Rainer Hamann

GOALDS - goal based damage ship stability and safety standards

The new probabilistic damaged stability regulations for dry cargo and passenger ships (SOLAS 2009), which entered into force on January 1, 2009, represent a major step forward in achieving an improved safety standard through the rationalisation and harmonization of damaged stability requirements. There are, however, serious concerns regarding the adopted formulation for the calculation of the survival probability of passenger ships, particularly for ROPAX and large cruise vessels. The present paper outlines the objectives, the methodology of work and main results of the EU-funded FP7 project GOALDS (Goal Based Damaged Stability, 2009-2012), which aims to address the above shortcomings by state-of-the-art scientific methods and by formulating a rational, goal-based regulatory framework, properly accounting for the damage stability properties of passenger ships and the risk of people onboard.

Towards Environmental Risk Acceptance Criteria

Risk evaluation criteria related to safety of human life have been available in the maritime industry for some time. However, only recently these criteria became formally accepted by including the CAF and ALARP-boundaries into the Formal Safety Assessment guidelines of the IMO. Risk evaluation criteria related to the protection of the environment are not yet agreed. A proposal for a cost effectiveness criterion related to accidental oil spills called CATS was suggested by the project SAFEDOR. However, a societal risk acceptance of environmental damages from shipping is not yet proposed. And, to effectively apply a cost-effectiveness criterion related to environmental protection, societal risk acceptance and the associated ALARP area need to be defined. To contribute to the ongoing discussion on environmental risk evaluation criteria, this paper presents a societal risk acceptance criterion related to oil spills of tankers which can be used within risk-based ship design and approval as well as for rule-making. The presented work adds to SAFEDOR’s contribution to risk evaluation criteria for the maritime transport in providing an ALARP area for risk assessment of oil transport by tankers. The paper first presents the current state of oil transportation by tankers and continues with providing suggestions how the ALARP boundaries may be derived in this context.© 2008 ASME

Analysis of tanker casualties after the Oil Pollution Act (USA, 1990)

A prime concern of maritime transport is to enhance ship safety and to reduce marine pollution related to ship incidents and accidents. Since the elimination of marine accidents is practically unrealistic, a reasonable target for the maritime industry and relevant regulatory bodies is the mitigation of accidents in terms of minimization of the probability of occurrence and of the associated consequences. The present study focuses on a comprehensive analysis of recorded accidents on medium and large oil tankers (deadweight over 20,000 t), which occurred after the introduction of the Oil Pollution Act (USA, 1990) up to the present. Raw casualty data were reviewed and re-analysed in order to produce appropriate statistics useful for the implementation of risk-based assessment methodologies. The main outcome of this particular study is the identification of the significant qualitative historical trends of tanker accidents and of the quantitative characteristics of particular tanker accidents, such as the overall frequencies of accidents per ship year, the frequency of each major accident category and per tanker ship size, the ship types or designs and ages, the degrees of severity of accidents and the tonnes of oil spilled per ship year.

Derivation or Ship System Safety Criteria by Means of Risk-Based Ship System Safety Analysis

Nowadays an increasing popularity of alternative designs can be observed challenging the IMO Regulations of SOLAS (International Convention for the Safety Of Life At Sea). Examples are passenger ships with larger main vertical zones, novel types of survival crafts and new materials. This desire for innovative solutions combined with the society’s need for increasingly safer transport is expected to be satisfied by risk-based ship design and approval. The process of alternative ship design and arrangements, as described in MSC/Circ.1002 and MSC.1/Circ.1212, requires a risk analysis to demonstrate that the risk contribution of the novel design is less or equal to the present design. Thus the application of this process can also be regarded as risk-based design. The application of risk-based design is driven by the need for continuous improvement of the efficiency leading to lower costs for design, manufacturing or operation, because it offers the required frame for the development of new innovative solutions. IACS defines safety as absence of unacceptable levels of risk to life, limb and health. Risk is defined as a measure of likelihood that an undesirable event will occur together with a measure of the resulting consequence within a specified time, i.e., the combination of the frequency or probability and the severity of the consequence. Risk-based design involves risk assessment and risk evaluation criteria that can be defined, for instance, on basis of historical data or the ALARP process (As Low As Reasonably Practicable) combined with cost-benefit analysis. In this paper the definition of a risk evaluation criterion for systems by means of ALARP and cost-benefit analysis is presented and illustrated by a sample design of a ship fuel oil system. The risk contribution tree used for the analysis is composed of fault trees and event trees. A cost-benefit analysis is applied to establish a target system risk criterion in form of a target system failure probability. Problems related to the discrete structure of systems are discussed. The work shows that different risk analysis methods are required to describe the escalation chain from a component failure to a potential accident and its consequences.Copyright

Goal-Based Standards and Risk-Based Design

Abstract In recent years risk-based design gained more importance in ship design. In parallel discussion started at the International Maritime Organisation (IMO) on the development of regulations based on risk-based methods, named Goal-Based Standards Safety Level Approach. Experience showed that engineering effort increases due to the introduction of risk-based methods, and therefore some stakeholders are reluctant to accept this innovation because of uncertainties concerning design classification and approval. This paper summarises the discussion until now on Goal-Based Standards, focusing in particular on the application of risk-based methods at IMO, and shows some examples of risk-based design in shipbuilding. Potential impact on IMO regulations and classification society rules is estimated.

Semi Automatic Failure Analysis Based on Simulation Models

Classical risk assessment and risk management which is gaining importance in many industries is usually based on well defined processes and uses techniques like FTA and FMEA. However, classical risk analysis techniques like FTA and FMEA should ideally be automated, at least to some extent and without loss of effectiveness, to enable fast and cost effective iterations of system modelling and risk analysis that can meet the tight cost and time constraints of most offshore projects. This paper is focused on the presentation of a new concept and tool extension for model-based synthesis of fault trees and FMEAs in which these failure analyses are automatically constructed from engineering design models, e.g. simulation models that have been augmented with information about the local propagation of failures. The simulation model is developed in the commercial system modelling tool SimulationX. The proposed process enables the automatic generation of both fault trees and FMEA tables in a single run of the tool, allowing the FMEA and fault trees to share failure data and allowing the FMEA to include failures caused by multiple basic events. As it is a largely automated process, it could be easily iterated to enable the continuous assessment of evolving designs. It provides an automatic generation of fault trees and FMEA tables for multiple top events in a single run of the tool. The potential benefits from application of this technique and tool are substantial and include simplifying the analysis, easing the examination of effects of design modifications on safety and keeping the safety analyses consistent with the design. Furthermore, the presented approach combines the benefits of simulation and risk analysis in one tool. The benefits of this approach are demonstrated by the example of a blow out preventer for a subsea installation valve.Copyright

Assessment of Typical Pipeline Flaws With SINTAP

The recently developed European flaw assessment procedure SINTAP is applied to a total of 88 full scale pipe tests (burst tests) with through-wall and surface cracks subjected to internal pressure. Based on the experimental results various analysis levels of SINTAP are discussed with respect to their potential for predicting the failure loads and the margins of conservatism. Different shape functions from Newman & Raju, Zahoor and API 579 were used for the assessment.Copyright