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Microsoft Teams, CAS Graduate Seminars and Defences

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Examiners: 
Dr. Richard Paige, Chair
Dr. Spencer Smith - Examiner
Dr. Mark Lawford – Co-Supervisor
Dr. Allan Wassyng – Co-Supervisor

A Systematic Approach to Hazard and Operability Study (HAZOP)

Overview

Abstract

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 (SEP) and its execution for the particular system. The SEP definition demonstrates the process' conformance to a set of normative documents such as standards, governance, and procedures built from operating experience and expertise. Assurance cases can be built using existing ones as basis. Modifica- tions to the design basis are subject to impact and traceability analysis which further affect verification and validation (V&V). To further minimize the effort in V&V and audit activities, the elements of the assurance case shall be formalizable, documentable, traceable, verifiable, and modular. An essential element in assuring safety 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 and heuristics of a multi-disciplinary team.

This thesis proposes a systematic approach to HAZOP that aims to create a concrete design basis and to minimize V&V and audit activities. The approach performs Requirement Decomposition (RD) in a hierarchical fashion over Functional Architecture Diagrams (FADs). As the proposed approach is hierarchical, this thesis also proposes the use of Goal Structuring Notation (GSN) to represent the structure of a HAZOP instance and its elements. HAZOP is then performed systematically on the requirements by traversing the decomposition and relationships defined in the GSN diagram and FADs. This proposed approach was developed after performing detailed analysis on how traditional HAZOP is performed in industry.

The proposed approach shows an objective, methodical, and traceable way of performing HAZOP over traditional methods that are otherwise subjective in nature, heuristic-driven, and expert-based. From a safety perspective, this thesis paves the way for a mathematically formal approach to HAZOP.