Introduction to Safety Science
For many years "safety technology" has constituted the essential instrument for the prevention of accidents as a direct result of handling new technology. Its awareness of the interactions prevalent in natural science causes safety technology to act on th
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A. Kuhlmann
Introduction to Safety Science With 234 Illustrations
Springer-Verlag New York Berlin Heidelberg Tokyo
A. Kuhlmann TVV Rheinland Postfach 10 17 50 SOOO KOIn 1 Federal Republic of Gennany
Library of Congress Cataloging in Publication Data Kuhlmann, A. (Albert) Introduction to safety science. Bibliography: p. Includes index . 1. Industrial safety. 2. System safety. I. Title. 85-20805 620.8'6 TS5.K85 1985 Tille of Original Gennan Edition: Einfiihrung in die Sicherheitswissenschajl, respectively the state Z. = 1, occurs is (4-19)
The Boolean linkages of the state variables Zi are equivalent to corresponding incident linkages. For example , As = AI /\ A2 /\ ... /\ A" means that the undesirable system incident will occur only when all components behave in an undesirable way . The statement Zs "" Z I /\ Z2 /\ . . . /\ Z2 indicates that the state variable Z, of the system is exactly 1 when the state variable Zi of the components are 1. These statements are equivalent.
4.2 Safety Analysis Work Methods
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Thus the following con nection results for the system description: Linkage of incidents Ai' Ai Equivalent Boolean function of state variables Z,. Equivalent mathematical system funct ion if's(Z;, ... , Zn)
For several basic forms of component link age, the Boolean system funclion, the mathematical system funct ion , and the probability q, are shown in Table 4.2. The assigned graphic presentation as it is used in th e case of fa ult trees is completed (see Section 4.2.2). In the case of the "AND " component linkage, the system failure occurs precisely when all components fail; in the case of the "OR" linkage , the system failure occurs when at least one of the components fai ls. The other linkages are combinations of both. In the formulation of the Boolean linkage funct ions , the name of the component is used to designate the state variables , for example , K], .. . ,Kn instead of Z], ... , Z". A component Kj can also represent a partial system made up of subcomponents and its behavior can be described by certa in linkage rules. In reliability theory , the state variables are frequently defined in a complementary manner by assigning Z ,: 0 to the failure and the va lue Z= 1 to the desired behavior. In standardized procedures used in safety analysis, the form used here has been successful (see Section 4.2.2) [4-10], [4-11[. Distribution Functions and Staristical Characteristic Quamities. The occur· rence probabilities of specifi c incidents involving components or subsystems of a complete system depend on properties with statistically distributed values and which can be described by distribution functions. In addition to the distribution function , a ew f types of characteristic data which are of particular interest in safety analysis will be discussed below. The s tochastic variable X and the parameter x are given. If the parameter x is permitted to run continuously from - x to +::c and the probability for values x ~ x is determined, the distribution function
F(x) = W(X5x)
(4-20)
is obtained. If X
