LLOYD'S REGISTER TECHNOLOGY DAYPROCEEDINGS

Working together for safer, more sustainable ships

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Lloyd’s Register EMEAT + 44 (0)20 7709 9166F + 44 (0)20 7423 2057E emea@lr.org

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February 2009

Services are provided by members of the Lloyd’s Register Group. Lloyd’s Register, Lloyd’s Register EMEA and Lloyd’s Register Asia are exempt charities under the UK Charities Act 1993.

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LLOYD'S REGISTER TECHNOLOGY DAYPROCEEDINGS

FOREWORD

The Lloyd’s Register Technology Day has beenestablished to provide an introduction to technologiesthat we are considering and developing in support of our mission to promote safety and environmentalprotection in the marine industry. The paperspresented at the seminar are intended to give an insight into the research and development workwe are undertaking within Lloyd’s Register, as well as through co-operation with others.

The Technology Day is not just an opportunity for us to provide information. It also creates a forum for discussion, through which we can gain an understanding of the views of technologypractitioners and users within the industry. Thisknowledge sharing will help strengthen our work and our contribution to the global marine community.

Our political and commercial independence enable us to adopt a broad, long-term approach to researchand innovation. We pursue some projects thatunderpin the advancement of our technicalknowledge base. Other projects are targeted at satisfying the identified business needs of the

different ship-type markets and the product lines that we offer to our marine stakeholders. Theseprojects utilise: the outcomes of the underpinningtechnology projects; the knowledge, experience and expertise of Lloyd’s Register’s technicalemployees; and knowledge gained from externalsources, either from published information or fromcollaborative ventures.

This year’s Technology Day comprises ten lectures and discussions – the accompanying papers for whichare presented in this publication. The papers embracesubjects ranging from statutory and risk issues,through propulsion and control, to structural,metallurgical and environmental topics.

I hope that you find them interesting and a usefulcontribution to your work within the marine industry.

John CarltonGlobal Head of Marine TechnologyLloyd’s Register.

February 2009

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LLOYD’S REGISTER TECHNOLOGY DAY PROCEEDINGS

Contents

Lloyd’s Register’s Approach to Research 1and Innovation. Vaughan Pomeroy M.A.,

C.Eng., F.I.Mech.E., F.I.Mar.EST., F.R.I.N.A.

Implications of Forthcoming 11International and Regional Legislation. Robert Smart B.Sc., C.Eng., M.R.I.N.A.

Ship Steels: A History of Continuous 21Development. David Howarth B.Met., C.Eng.,

F.I.M.M.M., F. Weld.I.

Structural Design Issues and Ongoing 33Developments. Alex Johnston C.Eng., F.R.I.N.A.

Ship Hydrodynamic Propulsion: 51Some Contemporary Issues of Propulsive Efficiency, Cavitation and Erosion. John Carlton D.Sc., B.A., C.Eng., M.I.Mech.E.,

M.R.I.N.A., M.I.Mar.EST.

Design Assessment of Engineering Systems 65with Particular Reference to Shaft Alignment.Andrew Smith B.Sc., C.Eng., F.I.Mech.E.

The Potential for Energy. Ed Fort B.Sc. 75

Configuration Management as a Risk- 87Based Tool in Managing Dependability of Complex Software-Based Systems. Bernard Twomey B.Eng., C.Eng., F.I.E.T., M.I.Mech.E.

and Renny Smith B.Sc., C.Eng., M.I.E.T.

The Influence of Ship Underwater 101Noise Emissions on Marine Mammals. John Carlton D.Sc., B.A., C.Eng., M.I.Mech.E.,

M.R.I.N.A., M.I.Mar.EST. and Emma Dabbs.

The Assurance of Safety in the 111Marine Environment. Vince Jenkins B.Sc.,

C.Eng., M.I.Mech.E.

Author biographies 119

Lloyd's Register, its affiliates and subsidiaries and their respectiveofficers, employees or agents are, individually and collectively, referredto in this clause as the ‘Lloyd's Register Group’. The Lloyd's RegisterGroup assumes no responsibility and shall not be liable to any personfor any loss, damage or expense caused by reliance on the informationor advice in this document or howsoever provided, unless that personhas signed a contract with the relevant Lloyd's Register Group entity forthe provision of this information or advice and in that case anyresponsibility or liability is exclusively on the terms and conditions setout in that contract.

© Lloyd’s Register 2009

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PAPER 1

LLOYD’S REGISTER’S APPROACH TO RESEARCH AND INNOVATION

Vaughan Pomeroy M.A., C.Eng., F.I.Mech.E.,

F.I.Mar.EST., F.R.I.N.A.

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LLOYD’S REGISTER’S APPROACH TO RESEARCH AND INNOVATION Vaughan Pomeroy SUMMARY As an introduction to this collection of papers, which outlines the current position of Lloyd’s Register in key areas of technology, this paper explains why research and innovation is important to a classification society. The approach taken to maintaining the technology base of Lloyd’s Register has changed over the years to reflect the structural changes within the marine industry. After a very short look backwards, the paper describes the aims of the considerable investment that we are making in research and innovation, how the objectives of this research are achieved and our increased dependence on collaboration and co-operation with clients, academia and industry. Finally, the role of the separate and independent charity, the Lloyd’s Register Educational Trust, in funding research activities is described. 1. INTRODUCTION Lloyd’s Register commits a considerable effort to the continual development of its technology base and to the improvement of its products and services. This investment is essential to help ensure that: • the Rules and the supporting procedures, which

form the basis of classification, are up-to-date and reflect best available technical knowledge and the current and likely future solutions that are, or will be, employed by industry

• the tools and methods used by Lloyd’s Register in the classification process for verifying that ship designs are compliant with the Rules and the requirements of statutory regulations are efficient and make use of sound methodologies

• the totality of the technology base of Lloyd’s Register, which is largely retained in the form of knowledge, experience and skills, is adequate to meet the demands of the provision of classification, statutory certification and consultancy services.

Our programme of research, development and innovation covers a large range of activities, from investigating new technologies and design concepts, which might become important in the future, through systematic development of analysis tools and the study of new approaches to the Rules, to the creation of new Rules, products and services. Our approach has evolved as industry has changed and is now more collaborative than before, depending more on co-operation with industry, research institutes and universities. 2. RETROSPECTIVE AND PERSPECTIVE The approach taken to research and innovation has to reflect the relationship between the classification society and the industry that it serves and this relationship changes with time. A review of Lloyd’s

Register’s publications illustrates this clearly, through the changing balance between reporting fundamental research over a wide spectrum (with the underlying technology often significantly in advance of an industry which was made up of a large number of suppliers) and more focused research which supplements the contribution of industry. By way of example, it is unlikely, nowadays, that Lloyd’s Register would develop and publish new analytical methods for the stress analysis of crankshafts as it did in the last century, in the late thirties and early eighties. The focus is now on developing appropriate methods for assessing designs and incorporating the appropriate assessment criteria into the Rules. There are now quite distinct areas in which industry expects Lloyd’s Register to undertake fundamental work. There are others where the fundamental work is undertaken by industry: Lloyd’s Register uses this knowledge as an input to development processes which determine the appropriate standards relating to safety, and then publishes these standards as Rules. This rule-making, or standards formulation, is a key element of the research and development activity of Lloyd’s Register. For any major classification society, the development and maintenance of rules represents a critical core competence. The Rules represent a collection of requirements for ship design and construction, and, thereafter, maintenance in operation. They are based on knowledge and experience. The style and form of the Rules varies, reflecting the relationship with industry. However, they are a somewhat unusual form of standardisation in that they represent a comprehensive set of requirements for a complete artefact, a ship of a specific type. The ship is, in effect, treated as a system, with the requirements disaggregated down to component level where appropriate. The depth of the Rules determines the focus of our programme of research and development. The Rules

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relating to the hull structure provide very detailed requirements, whereas for many of the engineering systems the focus is on arrangements and system level requirements. The approach to research and innovation is based on the different requirements for each topic. Furthermore, the overall scope is continually widening. Our involvement in human element matters and cold climate operations, for example, is increasing, which reflects the changing and expanding expectations of industry. The challenge is to construct a programme of research and innovation which provides the necessary outcomes across a wide range of technologies, industry expectations and applications. 3. APPROACH AND OBJECTIVES Therefore, the approach taken to research and innovation by Lloyd’s Register has to be balanced. It is imperative that the Rules and the supporting procedures, which form the basis of classification, reflect current technology. Conversely, the classification society is working at arms length from the principal research and development arena, which sits within academia and with industry, where decisions are made on which technologies will be adopted and offered to the marine industry for application. The essentials of the approach which is taken by Lloyd’s Register are illustrated in Figure 1, which shows that the development programme takes knowledge and experience as its inputs and translates these into new or improved products and services. The development programme also provides input to the skills and technology base of Lloyd’s Register, which maintains the value of the human capital and enhances service delivery.

Figure1: Essential elements

The research and innovation approach of Lloyd’s Register is, therefore, quite complex because of the interactions and outputs involved. Firstly, there are projects that underpin the technological knowledge base of Lloyd’s Register. These projects will not usually result in the direct development of a specific product or service, but provide the groundwork for further projects that will take the knowledge and use it to develop exploitable applications. These projects tend to focus on the technology sectors that have been identified as those in which Lloyd’s Register needs to carry out fundamental work. These projects include: • evaluation of new analysis methods in the core

technology areas and assessment of their potential usefulness and relevance to Lloyd’s Register

• monitoring developments in other technology sectors and evaluating the potential for their application in the marine sector

• developing fundamental engineering concepts into analysis tools and methods that could be used by Lloyd’s Register in providing its services to marine customers.

There are also a number of relatively small projects that look forward to develop a future research and development strategy. These projects include: • tracking of scientific and technological research

to determine any potential impact on Lloyd’s Register’s marine business

• developing future strategic plans for research and development

• preparing briefings for the marine industry on technology trends.

A number of activities in this programme of projects will be carried out collaboratively with other organisations.

Knowledge from research and innovation

Experience from survey

and application

Secondly, there are a number of projects targeted at satisfying the identified business needs of one or more of the segments or product lines that Lloyd’s Register offers, or wishes to offer, to its marine clients. These projects utilise: the outcomes of the underpinning technology projects; the knowledge, experience and expertise of Lloyd’s Register’s technical employees; and knowledge gained from external sources, either from published information or from collaborative ventures. These projects include:

Development programme

Technology and skills base

Products and services

• development of new or revised Rules for

Classification for all types of marine vehicles • development of new or revised procedures for

analysis or survey or other processes that form part of the classification system

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• preparation and maintenance of guidance documents for customers and surveyors

• development of new or revised tools and capabilities for specialist services that form part of the portfolio of services and products offered by Lloyd’s Register to marine clients, such as the investigation of engineering or materials failures or the analysis of substances.

The overall development programme comprises a number of individual projects that are a balance of the aforementioned types. These help: • ensure that Lloyd’s Register retains a sound

understanding of current and future technologies that are relevant or potentially relevant to the marine business

• deliver new products to the marketplace that enable Lloyd’s Register to provide a high quality service to its marine clients which reflects up-to-date knowledge and understanding of marine science and technology.

4. EXPERIMENTAL METHODS Until 1988, Lloyd’s Register operated a large research laboratory in Crawley which provided extensive facilities for metallurgical examination, NDE and mechanical testing. Major contributions were made by the work at a time when advances were being made in marine engineering and in the design of marine and offshore structures.

Figure 2: Fatigue testing of shaft components at Crawley Work of particular note included: • determination of the fatigue strength of marine

shafting systems (see Figure 2) • investigation of the fretting fatigue behaviour of

propeller/tailshaft connections, in particular the effect of keyways and the keyless arrangement

• development of design parameters for stress concentration at nodal joints for offshore structures based on small scale models

• development of procedures for reducing the risk of brittle fracture in ship steels

• determination of an improved approach to crankshaft stress analysis using experimentally-derived factors

• derivation of fracture mechanics assessment formulations for pressure vessels and piping.

The work at Crawley also involved failure investigations of a wide range of engineering components, making use of electron and optical microscopy, NDE and mechanical testing. This work was transferred in 1988 to a new laboratory in Croydon, where it continues to this day. Major experimental work has been undertaken in more recent times to fill gaps in the available knowledge base, by arranging contracts with research institutes and universities. This work has included large scale model testing in the open water basin of the Krylov Institute, in St Petersburg, to determine appropriate wave loads for special service craft (see Figure 3). Tests were conducted on monohull and catamaran models. The information derived from this test programme filled a gap in available knowledge and the results form part of the Rules for Special Service Craft.

Figure 3: Model catamaran in the open water basin The Krylov Institute also carried out some large scale fatigue tests of double hull oil tanker and bulk carrier sections to establish good design practice. A typical test specimen used to determine the fatigue behaviour of bulk carrier side frame connections is shown in Figure 4. The fatigue test programme carried out at the Krylov Institute, on both large scale and small scale specifics, has provided the baseline data which underpins the fatigue assessment approach of Lloyd’s Register for hull structures.

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Figure 4: Large scale fatigue testing of bulk carrier structure The other major contribution in terms of experimental methods has been the resort to full scale measurement of strain, vibration and other engineering parameters on ships in operation. Lloyd’s Register has, for more than sixty years, provided a skilled investigation service to shipowners to establish an understanding of the fundamental reasons for technical problems and to develop a solution. The output from these investigations often provides an essential input into the development of improved Rules or better assessment methodologies for use during the review of new designs. Less well known are the full scale measurement programmes that are instigated from time to time. These are generally carried out to acquire data of ship or system behaviour under realistic operating conditions. The data from full scale hull monitoring is analysed and used to confirm that the measured response is comparable with the calculated response, which is determined from the application of the Rules and the current or proposed assessment procedures. In recent years full scale measurements have been conducted for a double hull oil tanker, a fast container ship, an icebreaker and, currently, a post-panamax container ship. A collaborative programme to carry out full scale measurements on a LNG ship, which Lloyd’s Register is part funding, is currently being initiated. These exercises are carried out over extended periods to ensure that the likelihood of meeting more extreme operating conditions is sufficient to justify the expenditure. The results form part of the feedback mechanism which validates the Rules and the approaches used in assessing ship designs and these results are usually published. 5. COLLABORATION Research and innovation is often carried out in collaboration with others who share a common interest in the specific topic, sometimes even

competitors. The degree of collaboration depends on the stage within the research, innovation and product development cycle, as illustrated in Figure 5. Lloyd’s Register has found working with other organisations advantageous, particularly at the basic and applied research stages, following a number of different collaboration models.

Figure 5: Relationship between opportunities for collaboration and development stage

Of course, collaboration is also valuable, in terms of gaining access to specific technologies and expertise, in the product design and development stage, providing that ownership of the research outcomes and any intellectual property is clear. This usually, as far as Lloyd’s Register is concerned, results in sub-contracting of some tasks and this arrangement, while increasingly common, is not developed further in this paper. Suffice it to say; where a particular capability, which may be to access experimental facilities or particular individual expertise, is required, Lloyd’s Register will make use of sub-contractors where appropriate. Returning to the main theme, Lloyd’s Register has used a number of approaches to collaboration with organisations in industry and academia. Examples of these collaborative approaches include: • funding of post-graduate studies • joining Joint Industry Projects established by

research institutes or similar organisations as a funding body

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• taking an active part in a Joint Development Project, sharing funding with other project participants

• participating in a project with other organisations, with work packages divided amongst the participants, and sharing the research outcomes, often as part of a funded research programme such as those operated by the European Union.

Collaboration undoubtedly brings benefits through working with other organisations who share a common interest. However, achieving individual aims in a collaborative environment can be a challenge, since each organisation will come to the project with similar but fundamentally different needs and objectives. Collaboration also comes with an overhead attached, as a result of the need to manage across several organisations and to ensure that as many of the individual aims as possible are realised at the end of the project. Lloyd’s Register is a knowledge-intensive organisation, which means that the research and innovation investment has to enhance the corporate library of knowledge and advance the application of that knowledge in the delivery of classification, statutory certification and consultancy services. The link between the innovation programme and the acquisition and application of knowledge is illustrated in Figure 6. In practical terms, the knowledge generally derives from fundamental research, which is most effectively carried out in universities and specialist research institutes. Through collaboration with universities and research institutes, Lloyd’s Register gains the benefit of improved corporate knowledge. This basic tenet forms an essential part of the rationale for the relocation of Lloyd’s Register’s Marine London activities to Southampton, immediately alongside a premier research-led university with a keen focus on maritime sciences and technologies and wider interests in the maritime sector. Lloyd’s Register intends, with the active and essential collaboration of the University of Southampton, to promote a Maritime Institute, located on the University’s campus. This will physically link Lloyd’s Register and the university, and will actively encourage collaboration between industry and the research community. The application of research and the application of knowledge, in the development of innovative products and services, can be more effective when there is active collaboration with industry. Lloyd’s Register will continue to work with other organisations in joint projects whenever such an arrangement is advantageous. In fact, many developments cannot be undertaken without the active support and participation of others, such as shipowners who make their ships available for

measurement programmes or to allow Lloyd’s Register employees to observe operations.

Knowledge

from research

Improved application of

knowledge Innovation funded by investment

Fig 6: The wheels of knowledge Lloyd’s Register will also play a part within major research programmes, such as those funded by the European Union. When external funding is an essential element of a collaborative programme there is an additional concern about the total benefit which must be addressed, as preparing proposals can be costly and the project may be unsuccessful. It is unlikely that collaboration that is dependent on funding by others will ever form a significant part of the essential development programme of Lloyd’s Register simply because of the uncertainties involved. However, involvement in such projects can be beneficial in terms of gaining knowledge from shared experience. It is another example of the need for a pragmatic and balanced approach to research and innovation. 6. EXPERIENCE A key input to Lloyd’s Register’s research programme is feedback from operational experience. The Rules, which form the primary vehicle for transferring the outcomes from research and innovation to industry for exploitation, provide a set of standards for materials, equipment, components, systems and structures that relate to the complete life cycle of the ship from concept, through design, manufacture, construction, installation and testing, to operation and eventual recycling. One of the most important facets of the Rules is that they are not just a reflection of theory and design but they take full account of operational experience. As early as 1960, Lloyd’s Register began to gather data from periodical survey reports relating to

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damages and defects, and to build a database containing this information in a structured format to aid extraction of studies on actual service experience. This systematic collection of data relating to the total experience with the classed fleet continues and the database provides valuable input to the research and development programme. By carrying out specific studies it is possible to detect trends in service experience in terms of changes in defect incidence rates or changing patterns in the type of defects found. It is also possible to detect common issues across the fleet and, where appropriate, the Rules, or the guidance given during design review or survey, can be modified to reduce the risk of repetition in later designs or in future operation. The importance of the database is that it allows feedback to be kept in proportion. Feedback on failures is often accompanied by a suggestion that the Rules could be modified, but Lloyd’s Register has to make sure that additional requirements are only introduced when they are justified. A single major incident may indicate that a change is necessary, simply because of the risk involved. More often, it is a trend involving a number of similar incidents which provokes investigation to find a solution which would reduce the risk while still being proportionate to that risk. The primary source of data is the periodical survey report and this represents a snapshot in time. For the hull structure the database is reasonably complete since any significant damage or defect will result in a surveyor attending and reporting on the damage or defect and the recommended repair. With machinery and systems the database is less complete as many minor incidents are dealt with by the ship’s crew as routine maintenance. Nevertheless, this lengthy record of damage and defect history for a very large number of ships provides a very useful source of operational experience, particularly when supplemented by the experience from technical investigations and from anecdotal evidence collected from regular contact with shipowners. 7. LLOYD’S REGISTER EDUCATIONAL TRUST For many years, Lloyd’s Register has given donations to organisations in pursuit of its charitable objective, which is clearly defined within the Constitution of Lloyd’s Register. The current version requires Lloyd’s Register to undertake: “The advancement of public education within the transportation industries and any other engineering and technological disciplines, by the conducting of and support of research and the publication of the useful results of all such research and by the provision

of training, and the collation and dissemination of statistical data.” The remainder of this paper illustrates how Lloyd’s Register discharges this objective through additional funding provided through the Lloyd’s Register Educational Trust. Since 2000, Lloyd’s Register has taken a much more active approach to funding of organisations and the scale of the money available for this support programme, which is set aside for these purposes from the operating surpluses generated by the businesses of Lloyd’s Register, has been increased significantly. The support programme has been developed to provide funding, throughout the world, for: • activities in schools to promote interest in

engineering, science and technology • undergraduate and postgraduate studies for

exceptional science and engineering students • vocational training and professional development • research programmes at leading universities in

transportation, engineering, science and technology in fields related to Lloyd’s Register’s business activities.

