Page 541 - Marine Structural Design

Chapter 29 Risk Assessment Methodology 517

The purpose and scope of work for the risk analysis should be clearly defined in accordance
with the needs of the activity. The risk acceptance criteria need to be defined prior to the
initiation of risk analysis. It will be helpful to involve operational personnel in the project
execution. For the activity related to the design and construction of ships, mobile offshore
drilling units and floating production installations, applicable regulations, classification rules,
and industry standardsfspecifications may be useful.
When a quantitative risk analysis is carried out, the data basis should be appropriately selected.
A sufficiently extensive data basis is a must in order to draw reliable conclusions. In some
situations, comparative risk studies may lead to more meaningful conclusions.
To quantify accident frequency or causes, it is particularly important to establish a reliable
data basis. The data basis should be consistent with relevant phases and operations. The
analysis model shall comply with the requirements to input data and assumptions, etc. The
quality and depth of the frequency, escalation and consequence modeling determine how
detailed conclusions may be made for the systems involved in the analysis. The level of
accuracy in the results may not be more extensive than what is justifiable based on the data
and models that are used for the quantification of frequency and consequence. For instance,
risk may not be expressed on a continuous scale when the estimation of frequency andfor
consequences is based on categories.
29.1.4 System Description
The next step in a risk assessment is a detailed study of the system used, including a general
description of the system’s structure and operation, fimctional relationship between the
elements of the system, and any other system constraints. The description of the system
includes the technical system, the period of time, personnel groups, the external environment,
and the assets to which the risk assessment relates, and capabilities of the system in relation to
its ability to tolerate failures and its vulnerability to accidental effects
29.1.5 Hazard Identification
Hazard identification establishes the foundation on which subsequent frequency and
consequence estimates are made. The hazard identification yields a list of accidental situations
that could result in a variety of potential consequences. The potential hazards are identified in
order to avoid ignorance of the potential hazardous accidents in the risk assessment.
Identification of hazards also includes a ranking of the significance of each hazard in relation
to the total risk. For the subsequent analysis, hazards are roughly classified into critical
hazards and non-critical hazards. The criteria used in the screening of the hazards should be
stated. The evaluations made for the classification of the non-critical hazards should be
documented.
There are several approaches for hazard identification and the success in using these
techniques depends on the knowledge and information available. Possible data and tools for
the hazard identification are literature review, check-lists and accident statistics, HAZOP
(HAZard and Operability) studies, FMEA (Failure Mode and Effect Analysis). Safety audit,
brainstorming and experience from previous projects may be usefbl. It is also important to
involve operational personnel.