Bow Ties in Risk Management

A Concept Book for Process Safety

,

• Publisher: Wiley-AIChE
• Year: 2018
• ISBN:
  9781119490340
• Edition: 1
• Topic: Tecnología e ingeniería
• Subtopic: Ingeniería química y bioquímica

AN AUTHORITATIVE GUIDE THAT EXPLAINS THE EFFECTIVENESS AND IMPLEMENTATION OF BOW TIE ANALYSIS, A QUALITATIVE RISK ASSESSMENT AND BARRIER MANAGEMENT METHODOLOGY

From a collaborative effort of the Center for Chemical Process Safety (CCPS) and the Energy Institute (EI) comes an invaluable book that puts the focus on a specific qualitative risk management methodology – bow tie barrier analysis. The book contains practical advice for conducting an effective bow tie analysis and offers guidance for creating bow tie diagrams for process safety and risk management. Bow Ties in Risk Management clearly shows how bow tie analysis and diagrams fit into an overall process safety and risk management framework.

Implementing the methods outlined in this book will improve the quality of bow tie analysis and bow tie diagrams across an organization and the industry. This important guide:

• Explains the proven concept of bow tie barrier analysis for the preventing and mitigation of incident pathways, especially related to major accidents
• Shows how to avoid common pitfalls and is filled with real-world examples
• Explains the practical application of the bow tie method throughout an organization
• Reveals how to treat human and organizational factors in a sound and practical manner
• Includes additional material available online

Although this book is written primarily for anyone involved with or responsible for managing process safety risks, this book is applicable to anyone using bow tie risk management practices in other safety and environmental or Enterprise Risk Management applications. It is designed for a wide audience, from beginners with little to no background in barrier management, to experienced professionals who may already be familiar with bow ties, their elements, the methodology, and their relation to risk management.

The missions of both the CCPS and EI include developing and disseminating knowledge, skills, and good practices to protect people, property and the environment by bringing the best knowledge and practices to industry, academia, governments and the public around the world through collective wisdom, tools, training and expertise. The CCPS has been at the forefront of documenting and sharing important process safety risk assessment methodologies for more than 30 years. The EI's Technical Work Program addresses the depth and breadth of the energy sector, from fuels and fuels distribution to health and safety, sustainability and the environment. The EI program provides cost-effective, value-adding knowledge on key current and future international issues affecting those in the energy sector.

1
INTRODUCTION

1.1 PURPOSE

The purpose of this concept book is to establish a set of practical advice on how to conduct bow tie analysis and develop useful bow tie diagrams for risk management. It describes the intended audience, gives directions on how to use the concept book and provides a basic introduction to the method, which is expanded in the following chapters. It explains the rationale for developing bow tie diagrams and how they fit into an overall risk management framework.

CCPS concept books address newer techniques in process safety that have not yet become accepted standard practice or where there is not yet industry consensus on approach. In EI publications, concept books are termed Research Reports in its series of technical publications. Concept books introduce these valuable tools in a simple and straightforward manner. CCPS and EI encourage the use of this concept book to aid the industry in developing better quality bow tie diagrams with a consistent methodology and preferred terminology for their use. Implementation of the methodology outlined in this CCPS / EI book should improve the quality of bow tie analysis and bow tie diagrams across an organization and industry.

1.2 SCOPE AND INTENDED AUDIENCE

This concept book provides practical advice on how to develop bow tie diagrams and in their use. This will help to:

• ensure consistent use of methodology and terminology;
• establish a valid approach to defining hazards, top events, threats, and consequences;
• establish criteria for barriers and degradation controls linked to degradation factors;
• identify common errors which may occur when constructing bow ties;
• provide a method to incorporate human and organizational factor issues in bow ties;
• provide guidance on how bow ties can be used for risk management purposes through the effective depiction of barriers;
• discuss basic and advanced uses of bow tie diagrams; and
• review an overall strategy for barrier management.

The intended audience for this book is primarily anyone involved with or responsible for managing process safety risks, although the concepts within the book are applicable to all bow tie risk management practices and not limited to process safety (e.g., for other safety and environmental applications and Enterprise Risk Management). It is designed for a wide audience, from beginners with little to no background in barrier management, to experienced professionals who may already be familiar with bow ties, their elements, the methodology, and their relation to risk management.

The origin of bow ties and their main use to date has been in managing process safety risks particularly relating to major accidents. They have been applied in the chemical / petrochemical and oil and gas industries as well as other industries (such as maritime, aviation, rail, mining, nuclear, and healthcare). However, the logic and approach described here may also be used to manage strategic risks, financial risks, risks of losing critical sales, etc. As these applications are less common, the examples in this book are focused on safety risks but also include human health, environmental impact, asset damage, and reputation loss.

Several software tools are available to aid in the development of the diagrams. The level of detail displayed using software tools can be complete or partial depending on the audience needs. This book does not endorse any particular software too; however, Appendix A provides a summary of several widely available software tools known to the authors at the time of publishing.

1.3 ORGANIZATION OF THIS CONCEPT BOOK

This book is organized in a way that follows the logical flow of constructing bow ties and then conducting bow tie barrier analysis. Several examples are used to demonstrate this advice; however, these often only cover parts of a bow tie under discussion. More detailed, complete examples are found in Appendices B and C. The examples relate to the topics in each chapter and provide a story line concerning the development and use of bow ties. A summary of the content of each chapter is provided below.

Chapter 1 – Introduction

• Purpose and scope;
• Introduction to the bow tie concept;
• Linkage between bow ties, fault trees, and event trees.