This funding activity is now established within a separate charity, the Lloyd’s Register Educational Trust, which receives annual donations from Lloyd’s Register and is governed by its own Trustees who determine the distribution of the available funds. Since its establishment as an independent charity in 2004, the Lloyd’s Register Educational Trust has received a total of more than £30 million, which makes it a large funding organisation in the science, engineering and technology field. Once established the Lloyd’s Register Educational Trust took over all related funding activities from the Lloyd’s Register Group. In terms of funding research the Lloyd’s Register Educational Trust sets out to fund programmes of work, rather than a larger number of smaller projects, in defined subjects at internationally-renowned centres of excellence. The funding is granted for a fixed period, usually five years, although programmes may be extended by agreement. The current beneficiaries, along with their scope, are as follows: • Cardiff University, UK – marine human element

issues. • Imperial College London, UK – transportation,

particularly rail, risk management. • Lancaster University, UK – nuclear engineering

and decommissioning. • Loughborough University, UK – systems

engineering.

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• Open University, UK – materials fabrication. • Pusan National University, Korea – ship structures. • Seoul National University, Korea – hydrodynamics

and hydroelasticity. • National University of Singapore – offshore

engineering and LNG. • University of Southampton – hydrodynamics,

hydroelasticity and composite structures. The funding, now totalling some £10 million, is provided to support fundamental research with an obligation to publish and disseminate the results for the benefit of all. The research programmes are determined by the university with advice provided by the relevant experts, including Lloyd’s Register. In September 2008, the first international Marine Research Workshop was organised by the University of Southampton which brought together the five universities that are funded by the Lloyd’s Register Educational Trust and which are working in the marine field. The workshop was attended by invited participants from academia and industry. The objective was to encourage co-operation within the community that is supported by the Lloyd’s Register Educational Trust, to share ideas and to maximise the benefit to industry and the wider public. 8. CONCLUDING REMARKS Research and innovation is critically important to Lloyd’s Register in order to ensure that the services that are available to the marine industry are maintained at a high level. The demands from industry for investment and innovation are increasing and Lloyd’s Register is committed to providing appropriate and effective regulation, through classification, of ship safety along with a high quality portfolio of support through marine consultancy. The approach described in this paper, including the need for collaboration and sharing of fundamental research, will deliver the innovation necessary to develop the products, including the Rules, and services to meet the highest demands of the marine industry, taking full account of the opportunities offered by new technologies. 9. ACKNOWLEDGEMENTS The author wishes to acknowledge the assistance of his colleagues in developing this paper and the rationale explained therein.

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PAPER 2

IMPLICATIONS OF FORTHCOMINGINTERNATIONAL AND REGIONALLEGISLATION

Robert Smart B.Sc., C.Eng., M.R.I.N.A.

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IMPLICATIONS OF FORTHCOMING INTERNATIONAL AND REGIONAL LEGISLATION Robert Smart SUMMARY This paper considers aspects of some of the more important regional and international legislation, from that which is imminent through to recently proposed agenda items. The potential impact of this legislation on ships and their operation is discussed in some detail. Included in the discussion will be the revised SOLAS requirements for subdivision and damage stability, the developing ship recycling convention, the Maritime Labour Convention, which is expected to enter into force in 2011, and the marine underwater noise pollution debate, which is just commencing in the MEPC forum. The examples used highlight the complexity and diversity of topics that have materialised within the marine regulatory environment. The proliferation of legislation over the last few decades has made it more difficult for interested parties, irrespective of the level of detail needed, to keep abreast of actual requirements, present developments and future ideas. Awareness of legislation is not sufficient as it is also important in this highly competitive industry to understand its implications, both technically and commercially. 1. INTRODUCTION During the last 20 to 30 years, there has been a considerable increase in the regulatory publications applicable to ships; it is believed the volume has increased by some 300 to 400%. Part of this increase is due to expansion within existing areas, such as safety equipment and classification Rules. However, some are the result of the increasing diversity of topics (Annexes V and VI of MARPOL, for example). The number of initiators has also increased over this period, expanding from flag states and classification societies to include both international and regional organisations, such as the EU, port state control organisations (MOUs), the International Labour Organisation and coastal states. Keeping abreast of developments and understanding their implications has become a significant task, not only necessitating many specialists but requiring continuous engagement, which means it is no longer a part-time job. Consequently, many shipowners and managers can no longer address this in house and need reliable expert advice to manage the associated risks. While the regulatory changes encompass both hardware and operational requirements, this paper is generally restricted to safety and pollution prevention aspects. 2. RECENT LEGISLATION 2.1 SOLAS CHAPTER II-1 On January 1, 2009, the revisions to SOLAS Chapter II-1, Part B [1], which deals with subdivision and stability, came into force. The revised version has been referred to as ’SOLAS 2009’, which is unusual

as SOLAS versions are normally identified by the year of adoption: this seems to be an exception. 2.1 (a) Background Previously, subdivision and damage stability for passenger ships and cargo ships were developed on completely different concepts: the ‘deterministic’ concept was used for passenger ships and the ’probabilistic’ concept for cargo ships. Deterministic damage calculations were based upon clearly defined damages. A passenger ship, for example, should withstand two-compartment flooding. The probabilistic concept is a sum of all the probabilities of a given particular water-tight compartment flooding, multiplied by the ability to survive that particular flooding. This is calculated for all possible damage scenarios along the length of the ship. In the probabilistic concept, even if a water-tight compartment is relatively large, if the probability of damage in such a location is low, and/or the ability of the ship to survive the damage is high, the overall impact on the ship’s survivability will be small. In ‘SOLAS 2009’, in addition to the harmonisation of the damage stability requirements, there has also been revision to various flooding scenarios, including the assumed degree of damage, as initially this caused substantial differences in the results under the new requirements. In practice, these changes are likely to mean greater flexibility in the design of cruise ships and more subdivision on car carriers and small coastal ships. 2.1 (b) Noticeable Impacts The new assumed side penetration (B/5 to B/2) will consider that all piping is damaged, i.e. in order to avoid progressive flooding, pipes in water-tight compartments must be fitted with non-return valves.

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The minimum height of double bottoms is now clearly stated as 500mm, along with how they should be measured; however there is provision for alternative calculation using the deterministic concepts in areas such as below the main engines where this figure is not achievable. In calculating the necessary bilge pump capacity, crew spaces below the bulkhead deck are now to be included, which may increase the required number of bilge pumps. Under the deterministic concept, it was easier for a Master to assess whether his ship would sink or capsize under the damage conditions. However, under the probabilistic concept it is not possible for Masters to assess the situation. A supporting information tool will need to be employed, usually by means of a limiting GM (or KG) curve(s). Figure 1: Car carrier with list 2.1 (c) Stockholm Agreement The Stockholm Agreement implemented in European Waters is a regional agreement, adopted under the auspices of IMO, which requires calculation of the effects of water on deck. Presently it is still not clear whether SOLAS 2009 covers the Stockholm Agreement. Therefore it may become an addition to the Convention. 2.2 PROTECTION OF NORTH ATLANTIC RIGHT

WHALES – SHIP SPEED REDUCTION 2.2 (a) Background With only between 300 and 400 in existence, North Atlantic right whales are among the most endangered whales in the world. Their slow movements and the time they spend at the surface and near the coast make them highly vulnerable to ship strikes, especially in US East Coast waters where

shipping lanes into ports cut across their migration routes. A new regulation, which came into effect on December 9, 2008, requires that ships operating in the South-Eastern Atlantic and mid-Atlantic US waters must adhere to speed restrictions to protect endangered right whales. 2.2 (b) Noticeable Impacts The regulation requires ships of 65 feet (19.8 metres) or longer to restrict their speed to 10 knots or less in certain areas where right whales gather. The speed restrictions are now in effect in waters from Rhode Island to south of Jacksonville, and they will take effect in certain areas off New England from January, 2009, when whales begin gathering in the area as part of their annual migration. The 10-knot speed restriction will extend out to 20 nautical miles around major mid-Atlantic coast ports. The speed restriction also applies in waters off New England and the South-Eastern US, where whales gather seasonally. The speed restrictions apply each year in the following approximate locations and at the following times. This is based on the times that whales are known to be present in each area: • South-eastern US areas, from St. Augustine,

Florida to Brunswick, Georgia, from November 15 to April 15.

• Mid-Atlantic US areas, from Rhode Island to Georgia, from November 1 to April 30.

• Cape Cod Bay, from January 1 to May 15. • Off Race Point at the northern end of Cape Cod,

from March 1 to April 30. • Great South Channel of New England, from April

1 to July 31. The National Oceanic and Atmospheric Administration (NOAA) will also call for temporary voluntary speed limits in other areas at times when the presence of right whales is confirmed. Scientists will assess the regulations effectiveness before expiry in 2013. In the next session of the Maritime Environmental Protection Committee there will be some consideration of the influence noise emissions from ships have on marine mammals [2]. A compliance guide is available at: http://www.nero.noaa.gov/shipstrike/doc/complianceguide.pdf

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3. FUTURE LEGISLATION 3.1 THE MANDATORY INTERNATIONAL

MARITIME SOLID BULK CARGO (IMSBC) CODE

3.1 (a) Background Amendments to SOLAS will make the BC Code mandatory. It will now be called the International Maritime Solid Bulk Cargoes (IMSBC) Code. It can be implemented voluntarily from January 1, 2009, and is expected to become mandatory from January 1, 2011. 3.1 (b) Noticeable Impacts There are a number of changes made to the requirements, the impact of which will depend on cargoes carried. These changes may include possible alterations to the ship structure and/or equipment. Details are contained in the relevant IMO publications [3]. Procedurally, although the Code will be mandatory, IMO has not included any survey and certification requirements; this could cause problems if some port authorities look for compliance before implementation. 3.2 AMENDMENTS TO MARPOL ANNEX VI 3.2 (a) Background Revisions to Annex VI of the MARPOL Convention will enter into force on July 1, 2010; these define a reduced sulphur oxide (SOx) emission limit in the Baltic Sea and North Sea Emission Control Areas (ECAs). 3.2 (b) Noticeable Impacts From July 1, the current limit of 1.50% m/m will reduced to 1.00% m/m; and from January 1, 2015, it will further reduced to 0.10% m/m. The SOx emission limits outside ECAs will change from the current 4.50% to 3.50% from January 1, 2012: then, subject to a review of fuel availability, it is also proposed that a 0.50% fuel sulphur limit will be introduced from January 1, 2020 [4]. Lower nitrogen oxide (NOx) emission limits will come into effect for diesel engines installed on ships constructed after January 1, 2011. For ships built after January 1, 2016, operating in ECAs, an 80% reduction, approximately, in NOx emissions will be required.

Large diesel engines installed on ships constructed between 1990 and 2000 will also be required to meet current NOx emission limits [5], provided that an ‘Approved Method’ of achieving the required reduction is available. It is assumed that engine manufacturers are designing and testing modifications to subsequently submit for approval. 4. POSSIBLE LEGISLATION 4.1 BALLAST WATER TREATMENT 4.1 (a) Background The International Convention for the Control and Management of Ships' Ballast Water and Sediments will enter into force 12 months after ratification by 30 States, representing 35% of world merchant shipping tonnage. To date, there are 16 states (including South Africa, France and Liberia), representing 14.4% of the world’s tonnage, which have ratified the Convention. Countries that have been unable to ratify the Convention until the main guidelines are adopted will now be in a position to begin the ratification process due to the substantial progress made in developing guidelines and in approving ballast water treatment systems. 4.1 (b) Noticeable Impacts Once it enters into force, this Convention will apply to ships engaged on international voyages that carry ballast water on board. Existing ships (built before January 1, 2009) with ballast capacity over 1500 m3, will be required to retrofit ballast water treatment systems. IMO’s 25th Assembly adopted a resolution [6] which provides a period of grace for ships built in 2009 in order to accelerate ratification of the convention. Shipbuilders and shipowners are being encouraged to consider installation of the ballast water treatment system for ships scheduled to be built in 2010. At the least, owners should now be ensuring the vessel has space for fitting a ballast water treatment system, along with the necessary power capacity and ballast piping arrangements for the system to be installed. Crude oil tankers will be required to have an approved VOC management plan. A draft MEPC Circular on the guidelines for the plan prepared at MEPC 57 is subject to approval at MEPC 60 next year.

15

4.1 (c) Lloyd’s Register’s BallastTreatment Technology Guide

Water

Lloyd’s Register has prepared and updated a version of its Ballast Water Treatment Technology Guide publication. 4.2 SHIP RECYCLING 4.2 (a) Background The IMO is developing requirements covering: prohibited material; maintenance of inventories of hazardous materials on board; and survey and certification schemes, including approval of ship recycling plans. The text of the convention is scheduled to be adopted at the Diplomatic Conference in May 2009; however there are still substantive items to be concluded before the final adoption of the text. 4.2 (b) Noticeable Impacts During recent lengthy discussions, the Committee decided not to include dismantling in non-party states. Instead, a Conference resolution dealing with the issue will be developed. However, a couple of states have expressed reservation over this position. Figure 2: Present beach scrapping arrangements At the last Committee meeting it was recognised that when a ship is sold to a ’cash buyer’, the ship may no longer fly the flag of a particular state for a limited period immediately before her delivery to the recycling facility. It was suggested that it might be necessary to review this provision before its final adoption.

A formulation for the Article concerning the entry into force, which would require a minimum number of states, a tonnage threshold and a factor based on the ratio of ship recycling capacity to the combined tonnage of merchant shipping, has been proposed. It was agreed the issue would need further discussion. A large number of member states have expressed concerns over the possible existence of two standards (i.e., those developed by IMO and by ISO) which might confuse stakeholders, as the convention and its guidelines should be a primary instrument on issues relating to ship recycling. Figure 3: Scrapping arrangements for MSC Napoli A diplomatic conference for the adoption of the Convention is scheduled from May 11 to 15, 2009, in Hong Kong. Following this, it is anticipated that the guidelines will be adopted at MEPC 59 in July 2009. 4.3 INTERNATIONAL MARITIME LABOUR

CONVENTION (MLC, 2006) 4.3 (a) Background The MLC, 2006 sets minimum standards in areas relating to the health, safety and welfare of seafarers. This Convention has been referred to as a ‘bill of rights’ for seafarers and, in this respect, it is clearly intended to address maritime employment issues. The Convention has also been referred to as the ‘fourth pillar of maritime legislation’, which hints at its complexity and depth. It is designed to supersede all previous ILO conventions which have, at best, been implemented in a piecemeal fashion. To enter into force the Convention must be ratified by 30 ILO Member States representing 33% of the world’s gross tonnage. To date it has been ratified by the Bahamas, Liberia, and the Marshall Islands, representing an estimated 17% of world gross tonnage. The EU has advised that member states should have ratified the Convention by the end of 2010, which, with the year’s grace implementation, will probably be in 2011.

16

Figure 4: facilities on board a detained ship 4.3 (b) Noticeable Impacts With the enforcement and compliance through both flag state and port state inspections, ships may, in the future, be detained against this Convention, on issues such as incorrect payment of wages, lack of shore leave, poor working and living conditions, non compliance with hours of work and rest requirements. Lloyd’s Register understands that the Convention should be based on onboard ship inspections, rather than relying on any shore inspections. The Convention requires certain documentation, procedures and policies to be in place. It will be the responsibility of the owner’s representative on board (usually the Master) to provide evidence that such policies and practices are effectively being followed and that the vessel is in compliance with the requirements of the Convention. Through Title 5 of the Convention, which addresses ‘control and enforcement’, and through a certification process, the ‘no more favourable treatment’ requirement of the Convention should be achieved. However, there are characteristics of the Convention which could allow wide variations in interpretation of the requirements by flag states, port states and recognised organisations and which could ultimately be counter productive to achieving a level playing field. The Convention includes Part A, which contains the mandatory items to be inspected, and Part B which contains the non mandatory items (guidelines) on how Part A can be implemented. Since Part B is quite extensive in its scope and is open to different interpretations it is here where variations in inspection standards will most likely occur.

5. CONCLUSIONS The regulatory regime will continue to expand and be dominated by IMO and, increasingly, by regional interests like the EU. It is expected, however, that there will be increased pressure from industry on the EU to work within the international framework and to step back from regional solutions for international shipping, as recently indicated by the Commission. The focus at IMO has shifted to the environment, although a large number of wide-ranging initiatives continue which will impact on the certification activity of owners and Lloyd’s Register alike. In terms of following developments, Lloyd’s Register is well placed to track and assess submissions, attend meetings and provide active support through IACS or administrations. Attendance at all external regulatory events is now arranged so that for every appropriate work item reports are provided, along with synopses, for inclusion in our RuleOutlook Live service (available within ClassDirect Live). This is aimed at facilitating dissemination of knowledge and enhancing the implementation phase of these regulatory changes. The effective and timely management of information should encourage surveyors, owners and managers to rely on Lloyd’s Register for awareness of regulatory changes. Using this knowledge, and in order to enhance safety and reduce pollution incidents, Lloyd’s Register will listen to all interested parties so that, where appropriate, we can endeavour to influence future regulations and legislation to benefit the industry as a whole. All of these initiatives are designed to support Lloyd’s Register’s mission, which through its constitution, is directed to ‘secure for the benefit of the community high technical standards of design, manufacture, construction, maintenance, operation and performance, for the purpose of enhancing the safety of life and property at sea, on land, and in the air’, and to ‘advance public education within engineering and technological disciplines’. However, Lloyd’s Register’s efforts are proving more difficult to implement against a backdrop of a more litigious environment for recognised organisations. The issues they face include: • the potential for fines under the soon to be

published 3rd Maritime Safety Package (3MSP) • the investigation of IACS under competition

legislation by DG/COMP • the potential criminal charges under the revised

Ship Sources Pollution Directive

17

• unfair exposure to unlimited liability imposed by some EU flag states;

All of these issues can encourage an air of caution and lead to less creativity. 6. ACKNOWLEDGEMENTS The author would like to thank, in addition to those colleagues listed below, the numerous colleagues who attend IMO, IACS, ISO and other industry meetings on behalf of Lloyd’s Register’s External Affairs team and provide reports and synopses for inclusion in RuleOutlook Live. Specifically the author gratefully acknowledges the support and help from John Carlton, Graham Greensmith, Roland Ives, Stephen Machado, Vaughan Pomeroy, Gillian Reynolds, Manuela Sarris, Robin Townsend, Motonobu Tsuchiya and Rhoda Willson. 7. REFERENCES 1. IMO Resolutions MSC.194(80) and MSC.216(82), 2. MEPC Paper MEPC 58/19 3. IMO Resolution MSC.269(85), 4. IMO Resolution MEPC.176(58), 5. IMO Resolution MEPC.177(58), 6. IMO Resolution A.1005 (25) - Application of the

International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004,

18

NOTES

19

NOTES

20

PAPER 3

SHIP STEELS: A HISTORY OFCONTINUOUS DEVELOPMENT

David Howarth B.Met., C.Eng., F.I.M.M.M., F. Weld.I.

