消防系统运行可靠性的估计外文及翻译.doc

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文献、资料题目：Estimates of the Operational Reliability
of Fire Protection Systems
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院 （部）： 市政与环境工程学院
专 业： 给水排水工程
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外文文献：　
Estimates of the Operational Reliability of Fire Protection Systems
For 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 secure．The 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 fall．The standard is slated to go into effect next year．
Richard W. Bukowski, P.E.
Senior Engineer
MST Building and Fire Research Laboratory
Gaithersburg, MD 20899-8642 USA

Edward K. Budnick, P.E., and Christopher F. Scheme1
Vice President Chemical Engineer
Hughes Associates, Inc Hughes Associates, Inc.
Baltimore, MD 21227-1652USA Baltimore, MD 2 1227-1652USA

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 fireto permit occupant notification and escape, fire servicenotification, 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 building’s 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 component’s 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

Several broad based studies were identified that reported reliability estimates for fire detection
and fire suppression systems as well as construction compartmentation. These included (1) the
Warrington Fire Research study [1996] in the United Kingdom, (2) the Australian Fire
Engineering Guidelines [Fire Code Reform Center, 19961,(3) a compilation of fire statistics for
Tokyo, Japan [TokyoFire Department, 19971,and (4)results from a study of in situ performance
of fire protection systems in Japan [Watanabe, 19791.

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 Australian Fire Engineering Guidelines were developed as the engineering code of practice
supporting the new performance-based Building Code of Australia. Following the methods in
this guide, building fire safety performance is evaluated for smouldering, flaming non-flashover,
and flaming flashover fires. The performance (ie., probability of detecting, extinguishing or
controlling a fire event) of fire safety systems is predicted, accounting explicitly for the
operational reliability of the particular system. Reliability estimates from an expert panel rather
than from actual data are provided in the Guideline for this purpose.

Finally, operational reliability data were reported in two separate studies in Japan. One study
involved evaluation of fire incident reports from the city of Tokyo during the period from 1990
to 1997 [TokyoFire Department 19971. The other study involved review of fire incident reports
throughout Japan during an earlier time period ending in 1978 [Watanabe 19791.

Table 1provides a summary of the reliability estimatesprovided in these studies. Significant
differences exist in the individual reliability estimates depending on the parameters used to
develop these estimates. Depending on the required accuracy in predicting future operational
performance of fire protection systems, dependence on the range of estimates from these studies
could significantly alter the results. In addition, the uncertainty associated with a single estimate
of reliability or the existence of potentially important biases in the methods used to derive these
estimates may limit their direct usefulness in addressing either operational or performance
reliability of fire protection systems.

Table 1. Published Estimates for Fire Protection Systems Operational Reliability
(Probability of Success (YO))

NA= Not Addressed

Review of Available Reliability Data

Due to the limited applicability of the reliability estimates published in the general literature, the
literature review was extended in an effort to (1) develop an improved understanding of the
elements of each of the three strategies under consideration that influence reliability, and (2)
identify and evaluate quantitative data regarding individual system operability and failure rates.

Automatic Suppression Systems (i.e., sprinkler systems)

Table 2 provides a summary of reported operational reliability estimates from several studies that
evaluated actual fire incidents in which automatic sprinklers were present. As a group, these
studies vary significantly in terms of the reporting time periods, the types of occupancies, and the
level of detail regarding the types of fires and the sprinkler system design.

The estimates presented in Table 2 generally indicate relatively high operational reliability for
automatic sprinkler systems. While some of the references include fire “control” or
“extinguishment” as part of the reliability assessment, the reported data were not consistent.
Therefore, operational reliability was assumed to be limited to sprin