Integrated Structural and Safety Engineering for Fire and Blast Design - Case Studies and Lessons Learned
Authors: Hossain Adnan , Meek Ann , Warwick Alistair 
Published: October 2008

An integrated structural and safety engineering approach to addressing fire and blast hazards on offshore oil and gas production facilities is discussed. This paper aims to demonstrate how to apply a risk based approach in practice and how it may yield significant savings and improvements in the design of safety systems. Using an integrated approach, only the credible fire and blast scenarios that are of structural significance need to be fully analyzed, using a consistent level of rigor for the hazard risk assessment and the structural response assessment. The paper discusses how, the simplicity of the integrated approach enables such studies to be undertaken relatively early on in the design process, when layout and structural configuration can still be influenced.

Conclusions and observations from real case studies are presented and salient issues of industry importance are discussed.

Introduction

The demands of offshore construction continue to focus attention on improving health, safety and environmental (HSE) performance on offshore installations. This becomes particularly pertinent as production moves to the more remote, larger production units, which have greater production capacities and are located in deeper waters.

In recent years considerable effort has been put into the development of more comprehensive guidance on the design of offshore installations to withstand fire and blast loads. This has resulted in the introduction of, for example, Section 18 of API RP2A 21st Edition, [1]. Work is still on-going on the production of a new stand alone API standard and on an updated version of the FABIG interim guidance notes, sponsored by UKOOA and the UK HSE.

In the past, design of structures for fire and blast tended to be carried out to prescriptive standards i.e. specified design blast pressure/design fire duration. This often produced designs and mitigation measures, which were inappropriate for the actual fire and blast hazards associated with the facility. The latest trend is to move away from this type of rule based approach to a more risk based approach and guidance on how to achieve this is given in some of the latest standards.

This paper presents an illustration of how these risk based techniques can be practically applied to real design situations. It is the author's opinion that this cannot be efficiently and effectively achieved without close cooperation between safety and structural engineers in the definition of those credible fire and blast hazards, which will govern the fire and blast design.

The paper presents a relatively simple, integrated approach to fire and blast assessment, which may be undertaken early on in the design process when layout and structural configuration can still be influenced. The approach has also been successfully applied late in the design process and even post start-up, to optimize the requirement for mitigation provisions, which can have significant weight and cost penalties.

Recent advances in computer software and hardware capabilities have meant that non-linear progressive collapse analyses can be undertaken relatively inexpensively, to assess structural response to severe load conditions.