21

22

SHIP STEELS: A HISTORY OF CONTINUOUS DEVELOPMENT David J Howarth SUMMARY Constructional steels used in shipbuilding have a history that goes back to the end of the second world war, yet the steels of today bear no resemblance to those earlier steels. This has resulted from a process of continual improvement that has taken place since then, but, these materials are increasingly asked to perform in more onerous operating environments, where dangers of continuous service at low temperature are commonplace. Consequently, continuous improvement is needed to maintain the safety of commercial shipping. Constructional steels for ships have traditionally been benign in terms of processing, easy to fabricate and reliable in service. This may change as a move to more sensitive higher tensile steel may threaten this tradition. This paper looks at the developments that have taken place, especially applications at lower temperatures such as are found in the Arctic, the use of high strength steels, thick steel plates and new developments in terms of fatigue.

1. INTRODUCTION At the time of the second world war, the Rules for structural steel only specified tensile strength as a requirement for the material. However, following the instance of brittle fractures of the Liberty Ships, post war investigations [1] clearly identified the need for a minimum toughness in marine steels. Therefore, in 1957, Lloyd's Register’s Rules introduced for the first time minimum requirements for toughness of the steel with the aim for the steel to show some resistance to low temperature applications and or high strain rate. This was achieved by the introduction of requirements for the Charpy V-notch impact test; this was 47 Joules at 0°C. This requirement was quickly followed in 1961 by the use of standard steel grades with minimum toughness controlled by differences in Charpy requirements and the birth of the modern requirements for steel had begun. Since that time, standard shipbuilding steels have been continually improved and developed. Even so, these steels are increasingly asked to perform in more onerous operating environments where dangers of continuous service at low temperature are commonplace. Continuous improvement is therefore required to maintain the safety of commercial shipping. Constructional steels for ships have traditionally been benign in terms of processing – easy to fabricate and reliable in service. This may change as a move to more sensitive higher tensile steel could threaten this tradition. This paper looks at the developments that have taken place, especially applications at lower temperatures such as are found in the Arctic, the use of high strength steels, thick steel plates and new developments in terms of fatigue. 2. SHIP STEELS Requirements for steels intended for the construction of ships are today based on the IACS Unified Requirement W11 [2]. As indicated by the title these

are unified requirements and are the same for all classification societies. The steels are categorised in two groups based on the yield strength. The two groups are normal strength ship steel, more commonly referred to as mild steel, and higher strength ship steel, more commonly referred to as higher tensile steel. The majority of steel used in ship construction is still mild steel. It is perceived that higher tensile steels are related to fatigue cracking problems based on the memories of such difficulties when these steels were first used in a large way in tanker designs of the 1980s. Table 1 shows the basic mechanical property requirements of these steels. Higher tensile steels have a minimum specified yield strength which varies from 315 N/mm2 to 390 N/mm2. The Charpy V-notch impact minimum average requirement, measured in Joules, is also shown in this table and increases in the traditional way with the yield strength of the material.

Table 1: Basic material properties Within each strength level, a further categorisation into grades provides the required Charpy V-notch impact test temperature (Table 2).

Grade Normal strength steels

Higher tensile steels

A - 0°C B 0°C D -20°C -20°C E -40°C -40°C F -60°C -60°C

Strength level

Yield Strength (N/mm2)

Minimum energy (Joules)

Mild steel 235 27 Grade 32 315 31 Grade 36 355 34 Grade 40 390 41

23

Table 2: Charpy V-notch impact test temperature requirements It can be seen that mild steel grade A has no requirement for impact testing as a release test during manufacture of the material where the thickness does not exceed 50 mm. There is no higher tensile grade B. Again the absence of a requirement to test grade A steel is considered by some [3, 4, 5] to be an issue and this will be discussed in a little more detail later in the paper. The driver continuously to improve the quality of constructional ship steels used has been based on a number of factors: • increased productivity by the utilisation of new

construction designs and new materials • improvements in safety through product reliability

and structural sound design • structural weight saving through use of higher

tensile steels • increased productivity by use of new processes

such as high heat input welding techniques • the need to weld without preheat. These points can be illustrated by the developments that have taken place. The 1960s saw the development of controlled rolled steels with the use of niobium to retard recrystallisation during the rolling process. This enabled steels with good toughness properties to be manufactured without a separate normalising process, a heat treatment that was both costly and production throughput limiting.

Figure 1: Benefits of TMCP steel The late 1970s and early 1980s saw the biggest and most beneficial advance in steel production for use in

ships. This was the development of TMCP steel: Thermo-Mechanical Controlled Processed Steel. Figure 1 provides a good pictorial representation of the benefits of TMCP steels. The Y axis is yield stress; the X axis is the International Institute of Welding (IIW) Carbon Equivalent Value of the steel based on its composition.

1556CuNiVMoCrMn

CCEV+

+++

++=

When compared to traditional normalised steels, TMCP steels can be either produced with a higher strength level at the same carbon equivalent as normalised steels, or alternatively steels can be produced at the same yield stress as normalised steels, but at a lower carbon equivalent.

Figure 2: Gravilles diagram (weldability of steels) As stated earlier, the aim is to weld without preheat to reduce costs and increase productivity, therefore the TMCP process is used to produce steels at a lower carbon equivalent: a leaner composition. Leaner steels also allow the use of high heat input welding, again increasing productivity. Some commercial organisations within the industry, e.g. Intertanko, have held reservations [6] concerning the use of TMCP steel in ship construction, primarily with regard to accelerated corrosion in cargo oil tanks. There has never been any hard evidence to support this view. Indeed, research has been carried out which supports the view that there is no difference between conventionally rolled steel and TMCP steel. Chevron [7] reported that it found that general corrosion rates and pitting corrosion rates are similar for TMCP and conventional steels, although it stated that further research was required. Two joint Japanese industry reports [8, 9], based on two approaches – actual

24

corrosion tests and on-board measurements – also concluded that there is no difference between TMCP and conventional steels. The end of the 20th century began to see a slow but steady progression to the use of higher tensile steels. These steels typically have a specified minimum yield stress of 400 N/mm2 steel for the hull structure. More recently designs for container ships have started to propose steels with a specified minimum yield stress of 470 N/mm2 in way of the thick sections of the deck and hatch coamings. We also see deck cranes where steel with a specified yield stress of 690 N/mm2 is in common use and up to 980 or even 1100 N/mm2 is being considered. This is a major step change from the use of simple materials in shipbuilding leading to a need for a new set of skills for ship surveyors and constructors to understand the difficulties that face them with these higher strength materials. Figure 2 illustrates these problems in terms of the weldability of these new materials and clearly shows a move from the use of readily weldable materials to the use of materials that are difficult to weld. This can only increase the risk of in-service problems and difficulties of repair. For the determination of hull girder section modulus a higher tensile steel factor kL is required. With the use of higher tensile steels new factors are required, see Table 3.

Specified minimum yield stress N/mm2 (kgf/mm2)

kL

235 (24) 1.0 265 (27) 0.92 315 (32) 0.78 355 (36) 0.72 390 (40) 0.68 470 (46) 0.62*

* To be agreed by IACS

Table 3: Values of kL The material requirements for steel plates in terms of strength and Charpy V-notch impact toughness are shown in Tables 1 and 2. Table 4 shows how the construction material selection of steel takes place in terms of impact toughness grade. It can be seen clearly that this decision is based on thickness of material and risk of fracture by location in the ship. The grade of steel required for the construction of a ship is identified within Table 4 according to one of three classes, designated by the Roman numerals I, II and III. Material Class III identifies the most critical locations and Class I the least. In general the parts of the ship structure most highly stressed fall into Class III and tend to be within the mid 40% of the vessel’s length, where the highest bending moments exist.

Material Class

Thickness

(mm) I II III

t ≤ 15 A, AH A, AH A, AH 15 < t ≤ 20 A, AH A, AH B, AH 20 < t ≤ 25 A, AH B, AH D, DH 25 < t ≤ 30 A, AH D, DH D, DH 30 < t ≤ 35 B, AH D, DH E, EH 35 < t ≤ 40 B, AH D, DH E, EH 40 < t ≤ 50

D, DH

E, EH

E, EH

Table 4: Plate grade according to thickness and material class It should also be noted that for worldwide service the design temperature is minus 10° C [10]. This design temperature is not the absolute minimum temperature but is defined as the Lowest Mean Daily Average air temperature. This temperature is calculated from a data set of average temperatures collected over a minimum period of 20 years. This design temperature can then be combined with standard nautical temperature charts, such as the one shown in Figure 3, which shows the geographical extent of the acceptable trade of a vessel built for worldwide service. Indeed, minus 10°C will allow Baltic trade in the winter.

Figure 3: Standard temperature Isotherms As we look to the future of shipping, low temperature service will become more and more of an issue. There is now a general need to look at cold water service as new oil and gas fields are being found in much colder waters. Therefore ships with design temperatures below minus 10°C will be required.

25

0

5

10

15

20

25

30

35

40

45

50

-30 -20 -10 0 10 20 30 40Temperature (°C)

Ener

gy (J

oule

)

LR Lake Carling TestsCTSB Lake Carling ResultsCTSB Z GornoslaskaLR Z Gornoslaska

Table 5: Toughness test results both longitudinal and transverse samples There is also the effect of global warming to be considered. The polar ice caps are receding and it is estimated from global warming predictions that summer ice free passage could be the norm by 2050. This will provide a much shorter route from North East Asia to Northern Europe, making the possible use of such a route a very attractive proposition to shipping. It is therefore important to understand the effects of colder temperatures on the materials used in the construction of ships. In such cases Table 4 would have to be modified by moving the more impact resistant grades of steel to lower thicknesses. On March 19, 2002, the bulk carrier Lake Carling a DNV–classed vessel, was sailing in the Gulf of St Lawrence when it suffered a major brittle fracture in its side shell. The fracture was about 6 m in length, initiating below the water line. This caused major flooding of the hold and a rescue was mounted by the Canadian Coast Guard. The vessel was accompanied into port and an investigation initiated by the Transport Safety Board of Canada [11]. At the time of the casualty the air temperature was minus 6° C but the crack initiation temperature was considered to be 0° C because initiation was found to be below the waterline. The site of initiation was found to be a pre-existing fatigue crack.

Figure 4: Lake Carling Charpy V-notch test results The hull steel was grade A, which, as can be seen from Table 2, has no requirements for a Charpy V-notch impact test to be carried out during steel manufacture. However, the steel was subsequently impact tested during the investigation and found to just comply with implied toughness requirements of 27 J at +20° C for Grade A steel. This result raises concerns in the industry by suggesting that current design rules can specify the use of steel grades that may provide a situation where a brittle fracture can initiate in ships operating within the envelope of normal worldwide service, as was the case with Lake Carling. Table 5 summarises subsequent Charpy V-notch and fracture toughness tests [12] carried out by Lloyd’s Register on steel supplied by the Transport Safety Board of Canada from Lake Carling and one of her sister ships. The results confirm the borderline nature of the material used to construct this vessel. The results from the sister ship are marginally worse, however this ship has no history of cracking problems. Figure 4 shows a summary all the Charpy V-notch impact test results both from the Transport Safety Board of Canada’s investigation and Lloyd’s Register’s subsequent tests. These results are of concern, and Lloyd’s Register continues to lead discussions within IACS on this subject. It should be remembered however that such incidents are extremely rare. Why are such incidents of the type seen on Lake Carling so uncommon? The explanation for this anomaly would appear to lie in the general high level of Charpy V-notch impact properties of steel supplied to the industry today. This can be seen in the results shown in Figure 5, which are taken from a study carried out by Lloyd’s Register in 1997 [13]. It shows that the distribution of impact toughness of steel plates from 40 different manufacturers is indeed very good, being well above the values actually measured on the steel taken from Lake Carling. This high toughness of steels is probably a major factor in the prevention of similar incidents. However, a word of warning:

Steel Source Lake Carling ZGornoslaska1 [Note 1]

Charpy V-notch 27J transition temperature

L= +10°C T= +10°C

L= +20°C

Fracture appearance transition temperature FATT (50% Crystalline)

L= +10°C T= +15°C

L= +15°C

FATT (70% Crystalline) L= -5°C L= +5°C

Minimum CTOD (BS 7448) Tested at minus 19°C.

0.01 mm -

Minimum CTOD (BS 7448) Tested at 0°C.

0.25 mm -

Note 1, Z Gornoslaska is a sister ship to the Lake Carling.

26

Lake Carling was built in 1992, a time when you would expect steel to have had good toughness.

Figure 5: Grade A steel properties Lloyd’s Register continues to work to optimise its requirements for low temperature service. The consideration of the application of steel to cold climates is not restricted to hull steels. Deck equipment that may be made of forgings and castings will also need to operate at low temperatures, and therefore consideration needs to be given to mooring equipment, windlasses, deck piping systems, life boats, davits and deck cranes. Another major fracture issue under review within the industry deals with the thick section steel used in the hatch coamings and decks of container ships. Today, ships of 9,000 TEU are commonplace and ships up to a nominal 13,000 TEU are under consideration with steel thicknesses up to 90 mm. These vessels are designed with wide cargo openings and as a result hull bending stresses are carried in the structure around these openings, requiring thick section steel to carry the increased loads. At the same time higher strength steel with a specified minimum yield stress of 400 N/mm2 is commonplace and material with a minimum yield stress of 470 N/mm2 is now used to keep the thickness within reasonable limits. In 2005 a possible problem was brought to the attention of the classification societies. A number of large scale wide plate tests had been initiated to investigate the design of a new series of larger container ships. Figure 6, courtesy of Nippon Steel, shows the first test on a 70 mm thick EH40 steel containing a high heat input single pass electro-gas weld [14].

Figure 6 – Brittle fracture in 70 mm EH40 wide plate test

35 Mean impact energy 169J

30 Standard Deviation 55J

25

Frequency

20

15 10

5 0 120 150 180 210 240 30 60 270 300 90 0

Figure 6: Brittle fracture in 70 mm EH40 wide plate test Charpy impact energy (J)

It was anticipated that the crack, once initiated in the heat affected zone, would deviate and run into parent material where it would arrest. This assumption was based on the detailed research by the 147th Committee of the Shipbuilding Research Association of Japan who investigated the brittle crack arrestability of the high heat input welds of ship building steels in the 1980s. The Committee concluded that a long-running crack would be arrested by the crack deviating from the weld into the base material. The work was carried out on ship steels up to 40 mm thick by wide plate testing. In Figure 6 the crack in the test failed to deviate or stop. Further tests were carried out to investigate the effects seen, culminating in a plate with welded stiffeners across the projected line of fracture to aid arrest. This test was carried out at minus 10° C, and the plate still failed in a totally brittle manner. Lloyd’s Register is taking the results of this work extremely seriously even though it must be emphasised that no problems have been experienced with fractures in the operation of such large container ships to date. Lloyd’s Register, in collaboration with TWI, the UK based welding research establishment, is carrying out research to provide a better understanding of the science of the fracture effects seen. The initial literature review [15] looked at the issues raised with the crack arrestability of ship steel and the findings were quite interesting: • The results obtained in Japan could be predicted by

existing research. • Today’s ship steel requirements are based on steels

produced in the 1940s and 1950s, but for today’s modern steels these relationships no longer apply.

• The problem is not limited to thicker steels (>65 mm); it is a problem throughout the thickness range, the problem being less acute below 40 mm.

27

A series of tests is being funded by Lloyd’s Register at TWI to support the initial findings and the study will also look at establishing testing relationships for modern steels. Other work ongoing in Japan [16] suggests that ships would reach their second special survey (a service life of 10 years) before any fatigue cracks would be of a critical size for catastrophic fracture. Based on this information, Lloyd’s Register has initiated a project to monitor and assess existing container ships by non-destructive examination techniques. Assessments and examinations may be continued throughout the life of the ship.

Stre

ss r

ange

for

life

of 1

06 cyc

les

(N/m

m2 )

400

100

500

800

Tensile strength N/mm2

Figure 7: Effect of steel strength on fatigue strength 3. FATIGUE Ships are large complex structures which operate under stresses and strains that are difficult to quantify. Add to this the move by shipyards to optimise and reduce steel weight through the use of higher tensile steel and we have a recipe for fatigue cracking. It is well known [17] that fatigue behaviour in welded construction is based on the joint detail and not the material strength (Figure 7). Additionally owners are beginning to demand ships that will stay in service for up to 40 years.

Figure 8: S-N Fatigue curves using different welded joint improvement techniques: 1 – as-welded 2 – after UIT, using indenters of diameter 3 mm and 5 mm (random impacts) 3 – after air hammer peening 4 – after shot peening 5 – after TIG dressing 6 – after TIG dressing and UIT using indenters of diameter 5 mm (random impacts) 7 – after UIT using indenters of diameter 3 mm (with impact parameter control). The fatigue life improvement benefit of toe grinding, shot peening and Tungsten Inert Gas weld dressing has been known for many years (Figure 8) [18]. These processes can provide repeatable results but are not practical on large structures such as ships. Hammer or needle peening can also show improvements but here the results are inconsistent and the application process is difficult to monitor in terms of quality control. Ultrasonic Peening (UP) and Ultrasonic Impact Treatment (UIT) of welds are two similar techniques that have only been commercialised recently. They are promising technologies that have emerged from extensive development in Ukrainian and Russian research institutes. The results of fatigue testing show that the UP and UIT processes are the most efficient and economical technique for fatigue life improvement of welded elements and structures when compared to the existing improvement treatments such as toe grinding, TIG-dressing, shot peening or hammer peening. More importantly it is a process that can be used easily in the production environment of a shipyard. The equipment is lightweight and easy to use. Process parameters are controlled and can be recorded by a

28

computer to ensure application is uniformly applied throughout the structure. Such data recording facilities are essential to satisfy shipyard quality control requirements. The witness of peening is also easy to see (Figure 9). This makes it easy for the surveyor to confirm the process has been carried out on the fabrication, essential for quality control purposes.

Figure 9: Comparison of welded surfaces; the right hand weld has been peened Two effects arise from the peening process. The first is dimensional, the action of the process results in a smooth radius at the weld toe reducing stress concentration effects at that point: improving fatigue life (Figure 10). Secondly, deformation and transformation of the surface microstructure occurs to a depth of approximately 300 microns which introduces a beneficial compressive residual stress retarding crack growth.

