Page 553 - Marine Structural Design

Risk Assessment

Chapter 30 Risk Assessment Applied to Offshore Structures

30.1 Introduction

Use of offshore risk assessment started in the late 197Os, based on the methodologies and data
from the nuclear power generation industry. Following the Alexander L. Kielland accident in
1981 that resulted in total loss of the platform and 123 fatalities, the Norwegian Petroleum
Directorate issued their guidelines that required quantitative risk assessment be carried out for
all new offshore installations in the conceptual design phase (NPD, 1992). Another significant
step was the Safety Case Legislation in the WK in 1992, following the Piper Alpha accident
that resulted in total loss of the platform and 165 fatalities in 1988 (UK HSE, 1992, 1995).
There are several types of offshore risks, e.g.
structural and marine events
collisions
fires
dropped objects
blowouts
riserdpipelines leaks, process leaks
transport accidents
Risk due to structural failure is discussed in Part N. Risks associated with blowouts,
riserlpipeline hydrocarbon leaks, process leaks, transport accidents are discussed by CCPS
(1995) and CMPT (1999). Reference is made to specialized books (e.g. Vinnem 1999) on the
basic methodologies for risk evaluation such as
0 Hazard Modeling and Cause Analysis,
Fault Tree Analysis, Event Tree Analysis, and
Failure Mode and Effect Analysis.

In the following sections, discussions will be made on risks associated with collision,
explosion, fire and dropped objects, including:
Overview
Frequency analysis
Loads and consequence analysis
Risk reduction