Chapter 2 – The Bow Tie Model

• Define terminology and elements of the bow tie diagram;
• Illustrate robust and weak examples of bow tie elements;
• Define and discuss the types of barriers, including criteria for validity and quality.

Chapter 3 – Bow Tie Development

• Discuss the process of bow tie development including their initial development in team workshops;
• Discuss common errors and quality checks during development of bow tie diagrams.

Chapter 4 – Addressing Human Factors in Bow Tie Analysis

• Discuss how to include human and organizational factors in bow tie diagrams;
• Show how human factors can be addressed using a basic approach, but also introduce the concept of a multi-level bow tie which provides an extended analysis with greater utility, albeit with some complexity;
• Discuss metrics for human and organizational factors.

Chapter 5 – Basic Use of Bow Ties

• Discuss common uses of bow tie tools in analyzing barriers and identifying safety critical elements and tasks.

Chapter 6 – Management of Bow Ties

• Discuss use of bow ties as part of a barrier management strategy utiliing a lifecycle approach;
• Discuss links between bow ties and management system elements (e.g., Management of Change, maintenance, training, audits).

Chapter 7 – Additional Uses of Bow Ties

• Discuss the application of bow ties as a communication tool and to help demonstrate ALARP;
• Illustrate how bow ties are used to aid in decision making for various activities in an organization and for risk management;
• Show how real-time bow ties can interface with an organization’s management system.

Appendices

• Appendix A – Software Tools; provides a table listing various software tools available to develop bow ties and their capabilities;
• Appendix B – Case Study for a pipeline; provides an example of a full bow tie with an emphasis on technical threats;
• Appendix C – Case Study for Multi-Level Bow Ties; provides an example bow tie incorporating human and organizational factors and demonstrating the concept of multi-level bow ties.

1.4 INTRODUCTION TO THE BOW TIE CONCEPT

The oil and gas industry has achieved a very impressive improvement in occupational safety. The fatality rate within the IOGP member companies has declined by an order of magnitude over the past 20 years, Figure 1-1 (IOGP, 2015).

Figure 1-1. Fatal Accident Rate vs Total Hours Worked (Global Data)

However, the reduction in major process accidents has been less impressive than for occupational safety (Pitblado, 2011) and insured losses due to major accidents in the oil and gas and process industries have not reduced in the last 30 years (Marsh, 2016). Current risk approaches have tended to focus more on demonstrating design safety and less on maintaining operational safety.

The development and appropriate use of bow tie barrier diagrams have the potential to significantly improve process safety. They do this by focusing on the operational aspects, clearly highlighting all important safety barriers, helping in the assessment of barrier adequacy, communicating this visually to all staff and contractors, and providing a framework to continually monitor the effectiveness of these barriers. Bow ties can also be used in the design phase to test the adequacy and relevance of barriers and if additional barriers and degradation controls are required.

Once constructed, the bow tie purpose is best used to support risk management and risk communication. The bow tie diagram can provide a clear graphical representation of the output of the risk assessment and management process (threats, consequences, barriers and degradation controls) which is readily understood by people at all levels – from operational personnel and senior managers, to regulators, and to members of the public. The bow tie illustrates both the prevention barriers, which stop the top event from occurring, and the mitigation barriers, which reduce the consequence severity should the top event occur. For the full unmitigated consequence (i.e., major accident event), all of the barriers along the relevant pathway between the threat and the consequence must fail or be degraded. Other factors not related to barriers may also contribute to the magnitude of the consequence (release orientation, wind direction, etc.).

Major accidents rarely result from a single failure, but rather from multiple barrier failures, which collectively result in a loss of control situation that further escalates to significant consequences. Common mode failures can be relevant in multiple barrier failures (e.g., underfunding or delayed maintenance can affect many barriers simultaneously). The bow tie approach helps the operational and maintenance teams to focus on barriers and the degradation controls which are relied upon to maintain their effectiveness. The effective management of all barriers is a key aspect of risk-based process safety management (CCPS, 2007).

1.4.1 Reason’s Swiss Cheese, Models of Accident Causation and Bow Ties

James Reason (1990 and 1997) developed the idea of the ‘Swiss Cheese Model’ of system failure presented in Figure 1-2. The model builds on the principles of ‘defense in depth,’ with slices of Swiss cheese representing protective layers (i.e., barriers) preventing hazards from being realized and allowing consequences to happen. Reason observes that barriers are never 100% effective and each has unintended intermittent weaknesses. The holes in the cheese slices represent degradation factors (i.e., reductions in effectiveness or reliability) in individual parts of the system and are continually varying in size and position in all slices. For a major accident to occur, holes in the Swiss cheese need to align allowing for an ‘accident trajectory’ so that a threat passes through all of the holes in all of the defenses (i.e., barriers) leading to a failure or major accident. It also shows that if one barrier fails, then subsequent barriers are challenged. Using this model, a risk management strategy is successful when barriers are managed to ensure that they perform as intended at all times throughout the life cycle of t...

Table of contents

• Cover
• Title page
• Copyright page
• Acronyms and Abbreviations
• Glossary
• Acknowledgments
• Online Materials Accompanying This Book
• Preface
• 1: Introduction
• 2: The Bow Tie Model
• 3: Bow Tie Development
• 4: Addressing Human Factors in Bow Tie Analysis
• 5: Primary Uses Of Bow Ties
• 6: Barrier Management Program
• 7: Additional Uses of Bow Ties
• Appendix A – Software Tools
• Appendix B – Case Study
• Appendix C – Multi-Level Bow Ties
• References
• Index
• Wiley end User License Agreement