Figure 10: Radius formed by ultrasonic peening at the toe of the weld In conclusion, ultrasonic peening is an exciting process that has a huge implication in the fight to improve the fatigue life of weld detail in ship construction. As an alternative to improvement techniques, new steels are constantly being developed and improved.

One that is finding application in ship building is known as FCA steel or Fatigue Crack Arrest steel.

Figure 11: Microstructures of conventional steel compared with FCA steel These steels have a dual phase ferritic-bainitic microstructure (Figure 11) and have been shown to have an effect in retarding crack initiation and growth in the parent material. Two effects are reported [19]: first, the dual phase boundaries prove to be effective barriers to crack growth and secondly, the hard bainitic phase is effective in retarding crack growth.

100

1000

1.0E+04 1.0E+05 1.0E+06 1.0E+07

Number of cycles to failure

Stre

ss ra

nge,

MPa

J, untreated, 66J,R=10mm,66J,R=16mm,66G, untreated,66G, treated,66J,untreated,100J,R=15mm,100J,R=25mm,100G,untreated,100G, treated,100

Figure 12: Comparison of fatigue tests on FCA steel versus conventional steel Figure 12, taken from tests carried out by Lloyd’s Register, also shows a comparison of fatigue crack growth data between the FCA steel and conventional steels, and provides an indication of the benefits that arise [20]. Ships, however, are welded structures and FCA steels need to show benefits where the weld detail defines fatigue performance and not the parent material. Even here we can see that benefits accrue from the use of FCA steel, especially in the low stress high cycle regime [19].

29

4. CONCLUSIONS This paper has taken a brief look at the development of structural steels intended for ship construction. Traditionally, ship steels are forgiving in that they are easy to fabricate with little control and perform well in service. Occasionally, problems occur but the quality of steel produced today is sufficient to keep the risk of major incidents to an acceptable minimum. However, with the increased use of higher strength steels additional care during manufacture is necessary and this will mean greater vigilance during survey when compared to conventional steels. With demand for new, more efficient designs, greater life expectancy new steels and fabrication processes are becoming available to increase the fatigue life of welded components. 5. REFERENCES 1. US Government Printing Office, Washington [1947]. The Design and Methods of Construction of Welded Steel Merchant Vessels’, 2. International Association of Classification Societies], [Rev.7 April 2008]. UR W11 Normal and higher strength hull structural Steels. 3. Sumpter et al, Fracture Toughness of Ship Steels’, [Royal Institute of Naval Architects], [Transactions 131 (1989), pp.169-186]. 4. Bannister et al, Literature Review of the Fracture Properties of Grade A Ship Plate, 18th Int. Conf. on Offshore Mechanics and Artic Engineering, [July 1999]. 5. BSC Swindon Technology Centre, Fracture Properties of Grade A Ship Plate, [HSE Offshore Technology Report – OTO 2000 001, 2000]. 6. Intertanko Tanker Specification Awareness Guide – Appendix 1, Intertanko, Norway, 2003. 7. Chevron Shipping Company Corrosion Protection of Cargo Ballast Tanks, Tanker Structure Co-operative Forum 2000 Shipbuilders Meeting, Tokyo [October 2000]. 8. Yasunaga et al, Study on Cargo Oil Tank Upper Deck Corrosion of Oil Tanker, SNAME World Maritime Technology Conference, [San Francisco 2003]. 9. Katoh et al Study on Localised Corrosion on Cargo Oil Tank Bottom Plate of Oil Tanker, SNAME World Maritime Technology Conference, [San Francisco 2003].

10. Technical Background, IACS UR S6 Use of steel grades for various hull members - ships of 90 m in length and above’, International Association of Classification Societies, Revision 5, September 2007. 11. Transportation Safety Board of Canada, [19 march 2002], Marine Investigation Report - M02L0021 - Hull Fracture - Bulk Carrier Lake Carling - Gulf of St. Lawrence, Quebec. 12. British Standards Institution [BS 7448-1:1991], Fracture mechanics toughness tests - Part 1: Method for Determination of KIc, Critical CTOD and Critical J Values of Metallic Materials’. 13. Lloyd’s Register, [1999], Review of the Fracture Properties of LR Grade A Ship Steel. 14. Inoue et al, Long Crack Arrestability of Heavy-Thick Shipbuilding Steels, ISOPE, [May 28-June 2, 2006]. 15. Wiesner C, Review of Crack Arrest Properties and Characterisation Tests for Thick Section Steel Ship Applications, TWI, [18202/1/08 June 2008]. 16. Japan Ship Technology Research Association, [Undated 2007], Safety Related Issue of Extremely Thick Plates – Letter to IACS’. 17. Maddox, Fatigue Strength of Welded Structures, [ISBN 1 85573 013 8], Woodhead Publishing, 2nd Edition 1991. 18. Statnikov et al, Comparison of Ultrasonic Impact Treatment (UIT) and other Fatigue Life Improvement Methods, IIW Doc.XIII-1817-00, 2000. 19. Konda et al, Study on Improvement of Fatigue Strength of Welded Joints in Bridges by New Functional Structural Steel Plates, IIW Doc.XIII-2163-07, [2007]. 20. Polezhayeva et al, Effect of Plate Thickness and Corner Machining on Fatigue Strength of EH40 Steel Thick Plates: Phase 2, ISOPE, 2009 tbc.

30

NOTES

31

NOTES

32

PAPER 4

STRUCTURAL DESIGN ISSUES ANDONGOING DEVELOPMENTS

Alex Johnston C.Eng., F.R.I.N.A.

33

34

STRUCTURAL DESIGN ISSUES AND ONGOING DEVELOPMENTS Alex Johnston SUMMARY This paper has been written to increase the reader’s understanding of some of the projects which Lloyds Register’s has been, or is currently, involved in, both internally and externally, to enhance our structural capabilities and increase our technical reputation at a time when the industry faces many challenges from external bodies and a rapidly expanding shipbuilding industry in the Far East. It has become clear that some of the main concerns which will affect structural issues in the next decade will be the quality, or more correctly lack of quality, of orders emerging from very inexperienced yards, not only in terms of the quality of design and fabrication in the yards, but also in terms of the supply chain problems experienced with forgings and castings. The problems which other yards have experienced and solved over the years seem doomed to repeat themselves, perhaps in part due to a lack of knowledge transfer. Owners and class societies alike need to be aware of the problems of fatigue, buckling and yielding caused by lack of good detail design and fabrication inaccuracies. 1. INTRODUCTION As a class society, it is crucial to keep abreast of developing structural issues. This cannot be stressed too highly and is of particular importance when one considers some of the marine transport developments and issues which have come to light in recent years. These include: • the new oil exporting locations and the new

trade routes which they will demand, and, in particular, the differing environmental loads with respect to fatigue effects on the structure in association with differing operational procedures for VLCCs which are not presently catered for by traditional analytical methods

• structural integrity of vessels in an ice and cold environment in areas which export oil and gas from newly emerging oil and gas fields

• increasing use of Sandwich Plate System (SPS) construction for ship repair and construction

• increasingly high cargo loading rates on bulk carriers

• studies pertaining to sloshing in LNG ships • whipping and springing of ship’s hulls. All of these issues, and more, are set against a background of the Goal Based New Ship Construction Standards (GBS) being debated within the Intermational Maritime Organization (IMO). Such standards, which have been referred to as ‘Rules for Rules’ may see class societies, acting on behalf of flag administrations as their recognised organisation, re-examining the basic principles upon which their structural rules have been founded and used successfully for generations.

2. DESIGN ISSUES 2.1 TRENDS AND DEVELOPMENTS IN

FATIGUE ISSUES 2.1 (a) Background The Lloyd’s Register Structural Design Guide (FDA Level 1) [1] and Spectral Fatigue Analysis procedure (FDA Level 2 and Level 3) [2] [3] were first developed more than 15 years ago. Since then some features have become outdated and there is a need to update the procedures to meet market and client expectations. In the era of the IACS Common Structural Rules for Double Hull Oil Tankers (CSR DHOT) it is vital that we do not lose sight of the fact that, although the design life enhancement to 25 years and the default wave environment of the North Atlantic has been taken as a design basis, there are new routes and operational practices developing which may induce harsher fatigue environments when used on a regular basis. Examples of such trades are: • shuttle trade, US-Mongstad or US to Europe, for

example • West Africa to West Coast of US via Cape Horn. The CSR DHOT scantling criteria for fatigue are based on an idealisation of operating profile and structural response of ’standard’ oil tanker designs. The idealisation is sufficiently representative of typical oil tanker operation to be used reliably to design new ships to a common minimum standard. For loads induced by the sea, the CSR DHOT uses an idealised wave environment referred to here as ‘North Atlantic with Equal Probability of Headings’ (NAEPH). This idealised wave environment is based on documented

35

wave statistics corresponding to sea conditions in the North Atlantic (Figure 1).

Figure 1: Marsden areas used for IACS NAEPH wave environment This assumption is normally conservative since the North Atlantic is generally accepted as the most hostile wave environment. The wave environment is derived assuming the tanker design has equal probability of headings in accordance with IACS Recommendation 34 Standard Wave Data. It should also be noted that CSR NAEPH is more onerous than the pre-CSR minimum class society standards for worldwide trading. Also, the assumption of equal probability of heading is normally conservative and may generally be disregarded as an issue for the owner’s specification. However for some specialised or new trade routes, a detailed investigation may be required and Lloyd’s Register can advise on the exact requirements. Several recent damage cases on various oil tanker designs have encouraged Lloyd’s Register to re-assess its fatigue philosophy and put in place several projects to update its fatigue analysis procedures. This has been done with a view to incorporating the knowledge gained from over 15 years of in-service experience and taking account of the advances in fatigue industry knowledge of both high and low cycle fatigue. The objective of our wave induced high cycle fatigue (HCF) project is to prepare a revision of correction factors to existing SN curves, Stress Concentration Factors and thickness corrections used in Lloyd’s Register’s Fatigue Analysis procedures: FDA Level 1, FDA Level 2 and FDA Level 3 The wave induced high cycle fatigue (HCF) project will look at the following: • Revision of stress concentration factors for:

angular misalignment of joints, weld flank angle, cold laps, internal and external weld defects. This

research work is also important for the development of Guidelines for Weld Defect Tolerances required by Lloyd’s Register surveyors and is supported by the Materials Department.

• Revision of the free edge S-N curves for mild steel by fatigue tests at laboratory. (The existing S-N curves for mild steel were developed more than 30 years ago).

• Development of correction to free edge S-N curve for D-grade HT steel by fatigue tests at laboratory.

• Update of hot spot S-N curves and extrapolation methods currently used in FDA Level 3 fatigue analysis.

• Implementation of all the above into FDA Level 3 software and procedures.

The Lloyd’s Register low cycle fatigue (LCF) project addresses industry requirements to consider low cycle fatigue damage due to loading and unloading of FPSOs and tankers, but will have generic applicability to all ship types where large changes in ’still water’ stress occur over a period of hours or days. Low cycle fatigue is caused by large cycles of plastic strain which can cause significant fatigue damage from a relatively low number of cycles. The low cycle fatigue (LCF) development programme is part of an ongoing Joint Industry Programme which aims to: • deliver a generic procedure and software for

calculating low cycle fatigue damage due to long period (more than one hour) load cycles and combine them with high cycle fatigue damage

• combine low and high cycle fatigue in the time domain

• rationalise analysis of tanker and FPSO loading histories and implement it into procedure

• implement loading histories’ procedure software, linking it to time domain combination of HCF and LCF

• validate fatigue life criteria for plastic strain, strain life curves and SN curves with plasticity corrections.

This project will deliver a FDA low cycle generic procedure. The project will implement an LCF procedure in the LR-SDA/FDA ShipRight software. A separate project is planned for validation of the procedure with real strain data. In addition, we are also developing the following projects: • A procedure for fatigue arising from springing

and whipping response and an upgrade to our FDA2 software to make it more generally applicable with regard to ship type and the structural details it covers

36

4

• A revised ShipRight FDA1 & FDA3 guide incorporating: new S-N curves for HT steel; revisions to thickness correction and extension to thick plates (up to 100mm); guidance on use of S-N curves in corrosive environment; and revised guidance on weld improvement techniques

• A revision of the approach to mean stress effect on fatigue loading, which looks at the fatigue performance of welded connections in steel ship hulls and is aimed particularly at establishing whether some relaxation of the classification Rules is justifiable for joints subjected to part-compressive applied loading. A programme of fatigue tests on welded panels representing a typical welded ship detail has been carried out to:

⎯ establish fatigue design guidance for

welded joints subjected to compressive loading

⎯ investigate CrackFirst™ fatigue sensors for typical ship weld details

⎯ evaluate the relaxation of the residual stresses after loading cycles.

Completion of these projects will help provide confidence to industry that all modern technologies with regard to fatigue design assessment are reviewed and implemented and will strengthen Lloyd’s Register's profile as an innovative and technically leading class society. 2.2 TRENDS AND TECHNOLOGY FOR SHIPS

NAVIGATING IN COLD CLIMATES Lloyd's Register has seen an increase in orders for ice class ships, both for trade in first year ice, such as in the Baltic, and in the harsh environments of the Arctic and Antarctic. Alongside this increase in ice class ships, there has been a corresponding increase in the technology and innovation used in the construction of these specialised ships. The following overview highlights some of the notable studies and investigations undertaken by Lloyd's Register for ships operating in cold climates. 2.2 (a) Fatigue of Ship Hull Structures When

Navigating in Ice Ice loads are seen as one of the most challenging disciplines in naval architecture. Lloyd's Register has been actively involved in developing its knowledge of ice loads and, in particular, the interaction with the hull structure. One example of this is the investigation into the fatigue of ship hull structures when navigating in ice by Bridges et al [4]. Bridges highlights that there are an increasing number of LNG ships and oil tankers which are intended for navigation in ice, and as such there is a necessity to assess the risk of fatigue damage during the ice

navigation phase in these ships. There is currently little knowledge of the fatigue performance of ships operating in ice and the intention of this study was to address this deficiency and resolve some of the outstanding questions associated with operation in ice. The investigation was carried out, based on analysis of full scale measurements during navigation in the Baltic. The study consisted of evaluating the following components in relation to ice thickness and distance travelled: • Impact frequency. • Load distribution. The ice loads are determined for different winter conditions and ice thicknesses, based on ship routes and operational profiles. Using the ice load distributions and structural responses to the loads, the fatigue damage is estimated. From this, fatigue life assessment models were developed. In addition, the effects of low temperature on the material properties are discussed. The results can be used for establishing if measures need to be taken to reduce the risk of fatigue damage in the structural elements of ship hulls, with the preliminary analysis of results indicating that fatigue may be an issue for severe winters. In the future, an enhanced reliability of the ship structure will be achieved by combining Lloyd's Register’s current fatigue design assessment procedure for open water service with the developed fatigue procedure for navigation in ice. 2.2.(b) Methods and Approaches for the Classification of Ships Designed for Cold Climates There have been significant advancements in the classification requirements for ships in cold climates. Lloyd's Register recently introduced the International Association of Classification Societies (IACS) Polar Ship Rules into the Rules and Regulations for the Classification of Ships [5]. The new Rules allow the latest methodology to be applied for the determination of hull scantlings and machinery systems of ships intended for Polar waters. The impact of the Polar rules is examined by Bridges et al [6] in the EU project ArcOp which discusses the equivalency between the IACS and Russian Maritime Register of Shipping (RMRS) Ice Class Rules and investigates the underlying assumptions they contain. Development activity has also been undertaken in co-operation with the Finnish Maritime Administration, and, in particular, the development of the Guidelines for the Application of the Finnish Swedish Ice Class Rules (FSICR) [7]. An aspect that Lloyd's Register was

37

specifically involved in was the development of requirements for longitudinal frame arrangements for Suexmax and Aframax tankers which are outside the conventional scope of the FSICR. There has also been the emergence of new trade routes in cold regions, which pose new design conditions and challenges. In addition, not all builders have experience of designing ships intended for ice and cold environments. As a result there is a pressing need for rules and standards to give clear requirements for shipbuilders to develop suitable designs for cold climate operation. A major inclusion to Lloyd's Register’s Rules is the development of requirements for the winterisation of ships. The paper on this subject, by Bridges [8], provides an insight into the background and development of winterisation rules, an introduction to the framework of the Rules and explanation of some of the key features. The development of the winterisation Rules has included a number of notable aspects, including the balance between prescriptive requirements and diversity in arrangements and environmental conditions.

Figure 2: Stern first ice class ship, Mastera 2.2. (c) Stern First Operation in Ice The first purpose-built large tankers optimised for stern first operation in ice, Mastera and Tempera entered service in 2002 and 2003 (Figure 1). These ships were designed and constructed under survey to Lloyd’s Register standards and have now had over five years’ operational service in the Baltic Sea. Application of podded propulsion units and azimuthing thrusters has subsequently been applied on a number of ice class ships. Podded propulsion units, or azimuthing thrusters, have enabled the development of commercial ships with hull forms optimized for bow first operation in open water, or light ice conditions, combined with an icebreaking stern optimized for stern first operation in ice.

Methods and approaches for the classification of ships designed for stern first operation in ice, by Hindley et al. [9], provides an overview of some of the associated issues for classification using two ships specified and designed for stern first operation in ice. The paper discusses the interpretation of classification and ice class rules, as well as the adoption of first principle methods to assess the ship structural arrangements and propulsion systems. The phrase ‘stern first ice class ship’ has been used in the paper to identify ships equipped with podded propulsion units or azimuthing thrusters, that have been designed to operate stern first in ice as part of their operational profile. The case studies considered in the paper are: • Ice class 1AS aframax tankers, Tempera and

Mastera, built to Lloyd's Register class (included as examples of stern first ice class ships for Baltic Sea service).

• LU6 ice category shuttle tankers Mikhail Ulyanov and Kiril Lavrov, under construction to Russian Register and Lloyd's Register dual classification (included as examples of stern first ice class ships for Pechora Sea service, further details of which may be found in the paper by Tustin et al. [10]).

The paper summaries the methods and approaches adopted for classification of stern first ice class ships, as follows: • Application of classification and ice class rules for

bow first operations. • Approval of structural design of the stern to

withstand loads identified by the stern first operational scenario.

• Approval of structural design of the propulsion unit and adjacent structure to withstand loads identified by the stern first operational scenario.

• Approval of design of the propulsion unit and components to withstand loads identified by the stern first operational scenario.

• Approval of design of the bridge and location of navigational equipment for operating bow first and stern first.

