外文翻译消防系统运行可靠性的估计本科毕业论文.doc

外文文献：Estimates of the Operational Reliability of Fire Protection SystemsFor the past three years，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government information secureThe organization is in the final stages of an open process of selecting one or more algorithms，or data-scrambling formulas，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summer or early fallThe standard is slated to go into effect next year INTRODUCTION Background Fire protection strategies are designed and installed to perform specific functions. For example, a fire sprinkler system is expected to control or extinguish fires: To accomplish this, the system sprinklers must open, and the required amount of water to achieve control or extinguishment must be delivered to the fire location. A fire detection system is intended to provide sufficient early warning of a fire to permit occupant notification and escape, and in some cases activation of other fire protection features (e.g., special extinguishing systems, smoke management systems). Both system activation (detection) and notification (alarm) must occur to achieve early warning. Construction compartmentation is generally designed to limit the extent of fire spread as well as to maintain the buildings structural integrity as well as tenability along escape routes for some specified period of time. In order to accomplish this, the construction features must be fire “rated” (based on standard tests) and the integrity of the features maintained. The reliability of individual fire protection strategies such as detection, automatic suppression, and construction compartmentation is important input to detailed engineering analyses associated with performance based design. In the context of safety systems, there are several elements of reliability, including both operational andperfornzance reliability. Operational reliability provides a measure of the probability that a fire protection system will operate as intended when needed. Performance reliability is a measure of the adequacy of the feature to successfully perform its intended hnction under specific fire exposure conditions. The former is a measure of component or system operability while the latter is a measure of the adequacy of the system design. The scope of this study was limited to evaluation of operational reliability due primarily to the form of the reported data in the literature. In addition to this distinction between operational and performance reliability, the scope focused on unconditional estimates of reliability and failure estimates in terms offail-dangerous outcomes. A discussion of these terms is provided later in the paper. Scop This paper provides a review of reported operational reliability and performance estimates for (1) fire detection, (2) automatic suppression, and to a limited extent ，(3) construction compartmentation. In general, the reported estimates for fire detection are largely for smoke detectiodfire alarm systems; automatic sprinklers comprise most of the data for automatic suppression, and compartmentation includes compartment fire resistance and enclosure integrity. It should be noted that in some cases the literature did not delineate beyond the general categories of “fire detection” or “automatic suppression,” requiring assumptions regarding the specific type of fire protection system. Several studies reported estimates of reliability for both fire detection and automatic sprinkler system strategies. However, very little information was found detailing reliability estimates for passive fire protection strategies such as compartmentation. A limited statistical based analysis was performed to provide generalized information on the ranges of such estimates and related uncertainties. This latter effort was limited to evaluation of reported data on detection and suppression. Insufficient data were identified on compartmentation reliability to be included. This paper addresses elements of reliability as they relate to fire safety systems. The literature search that was performed for this analysis is reviewed and important findings and data summarized. The data found in the literature that were applicable to sprinkler and smoke detection systems reliability were analyzed, with descriptive estimates of the mean values and 95 percent confidence intervals for the operational reliability of these in situ systems reported. ELEMENTS OF RELIABILITY ANALYSIS There is considerabIe variation in reliability data and associated anaIysesreported in the literature. Basically, reliability is an estimate of the probability that a system or component will operate as designed over some time period. During the useful or expected life of a component, this time period is “reset” each time a component is tested and found to be in working order. Therefore, the more often systems and components are tested and maintained, the more reliable they are. This form of reliability is referred to as unconditional. Unconditional reliability is an estimate of the probability that a system will operate “on demand.” A conditional reliability is an estimate that two events of concern, i.e., a fire and successful operation of a fire safety system occur at the same time.Reliability estimates that do not consider a fire event probability are unconditional estimates. Two other important concepts applied to operational reliability arefuiled-safe andfailed- dangerous.when a fire safety system fails safe, it operates when no fire event has occurred. A common example is the false alarming of a smoke detector. A fire safety system fails dangerous when it does not function during a fire event. In this study, thefailed-dangerous event defines the Operational probability of failure (1-reliability estimate). A sprinkler system not operating during a fire event or an operating system that does not control or extinguish a fire are examples of this type of failure. The overall reliability of a system depends on the reliability of individual components and their corresponding failure rates, the interdependencies of the individual components that compose the system, and the maintenance and testing of components and systems once installed to veri operability. All of these factors are of concern in estimating operationaz reliability. Fire safety system performance is also of concern when dealing with the overall concept of reliability. System performance is defined as the ability of a particular system to accomplish the task for which it was designed and installed. For example, the performance of a fire rated separation is based on the construction components ability to remain intact and provide fire separation during a fire. The degree to which these components prevent fire spread across their intended boundaries defines system performance. Performance reliability estimates require data on how well systems accomplish their design task under actual fire events or full scale tests. Information on performance reliability could not be discerned directly from many of the data sources reviewed as part of this effort due to the form of the presented data, and therefore, it is not addressed as a separate effect. The cause of failure for any type of system is typically classified into several general categories: installation