More Effective Bow Ties and Better Siting and Layout of Facilities

First, the CCPS and the Energy Institute are jointly publishing ‘Bow Ties in Risk Management’, with the aim of providing a basis for greater consistency in the approach adopted and terminology used in developing and using bow ties within the chemical, oil & gas and other high hazard industries. The primary author is DNV GL and significant contributions have been made by over twenty major companies and also by the European Commission Major Accident Hazard Bureau. This paper describes the book’s key recommendations for developing, using and maintaining bowties: Barriers must be ‘effective, independent and auditable’ i.e. capable of stopping completely the threat from leading to the top event and be independent of the threat and other barriers linked to a particular threat; Barriers are either active or passive, and if active, must have separate elements to Detect what is going wrong, Decide what to do about it and Act to stop the threat from progressing further. Five main types of barrier are defined: ‘Passive Hardware’, ‘Active Hardware’ (all elements of detect-decide-act are hardware), ‘Active Hardware + Human’ (elements of detect-decide-act are a mix of hardware and human) ‘Active Human’ (all elements of detect-decide-act are human) and ‘Continuous Hardware’ (only the act element is present, the detect and decide elements were determined during the design of the barrier). The mechanisms by which barriers may fail or become degraded are portrayed as ‘degradation factors’. The ‘barriers’ against degradation are referred to as ‘degradation safeguards’. Such safeguards may not meet the barrier criteria of being ‘effective, independent and auditable’ or have all of the detect, decide, and act elements. Human and Organisational Factors are portrayed as safeguards preventing the degradation of barriers by human error. The paper also discusses the design of bow ties for their target audience, whether front-line operators, managers or others, the incorporation and standardisation of meta-data such as barrier inherent or as-designed strength, barrier ownership and current barrier condition or performance, and includes an example bow tie for a gasoline storage tank facility similar to Buncefield to demonstrate the application of the recommended approach and terminology.

It is proposed that bow ties developed and applied using the ideas presented in this new CCPS/EI book will significantly improve their practical value in reducing risks and eliminating major incidents. It will be of great value to operations managers and engineers involved in design and asset integrity as well as specialists in process safety and human factors.

Second, the ‘CCPS Guidelines for Siting and Layout of Facilities’ 2^nd Edition addresses developments in how organizations select new sites, evaluate acquisitions and expand existing facilities for hazardous chemicals. The scope is the geographical siting of a facility within a community as well as the layout of plant units and buildings within a facility. This 400 page textbook (the 1^st Edition was published in 2003) is an important reference for facility layout specialists, engineers and managers, and will be of use to a wide range of other readers including regulatory authorities, insurance companies and the public. The 2^ndEdition adds discussions on modelling toxic dispersion and explosions, life cycle and long-term risks and the management of change, and includes a number of detailed appendices providing tables of recommended separation distances between equipment, checklists for project teams and major incident case studies.

Based on the history of major incidents, it is clear that following this latest CCPS guidance on siting and layout will significantly reduce the risk of incidents and mitigate their effects if they do occur. It should be read and adopted by all managers and engineers involved in operating hazardous facilities and in projects to build or change them.