For both cases described, a consistent approach has been adopted for classification, even though sea areas of operation and the ice class rule sets are different 2.2 (d) Summary As new trade routes emerge and shipping activity increases in cold climates, there are many challenges in store for the future. These include Arctic LNG carriers [11], drill ships, and icebreakers, as well as merchant ships operating in harsher and more

38

demanding regions for longer periods of time. Lloyd's Register is actively involved in the technology and innovation for ships in ice and cold operations, and is committed to furthering its expertise and capability to ensure the safety of the ship, crew and environment. 2.3 TRENDS AND DEVELOPMENTS

IN SANDWICH PLATE SYSTEMS 2.3 (a) Advances and Examples of the Sandwich

Plate System Since the introduction of the Sandwich Plate System (SPS) technology, its use in ship repair and construction has evolved steadily over the years. Responding to this situation, Lloyd's Register developed and published in 2006 the Provisional Rules for the Application of Sandwich Panel Construction to Ship Structure (Sandwich Construction Rules) [12] to provide the framework and standards for its use within the maritime industry. Classification rules depend on the feedback of service experience to establish that they are effective in achieving an appropriate level of safety and reliability. Feedback from designers and builders are, in the same way, important as the rules must provide a suitable framework for the owner and builder in achieving a suitable new product. The following highlights briefly some of the studies and investigations Lloyd's Register has undertaken, since the publication of the Sandwich Construction Rules to update them. 2.3 (b) The Rule Updates Recognising that the use of SPS would have its major advantages in certain applications, Lloyd's Register has focused initially on developing a series of amendments to address: • Watertight and deep tank bulkheads Net scantling calculation of the sandwich panel is developed from the principles of mechanics and direct calculation using finite element analysis methods with a safety factor calculation check against the development of a simplified plastic mechanism. The first criterion is based on reaching some flexural capacity defined as the development of a plastic hinge on the long edge over a limited length. The second criterion is based on limiting the maximum shear bond stress to a value defined statically by tests and specified in the Rules to give the desired level of safety for a given surface preparation. The final thickness is determined as the net thickness plus the appropriate corrosion margin as required for

the given application, half of which may be applied to both faceplates. • Design example: Deep tank bulkhead The design example is a section of an all-steel deep tank bulkhead illustrated schematically in Figure 3 and designed in accordance with the Lloyd's Register’s Rules. The Rule calculation for plating of deep tank bulkheads for the design pressure results in an 11 mm plate and 250x90x10/15 stiffener combination. The SPS scantlings, sized in accordance with the proposed rule formulation, result in an SPS panel of 5.5-25-5.5 plate with a single 250x90x10/15 vertically oriented stiffener with a weight of 122 kg/m2. The corresponding weight for the all-steel structure is 123 kg/m2.

Figure 3: Schematic Illustration of all steel deep tank bulkhead and SPS bulkhead • Decks loaded by wheeled vehicles Realising the difficulties in not having a closed form solution, the proposed Rules for SPS decks loaded by vehicles were based on several thousand FE

39

simulations for geometries (plan dimensions), faceplate and core thicknesses, aspect ratios, wheel load dimensions and locations that will cause the maximum load effect and for the range of loads and expected geometries. The derivation of the equation for normal stress due to flexure from which the faceplate and core thicknesses is developed is founded on the same engineering principles as closed form solutions with the net scantling being calculated on the basis of a limiting flexural stress and elastic behaviour. The semi-empirical portion of the calculation relates to determining the curvature factor. The curvature factor, α is directly related to the deformed shape and in turn is a function of the plate aspect ratio, smallest plate dimension, the faceplate and core thicknesses, and the ratio of the normal stress to the wheel load. Since there are numerous combinations of wheel load position and sandwich plate geometry, it is expedient to calculate the curvature factor from a semi empirical equation which has been determined as a function of the variables and numerical coefficients given below.

⎟⎠⎞

⎜⎝⎛=

Pdtba

baf cf

σα ,,,or ,

where α is the curvature factor a, b are SPS plate dimensions tf is the SPS face plate thickness dc is the elastomer core thickness

Pσ

is the ratio of normal stress to concentrated wheel

load for that given load A general description of this relationship is given in the following :

( )

( )3

98

2

765

4321

10−⋅⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

+⎟⎠⎞

⎜⎝⎛+⎟

⎠⎞

⎜⎝⎛+++

+++

=C

baC

baCCsC

CtCdCtC fcf

α

where s = a or b, whichever is the shortest span. The numerical coefficients (C1 to C9) for the curvature factor were determined by conducting a series of finite element analyses on the vehicle deck model illustrated in Figure 4 for varying geometry ranges that are representative and wheel load positions and wheel load dimensions. The proposed Rules give an equation for determining the net scantlings for any given wheel load for vehicle decks governed by truck loads or for lighter decks

specifically designed for transporting cars. The general equation is based on limiting the flexural stresses in the faceplates of an SPS plate so that the combination of the maximum value due to the wheel loads in conjunction with the maximum due to in-plane loading from hogging and sagging is consistent with current Rule limits. The modification factor for wheel load width provides a mechanism to use these simple formulations for varying wheel load dimensions. The corrosion, wear and wastage margins that have been defined are used with the simple variation that the total value is distributed and applied to both faceplates. Comparisons with the proposed equations with the results of advanced finite element analyses for similar structures show excellent correspondence with a very small coefficient of variation. • Design example: liftable car deck A liftable car deck has been analysed by finite element methods and the stress results are compared to Rule formulations. The car deck plating is composed of a SPS 3.2-19-3.2 supported by longitudinal and transverse girders spaced as illustrated in Figure 4. A single wheel load placed centrally between the longitudinal and transverse girders is analysed. The average normal stress in the longitudinal direction is 72 MPa, and is comparable to the predicted normal stress of 68 MPa from the Rules. Summary Lloyd’s Register’s Provisional Rules for the Application of Sandwich Panel Construction to Ship Structure were developed and published in 2006 to provide the framework and standards for the use of SPS within the maritime industry. As new technologies emerge and start being used there are many challenges and problems to overcome. Considerable investigations have been undertaken in the development of these Rules and Lloyd’s Register is continuously seeking feedback to its Rules to improve safety and reliability. Lloyd's Register is actively involved in the application of emerging technologies to address the difficulties imposed on ships. Areas where sandwich structure can be used with benefit are structure designed to resist high impact loading, bulk carriers with high loading rates, for example.

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Figure 4: Design example of liftable car deck 2.4 RISK INVESTIGATION OF BULK CARRIER

AT HIGH CARGO LOADING RATE 2.4 (a) Background Demand in the iron ore and coal markets is rapidly expanding and is expected to continue developing over the next few decades. Most major iron ore and coal port authorities have significant investment plans in place to improve the infrastructure of their port terminals to better expedite the transfer of these commodities. In addition, terminals are demanding that ships are loaded in the shortest possible time. This would imply the use of maximum possible loading rate, single loading pour for each cargo hold and minimum ballast (i.e. shallow draught) condition during some stage of the loading procedure. Of these development works, the intention to increase cargo loading rates is of critical interest to the shipping community. Current loading rates for iron ore and coal carriers can be in excess of 16,000 t/hr (Figure 5). Some shipowners and operators are of the opinion that these loading rates are already pushing the limits for the safe loading and operation of such vessels. There is real concern as to whether current bulk carriers and ore carriers have adequate local and global structural strength to withstand the consequences of the highest cargo loading rates, particularly pertinent for older vessels. An additional concern is that the ships’ load indicators (loading computers) are not advanced enough to protect the vessel from becoming overloaded.

Figure 5 : Loading of Iron-ore cargo onto bulk carrier at port

As a significant and high profile safety issue, it is imperative that Lloyd’s Register investigates the implications of increased cargo loading rates on bulk carrier structures. Such an investigation will help ensure the integrity of Lloyd’s Register classed vessels operating under likely future cargo loading conditions. 2.4 (b) Project Currently, it is commonly understood that undesirable loading conditions and loading sequences can result from employing high cargo loading rates which can cause high stresses in the hull girder and primary and secondary structure. The effect in a static sense can be investigated using existing analytical (Rules) and finite element (SDA) type analysis based on the distribution of cargo and ballast by considering the cargo loading rates into the holds and the pump deballasting capacities. However, the dynamic response of the structure as a result of the impact loads generated by high cargo loading rates is yet to be understood. This project aims to study the static and dynamic response of the hull structure of typical bulk and ore carrier designs under high cargo loading rates. The objectives of the work are to establish suitable methods for accessing the cargo impact loads and the resulting structural responses for a range of parameters as shown in the following: • Static and dynamic responses of hull girder. • Cargo impact loads under high loading rates. • Hull girder springing/whipping response. • Strength of structural details. The proposed project framework consists of two phases. For the first phase, the objective is to carry out the investigation upon the static and dynamic response of the ship structure under the cargo impact load by numerical simulations and model tests.

41

Typical FE analyses for hull girders and local structures will be simulated and studied under continuous cargo loads (see Figures 6 and 7). Phase one of the project also includes measurement of hull girder response for correlation with theoretical analysis on one ship. In phase two, further full full-scale measurement is to be carried out for the study of response of localized structure. The aim is to validate and calibrate the theoretical results obtained through phase one. 2.4 (c) Cargo Impact Model Tests The dynamic loading (load-time history) due to the impact of a continuous stream of ore particles (or ore like materials) is to be investigated using drop impact tests. The tests will also establish the cushion effect of build-up cargo. The tests are to be carried out at a UK University or similar test facility. The drop-test will be simulating, under laboratory conditions, the free drop of an ore like substance into a small scale stiffened panels. The main objectives of the tests are: • To obtain the impact load time history and

distribution due to the continuous pour (drop) of cargo at different heights and different rates.

• To measure the dynamic response of the structure in way of the local structures (stiffened panels).

• To calibrate numerical simulation procedures.

Figure 6: Dynamic Impact Simulation modeled from LS-DYNA software 2.4 (d) Static Response of Hull Girder The static response of the hull girder under various loading sequences will be investigated based on Lloyd’s Register’s in-house/NAPA software. Various loading sequences, cargo loading rates and deballasting capacities are considered using still water load calculation. In addition, asymmetric cargo

distributions within the cargo holds are also considered. The objectives of this task are: • To investigate hull girder bending moment and

shear force in all possible loading scenarios. • To assess and compare with the Rules criteria,

permissible shear force, bending moment and cargo-hold mass curves.

• To establish the relationship between deballasting capability and loading rate.

• To perform 3D FE full ship model static response analyses and to compare 2D and 3D FE results to establish a suitable approach for future analyses.

Figure 7: Finite Element Analysis for hull girder stress response 2.4 (e) Dynamic Response of Hull Girder The dynamic response of the hull girder under continuous cargo impact will be investigated based on: • a 2D beam model for the hull girder • a 3D FE model for the full ship. Added mass effect of surrounding water should be taken into account. Possible single and multi- pour/hold loading sequences are considered. In addition, various mass distributions, impact loads and positions are simulated to identify critical combinations that excite hull girder responses. The objectives of this task are: • To examine the hull girder vibration frequencies

and modes. • To investigate hull girder dynamic response at

high cargo rates. • To compare 2D and 3D results and to establish a

suitable approach for future analyses.

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2.4 (f) Full Scale Measurements It is proposed to carry out full scale measurement on board ships to collect cargo impact loads and stress/hull responses during cargo loading to verify the theoretical calculations. This will involve installation of a dedicated full scale measurement system on board a Lloyd’s Register classed ship to collect a wide range of data, including: • accelerations • stress responses of hull girder • stress response of secondary structural members

and structural details • impact loads on tank bottom. Information on ship’s draughts, loading sequence, loading rate, cargo properties are also to be collected for simulation of the dynamic responses by calculation using different levels of modelling. 2.5 STUDIES PERTAINING TO SLOSHING IN

LNG SHIPS With ever increasing demand for cleaner forms of alternate fuels like liquefied natural gas (LNG), the LNG fleet has come a long way, from the converted 5,000 m3 Methane Pioneer in 1958, to the first purpose built LNG Ship, the 27,000 m3 Methane Princess, in 1964, to the world’s largest LNG ship, the 266,000 m3 Mozah, in 2008. Mozah is the first Q-max sized vessel, classed by Lloyd’s Register and built by Samsung Heavy Industries, Korea, for Qatar Gas Transport Company Limited (Nakilat). Lloyd’s Register is the world’s leading classification society for LNG vessels, with more than 33% of LNG ships in service and on order under its class. Construction of these LNG ships is governed by the classification rules and the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code). Lloyd’s Register has put considerable effort into establishing assessment procedures for tank structures due to sloshing loads and comparative and absolute assessment of containment systems in addition to the analysis of pump tower and its base in LNG tanks [13 - 17]. 2.5 (a) Sloshing Issues

Figure 8: Bore wave impact in an LNG tank

Carrying liquid cargo in a seaway has always been a challenge due to the additional hydrodynamic loads caused by the violent motion of liquid within the enclosed tanks due to the motion of the ship in a seaway. The large size of the tanks in LNG ships, due to the complicated structure of the containment system and associated equipment, has resulted in a further increase in hydrodynamic loads acting on both

the containment system and the hull structure. Design and construction of the containment system and hull structure therefore needs to ensure they can withstand these enormous hydrodynamic impact loads. Accurate assessment of ship tank structures of partially filled tanks and the pump tower used for transporting LNG due to sloshing loads is the key to the safe and successful transportation of Liquid Nitrogen Gas (LNG) by sea and this is one of the greatest challenges that designers and assessors currently face. Rectangular shaped tanks with sharp chamfers (membrane containment systems) are prone to severe impact loads depending upon the fill level. Further, the severity of the sloshing phenomena and the resulting impact loads depend upon the loading condition and the seakeeping characteristics of the ship. Additionally, resonance between encountering the period of the waves, and the natural period of liquid motion within the tank, and natural response period of the combined containment system and hull structure and the rise time of sloshing pressure impulses could substantially increase the intensity of the sloshing loads. Recent experiences of damages to membrane containment systems due to partial filling conditions indicate the complexity of LNG transportation and the need for better design and operation practices. 2.5 (b) Experimental studies on sloshing loads The traditional method of predicting sloshing loads is through experiments on a scale model cargo tank using water, considering the different critical ship motion conditions. In support of design appraisal studies for the new generation of large LNG carriers, Lloyd’s Register has initiated several model test programmes on obtaining membrane impact pressures and pump mast forces on a 1:60 model of a 138,000 m3 ship tank [18] and 1:50 model of a 210,000 m3 ship tank [19 and 20] for regular and irregular ship motions. However, insufficient knowledge exists in extrapolating sloshing loads from model to full scale and water-air to LNG-LNG vapour.

43

To fill this gap, Lloyd’s Register, together with the designers of containment systems, shipowners and operators, is progressing in acquiring full-scale data on sloshing loads and corresponding ship motions from a selection of standard-size to large LNG ships. 2.5 (c) Numerical Predictions of Sloshing Loads Lloyd’s Register was the first to develop a comprehensive numerical assessment procedure through ShipRight SDA Sloshing software [ 13 ]. With the emergence of improved computational techniques and computer hardware, significant progress has been made by the industry in general, and by Lloyd’s Register in particular, to explore the feasibility of using Computational Fluid Dynamics (CFD) techniques as an improved design and assessment tool for analysing sloshing loads on containment systems and pump towers. Figure 8 shows a typical numerical simulation of bore wave type sloshing impact in an LNG tank.

Figure 9 : Flow around Pump Tower in an LNG Another study by Reddy & Radosavljevic, [21] has identified different uncertainties involved with the present numerical and experimental techniques in obtaining fluid forces on pump towers in an indirect way using Morison’s equation. As an alternative to the use of the Morison equation, further investigations into the feasibility of direct numerical estimation of fluid forces on a pump tower within an enclosed tank resulting from the sloshing of liquids is carried out (Figure 9). Lloyd’s Register made further progress in establishing both the commercial and open source CFD codes for sloshing applications [22] and passed on this knowledge to the shipyards and other customers for the wider benefit of the industry. These studies pertain to both 2D and 3D tanks by considering tank

motions in 3 or 6 degrees of freedom both in frequency domain, similar to the current LR-SDA procedure, and time domain considering a particular sea spectrum. The present ShipRight SDA Sloshing software is currently being enhanced to consider 3D LNG tanks and compressibility effects during sloshing. 2.5 (d) Strength Analysis of Containment

Systems and Hull Structure Lloyd’s Register is currently working on a number of projects related to LNG sloshing. The recent orders of large membrane LNG ships to class has focused attention on the need to consider the interaction between the containment system and the hull structure. The aim is to review the effect of the sloshing impact loads on the containment system, taking into account the local hull flexibility. The review of the resulting dynamic responses of the containment system and the local and global hull structures will allow the procedures presently applied for this aspect to be refined. In association with the sloshing work, we are undertaking a combined Computational Fluid Dynamics (CFD) and FE analysis to review fluid-structure interaction (FSI) effects. The aim of this research is to understand FSI better and to optimise the use of FE analysis, CFD and combined FE/CFD tools. An absolute approach to addressing all aspects of sloshing is very complex in that it demands better knowledge of the sloshing loads and the containment system load capacity. This work is already contributing to our review of the containment systems of the current large membrane LNG ships on order, and is likely to play a key role in the approval of floating LNG process, storage and regasification vessels, which will need to have maximum flexibility of tank filling levels. This work is necessary for the approval of new containment systems and could also help to optimise filling levels in both new and existing membrane LNG ships in the future. 2.6 WHIPPING AND SPRINGING OF SHIPS’

HULLS It has long been recognised that slender and high speed ships are prone to whipping and springing of the hull girder. Fast slender containerships, cruise ships and Great Lakes bulk carriers are typical ship types that fall into this category (Figure 10). Whipping and springing are both vibratory dynamic responses of the hull girders. Whipping response is usually excited by wave slamming impact causing the hull structure to vibrate which decays with time. Springing is a continuous vibratory response excited by waves with frequencies close to the natural resonance frequencies of the hull. Slamming induced whipping normally occurs in high sea states hence it

44

has a relatively lower probability of occurrence than that of a springing response. However, the induced dynamic hull stress amplitude can be significant due to the magnitude of the wave impact load involved. Springing can occur in low and modern sea states. Although the springing dynamic hull stress level is lower in comparison with a whipping response, springing is an important phenomenon in considering the fatigue properties of the hull structure due to the many stress cycles involved.

Raw measurement data

After application of frequency filter showing

component of springing and whipping responses

Figure 10: Whipping and springing hull girder stress responses measured on a large container ship from a recent full-scale measurement project Hydroelasticity analysis is an advanced computation method studied by Lloyds Register for the prediction of whipping and springing responses of hull structures. This technique involves modelling of the fluid-structure interaction, i.e. integration of hydrodynamic loads and structural mechanics, to determine the behaviour of a flexible structure moving through a fluid. The technique allows the mode shapes and responses of the hull at resonance frequencies to be determined, which cannot be encompassed in the rigidity body assumption used in normal analysis. Where considered relevant, hydroelasticity analysis can be applied in the design stage to provide a better estimation of hull stress responses for the assessment of hull strength and fatigue damages. This technique is also applied to determine the service factor of specific ship types (Figure 11).

Any analysis method must be validated to ensure that its prediction is an adequate representation of the phenomenon which occurs in reality. Lloyd’s Register has been carrying out full-scale measurement on board ships for many years.

Twisting Vertical Bending

Figure 11: Hydroelasticity analysis - mode shapes of a container ship The typical data collected are hull stresses, ship motions, loads, and ship’s navigation information, as well as the associated sea wave information obtained by dedicated wave radar measurement systems installed on board and from wave buoys. This measurement provides invaluable data for the validation and correlation of many analysis procedures. The correlation with the full-scale measurement data so far has indicated that the hydroelasticity analysis technique can predict hull vibration response with reasonably good accuracy. However, more work still has to be done to further improve the accuracy and reliability of the analysis method before it can be applied on a routine basis in the design process. The development work is ongoing.

