Identifying hazards is fundamental for ensuring the safe design and operation of a system in process plants and other facilities. Several techniques are available to identify hazardous situations, all of which require their rigorous, thorough, and systematic application by a multi-disciplinary team of experts. Success rests upon first identifying and subsequently analyzing possible scenarios that can cause accidents with different degrees of severity. While hazard identification may be the most important stage for risk management, it depends on subjectivity issues (e.g., human observation, good judgment and intuition, creativity, expertise, knowledge) which introduce bias. Without a structured identification system, hazards can be overlooked, thus entailing incomplete risk-evaluations and potential loss. The present Thesis is focused on developing both managerial and technical aspects intended to standardize one of the most used techniques for hazard identification; viz. HAZard & Operability (HAZOP) study. These criteria have been carefully implemented not only to ensure that most of the hazardous scenarios will be identified, but also that US OSHA PSM Rule, EPA RMP, and Seveso Directive requirements will be accomplished. Chapter I pioneers the main research topic; from introducing the process safety concept up to the evidence of more detailed information is required from related regulations. A review of regulations (i.e., US, Europe legislation) focused on Hazard Identification has been conducted, highlighting, there is an absence of specific criteria for performing techniques intended to identify what can go wrong. Chapter II introduces the risk management system required to analyze the risk from chemical process facilities, and justifies that hazard identification stage is the Process Safety foundation. Hereafter, an overview of the key Process Hazard Analyzes (PHA) has been conducted, and the specific HAZOP weaknesses and strengths have been highlighted to establish the first steps to focus on. Chapter III establishes the scope, the purpose and the specific objectives that the research covers. It answers the following questions on the spot: why the present research is performed, which elements are included, and what has been considered for acquiring the final conclusions of the manuscript. Chapter IV gathers HAZOP-related literature from books, guidelines, standards, major journals, and conference proceedings with the purpose of classifying the research conducted over the years and finally define the HAZOP state-of-the-art. Additionally, and according to the information collected, the current HAZOP limitations have been emphasized, and thus, the research needs that should be considered for the HAZOP improvement and advance. Chapter V analyzes the data collected while preparing, organizing, executing and writing HAZOPs in five petroleum-refining processes. A statistical analysis has been performed to extract guidance and conclusions to support the established criteria to conduct effectively HAZOP studies. Chapter VI establishes the whole set of actions that have to be taken into account for ensuring a wellplanned and executed HAZOP study. Both technical and management issues are addressed, criteria supported after considering the previous chapters of the manuscript. Chapter VI itself is the result of the present research, and could be used as a guideline not only for team leaders, but also for any related party interested on performing HAZOPs in continuous chemical processes. Chapter VII states the final conclusions of the research. The interested parties should be released about the hazard identification related-gaps present in current process safety regulations; which are the key limitations of the HAZOP study, and finally, which are the criteria to cover the research needs that have been found Annex I proposes the key tools (tables, figures and checklists "ready-to use'') to be used for conducting HAZOPs in continuous chemical processes. The information layout is structured according to the proposed HAZOP Management System. This information is intended to provide concise and structured documentation to be used as a reference book when conducting HAZOPs. Annex II is intended to overview the most relevant petroleum refining processes by highlighting key factors to take into account in the point of view of process safety and hazard identification, i.e. HAZOP. In this sense, key health and safety information of specific petroleum refining units is provided as a valuable guidance during brainstorming sessions. Annex III illustrates the complete set of data collected during the field work of the present research, and also analyzed in Chapter V of the manuscript. Additionally, it depicts a statistical summary of the key variables treated during the analysis. Finally, the Nomenclature, References, and Abbreviations & Acronyms used and cited during the manuscript have been listed. Additionally, a Glossary of key terms related to the Process Safety field has been illustrated. / La present Tesis doctoral té com a objectiu estandarditzar l'aplicació d'una de les tècniques més utilitzades a la industria de procés per a la identificació de perills; l'anomenat HAZard & OPerability (HAZOP) study, específicament a processos complexes, com per exemple, unitat de refineria del petroli.El capítol I defineix el concepte de Seguretat de Processos, i progressivament analitza les diferents regulacions relacionades amb la temàtica, detallant específicament les mancances i buits d'informació que actualment hi ha presents a la primera etapa de la gestió del risc en industries de procés: la identificació de perills.El capítol II defineix el sistema de gestió del risc tecnològic que aplica a les industries de procés, i es justifica que l'etapa d'identificació de perills és el pilar de tot el sistema. Finalment, es mencionen algunes de les tècniques d'identificació més utilitzades, els anomenats Process Hazard Analysis (PHA), i es detallen les seves mancances i fortaleses, característiques que han acabat definint la temàtica específica de la Tesis. Concretament, es dóna èmfasis a la tècnica anomenada HAZard & OPerability (HAZOP) study, objecte principal de la recerca.El capítol III defineix l'abast, el propòsit i els objectius específics de la recerca. La intenció d'aquest capítol és donar resposta a les següents qüestions: el perquè de la recerca, quins elements han estat inclosos i què s'ha considerat per tal d'assolir les conclusions de la Tesis.El capítol IV descriu l'estat de l'art de la literatura relacionada amb el HAZOP. Aquesta revisió no només permet classificar les diferents línies de recerca relacionades amb el HAZOP, sinó que també permet assolir