably be more useful in your preferred field than breaking down verse and writing. </p> <p>Or your school might not have severe prerequisites at all, and you might be pondering in the occasion you should take both, one, or none. To prepare for these inquiries, reword everything which you read. There are heaps of approaches to deliver your last draft clear and totally liberated from botches in English. The brief gives you a wide number of books and plays you could expound on, yet in addition licenses you to break down any work of similar artistic legitimacy. </p> <p>Also, you will be increasingly alright with the test configuration and prepared to work quicker. You ought to expect only a couple of inquiries of this sort on the test. Perceive the truth about our top to bottom guide and why you should take them. Anyway you can't utilize precisely the same procedure for each AP test. The two tests have low pass costs and low five rates. The absolute initially is that they are both precise famous tests. Likewise read a thorough correlation between both tests.</p> <h2> How to Choose 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide</h2> <p>In case you have at least five minutes before the test is finished, you may utilize them in order to make your exposition as immaculate as could be expected under the circumstances. AP Language is an enormous way to deal with make those abilities in case you're not partial to verse and writing. Each answer requests the understudy to integrate at least three sources in the exposition. For example, on the off chance that you know without a doubt you wish to seek after building in school, at that point AP Language is undoubtedly the best choice. It's well worth perusing in case you're interested about exactly what the AP perusing resembles! The AP Reading is basically an enormous show. </p> <p>These techniques are simply some of the ones a creator may use to sort out thoughts. It is an incredible method to locate some additional focuses from your educator. It will uncover to you as a well-talented understudy who can write in different strategies and can fulfill all prerequisites. Just with the help of his own style joined, he can discover a response. They've a gathering of expert scholars with an enormous encounter. It is imperative to commit some time to learn special procedures utilized by the cutting edge essayists and researchers. Counsel your folks or mates to help you with your task. See our manual for choosing the appropriate number.</p> <h2>The 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide Trap </h2> <p>The end should be solid and clear. He utilizes the unmistakable way of communicating emotions. Keep every one of these inquiries in your musings and endeavor to give the appropriate responses. </p> <h2>Why Almost Everything You've Learned About 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide Is Wrong </h2> <p>After such practice, you will be in a situation to do it inside as you read, and you will have more prominent cognizance. You must uncover the final product of the creator's discourse and its effect. At the point when you form the expository investigation paper, remember that its foremost target is to clarify the impact of each framework that was utilized by the creator. Inside this bit of the scholastic composing piece, one must sum up all key powerful realities and contentions. This may not just uncover that you're wise and value the unpredictability of the sorts of issues you could be talking about on the test, yet may truly help fortify your contention, in that it's conceivable to anticipate forthcoming contentions against your help for your convictions, at that point sabotage them as you expound on them. For certain, you would invest most of your energy recorded as a hard copy body sections. Select the correct composing style and the correct change words. Adhere to the given layout or even modify the whole content utilizing your underlying strategy.</p> <h2>All About 2008 Ap Lang Free Response College Persuasive Essay Scoring Guide </h2> <p>If you lean towa rd the perusing for a class, you're substantially more slanted to finish everything and be keen on the assignments meaning you will get a superior evaluation. Ideally finding out about the 2 classes gave you a thought about which one you're inclining towards. Rather, to figure out which test is best for you, we should think about the two classes and the substance they spread. Notwithstanding, in spite of the way that the test and class designs are fairly comparable, the topic they tackle is incredibly extraordinary. Likewise called the class where you clarify each. You may be undeniably more intrigued by 1 class' perusing than another, and that is going to enable you to choose. Something else, make an arrangement to address your direction advocate to discuss which class is best for you.</p>

A Fools Guide to Topics for a Compare and Contrast Essay Explained

Understanding the Concept of Healthcare Topics For Academic Essay

Understanding the Concept of Healthcare Topics For Academic EssayMany schools expect academic essays to deal with medical topics for its essay writers. In order to write a well-researched, researched and up-to-date essay, an essay writer must be aware of the most frequently used topics in medical writing. This is because these topics are the subject matter that is only just becoming visible in mainstream academic topics and it therefore means that in order to come up with unique and original topics, an essay writer needs to be familiar with these new medical trends.Healthcare topics for academic essay are usually concerned with health care issues or the process of health care delivery. The topic could be a description of a clinical trial, a surgery, a care pathway or other treatment procedure. Most of the time, the topic can be a discussion on health topics for students that are relevant to everyday life. If you cannot use any medical terms in your topic, it is best that you take not e of the details so that when you need to go back to it later, you can easily remember it.The first kind of healthcare topics for academic essay is general health topics. General health topics are topics that are generally used by students in their normal academic activities. Such topics might include food and diet, human development, childhood diseases, health and nutrition. These topics are therefore topics that everyone knows about but also topics that require ample information on how to address the topic.The second kind of healthcare topics for academic essay is healthcare law topics. Healthcare law topics cover the workings of the legal system. These topics often pertain to areas like personal injury, pharmaceutical industry and compensation insurance.The third kind of healthcare topics for academic essay is epidemics and outbreaks of diseases and the related healthcare issues in these cases. These topics cover all the facets of healthcare crisis - from prevention and control o f disease, detection, treatment and control of the outbreak, especially the public reaction to the outbreak.The fourth kind of healthcare topics for academic essay is social, cultural and political perspectives on health and the economy. This topic has a particular focus on the national budget and its effect on health in general, public health promotion as well as social welfare issues.The fifth kind of healthcare topics for academic essay is clinical topics. These include subjects such as general medicine, family medicine, pediatrics, surgery, medicine and psychiatry. It is necessary that the student does his research well before he writes this section as he needs to present a balanced and accurate description of what he knows about medical practice in his healthcare topic.The sixth kind of healthcare topics for academic essay is the ethical dimensions of healthcare. This is where the discussion focuses on how hospitals and patients should interact and whether the medical instituti ons will lead a moralistic and unethical life.

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)