0.00E+00

1.00E+10

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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

we (r/s)

Spec

tral D

ensi

ty (k

Nm)^

2 s

H1/3=2.1m,T1=5.5sH1/3=3.0m,T1=5.5sH1/3=4m,T1=5.8smeasured

Figure 12: Comparison of amidships vertical wave bending moment response spectra (kNm)2s predicted hydroelasticity analysis against full scale measurements for a Great Lakes bulk carrier [23]

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2.7 GOAL-BASED CONSTRUCTION STANDARDS FOR NEW SHIPS

The premise behind the development of goal-based standards (GBS) is that the IMO should play a larger role in determining the fundamental standards to which new ships are built. There is no intention that the IMO would take over the detailed work of the classification societies, but rather that the Organization would state what has to be achieved, leaving classification societies, ship designers and naval architects, marine engineers and ship builders the freedom to decide on how best to employ their professional skills to meet the required standards. At present there is no international legislation or guidance on these matters.

Figure 12 : IMO five tier system

2.7.(a) Background

The notion of GBS was introduced within the IMO at the 89th session of the Council in November 2002, through a proposal by the Bahamas and Greece suggesting that the IMO should develop initial ship construction standards that would permit innovation in design but ensure that ships are constructed in such a manner that, if properly maintained, they could remain safe for their entire economic life. The standards would also have to ensure that all parts of a ship can easily be accessed to permit proper inspection and ease of maintenance.

The IMO’s Maritime Safety Committee (MSC) agreed to a proposal for the development of GBS based on a five tier system following proposals by the Bahamas, Greece and IACS (Figure 12).

2.7 (b) Current Status

At its 82nd session in 2006, the MSC approved the plan for a pilot project on trial application of the Tier III verification process using the CSR for oil tankers to

benchmark the verification process. The objective of the pilot project was to conduct a trial application of Tier III for CSR oil tankers and bulk carriers with the intention of validating the Tier III verification framework, identifying shortcomings and making proposals for improvement.

Lloyd’s Register, through its IACS hull panel member, assumed the project managing role of the GBS-CSR project team in 2008 to provide a documentation package for the IMO pilot panel [24]. The objective of this submission from IACS was to provide the pilot panel with a working example of how class societies in the future may provide the background documentation illustrating how class rules will meet GBS.

Submission of this report in March 2008 allowed the pilot panel to finalise its deliberations and submit a draft SOLAS amendment to the MSC’s 85th session (MSC 85) to make GBS for bulk carriers and oil tankers mandatory [25]

In essence, the process for establishing that class rules meet the Tier III verification criteria is dependant on verifying that 15 differing Tier II functional criteria have been satisfied, covering:

• Design

⎯ II.1 Design life ⎯ II.2 Environmental conditions ⎯ II.3 Structural strength ⎯ II.4 Fatigue life ⎯ II.5 Residual strength ⎯ II.6 Protection against corrosion ⎯ II.7 Structural redundancy ⎯ II.8 Watertight/weather tight Integrity ⎯ II.9 Human element consideration ⎯ II.10 Design transparency

• Construction

⎯ II.11 Construction quality procedures ⎯ II.12 Survey

• In-service Considerations

⎯ II.13 Survey and maintenance ⎯ II.14 Structure accessibility

• Recycling

⎯ II.15 Recycling considerations.

Tier I

Tier III

Tier V

Tier IV

Tier II

Applicable Industry Standards & Codes of Practice

Prescriptive Regulations & Class Rules

Verification Process

Goals

Functional Requirements

46

2.7 (c) Future Work

The draft SOLAS amendment proposed by the Pilot Panel was not adopted at MSC 85. Many delegations were of the opinion that there were currently still too many uncertainties with regards to the verification process, the financial resources needed and liability issues. They considered that the complete package of SOLAS amendment, draft GBS guidelines, verification process guidelines, contents of SCF and financial and resource issues should be considered holistically.

Many other delegations considered that significant progress had been made and that the draft SOLAS amendment should be approved at MSC 85 to give members a level of certainty and provide a basis for further work in the matter. The Committee agreed to postpone approval of the draft SOLAS amendment to MSC 86 on the understanding that the text of the draft amendments and the draft standards had been agreed by the Committee and would form the basis for any further work at MSC 86.

In conclusion, the Committee invited member governments and international organisations to submit proposals to MSC 86 with a view to finalising the GBS for bulk carriers and oil tankers. In particular, submissions should address:

• finalisation of Part A of the Guidelines for the verification of compliance with goal-based ship construction standards for bulk carriers and oil tankers (MSC 85/WP.5, annex 3), taking into account the discussions of the working group

• finalisation of the Guidelines for the information to be included in a Ship Construction File

• development of an alternative verification process based on self-assessment only, taking into account the comments in paragraph 37 of document MSC 85/WP.5

• The possible need for amendments to other IMO instruments, following the finalization of the GBS for bulk carriers and oil tankers, taking into account document MSC 84/5/1.

Figure 10: IMO 5 tier system as of Nov. 2008 at MSC85 3. CONCLUSIONS This paper has taken a brief look at some of the ongoing structural issues affecting the marine industry in general and Lloyd’s Register in particular. As mentioned in the introduction it is imperative that we try to learn from the lessons of the past if we are to prevent their recurrence in the future and in an era of new inexperienced shipyards in Asia, and reducing technical departments within the owning community, it is vital that Lloyd’s Register stays abreast of the latest developments to help ensure safe and sustainable shipping operation. Lloyd’s Register is doing its utmost to help ensure that this knowledge is shared with the industry and is heavily involved in the IMO GBS issues. 4. ACKNOWLEDGEMENTS The author would like to acknowledge the help, time and effort given to him in the preparation of this paper by his colleagues within Lloyd’s Register, in particular, Rob Bridges, Hasan Ocakli, Reddy Devalapalli, Nigel White, Shengming Zhang, Jimmy Tong, Norbert Bakkers and Chris Thornton. 5. REFERENCES 1. Lloyd’s Register ShipRight FDA - Structural Detail

Design Guide. 2. Lloyd’s Register ShipRight FDA - Software User

Manual. 3. Lloyd’s Register ShipRight FDA Level 3 – Guidance

on direct calculations.

Tier I

Tier III

Tier V

Tier IV

Tier II

Applicable Industry Standards & Codes of Practice

Prescriptive Regulations & Class Rules

Verification Process

FunctionalRequirements

GoalsTier I

Tier III

Tier V

Tier IV

Tier II

Applicable Industry Standards & Codes of Practice

Applicable Industry Standards & Codes of Practice

Prescriptive Regulations & Class Rules

Prescriptive Regulations & Class Rules

Verification Process

Finalized but not

Approved

Verification Process

FunctionalRequirements

FunctionalRequirements

GoalsGoals

Not Finalized

47

4. Bridges et al., Preliminary Results of Investigation

on the Fatigue of Ship Hull Structures when Navigating in Ice, IceTech, 2006

5. Lloyd's Register, Rules for Ice and Cold Operation,

Part 8 of the Rules and Regulations for the Classification of Ships, July 2008

6. Bridges et al., Current Hull and Machinery Ice

Class Rules Requirements and impact of IACS Polar Rules, ARCOP Report W2.2.2, 2005

7. Finnish Maritime Administration, Guidelines for

the Application of the Finnish Swedish Ice Class Rules, Bulleting No. 14/20.12.2005

8. Bridges, Development of Requirements for the

Winterisation of Ships, IceTech, 2008 9. Hindley et al, Methods and approaches for the

classification of ships designed for stern first operation in ice, lce Tech, 2008.

10. Tustin et al, Development of Arctic double acting

shuttle tankers for the Prirazlomnoye project, TSCF Shipbuilders Meeting, 2007

11. Tustin, Recent developments in LNG and Ice Class

Tanker design and the potential application to future Arctic LNG ships, Arctic Shipping, 2005

12. Lloyd’s Register’s Provisional Rules for the

Application of Sandwich Panel Construction to Ship Structure 2006

13. Lloyd’s Register, Sloshing loads and scantling

assessment for partially filled tanks. 2004 14. Lloyd’s Register, Comparative Sloshing Analysis

of LNG ship Containment Systems, 2005 15. Lloyd’s Register, Rules and Regulations for the

construction and classification of ships for the carriage of Liquefied gases in bulk, 2008(a)

16. Lloyd’s Register Procedure for analysis of pump

tower and pump tower base. 2008(b) 17. Lloyd’s Register, Absolute Sloshing Assessment

Procedure for Membrane LNG Ships, Draft. 2008(c)

18. Sloshing loads in partially filled prismatic LNG

Tanks-Phase II, MARINTEK. (2003): Report no. MT60 F03-069/820013.00.01

19. Sloshing Model Test of DSME 210k LNG Ship

with 5 tanks for Partial Filling Conditions, MARINTEK. (2006a): Report no. MT57 F06-012/570026.00.02

20. Fluid force Measurements on Pump Tower in an

LNG tank, MARINTEK. (2006b): Report no. MT57 F06-012/570026.00.02

21. Reddy, D.N. and Radosavljevic, D. (2006):

Verification of Numerical Methods applied to Sloshing studies in Membrane Tanks of LNG Ships, RINA Lloyd’s Register, London, UK

22. Reddy, D.N. (2008): Review of CFD software

OpenFOAM for its application to Sloshing simulations, Lloyd’s Register internal report no. MPD/08/03, V1.

23. Spyridon E. Hirdaris¥‡, Norbert Bakkers*, Nigel

White*, Pandeli Temarel, Service Factor Assessment of a Great Lakes Bulk Carrier Incorporating the Effects of Hydroelasticity,

24. IACS Documentation Package for the IMO GBS Pilot Project [2nd Trial Application]

25. Goal-Based New Ship Construction standards,

Draft SOLAS amendments to make the GBS for bulk carriers and oil tankers mandatory and related matters MSC 85/5

48

NOTES

49

NOTES

50

PAPER 5

SHIP HYDRODYNAMIC PROPULSION:SOME CONTEMPORARY ISSUES OFPROPULSIVE EFFICIENCY, CAVITATIONAND EROSION

John Carlton D.Sc., B.A., C.Eng., M.I.Mech.E., M.R.I.N.A.,

M.I.Mar.EST.

51

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SHIP HYDRODYNAMIC PROPULSION: SOME CONTEMPORARY ISSUES OF PROPULSIVE EFFICIENCY, CAVITATION AND EROSION John Carlton SUMMARY A number of topics ranging from the analysis of hull flows through to propeller design are considered. In particular, the interaction between measures to enhance efficiency and the possible consequences these measures may have for cavitation development are explored, both in terms of enhancing the potential for material erosion and ship vibration. This is achieved in the context of both Lloyd’s Register’s ongoing research activities and the practical application of these initiatives to ship operation. Additionally, a new method for the detection of propeller erosion based on acoustic emission techniques is introduced. 1. INTRODUCTION In keeping with earlier periods in history, most notably in the early 1970s and then more recently, marine fuel prices have shown significant increases in the last few years. While the underlying price behaviour for both marine diesel oil and heavy fuel oil has demonstrated increasing trends, there have been perturbations about these mean trends: sometimes these have shown marked reductions, as is presently the case, while at other times the opposite has been true. From a historical description of the price of fuel, and set against the background of international politics and relationships, there is little reason to suppose that marine fuel prices will not continue to exhibit a generally increasing trend, albeit, from time to time, with some intermittent and localised reductions. Furthermore, history suggests that when fuel prices rise, ship speeds tend to reduce. Alternatively, when fuel prices stabilise and freight rates increase for a reasonable period of time, there is then a tendency for ship speeds to increase. Such a background scenario demands careful consideration in terms of its implications for ship design and operation. The ship propulsion hydrodynamic considerations in this context embrace the initial hull and propulsion concept design in the case of new ships or, more generally, the introduction of energy saving systems for existing ships. In either case, it is helpful if the enhancement to the propulsion efficiency sought is significant enough for it to be distinguished from the normal scatter of the in-service data returned from the ship.

When considering the design or retro-fitting implications of efficiency improvements, the pay-off between the steps necessary to improve the propulsion efficiency and the potential introduction of more onerous cavitation, which may lead to an increased erosion and vibration potential, requires careful consideration. This paper, which is based on Lloyd’s Register’s research and development activities in ship propulsion technology, considers some of the contemporary issues in design and the application of various techniques to aid that process. Additionally, the paper discusses some of the innovative techniques that Lloyd’s Register has introduced and demonstrates the ways in which these are being developed to improve the understanding of marine propulsion technology. 2. HULL DESIGN AND PROPULSION It is self evident that there is no substitute for a well designed hull which endeavours to maximise propulsion efficiency within the constraints of good seakeeping and manoeuvrability, as well as cargo handling and port and operational constraints. When considering the propulsion aspects of the design, the use of model testing and analysis centred on computational fluid dynamics, coupled with sound design experience, is advisable. Indeed, given this scenario it is surprising that only some 5% or so of newbuild projects have the benefit of resistance and propulsion and propeller cavitation model testing during their design and construction phases. This is particularly significant when one considers the through-life financial implications of poor performance against the initial cost of

53

model testing. Model testing, however, is subject to uncertainties regarding scale effects which need careful consideration. In particular, the choice of model scale can assist, in some way, to resolving these issues, but care also needs to be taken when selecting the appropriate test establishment, particularly in relation to its experience with the type of ship being considered in terms of scaling factors and correlation allowances. Analysis by computational fluid dynamics procedures has matured significantly in recent years and, as well as beginning to yield good quantitative estimates of resistance, it enables the designer to gain insights into the flow field around the ship. This is particularly important in the after-body region of the hull where unpleasant vorticity and separation effects may manifest themselves and adversely affect propeller performance. Within the context of a numerical analysis carried out by Lloyd’s Register, Figure 1 illustrates this point in connection with the flow around the after-body of a container ship destined to be fitted with a system of vortex generators in order to resolve a propeller cavitation induced vibration problem. In comparison to model testing, computational fluid dynamic analyses are relatively new and the correct choice of turbulence modelling has been an issue throughout its development in ship analytical practice. It has been established that the computationally intensive Reynolds stress models have both improved the accuracy of the numerical prediction for the finer hull forms and, moreover, extended the range of applicability to full form ships. Nevertheless, from Lloyd’s Register’s experience in using these methods the less computationally demanding k-Ω SST

method of turbulence modelling has also been shown, in many cases, to give acceptable engineering results. At present, fully integrated friction and free surface models can present some difficulties; consequently the residual resistance components are mostly estimated from the use of inviscid panel methods. However, methods based on the transportation of species concentration are under development and show promise for the implementation of an integrated resistance computational fluid dynamic solution. Notwithstanding these advances in the mathematical modelling processes, it is considered that they should not at present totally replace the conventional and well validated model testing procedures for which much correlation data exists. Rather, they should be used to augment the design approach by allowing the designer to gain insights into the flow dynamics and develop any necessary remedial measures before the hull is constructed. A further application of computational fluid dynamics techniques is in the prediction of the wake field that enters the propeller disc. Over the last quarter of a century this has been estimated using a number of scaling techniques, sometimes dependent on ship type, which transform the model nominal to the ship effective wake field. However, the developments in computational fluid dynamics have, in their current state of development, permitted the investigation and quantification of flow features that would not normally be possible when using model tests. This can be appreciated by recognising that at model scale, the typical computational grid size would be about 2 mm and it is unusual to see model test data with such a high resolution: indeed, this would be unattainable when using conventional pitot tubes. Typical of these features is vorticity in the wake field which

Figure 1: CFD flow study of a container ship hull fitted with vortex generators

54

is demonstrated by Figure 2 and is the result of a full scale flow computation around the ship.

Figure 2: CFD computation of a ship full scale wake field A considerable research effort is being expended internationally on the subject of drag reduction methods, particularly in relation to the ship’s boundary layer. The potential benefit for this is significant. For example, in the case of a container ship the approximate ratio of the frictional to total resistance is of the order of 0.65. Consequently for these types of ship, those initiatives dealing with the frictional resistance are directed towards influencing the major component of resistance. In the alternative case of a bulk carrier or tanker, this ratio will rise to around 0.8 to 0.85. Within the spectrum of methods focussed on reducing the frictional resistance are fluid injection methods and coating development. Methods involving the injection of small quantities of long-chain polymers, such as polyethylene oxide, into the turbulent boundary layer of underwater vehicles were shown in the 1960s to significantly reduce resistance, provided the molecular weight and concentration were chosen correctly. This type of approach, which worked by stabilising the inner parts of the ship’s boundary layer by fluid injection, however, is unlikely to be environmentally acceptable today. Current research efforts, therefore, are focussing on a range of approaches involving boundary layer fluid injection and manipulation without the need to inject foreign fluids into the sea. Typical of such methods is the use of air-injection techniques, where some benefit in the case of small fishing boats and passenger ferries, of the order of 15 to 20% in the frictional component of resistance, has been claimed by the inventors of the system [1, 2]. These

types of systems rely on air at low pressure being injected through a piping system comprising a number of underwater outlets, into the ship’s boundary layer in the forward parts of the hull. Figure 3 shows a typical injection port. The injected air is formed into a micro-bubble layer, with bubbles nominally of the order of 10 microns in diameter, by the outlet geometry of the injection port which relies on the Kelvin–Helmholtz principle. The injected air is then assumed to follow the flow streamlines around the hull.

Figure 3: WAIP air injection port Should such systems be contemplated for large seagoing cargo or passenger ships, then care in selecting the orifice positions in the hull is required. From research carried out, these penetrations in the hull, since there will be many of them, need to be considered in the context of the hull bending moments and shear forces with respect to the global and local stresses introduced. Nevertheless, it has been found possible to establish positions in the hull that satisfy both the streamline flow and hull integrity constraints in a seaway. This may imply that the orifices need to be positioned such that they are not aligned in vertical lines, but in curvelinear lines set around particular longitudinal stations. Additionally, from these research studies, it is not anticipated that the pipe flow dynamics, when the ship is working in a seaway, are likely to be a source of significant concern. The ship’s intact and damage stability behaviour, however, needs careful evaluation, particularly in relation to the location of the various components of the system and the possible ingress of sea water into the ship should part of the internal piping system rupture. Within a related context, the air-water emulsion that is created over the hull surface is likely to influence the roll-damping and frequency roll characteristics of the ship. This also

55

requires consideration when contemplating an installation of this technique. Recent IMO developments have resulted in a restriction on the use of hull coatings with bio-active compounds designed to kill fouling. This represents a significant challenge given that the fouling sequence normally commences with slime, comprising a mixture of bacteria and diatoms, which then progresses to algae. Following this, animal foulers, such as barnacles, tend to take up residence, which then culminate in the climax community. Prior to the introduction of bio-active compounds, hull fouling led, in ship performance terms, to regular and frequent increases in hull resistance which originated from periodic increases in the ship’s apparent wake fraction over a docking cycle. This then had adverse implications for propulsion efficiency. With the introduction of anti-fouling paints, the saw-tooth form of the apparent wake fraction largely disappeared and the necessity to dry-dock for fouling reasons was reduced. Hull roughness, in both its temporary and permanent forms, plays an important role in maintaining a low ship resistance. In this context, permanent roughness refers to the unevenness of the plates and the results of contact damages, while temporary roughness includes the amount and composition of marine fouling and local damage to a coating, including that caused from the debris from earlier coatings. Since only limited action can be taken with permanent roughness, the focus of attention has to be on the temporary roughness component. A number of coating solutions have been evolved for use in the post-biocide era, with various benefits claimed. In the case of faster ships that do not spend too much time alongside in port or at anchor, a potential solution for the hull may lie in the silicone-based elastomeric coatings. The properties of silicone coatings are such that they prevent marine life from adhering to the hull surface provided that the ship speed is maintained above certain critical values, typically in the region of 17 to 18 knots and sometimes lower, as a result of more recent developments in this type of painting technology. Furthermore, some advantage in terms of a reduced turbulent flow wall shear stress is also likely.