un coneixement profund de les diferents particularitats de la pròpia tècnica. El capítol finalitza amb un conjunt de mancances tant de gestió com tècniques, així com les necessitats de recerca que poden millorar l'organització i execució dels HAZOPs.El capítol V analitza la informació que ha estat recopilada durant la fase experimental de la tesis. Les dades procedeixen de la participació en cinc estudis HAZOP aplicats a la industria de refineria del petroli.En aquest sentit, el capítol V desenvolupa una anàlisi estadística d'aquestes dades per extreure'n conclusions quant a la preparació, organització i execució dels HAZOPs.El capítol VI estableix el conjunt d'accions que s'ha de tenir en compte per tal d'assegurar que un estudi HAZOP estigui ben organitzat i executat (la metodologia). Es defineix un Sistema de Gestió del HAZOP, i a partir de les seves fases, es desenvolupa una metodologia que pretén donar suport a tots aquells punts febles que han estat identificats en els capítols anteriors. Aquesta metodologia té la intenció de donar suport i guia no només als líders del HAZOP, sinó també a qualsevol part interessada en aquesta temàtica.El capítol VII descriu les conclusions de la recerca. En primera instància s'enumeren les mancances quant a la definició de criteris a seguir de diferents regulacions que apliquen a la Seguretat de Processos.Seguidament, es mencionen les limitacions de la pròpia tècnica HAZOP, i finalment, es descriuen quins són els criteris establerts per donar solució a totes aquestes febleses que han estat identificades.L'Annex I és una recopilació de diferents criteris que han estat desenvolupats al llarg de l'escrit en forma de taules i figures. Aquestes han estat ordenades cronològicament d'acord amb les diferents fases que defineixen el Sistema de Gestió HAZOP. L'annex I es pot utilitzar com a una referència concisa i pràctica, preparada i pensada per ésser utilitzada directament a camp, amb la intenció de donar suport a les parts interessades en liderar estudis HAZOP.L'annex II recopila informació relacionada amb aspectes clau de seguretat i medi ambient en diferents unitats de refineria. Aquest informació és un suport per tal de motivar el "brainstorming" dels diferents membres que conformen l'equip HAZOP.L'Annex III recopila les dades de les diferents variables que han estat considerades a la fase experimental de la recerca, juntament amb un conjunt de figures que mostren la seva estadística bàsica.

A system safety assurance case aims to demonstrate that a system is reasonably safe within the parameters defined according to its intended use. A system safety assurance case involves the definition of a Safety Engineering Process and its execution for the particular system. An essential element in the Safety Engineering Process is hazard analysis. An often used version of hazard analysis is HAZOP. HAZOP identifies hazards and hazardous events in the system's design. Traditionally, HAZOP is performed based on the expertise of a multi-disciplinary team. This team uses a heuristic based approach that results in documented output that often does not include adequate traceability as to how the output results were obtained. This thesis proposes a systematic approach to HAZOP that was developed after performing detailed analysis on how traditional HAZOP is performed in industry. It aims to produce documented output in which the output results are traceable to interim steps in the process. We call this systematic approach HAZOP+, because it was designed to provide sufficient detail so that it can form the basis of a HAZOP metamodel created in Workflow+ - a relatively new model driven methodology for developing assurance cases. Workflow+ has well-defined semantics, and so we refer to HAZOP+ as formalizable. HAZOP+ has a number of benefits over traditional HAZOP, and these benefits are demonstrated by comparing a traditional application of HAZOP with the application of HAZOP+, both applied to a typical Lane Keeping Assist feature. A long term objective of system safety assurance is to be able to perform incremental safety assurance, for example, by updating the system safety assurance case after a modification to the system or its environment. Since the safety assurance case for a system depends on elements of the Safety Engineering Process, as well as the outputs of that process, the ability to perform an incremental hazard analysis after a modification to the system or environment can be a real benefit. This thesis further describes how HAZOP+ can be enhanced/extended to HAZOPdelta - an incremental version of HAZOP+. / Thesis / Master of Applied Science (MASc)

Process plants that produce chemical products through pre-designed processes are fundamental in the Chemical Engineering industry. The safety of hazardous processing plants is of paramount importance as an accident could cause major damage to property and/or injury to people. HAZID is a computer system that helps designers and operators of process plants to identify potential design and operation problems given a process plant design. However, there are issues that need to be addressed before such a system will be accepted for common use. This research project considers how to improve the usability and acceptability of such a system by developing tools to test the developed models in order for the users to gain confidence in HAZID s output as HAZID is a model based system with a library of equipment models. The research also investigates the development of computer-aided safety applications and how they can be integrated together to extend HAZID to support different kinds of safety-related reasoning tasks. Three computer-aided tools and one reasoning system have been developed from this project. The first is called Model Test Bed, which is to test the correctness of models that have been built. The second is called Safe Isolation Tool, which is to define isolation boundary and identify potential hazards for isolation work. The third is an Instrument Checker, which lists all the instruments and their connections with process items in a process plant for the engineers to consider whether the instrument and its loop provide safeguards to the equipment during the hazard identification procedure. The fourth is a cause-effect analysis system that can automatically generate cause-effect tables for the control engineers to consider the safety design of the control of a plant as the table shows process events and corresponding process responses designed by the control engineer. The thesis provides a full description of the above four tools and how they are integrated into the HAZID system to perform control safety analysis and hazard identification in process plants.