Fault Tree Analysis of Sequential Systems

Shaeiwitz, Joseph A.; Lapp, Steven A.; Powers, Gary J.

doi:10.1021/i260064a017

Cited by 26 publications

(12 citation statements)

References 3 publications

(4 reference statements)

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“…Lapp and Powers algorithm has been extended by Shaeiwitz et al (1977) so that it may be applied to batch processes. The arcs of the SDG's are made conditional on system events so that successive behaviour within the batch system can be modelled.…”

Section: Z3 Lz Constructing Fauft Treesfrom Signed Directed Graphsmentioning

confidence: 99%

Creating Signed Directed Graph Models for Process Plants

Palmer

Chung

2000

Ind. Eng. Chem. Res.

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The concept of qualitative modeling is briefly described. This paper focuses on the use of signed directed graphs to model fault propagation in process plants. It is common to use a unit-based approach for modeling. Two kinds of problems, which arise when constructing unit-based qualitative models, are identified: (1) The models are difficult to construct. (2) Ambiguities due to multiple causal paths may occur when the models are combined. A method that allows models to be built simply and correctly is proposed. The method incorporates features from the knowledge acquisition field, and a computer-aided modeling tool, Equipment Model Builder, has been built to support this method. A new modular approach is presented which overcomes the problem of ambiguous inference when qualitative models are combined. Two case studies were used to evaluate the method developed and the support tool.

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Section: Z3 Lz Constructing Fauft Treesfrom Signed Directed Graphsmentioning

confidence: 99%

Creating Signed Directed Graph Models for Process Plants

Palmer

Chung

2000

Ind. Eng. Chem. Res.

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“…Finally, the potential of practical applications is limited by the inherent nature of digraph models. In particular, it is not convenient to use them for describing dynamic systems in sequential operations; see, for example, Shaeiwitz et al (1977), and thus the current version of IHAS is incapable of carrying out the procedure HAZOP analysis.…”

Section: Applicationsmentioning

confidence: 99%

“…Generally speaking, digraph is one of the most popular models. Numerous publications exist in the literature (Shaeiwitz et al, 1977;Chamow, 1978;Lambert, 1979;Lapp and Powers, 1979;Allen and Rao, 1980;Cummings et al, 1983;Allen, 1984;Andrews and Morgan, 1986;Andrews and Brennan, 1990). Although it has been shown in these works that the digraph-based techniques are useful in practical applications, the original method proposed by Lapp and Powers (1977) is still deficient under certain conditions (Andow, 1980(Andow, , 1981Galluzzo and Andow, 1984).…”

Section: Introductionmentioning

confidence: 99%

Prototype for intergated hazard analysis

et al. 1997

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The prototype of an integrated hazard-analysis system (IHAS) was developed. Essentially any process can be analyzed with this sofhvare if the system topology is correctly supplied by the user. Since all algorithms adopted are digraph-based, the system digraph must be constructed first with IHAS. The embedded feedfonvard and feedback loops are then identified and classified. On the basis of this information, three widely accepted hazard-assessment procedures-FTA, ETA, and HAZOP -can be peflormed automatically. From the results obtained in practical applications, one can see that the quality of hazard analysis is indeed improved if IHAS can be used as an aid to the human experts.

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“…The directed edge (G1,C2) enters node Gz and leaves node G1 and designates that the variable GI affects the variable Gz (Shaeiwitz et al, 1977;Govind, 1978a).…”

Section: I N T E R a C T L O N A Nmentioning

confidence: 99%

Control system synthesis strategies

Govind¹,

Powers²

1982

AIChE Journal

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= stream function 7 = nondimensional time Subscripts S = steady state conditions W m = conditions at the wall = conditions far away from the wall Superscript * = physical variablesThis paper is concerned with an important aspect of process control designsynthesis of the control structure. Synthesis of control structures has long been practiced by experienced control engineers, who relied on intuition, insight and judgment to pick a feasible solution from the vast number of alternatives that were possible. This paper describes a systematic procedure to generate these alternatives based on the cause-andeffect representation of the process. The final product is a set of control schemes from which the final system may be selected or evolved. The work is significant in that it is the first attempt to apply non-numerical problem-solving techniques to the problem of synthesizing process control structures. As such, it gives a new way of studying and teaching chemical process control. SCOPEWhich variables should be measured, which inputs should be manipulated, and what links should be made between these two sets? This is the essence of the synthesis of control structures in the chemical process industries. This problem is routinely solved by experienced engineers who have the ability to simultaneously consider: 1. 2.3. 4. 5.The economic, safety and reliability goals of a given process The steady-state and dynamic behavior of the complete process and of the pieces of equipment within it The interaction which might occur between control structures The failure modes of the components within the process including the process operator Possible changes in the process to improve control These engineers have evolved logical procedures for proceeding from loosely defined flowsheets and goals to welldefined piping and instrument diagrams (P&ID's). Most of these procedures do not involve the use of detailed dynamic models of the process. How do they do it? This paper is our initial attempt to capture at least part of the logic involved in transforming steady-state flow diagrams into P&IDs.Our approach is based on three main ideas:1. The models used in the synthesis of control systems must be simple. 4.Environmental Regulations: Various federal and state laws may specify that the concentrations, temperatures, flowrates, or combinations of these must be within certain limits. For example, the concentration of vinyl chloride in the air leaving a PVC drier must contain less than 1 ppm when it is discharged into the environment. Economics:(a) Yield: The yield of a reactor may depend on the inlet temperature, concentrations, flowrate, or phase.Hence, it may be important, as in the chlorination of alkenes, to keep the concentration of chlorine in the reactor feed to 2.5 mol % or less.(b) Energy: The economic operation of a process often depends on the efficient use of energy within the process. A control objective might be to maintain the approach temperature of the ethylene column precooler at 2°C. The safety parameters, operational cons...

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Fault Tree Analysis of Sequential Systems

Cited by 26 publications

References 3 publications

Creating Signed Directed Graph Models for Process Plants

Creating Signed Directed Graph Models for Process Plants

Prototype for intergated hazard analysis

Control system synthesis strategies

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