3. PROPELLER DESIGN When designing the propeller for a particular application, the expected operational profile of the ship needs to be carefully considered, particularly if the ship has a number of operating modes, for example, in the case of a cruise ship. Not only is this important in order to achieve the most efficient performance over the spectrum of operation, but also to minimise the probability of unwelcome harmonic or broadband cavitation excited vibration when operating over the range of powering conditions [3]. In previous times of high fuel prices and poor freight rates, it has been found that an effective way of reducing operating costs has been to reduce ship speed. While such action is clearly beneficial from a fuel consumption point of view, under the simple considerations of the cube law, relating absorbed power to ship speed, further financial savings can frequently be made by changing the propeller design if a prolonged service at a different operating condition is anticipated. By deploying conventional propeller design techniques, in which a re-designed slow running propeller is permitted to have the same margins against cavitation as an existing higher speed design, it is possible to optimise the benefit in terms of enhanced efficiency. In effect this permits the blade area to be reduced and, hence, also the drag of the blade sections. Following such an analysis for a particular ship, and including the implicit engine efficiency changes, it is then possible to assess whether it is beneficial to incur the cost of redesigning and manufacturing a new propeller for a slower service speed. Notwithstanding these broad palliative considerations of efficiency versus cavitation excitation, there is significant scope to enhance performance in the propeller design process by correctly considering the balance of permissible face and back cavitation in relation to section chord length and hence drag of the blade sections. This subject is far from trivial since it also involves material erosion considerations and is currently the subject of considerable research, both within Lloyd’s Register and at other institutes around the world. Much inter-disciplinary research has been taking place on the subject of cavitation in

56

Newtonian and non-Newtonian fluids. This applies to: ships’ propellers and appendages; steel and rock cutting processes; and hydraulic machines and medical applications involving heart valves and the breaking up of kidney stones. From research of this type, a consensus of cavitation dynamics statistics has been derived for hydrodynamic machinery and Table 1 summarises some of these dynamic properties. The collapse of a 10 mm radius vapour filled cavity takes about one millisecond The duration of the final phase of a cavitating vortex collapse or that of a bubble is about 1 microsecond The pressures induced by cavitation collapse are considered to be in the region of 100 MPa to upwards of 1 GPa

Table 1: Some cavitation statistical parameters The prediction of the cavitation characteristics of a propeller is a complex process. In terms of numerical analysis, the computations are frequently based on lifting surface methods. From these, good predictions of the blade sheet cavitation on the suction side of the propeller blades can be obtained given that a proper scaling of the ship’s wake field has been undertaken or, alternatively, that the wake field has been derived from computational fluid dynamics procedures. In recent years, Lloyd’s Register has actively participated with other collaborative partners in developing an advanced boundary element method for the analysis of propeller characteristics. Figure 4 shows a typical result of such a computation in terms of the leading edge cavitation extent on a highly skewed propeller.

Figure 4: A propeller cavitation prediction using based on a CFD wake prediction

The results of this boundary element code, together with the results of other engineering initiatives, are validated using our in-house investigation capabilities by comparing the results to full scale behaviour. Within this context of the validation of ship hydrodynamic computational procedures or, alternatively, of hypothesis testing, validation is often achieved through the use of boroscope techniques which were pioneered by Lloyd’s Register some years ago. This technique has proved particularly beneficial when undertaking hydrodynamic investigations without incurring the necessity of drydocking the ship [4]. Sheet cavitation, which most commonly forms the subject of numerical prediction capabilities, is generally only problematic if instability in its behaviour is detected. However, this is only one form of cavitation and Figure 5 shows schematically the majority of the other types of cavitation that may be encountered.

Figure 5: Common types of cavitation on propellers These other forms of cavitation, within the current state of the art, do not readily lend themselves to analysis by computation, although significant progress is being made using advanced computational fluid dynamics codes. Among the most problematic of these cavitating structures are the various forms of cavitation relating to the tip vortex and the blade root. These forms of cavitation normally have to be assessed by undertaking tests in large cavitation tunnels or in the depressurised towing tank. Indeed, cavitation tunnel studies are still the most helpful procedures to adopt when considering the behaviour of cavitating structures on ships’ propellers. However, it is critical to this process to simulate the actual wake field as accurately

57

as possible. Moreover, recognising the industry knowledge of current testing practices, it is insufficient to model the wake field by simple grid structures as was the case several years ago. To do so may lead to misleading or incorrect results in relation to the eventual performance of the propeller. Erosive cavitation is induced by the way in which the cavitating structures collapse and break up and the energy that is transferred within that process. Since all merchant propellers cavitate to some extent, but only a smaller number suffer erosion, the energy clearly varies and is dependent upon the cavitation structures and dynamics encountered. In the case of sheet cavitation the behaviour of the re-entrant jet is particularly important since this has been found to determine the subsequent structure of the cavities during collapse. In Figure 6 it can be seen that the re-entrant jet tends to stimulate vortices which are broadly parallel to the trailing edge geometry of the cavity.

Figure 6: Idealisation of the re-entrant jet mechanism When this occurs these vortices eventually separate and form, because of Kelvin’s Theorem of vorticity, closed loop ring or doughnut type structures. These structures, based on experimental holographic images [5], are thought to comprise systems of micro-bubbles, which due to the flow direction, tend to congregate at the sides of the doughnut rings which are parallel to the direction of flow. These bubbles then collapse, probably initiated by a single bubble in the cluster collapsing, in a rapid manner, the speed of which is indicated by Table 1, and energy is then transferred to the propeller blade surface.

Indeed, from our model and full scale observations, whenever these discrete ring structures have been observed it has always been a precursor to severe erosion being encountered. Figure 7 shows just such an example manifesting itself in the root of a full scale propeller blade: this blade suffered complete penetration of the section in just a few hours.

Vortex Loop

Figure 7: Vortex loop structure in the root of a propeller blade The mechanism of energy transfers from macro to micro-bubbles and then into the material surface has been explored by Fortes-Patella and her colleagues [6]. It is this model, shown schematically in Figure 8, which forms the present basis of Lloyd’s Register’s research into propeller blade, and for that matter rudder, erosion mechanisms. As can be seen from the Figure the model comprises a system of energy transfers encompassing the behaviour from macro-cavity structures through to the response of the material.

Figure 8: The Fortes-Patella model energy transfers during cavitation collapse

Face cavitation has long been an anathema to propeller designers, principally because of its potential link to the possibility of material erosion, coupled with the knowledge that the face of the propeller blade, under normal operational circumstances, has a tensile stress field distributed over its surface. This may then facilitate crack propagation if the erosion potential becomes critical. Consequently, an operational margin against face cavitation occurring was commonly introduced; this

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was sometimes of the order of 25% of the thrust coefficient. However, recent research within the EROCAV grouping, of which Lloyd’s Register was a member, has suggested that this level of conservatism is perhaps not as well founded as previously thought. This is, in part, due to a greater understanding of the physics associated with face cavitation. Experience from modern propeller designs shows that face cavitation tends not to be as erosive as originally anticipated and by permitting greater flexibility in considering margins against face cavitation, gives an enhanced potential to deal with propeller blade back cavitation issues. The underlying physical basis for these considerations stems from the realisation that the blade surface pressure distribution giving rise to face cavitation, is of a rather different character to that which develops into back cavitation and, furthermore, that face cavitation tends to have a more two-dimensional character than its back cavitation counterpart. This then influences the behaviour of the re-entrant jet into the cavity which results in different shedding mechanisms. Recognising that these enhanced understandings of face cavitation dynamics [7] give greater flexibility to the designer in controlling back cavitation, it is then important to understand the relationship between back cavitation collapse and material erosion. This is a complex issue since the presence of erosion always implies the presence of cavitation, but not vice-versa. Lloyd’s Register has been undertaking an ongoing research programme into the fracture mechanics of the underlying erosion process. This study has included endeavouring to define energy threshold values above which erosion will occur and gaining an understanding of the fundamental mechanism of the erosion process. While this is a continuing initiative, some success has been achieved with the use of acoustic emission techniques in defining threshold energy levels for the incidence of erosion and in understanding the work hardening and polycrystalline plasticity regimes that accompany the initial development of erosion. Figure 9 demonstrates the work hardening process that occurs in nickel-aluminium bronze during the development of the erosion process. Similar changes are also observed in duplex stainless steels.

400

350

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Figure 9: Increase in material hardness with cavitation damage development

These increases in hardness imply that the ductility of the material in the vicinity of the erosion reduces and, consequently, the fracture mechanics process comprises fracture dynamics within a material of varying mechanical properties. Moreover, the fracture mechanism for cracks developing from the surface of the material must include a contribution from corrosion. This is due to the presence of the sea water if the erosion process takes a significant time to manifest itself. This is perhaps not the case for very aggressive erosion situations. However, any sub-surface developing cracks are unlikely to be subject to such an influence of corrosion. Indeed, within our present knowledge it is believed that both crack mechanisms apply in the erosion process. A further complication in describing the fracture mechanics model for erosion is suggested because sometimes, in cases of cavitation erosion damage to propeller blades, a discolouration, reminiscent of blueing during metal tempering, is observed. This may imply that the temperature of the propeller blade has significantly increased during the cavitation attack. Furthermore, from considerations of the collapse of single or streams of bubbles in the vicinity of the blade surface, it is not difficult to support a simple heat transfer description of the collapse process where surface heating of the material is induced. This then introduces an additional factor in the complex fracture mechanics process previously described. Given the eventual ability to quantitatively play-off the back and face cavitation and erosion characteristics of propeller blade sections, it is then possible to consider the

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required chord length at each radial station of the propeller in order to provide the minimum surface area for the propeller and, hence, minimise its drag while satisfying the harmful cavitation constraints. Recognising that the prediction of cavitation erosion is still some way in the future from a theoretical standpoint, Lloyd’s Register has been examining the potential of using acoustic emission methods to predict propeller blade erosion. This research is, in effect, extending the particularly successful application of this technique to the prediction of rudder erosion which was again pioneered by Lloyd’s Register some years ago. Figure 10 shows an installation fitted to the shaftline of a tanker in which acoustic emission signals, developed on the propeller blade surfaces, are transmitted from a shaft mounted telemetry system. At present, the only constraint on the system is thought to be that the propeller is fitted to the shaft by means of a shrink fitting method.

Figure 10: Shaft mounted acoustic emission system Typical results from this innovation are seen in Figure 11. This figure illustrates that the level of acoustic emission is periodic with the propeller blade passage, which suggests that cavitation is the source of the emission and the travelling direction of the signal reinforces this conclusion. Then by superimposing previous material laboratory tests, which were conducted to define threshold levels for erosion to take place, the acoustic emission signature on the

actual propeller can be analysed in the context of its susceptibility to blade erosion as seen in the Figure.

Figure 11: Typical acoustic emission signature for a propeller 4. PROPELLER DIMENSIONING

AND MAINTENANCE The tolerances to which propeller blades are manufactured have a profound influence on the cavitation and power absorption characteristics of marine propellers. In the case of merchant ship propellers, the ISO 484/1 and 484/2 dimensional specifications form the basis of the manufacturing tolerances. However, for the majority of ship applications it is only the Class S and 1 tolerance specifications that are of practical interest, since Classes 2 and 3 only impose very limited control over the finished blade geometry. Table 2 highlights some of the primary and secondary effects of the various blade geometrical parameters In many instances of propellers having a high power density it has been found necessary to enhance the propeller blade specifications beyond those given in the ISO standards. These measures have been introduced in order to control the cavitation performance of the propeller effectively. This has been found to be particularly true when trying to control cavitation in the propeller root regions by maintaining tight tolerances on the blade fillet design. Similarly, control is frequently necessary at the blade tips. Additionally, it has been found on occasions that it is necessary to enhance the leading edge template specification, again where greater control is required over cavitation inception and development. It is particularly important, however, that each application is considered

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on its merits. Parameter Primary Effect Secondary Effect Diameter Power absorption. - Mean Pitch Power absorption. Cavitation extent. Local section pitch Cavitation inception and extent. Power absorption. Section thickness Cavitation inception, blade strength Power absorption. Section camber Power absorption, cavitation inception. Blade strength. Section chord length Cavitation inception and extent. Blade strength and power

absorption. Blade form Generally small effects on cavitation

inception and shaft vibratory forces at frequencies dependent on wake harmonics and blade irregularities.

-

Leading edge form Critical to cavitation inception. - Rake and axial position Cavitation control and minor

mechanical vibration. -

Surface finish Blade section drag and hence power absorption.

-

Static balance Shaft vibratory loads. -

Table 2: Principal effects of the various propeller geometric variations

Propeller maintenance is another important consideration since fouling will increase the blade section drag. If this occurs, the hydrodynamic efficiency of the sections will deteriorate. It is consequently beneficial for the propeller to be polished at regular intervals by personnel experienced in propeller cleaning and maintenance. If they are not experienced then inadvertent damage can be done to the propeller blades, particularly in their leading and trailing edge regions. If leading edge damage occurs then this most commonly affects the cavitation inception and development characteristics of the blade sections. This is because the flow in this region of the blade is particularly sensitive to the subtleties of the blade sections’ geometric curvatures. In contrast, the power absorption characteristics of the propeller blade are sensitive to changes in the trailing edge geometric configuration. 5. CONCLUDING REMARKS The paper has given an overview of a number of the research and development initiatives in ship propulsion hydrodynamics that are currently active within Lloyd’s Register. In addition, some commentary has been given on the practical application of these techniques to ship practice.

6. ACKNOWLEDGEMENTS The Author wishes to thank Mr P.A. Fitzsimmons, Mr A. Boorsma and Dr D. Radosavljevic for their valuable contributions to, and advice on, various parts of the work. 7. REFERENCES 1. Takahashi, Y. Reduction Loss by

Injecting Negative Pressure Type Micro Bubbles. J Code N20040336, pp528-531, 2003.

2. WAIP – Development of a New Technology for Reduction of Frictional Resistance. The Motor Ship, April 2007.

3. Carlton, J.S. Some Current Issues with Cavitation and Propeller Rudder Interaction. SWZ Journal, December 2008.

4. Carlton, J.S. and Fitzsimmons, P.A. Cavitation: Some Full Scale Experience of Complex Structures and Methods of Analysis and Observation. Proc. 27th ATTC, St John’s Newfoundland, August 2004.

5. Kawanami, Y., Kato, H., Yamaguchi, H., Maeda, M and Nakasumi, S. Inner Structure of Cloud Cavity on a Foil Section. Proc. CAV2001, 2001.

6. Fortes-Patella, R. Rebould, J.L. and Briacon-Marjoilet, L. A Phenomenological and Numerical Model for Scaling the Flow Aggressiveness in Cavitation Erosion.

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EROCAV Workshop, Val de Reuil, May 2004.

7. Bark, G. Berchiche, N. and Grekula, M. Application of Principles for Observation and Analysis of Eroding Cavitation – The EROCAV Observation Handbook. Edition 3.1. Dept. of Naval Architecture and Ocean Engineering. Chalmers University of Technology, 2004.

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PAPER 6

DESIGN ASSESSMENT OFENGINEERING SYSTEMS WITHPARTICULAR REFERENCE TO SHAFT ALIGNMENT

Andrew Smith B.Sc., C.Eng., F.I.Mech.E.

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DESIGN ASSESSMENT OF ENGINEERING SYSTEMS WITH PARTICULAR REFERENCE TO SHAFT ALIGNMENT Andrew B Smith SUMMARY The length of time between design conception and delivery for all ship types is becoming shorter. This introduces problems associated with reduced manufacturing and installation times, including prototype testing, and these have the potential to increase manufacturing defects and operational issues. This scenario creates two principal areas of concern: first is the control of sub-contractors during manufacture and second is the available time to complete design approval in a meaningful fashion. Classification rules are written to be fairly simplistic, easy to use and to apply to all ship types. By definition, this leads to most designs being conservative. In the general engineering world this is thought of as undesirable, but in the world of marine engineering this conservatism allows for the unknowns and variable parameters which can occur during the operational life of the ship imposing higher than expected design loads. One area which is still proving to be problematic is shaft alignment; recent alignment problems required Lloyds Register to look more closely at the methods of assessing alignment issues. 1. INTRODUCTION The control of quality in design and manufacturing is at the heart of the classification process. In past years, when life moved at a more sedate pace, this control was relatively easy and classification societies had the time to become involved in all aspects of the design and manufacturing cycle. This led to a fundamental understanding of the design and operation of the component or system. Now the aim is to make the time to delivery as short as possible. This is understandable, but it has left classification societies with very little time for approval before production starts and clients are not willing to wait. Lloyd’s Register has to adapt to this new way of working while maintaining acceptable standards and quality of service. 2. DESIGN APPROVAL Over the last few years, manufacturers have significantly reduced the time between design completion and production, so much so that production has started almost before the plans have arrived at the classification society. Obviously, this is undesirable since any discussions on the design will be carried out late in the production cycle, making any required modifications costly to undertake. The aim must be for classification societies to become involved at the design concept stage and move the class approval much further forward in the design cycle. By doing so, they will be able to give a ’clean’ classification approval earlier, thereby avoiding time consuming discussions of equivalence to the rules for those designs outside the classification acceptance criteria. In addition, earlier involvement can remove the potential for failures during operation, while the class society’s in-depth experience and knowledge

can be passed back into the marine industry to the benefit of all. Furthermore, appraisal over and above routine class approval can be considered at this time. As an example, stern bearing failures are still high on the list of machinery failure statistics. Defect statistics over the last 20 years indicate that the aft stern bush represents 10% of shaft line failures, with the forward stern bush representing 4% of total failures. Interestingly, the aft stern gland and forward stern gland represent 43% and 24% of failures respectively. A number of these bush failures have been attributed to poor shaft alignment. It can be conjectured that the glands have also been affected by poor alignment. Lloyd’s Register’s Rules have been modified regularly since they were introduced in 1976, to take account of the experience that has been gained, but problems still arise. This is an indication of designs evolving and moving outside the scope of the Rules, no matter how meaningful and relevant they are made. It can be argued that these problems have followed the emergence of ship building nations over the last 30 years or so, since the same trend of failures has been repeated in approximately 10-yearly cycles. Classification societies are the guardians of knowledge and many technical papers have been written and presented detailing these failures and their solutions in order to pass this knowledge on. Class rules are written to be fairly simplistic and easy to use. By definition, this leads to most designs being conservative. In the general engineering world this is thought of as undesirable, but in the sphere of marine engineering this conservatism allows for the unknowns and variable parameters which can occur during the operational life of the ship imposing higher than expected design loads. In light of the above factors, Lloyd’s Register looked more closely at the methods of assessing alignment issues. This paper explores our ongoing investigations in detail.

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3. SHAFT ALIGNMENT APPRAISAL Figure 1 shows a failure in the top half of an aft stern bearing. This is an unusual occurrence and has happened on three ships of differing design. Stern bearings tend to fail in the bottom half; the subsequent check and recheck of the theoretical analysis did not suggest any errors in the assumptions which were made. As a result, we looked in more detail at the shafting system.

