State-based modelling in hazard identification

Reliability Engineering & System Safety, 2009

A widely used hazard identification technique within the process industry is HAZOP (hazard and operability study). To overcome the repetitive and time-consuming nature of the technique automated systems are being developed. This work considers batch processes, in which material undergoes processing in distinct stages within the plant equipment items according to a set of operating procedures, rather than each equipment item remaining in a "steady state", as is normal for continuous plants. In batch plants deviations which can lead to hazards can arise both from deviations from operating procedures and process variable deviations. Therefore, the effect of operator actions needs to be considered. CHECKOP is an automated batch HAZOP identification system being developed as a joint project between HAZID Technologies Ltd and Loughborough University. CHECKOP uses a state-based approach to HAZOP analysis. CHECKOP takes a plant description and a set of operating instructions as input and produces a HAZOP report automatically. The overall system architecture and the details of the major components of the systems will be described. Examples of incorrect plant operation along with the resulting output generated by CHECKOP will be shown. The advantages and limitations of CHECKOP will be discussed.

Journal of Loss Prevention in the Process Industries, 1997

In this article, a new methodology for developing a chemical process model suitable for automated hazard analysis is presented. The devised model is composed of four sub-models: unit function model, unit behaviour model, organizational knowledge base and material knowledge base. Each represents a chemical process in terms of function, behaviour, structure, and material property, respectively. These four models are capable of capturing the information which is needed for hazard analysis but is not captured by any other existing model. 0 1997 Elsevier Science Ltd. All rights reserved

Algerian Journal of Signals and Systems

The main objective of this paper is to present the use of D-higraph to perform hazard analysis. D-higraph is a functional modeling technique; it is used to capture the functional and structural aspects of process plants. It presents not only the functionality of the system with its goals, but also the relation existing between these functions/goals and the devices that perform/achieve them. This work is applied to the study of an industrial case in a petroleum plant in Skikda refinery.

IFAC-PapersOnLine, 2018

In a previous research, a tool integrating the HAZOP analysis method and Coloured Petri Net formalism to support the analysis carried out by specialists during a HAZOP brainstorming session has been provided. In that work, the tool was used to simulate the behaviour of a few components of a chemical plant while diverse abnormal scenarios occur. In the present work, other types of components have been modelled and the behaviour of the plant has been simulated demonstrating its ability to model more complex components, simulate diverse failure types, hence, reducing the total time required to complete the analysis compared to a standard HAZOP assessment approach.

Industrial & engineering chemistry …, 2000

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.

Chemical Engineering Transactions, 2016

In the age of chemical processes operated at extreme pressures and temperatures it is necessary to perform a detailed process safety analysis. Hazard and operability study (HAZOP) is one of the most used and highly efficient techniques for the identification of potential hazards and operability problems. Model-based HAZOP study is based on the implementation of a detailed mathematical model of chemical productions. Possibilities and limitations of model-based HAZOP study using Aspen HYSYS are discussed in this work. Results of numerical simulations are collected and directly transformed into standard HAZOP tables. Advantages and disadvantages of the presented software tool are shown in the process hazard analysis of a chemical production with strong nonlinear behavior, an ammonia synthesis reactor system.

Computers & Chemical Engineering, 2000

Process safety, occupational health and environmental issues are ever increasing in importance in response to heightening public concerns and the resultant tightening of regulations. The process industries are addressing these concerns with a systematic and thorough process hazards analysis (PHA) of their new, as well as existing facilities. Given the enormous amounts of time, effort and money involved in performing the PHA reviews, there exists considerable incentive for automating the process hazards analysis of chemical process plants. In this paper, we review the progress in this area over the past few years. We also discuss the progress that has been made in our laboratory on the industrial application of intelligent systems for operating procedure synthesis and HAZOP analysis. Recent advances in this area have promising implications for process hazards analysis, inherently safer design, operator training and real-time fault diagnosis.

Journal of Loss Prevention in the Process Industries, 2017

HAZOP method does not provide the completeness of risk analysis, especially indicating all causes of deviations of the process parameters which are the main risk. Particular difficulties occur when complex objects are concerned, which are decomposed into nodes for the needs of the HAZOP analysis. In the majority of cases, particular nodes are not independent-there are interactions between them, that may be overlooked. The presence of feedbacks between the nodes in the process is particularly dangerous. This paper proves that the completeness of this analysis may be increased by applying the qualitative model of the process in the form of a graph of a process. Definition of the graph of a process is provided, as well as discussion on the methodology of the process modelling with the use of such graph. Intelligent Accident Prevention System is also presented allowing for supporting HAZOP analysis by a model in form of a graph of a process.

Safety Science, 2018

To improve industrial safety, several hazard analyses of processes are available. The HAZOP is one of the most frequently employed and analyzes hazardous process deviations based on heuristic knowledge. Despite the wide application of the technique, new developments are especially important to enhance industrial safety. In this sense a systematic procedure is proposed for hazardous process deviation identification and analysis that employs process simulation and heuristic evaluation. Process simulation enables the analysis of process behaviors caused by device malfunctions and the performance of deviation analysis that considers the process non-linearities and dynamics. A comparison between the HAZOP and the proposed procedure is presented using a pump startup system case study, wherein the better system interpretation and results regarding abnormal process conditions are highlighted. A second case study applies the procedures to an offshore oil production process, showing the advantages of employing process simulation for studying deviation during a dynamic process's abnormal behavior.

Computers & Chemical Engineering, 1997

Hazard and Operability analysis (HAZOP) is a popular method for performing hazards analysis of che,_ ical plants. It is labour-and knowledge-intensive and could benefit from automation. Recently, a knowledge based framework for automating HAZOP analysis, called HAZOPExpert, was proposed. Dimitriadis et al. 0995) proposed a quantitative model based approach for hazard evaluation, This approach used a dynamic model of the plant and bounds on the process disturbances (including failure modes) and parameters to identify possible unsafe situations. The qualitative analysis performed by HAZOPExpert is thorough and cumputationally efficient, However, in some situations it suffers from ambiguity. The quantitative analysis has the capability to perform an exact analysis without ambiguities, but a complete quantitative analysis can he computationally prohibitive, in this paper, we present an integrated qualitative-quantitative approach for hazard identification and evaluation which overcomes the shortcomings of qualitative and quantitative methods. In the integrated framework, the broad details of a particular hazardous scenario are extracted by inexpensive qualitative analyses. A detailed quantitative analysis is then performed if needed and only on those parts of the plant identified by the qualitative analysis to contribute to the hazard. This framework is illustrated using an industrial case study.