errors, design mistakes, manufacturing/equipment defects, lack of maintenance, exceeding design limits, and environmental factors. There are several approaches that can be utilized to minimize the probability of failure. Such methods include (1) design redundancy, (2) active monitoring for faults, (3) providing the simplest system (i.e., the least number of components) to address the hazard, and (4)a well designed inspection, testing, and maintenance program. These reliability engineering concepts are important when evaluating reliability estimates reported in the literature. Depending on the data used in a given analysis, the reliability estimate may relate to one or more of the concepts presented above. The literature review conducted under the scope of this effort addresses these concepts where appropriate. Most of the information that was obtained from the literature in support of this paper were reported in terms of unconditional operationaZ reliability, i.e., in terms of the probability that a fire protection strategy will not faiZ dangerous. LITERATURE REVIEW A literature search was conducted to gather reliability data of all types for fire safety systems relevant to the protection strategies considered: automatic suppression, automatic detection, and compartmentation. The objective of the literature search was to obtain system-specific reliability estimates for the performance of each type of fire safety system as a function of generic occupancy type (e.g., residential, commercial, and institutional). Sources of information included national fire incident database reports, US Department of Defense safety records, industry and occupancy specific studies, insurance industry historical records and inspection reports documented in the open literature, and experimental data. Reports on experimental work and fire testing results were utilized only when fire detection, automatic suppression, or compartmentation strategies were explicitly evaluated. Tests of systems used for qualification, approval, or listing were also reviewed for information on failure modes. Published data from the United Kingdom, Japan, Australia, and New Zealand were included. General Studies The Warrington Fire Research study addressed the reliability of fire safety systems and the interaction of their components. A Delphi methodology was used to develop discrete estimates of the reliability of detection and alarm systems, fire suppression systems, automatic smoke control systems, and passive fire protection (e.g., compartmentation). The data obtained from the spray system, another important limitation is that most of the Automatic Sprinkler System records sprinkler accident. In these studies, very limited accident data with reference to the rapid response or a suitable water jet technology. Assess the reliability of the appropriate sprinkler system should be particularly concerned about several factors, including (1) allows coverage within, (2) lower water supply capacity, (3) remote control or alarm systems have great potential in the fire . Based on this, there are other factors related to these technologies (such as maintenance level) can directly affect the operational reliability of these types of Automatic Sprinkler System. In addition, you also need to resolve these problems, the system data, but based on later observations and general housing is generally less likely to maintain normal, some designed to ensure the residence what spray system reliability may be reduced. Fire detection or alarm systemsThe fire district to rely on various types of equipment such as: doors (including fixed equipment), wall, floor / ceiling penetration holes, windows, fire shutter, smoke materials and buildings. When the fire district is considered to be the focus in the fire plan, in the literature, there is little data that the individual components of the operating role in the fire district. The single is mentioned for the building assessment and operational reliability WARRIGTON research and the Australian Fire Engineering Index. These assessments are based entirely on expert judgment. Therefore does not provide more in-depth analysis.Automatic sprinkler systems analysis On Table 2, the sprinkler system reliability analysis is to analyze according to the type of each live. It should be noted that only one source MILNE, 1959 on the reliability of public buildings and residential housing estimates, and these early data do not provide the reliability of the data of modern residential sprinklers. The distribution histogram of Figure 1 lists the reliability estimates for each housing type. Average and 95% confidence interval limit is suitable for general residential (in the study does not distinguish between commercial buildings, the category of residential buildings and public buildings) and commercial buildings, and is applicable to the building (commercial, public buildings, residential) reliability assessment. These results are shown in Table 4. Commercial buildings and public buildings, reliability assessment, the average of control in other residential type 95% confidence interval. Livable and public buildings in a single point estimate, an increase of some useful things and operational reliability, and also increased the capacity of the database. 18 estimated four separate categories. However, the point on residential and public buildings of the estimates should not be used alone to draw any conclusions. The reliability of commercial buildings, residential and construction is estimated to provide some useful information. Based on the analysis of the sprinkler system can make use of the data is the reliability of operation is estimated at more than 88%, if you do not consider commercial buildings, the reliability of the sprinkler system can reach more than 92%. However, the judge this particular sprinkler system with those mentioned in the assessment system similarity is very important. The reliability of the commercial buildings is in the range 80-98%, 94-98% in the general construction. Fire detection system analysis The data on estimates of the reliability of fire detection system is comprehensive. This data spans a decade, and every year the Reliability Assessment Report (reflected in Table 3), it is done for the housing of a variety of different uses. Where the analysis is based on the use of the house divided into several building level. After each use housing derived data and then calculate the reliability of each housing estimates. Figure 2 shows the reliability estimates of all smoke detectors on all residential types. These housing types in the average reliability estimates and 95% confidence interval estimate for separate analysis. The results are listed in Table 5, for each type of results are significantly different. Confidence interval from the spray system reliability for a variety of residential types of estimated confidence intervals do not overlap. This may make more data for the analysis of the smoke detectors, are listed in Table 5, the reliability of various residential types of smoke detectors is estimated to determine the reason for the difference of non-relevant data beyond the scope of this analysis.Summary and conclusions The above analysis can easily be applied to other fire operation of the system reliability