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@ -12,11 +12,11 @@ The initial motivation for this study was to create a system
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applicable to industrial burner controllers\footnote{Burner Controllers cover the disiplines of
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applicable to industrial burner controllers\footnote{Burner Controllers cover the disiplines of
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combustion, high pressure steam and hot water, mechanical control, electronics and embedded software.}.
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combustion, high pressure steam and hot water, mechanical control, electronics and embedded software.}.
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The methodology developed was designed to cope with
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The methodology developed was designed to cope with
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both the deterministic\footnote{Deterministic failure mode analysis traces failure mode effects} and probablistic approaches
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both the deterministic\footnote{Deterministic failure mode analysis, traces failure mode effects at the SYSTEM level to lower level causes in components or sub-systems.} and probablistic approaches
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\footnote{Probablistic failure mode analysis tries to determine the probability of given SYSTEM failure modes, and pfrom these
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\footnote{Probablistic failure mode analysis tries to determine the probability of given SYSTEM failure modes, and pfrom these
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can determine an overall failure rate, in terms of probability of failure on demand, or failure in time (or Mean Time to Failure (MTTF).}.
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can determine an overall failure rate, in terms of probability of failure on demand, or failure in time (or Mean Time to Failure (MTTF).}.
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\glossary{name={safety critical},description={A safety critical system is one in which its failure may result in death or serious injury to humans, an environmental catastrophe or severe loss or damage}}
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\glossary{name={safety critical},description={A safety critical system is one in which its failure may result in death or serious injury to humans, an environmental catastrophe or severe loss or damage}}
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\fmodegloss
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\paragraph{Safety Critical Controllers, knowledge and culture sub-disiplines}
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\paragraph{Safety Critical Controllers, knowledge and culture sub-disiplines}
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The maturing of the application of the programmable electronic controller (PEC)
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The maturing of the application of the programmable electronic controller (PEC)
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@ -4,15 +4,30 @@
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\ifthenelse {\boolean{paper}}
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\ifthenelse {\boolean{paper}}
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{
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{
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\abstract{ This chapter looks at current methodologies
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\abstract{
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This paper looks at current methodologies
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for static analysis of safety critical systems
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for static analysis of safety critical systems
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and looks at the statistical justifications for their application.}
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and looks at the statistical justifications for their application.}
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}
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}
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{}
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{
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This chapter looks at the current state of
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safety critical systems
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and provides background to concepts and
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standard practises.
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Its aims to bridge
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}
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\section{Introduction}
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\section{Introduction}
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\section{Product}
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\subsection{life cycle}
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\subsection{parts list}
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Important document, used for quality inspection and production validation etc
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\subsubsection{BOM}
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\subsection{Components and Sub-systems}
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How can have failure modes
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\section{Safety and Reliability}
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\section{Safety and Reliability}
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- How these are different.
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- How these are different.
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@ -85,6 +85,7 @@
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\newcommand{\fmmdgloss}{\glossary{name={FMMD},description={Failure Mode Modular De-Composition, a bottom-up methodolgy for incrementally building failure mode models, using a procedure taking functioal groups of components and creating derived components representing them, and in turn using the derived components to crate higher level functional groups, and so on, that are used to build a failure mode model of a SYSTEM}}}
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\newcommand{\fmmdgloss}{\glossary{name={FMMD},description={Failure Mode Modular De-Composition, a bottom-up methodolgy for incrementally building failure mode models, using a procedure taking functioal groups of components and creating derived components representing them, and in turn using the derived components to crate higher level functional groups, and so on, that are used to build a failure mode model of a SYSTEM}}}
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\newcommand{\fmodegloss}{\glossary{name={failure mode},description={The way in which a failure occurs. A component or sub-system may fail in a number of ways, and each of these is a
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\newcommand{\fmodegloss}{\glossary{name={failure mode},description={The way in which a failure occurs. A component or sub-system may fail in a number of ways, and each of these is a
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failure mode of the component or sub-system}}}
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failure mode of the component or sub-system}}}
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\newcommand{\fmeagloss}{\glossary{name={FMEA}, description={Failure Mode and Effects analysis (FMEA) is a process where each potential failure mode within a SYSTEM, is analysed to determine SYSTEM level failure modes, and to then classify them {\wrt} percieved severity}}}
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@ -210,6 +210,8 @@ gives a risk probability number (RPN), given by $RPN = S \times O \times D$.
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This gives in effect
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This gives in effect
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a prioritised `to~do~list', with higher $RPN$ values being the most urgent.
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a prioritised `to~do~list', with higher $RPN$ values being the most urgent.
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\fmeagloss
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\subsubsection{ FMEA weaknesses }
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\subsubsection{ FMEA weaknesses }
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\begin{itemize}
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\begin{itemize}
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@ -510,7 +512,7 @@ be linked to a dangerous system level failure in an FMEDA study.
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%guess work than science.
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%guess work than science.
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%
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%
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With FMEDA, there is no rigorous cause and effect analysis for the failure modes
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With FMEDA, there is no rigorous cause and effect analysis for the failure modes
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and how they interact on the micro scale (the components adjacent to them in terms of functionality).
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and how they interact on the micro~scale (the components adjacent to them in terms of functionality).
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Unintended side effects that lead to failure can be missed.
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Unintended side effects that lead to failure can be missed.
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Also component failure modes that are not
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Also component failure modes that are not
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dangerous, may be wrongly assigned as dangerous simply because they exist in a critical
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dangerous, may be wrongly assigned as dangerous simply because they exist in a critical
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@ -539,9 +541,6 @@ and its international analog standard IOC5108.
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\end{itemize}
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\end{itemize}
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%AND then how we can solve all there problems
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%AND then how we can solve all there problems
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\subsection{Deterministic FMEA}
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EN298 no two individual component failures may give rise to a dangerous condition.
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\section{FMEDA Failure effect Mode Diagnositic Analysis}
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\section{FMEDA Failure effect Mode Diagnositic Analysis}
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@ -838,6 +837,9 @@ Discuss hardware failsafes (good example over pressure saefty values).
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Keep relating these back to bayes theorem.
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Keep relating these back to bayes theorem.
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\subsection{Deterministic FMEA}
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# FMEA cannot handle simultaneous failure modes.....
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EN298 no two individual component failures may give rise to a dangerous condition.
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typeset in {\Huge \LaTeX} \today
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typeset in {\Huge \LaTeX} \today
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