Formal Safety Assessment and Risk Analysis of Offshore

Structures

Presented by:

Abdelrahman Abo El Naga

Mohamed Hamdy Abdel AalYousri Ali FadelIslam Ramadan Amgad AhmedMohamed Nagy

This presentation aims to discuss the Formal Safety Assessment (FSA) tool and produce a risk analysis of offshore structures.

Table of contents

Introduction

The Piper Alpha accident

Formal Safety Assessment

Risk elements in offshore structure

Risk Presentation

Introduction

Formal Safety Assessment (FSA) has been a risk analysis tool for some time, having been particularly widely used in:

1-The nuclear industries.

2-petrochemical industries.

and some administrations have been encouraging IMO to recognize FSA as an aid to the maritime rule-making process.

The Piper Alpha accidentPiper Alpha was a North Sea oil production platform. The platform began production in 1976 first as an oil platform and then later converted to gas production.

An explosion and resulting fire destroyed it on 6 July 1988, killing 167 men with only 61 survivor. The death toll includes two crewmen of a rescue vessel. Total insured

loss was about £1.7 billion.  

Following the public inquiry into the Piper Alpha accident (Department of Energy, 1990), the responsibilities for offshore safety regulations were transferred from the Department of Energy to the Health & Safety Commission (HSC) through the Health & Safety Executive (HSE) as the single regulatory body for offshore safety.

Regulations was produced (HSE,1992). It was then modified, taking into account the comments arising from public consultation.

The regulations require operational safety cases to be prepared for all offshore installations. Both fixed and movable installations are included.

The HSE framework for decisions on the tolerability of risk is shown in Fig. 1, where

there are three regions :

)a (intolerable ,

)b (As Low As Reasonably Practicable (ALARP),

and (c) broadly acceptable.

Fig.1

Formal Safety Assessment

The philosophy of formal safety assessment is essentially the same as the one for the safety case approach. It has been noted that many leading classification societies including Lloyds Register of Shipping and American Bureau of Shipping are moving toward a risk-based regime. It is believedthat the framework of formal safety assessment can facilitate such a move.

The concept of the safety case has been derived and developed from the application of the principle of system engineering for dealing with the safety of systems or installations for which little or no previous

operational experience exist .

The five key elements of the safety case are discussed as follows :

1 .Hazard identification:

This step is to identify all hazards with the potential to cause a major accident.

2 .Risk estimation:

Once the hazards have been identified, the next step is to determine the associated risks

Hazards can generally be grouped into three risk region as the intolerable, tolerable and

negligible risk regions as shown in Fig.1.

3 .Risk reduction:Following risk assessment, it is required to reduce the risks associated with significanthazards that deserve attention.

4 .Emergency preparedness:The goal of the emergency preparedness is to be prepared to take the most appropriate actionin the event that a hazard becomes a reality so as to minimise its effects and, if necessary, totransfer personnel from a location with a higher risk level to another one with a lower risklevel.

5 .Safety management system:

The purpose of a safety management system (SMS) is to ensure that the organisation is

achieving the goals safely, efficiently and without damaging the environment .

One of the most important factors of the safety case is an explanation of how the operator’s

management system will be adopted to ensure that safety objectives are actually achieved.

Risk elements in offshore structure

1-Personnel Risk

When personnel risk is considered in the case of an offshore installation, only risk

for employees is considered, whereas risk for the public is not applicable .

For risk to personnel, the following may be considered as elements of risk:

1-Occupational accidents

2-Major accidents

3-Transportation accidents

4-Diving accidents.

2-Risk to Environment

The following hazards relating to production installations and associated operations

may lead to damage to external environment:

1-Leaks and seepages from production equipment on the platform as well as subsea.

2-Excessive contamination from production water and other releases.

3-Large spills from blowouts

4-Pipeline and riser leaks and ruptures

5-Spills from storage tanks

6-Accidents to shuttle tankers causing spill.

3-Risk to Assets

Risk to assets is usually considered as non-personnel and non-environment consequences of accidents that may potentially have personnel and/or environment consequences. It may be noted that modelling of risk to assets in many circumstances is relatively weak.

The following types of hazards may cause accidental events which have the potential to damage the assets:

1-Ignited and unignited leaks of hydrocarbon gas or liquid

2-Ignited leaks of other liquids, such as diesel, glycol, jet fuel, etc.

3-Fires in electrical systems.

4-Fires in utility areas, accommodation, etc.

Crane accidents

5-External impacts, such as vessel collision, helicopter crash, etc.

6-Extreme environmental loads.

Risk Presentation

The main objective in the presentation of QRA results is to illustrate relative comparisons of contributions and mechanisms that may show the elements of the risk picture. Thus as many details and illustrations as possible should be presented.

Some general principles for presentation of results are stated next slide.

Thanks