Figure 1: Bearing failure in top half of bearing The following parameters influence shaft alignment: • stiffness of bearing supports • shaft stiffness • propeller mass and dynamic loads • bearing material and lubrication. 3.1 STIFFNESS OF BEARING SUPPORTS This value is taken to be the summation of the bearing material, lubrication and the support stiffness. Experience over the years has given Lloyd’s Register a good understanding of the overall value of stiffness to be used in the analysis. However, the introduction of thinner scantlings for the hull structure has started to affect the overall stiffness of the aft end, including the bearing supports, thereby negating the generalised assumptions made during analysis. The advent of more efficient and powerful computers has allowed this to be investigated theoretically in an easier fashion than was the case ten or so years ago. Figure 2, which is a model of an LNG Carrier, provides an example. This vessel is in a fully laden condition and the aft end is experiencing a deflection of 50mm relative to the plummer bearings; this is not inconsiderable and needs to be taken into account during the design phase. Figure 3 has been included to show, in easier terms, the deflection to be expected at the aft end under various loading conditions when afloat. It has been the assumption in

the past that the aft end will remain relatively rigid, with a standard value, based on experience, being used for a change between full and ballast conditions. Figure 2 shows that we need to rethink the ’rules of thumb’ for generalised cases. It is interesting to note that the deflection is not symmetrical about the ship centre line. This was due to the differences in the load capacity of the port and starboard heavy fuel oil tanks, situated aft on the vessel. A twisting moment (torsion) was generated along the length of the vessel, causing a list, and was reacted against by the buoyancy effects of the generated list. This will introduce misalignment in the athwartship direction. Normal convention dictates that alignment of the shaft line is a straight line in the horizontal plane, which is not the case in this example. The vertical alignment is also affected by the positioning of hot tanks in way of bearing stools, which is a fact often not appreciated during analysis.

. Figure 2: Vertical deflection fully loaded

Case 1- Light ballast condition with aft peak tank empty Case 2- Normal ballast condition with aft peak tank empty Case 3- Normal ballast condition with aft peak tank full Case 4- Loaded condition with aft peak tank empty Case 5- Loaded condition with aft peak tank full Figure 3: Tank top deflections

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3.2 SHAFT STIFFNESS Shaft stiffness, meanwhile, has moved in the

cal shaft systems – stiff

.3 PROPELLER MASS AND DYNAMIC LOADS

ith increases in power come increases in propeller

yd’s Register has been examining the problem over

igures 6 and 7 indicate the change that the shaft

opposite direction. Ships have been ordered with greater installed power for higher speed and the machinery space has been moved further aft to increase the cargo carrying capacity; therefore the shaft system has become stiffer. The stiff shaft somehow has to follow the flexible aft end structure. Ship designs with more flexible shaft arrangements, such as twin screw, have also given rise to concerns. Shaft designs using electric motors as prime movers and using high ultimate tensile strength shaft material have become more flexible. The Rules allow for a smaller shaft scantling when driven by electric motors and this, coupled with the fact that these are often twin screw with long shafts, has resulted in the shaft system becoming rather more flexible. As a result, it cannot resist the dynamic loads being applied and therefore is more susceptible to taking up a position dictated by the direction of the propeller force vector. Compare Figures 4 and 5. There are two avenues to explore; aft end flexibility with stiff shafts and flexible shaft lines.

Figure 4: Typi Figure 5: Typical shaft systems – flexible 3 Wsize and mass. It follows therefore that there is an increase in propeller dynamic loads which is well known and predictable in the ahead maximum continuous rating operation condition. Less well

known are the forces applied during ship turning manoeuvres and, with the increase in power and speed, these too have been increasing. Llothe last few years to establish exactly what happens. With the help of full scale trials undertaken by Lloyd’s Register’s Technical Investigations department, and with the full co-operation of a Lloyd’s Register owner, a better idea of what occurs is beginning to emerge. Fexperiences during manoeuvring operations. The shaft would normally operate in the bottom half of the bearing at approximately the 4 o’clock or 8 o’clock position. However, during a turning manoeuvre the shaft tends to be lifted to operate, in the case shown, at 10 o’clock.

A.P.T

Figure 6: Shaft position during 35 degree turn

Figure 7: Shaft position readings during

C.W.T

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Engine Stopped

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ring manoeuvres at high speed, the propeller in-

.4 BEARING MATERIAL AND LUBRICATION

f all the parameters, this is perhaps the one that has

Figure 8: Comparison of measured and

a quasi-static analysis, the position of the oil

his approach is also being extended to research into

easurements havscrew container ship of less than 10, 000 teu. It is interesting to note that for this bearing the oil wash ways were positioned at 10 o’clock and 2 o’clock. In the normal course of events this can be a desirable move to counteract the shaft movement during turning, but in this case it highlights that sometimes forces act against well founded and accepted assumptions and serves to highlight the thread of the argument in this paper. Duplane loads can increase five to six times over and above the full ahead position. This may be more critical for the slender shafts of electric motor driven, twin screw designs, since the shafting system does not have the stiffness to react to these forces and, therefore, is more willing to move to align with the propeller. That is not to say that the stiffer shaft systems are less problematic: they are equally affected since they will be installed in aft end designs which have become flexible through modern design. 3 Onot altered. The majority of systems are white metal with oil lubricated gravity feed. The influence of the oil is one of those factors taken into account in the overall stiffness value. However, recognising the importance of the lubrication medium, Lloyd’s Register has been assessing this influence using hydrodynamic analysis and combining this with the action of the propeller shaft system. Figure 8 indicates results of a quasi-steady static analysis, based on mean propeller forces and moments, to assess the lateral movement of the shaft centreline in way of the rope guard, through a simulated run-up trial. There is good agreement on the trend between predicted and measured results, but the results are not accurate enough in terms of magnitude to enable full confidence in the outcome and for them to be used at the design stage. However, the trend is encouraging and the challenge is now to extend this work to manoeuvring operations.

measured

predicted

predicted shaft centre in way of rope guard

Insupport can be predicted as shown in Figures 9 and 10. The figures indicate calculations based on a shaft to bearing mismatch of 0.0002 rads. Not only the shaft support position, but also the parameters of stiffness and damping, can be predicted and these values can be fed back into the alignment and shaft whirling analyses in the form of an iterative process until the results converge. Twater lubricated bearings with similar results, though presently they are not as accurate. Water lubricated bearings are as important as oil lubricated bearings, and may be more so in the future, as the shipping industry focuses on its green credentials.

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Figure 9: Pressure with 0.0002 rad mismatch

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This will help make the plan approval process more efficient and there will be more time available to discuss changes to design or material specification. In this way, design issues will be able to be addressed earlier, during the design phase, rather than while the component is approaching the final stage of manufacture.

Figure 9: Point of support at 0.002 radian mismatch looking athwartships

Although this paper has discussed alignment issues, shaft whirling characteristics of a shaft system are very much influenced by the decisions taken in the alignment analysis. Consequently, the two should be assessed together when the values of bearing stiffness and damping, especially, have a significant effect on the whirling response. For that reason it is recommended that the shaft transmission system is treated as an integrated dynamic system in which all

forces are accounted for and assessed for alignment, shaft whirling, axial and torsional vibration at the same time. 4. CONCLUSIONS It has been shown that alignment is a complex issue which depends on a number of interacting parameters. Some years ago, Lloyds Register developed the analytical tools to consider a shaft line as a system in order to provide concurrent results of the individual analyses of: alignment; whirling; and axial and torsional vibration. Currently, these analyses are undertaken by different sub-contractors and the results are submitted to Lloyd’s Register and brought together as a system by the ship yard. The challenge now is to alter this approach so that a systems approach becomes the norm. This will help surveyors undertaking approvals to have a better understanding of the critical design issues and should lead to a more efficient plan approval process by replacing four analytical routines with just one. At the very least, alignment should be undertaken together with shaft whirling as design decisions resulting from one will affect the other. There is no need to consider these analyses in isolation from each other. It must be emphasised that there are still unknowns and the more detailed analyses of a shaft system design described in this paper will not guarantee faultless operation. However, the theoretical results will be closer to reality. This analysis takes time and can only be carried out with the co-operation of the yard and component designers. Therefore, this means it can only be undertaken pre-contract and preferably at the birth of the design. Looking ahead to the future for design approval, it could involve a ’self certification’ process for the less complex component and system designs in much the same way as manufacturers use the Lloyd’s Register Quality Assurance Machinery Scheme for serial production of components. There is no reason why the design activity cannot be part of the complete Quality Assurance process.

It should be noted, however, that there are dangers in the audit process and a successful outcome will depend upon having full co-operation between the designer and Lloyd’s Register. The audit regime will require close monitoring, but this would appear to be

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a price worth paying if it allows for a more efficient design and manufacturing process. 5. ACKNOWLEDGEMENTS The Author wishes to thank Kian Banisoleiman and Peter Filcek of Lloyds Register’s Department of Technical Investigations for providing the slides and technical background.

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PAPER 7

THE POTENTIAL FOR ENERGY

Ed Fort B.Sc.

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THE POTENTIAL FOR ENERGY Ed P Fort SUMMARY However it is defined, sustainability with regard to the provision of shipboard energy, is arguably the marine industry’s greatest challenge. Lloyd’s Register is striving to ensure that its Rules and Regulations, intended to protect life and the environment, facilitate the introduction of the technologies and developments needed to help ensure that the industry can respond to this challenge. This paper outlines some of the potential options for future marine power generation, focusing on particular options for which such Rules and Regulations are already in place. NOMENCLATURE

Nitrogen Oxides (NOx) Sulphur Oxides (SOx)) Carbon dioxide (CO2), Particulate Matter (PM), Heavy Fuel Oil (HFO), Marine Diesel Oil (MDO), International Maritime Organization (IMO), International Association of Classification Societies (IACS), Solid Oxide Fuel Cell (SOFC), Proton Exchange Membrane Fuel Cell (PEMFC). 1. INTRODUCTION Sustainability means different things to different people. According to the Renewable Energy & Energy Efficiency Partnership [1], sustainable energy has two key components; renewable energy and energy efficiency. In the longer term, such a definition may well be appropriate. In the near term, however, with respect to the provision of shipboard energy, sustainability is really about achieving two objectives. Harmful emissions, particularly airborne pollutants and greenhouse gases, need to be reduced. However unjustifiably [2], ships are increasingly portrayed as among the worst offenders in the struggle to combat climate change. Whether sustainable power generation will ultimately mean zero emissions remains to be seen, but in the near term, at least, the perception is that the emission of nitrogen oxides, sulphur oxides, carbon dioxide and particulate matter from the ship’s power plant needs to be significantly reduced compared to current levels. Inextricably linked to reducing emissions is the need to reduce oil fuel consumption. While the effect of pollutants and greenhouse gases on climate change remains the subject of intense debate, it is universally recognised that society’s dependence on fossil fuels is unsustainable. It may be assumed that sustainable power generation will ultimately mean an end to the combustion of fossil fuels. In the near term, however, ships need to become significantly more efficient than they are at present. This paper looks at a number of less controversial power generation technologies which have the

potential to play a part in achieving the aforementioned aims. It focuses particularly on fuel cell technology, widely regarded as a panacea to the challenges of sustainable marine power generation, and, indeed, power generation generally. The paper also looks at how Lloyd’s Register plans to support the marine industry in meeting sustainability goals through the publication of timely and appropriate Rules, Regulations and guidance. 2. ENERGY DEMAND 2.1 EFFICIENT SHIPS Although this paper focuses mainly on future power generation technologies likely to contribute in achieving sustainable shipping, it should not be overlooked that very significant reductions in both fuel consumption and emissions can be achieved using a range of existing technologies. A recent study estimates that fuel consumption could be reduced by up to 30% in new ships by including a range of technical features in the design of the ship as a whole, features such as waste heat recovery, improved steering configurations, improved hull form and antifouling, for example. Equally large reductions, of up to 30%, are estimated from a range of operational improvements, such as enhanced weather routing, optimised trim and ballasting [3]. Clearly, the adoption of such measures alone would be a massive step towards sustainable shipping. 3. ENERGY CONVERSION 3.1 GAS FUELLED ENGINES Major engine manufacturers have been delivering engines capable of running on natural gas for some time. Switching to natural gas has several advantages compared to burning HFO or even MDO. Significant reductions in all emissions are claimed [4], including:

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• 30% lower CO2; • 85% lower NOx (due to high air/fuel ratio) • no SOx (due to sulphur removal from fuel) • very low particulates • no visible smoke • no sludge deposits. The large reductions in CO2 compared with HFO and MDO are due quite simply to the fact that the main component of natural gas, methane (CH4), contains significantly less carbon than HFO or MDO. Indeed, methane is the most efficient hydrocarbon when comparing energy content against carbon content. Disadvantages include the relatively limited worldwide availability of natural gas and the lower volumetric energy density of the fuel compared to MDO, for example. Even when liquefied, the storage space required for liquefied natural gas (LNG) could be up to four times greater than equivalent MDO tanks. Even more limited is the worldwide availability of LNG. With a clear understanding of the risks associated with gas-fuelled engines, Lloyd’s Register has been working closely with industry to develop Rules and Regulations for using methane gas as a fuel in order to facilitate its introduction [5]. 3.2 PHOTOVOLTAIC CELLS Under pressure to reduce CO2 emissions from cars over their entire lifecycle including shipment, Pure Car and Truck Carrier (PCTC) ships are likely to emerge as some of the first examples of energy efficient ships. In demonstrating the potential contribution of solar power, a 40 kW photovoltaic (PV) array comprising 328 modules of PV cells has recently been installed on the upper deck of an operational PCTC. Connected to the ship’s 440 V AC electrical distribution network, the performance of the array will be evaluated in sea-going conditions with particular regard to the effects of salt water exposure and vibration. Since they are capable of harnessing renewable solar energy, the advantages of solid state photovoltaic arrays are clear. The primary disadvantage, however, is the very large exposed surface area required per kW of power generated. 3.3 WIND ENGINES With claims of a potential reduction in shipboard fuel consumption of 30%, the contribution of wind engines, better known as ‘Flettner rotors’, to sustainable marine power generation could be very significant.

They utilise a phenomenon known as the Magnus effect, in which the force of the wind on a rotating vertical cylinder creates a low pressure on one side, generating thrust in much the same way that a sail does, only with a magnitude which is 10 to 14 times greater. At least two full scale demonstration projects are currently underway. Lloyd’s Register is currently working closely with the Wind Assisted Ship Propulsion (WASP) project, with designs for four 2.3-metre diameter and 17-metre high rotors currently undergoing review. Following review, testing will be carried out ashore, followed by their installation on board a bulk carrier [6]. 3.4 ON-SHORE POWER SUPPLIES The use of on-shore power supplies for ’cold-ironing’ while in port may become a de facto facet of port operations in the future. Regulators have begun to encourage the use of such installations. 'Cold-ironing' is the US Navy’s way of describing the practice of connecting a ship to a shore-side power supply in port, allowing the ship’s machinery to be shut down and causing the installation to become ‘cold’. The term is now commonly used to describe a new generation of different high-voltage shore connections with fast plug connections and seamless load transfer without blackouts, which allow the full range of in-port activities to continue while the ship is discharging and loading cargo. Already, a variety of equipment manufacturers and on-shore power supply designers are offering a variety of different solutions and configurations. Major differences between these installations which could have an impact on ship safety and operability include: • Operating frequency – many of the world’s on-

shore electrical systems operate at 50 Hz, while most ship systems operate at 60 Hz, making these incompatible without expensive frequency conversion.

• Voltage levels – transformers are normally required to change the shore voltage to the ship voltage. Different ships have different operating levels (11 kV, 6.6 kV and 440 kV being common), necessitating transformers with multiple tapings or similar.

• Power rating – different ships have differing power-use profiles in port.

• Cable and connector types – there are currently no construction or test standards for flexible marine cables or high voltage plug and socket outlets.

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• Cable management and lifting appliances – for the power levels required, cables and connectors will be too heavy for simple manual handling. Cable reels or cranes can be installed on board to extend ship cables to shore sockets or shore cable reels and cranes can be used to extend shore cables to shipboard sockets.

• Control and safety arrangements – the available solutions have been diverse, ranging from simple to highly sophisticated. They can range from manual operation with no automatic safety measures, to automatic connection and disconnection of submersible electrical equipment, fully integrated into the ship and shore-side emergency shutdown systems.

Where shore power is provided by renewable energy, typically local wind turbines, the benefits are greater and obvious. Where power is provided from the national power distribution network, in addition to the local benefits of reduced emissions and noise, it may be expected that such power consumed has been generated with higher efficiency than if it were generated on board. With a clear understanding of the risks associated with shore power, Lloyd’s Register has been working closely with industry to develop Rules and Regulations for the connection of on-shore power in order to facilitate its introduction [7]. 3.5 FUEL CELLS Fuel cells share many of the characteristics and utilise many of the same components as the cells of a battery. Both fuel cells and batteries convert stored chemical energy into electricity in a silent, efficient electrochemical reaction. Despite the similarities, however, one fundamental difference between a fuel cell and a battery suggests that a more appropriate comparison may be with that of a conventional generator set. Unlike a battery, in which the reactants consumed in the energy conversion process are stored internally and are eventually depleted, the reactants consumed by the fuel cell are stored externally and are supplied to the fuel cell in the same way as a conventional generator set is supplied with fuel and air. Such an arrangement means that a fuel cell, unlike a battery, has the potential to supply power as long as the supply of reactants, hydrogen and oxygen is maintained. The ability of the fuel cell to provide a continuous supply of electrical power has important implications. Sharing characteristics of batteries and generators, the fuel cell has the potential to displace virtually all sources of shipboard power, ranging from batteries providing just a few watts of power intermittently, through to main and auxiliary power generating plant delivering megawatts of power continuously. The

relatively low power of individual fuel cells requires the use of multiple cells to achieve usable power levels. Such a replication of components lends itself to high volume production and the design of modular fuel cell power plant with the potential for high reliability, good fault tolerance and potentially low capital cost. The benefits of fuel cell technology are greatest when the fuel cell is operated on high purity hydrogen and oxygen and when the by-products of the energy conversion reaction (heat and water) can be utilised. In such circumstances, the power plant is relatively simple, extremely efficient and produces no undesirable emissions. Such an ideal operating environment is exemplified by manned space and sub-sea applications. Although the ultimate goal, a number of considerations make the use of hydrogen as a fuel for marine fuel cell power generation unlikely in the near term, in particular its worldwide availability and its very low volumetric energy density, which necessitates unfeasibly large storage spaces. The operation of fuel cells on conventional marine fuel oils, however, is a problem. The fuel cell would need to be capable of converting the marine fuel oil into hydrogen. The development of fuel processing equipment capable of converting such fuels into hydrogen is unlikely to be realised in the near term. Despite considerable investment by the automotive industry, a reliable fuel reformer capable of converting gasoline into hydrogen proved elusive. It is, therefore, unlikely that reformation of heavier marine fuel oils would be realised by the marine industry, the only possible exception being US Naval research programmes. A much more realistic scenario for near term marine fuel cell power generation is operation on natural gas. A number of ‘high temperature’ fuel cells are capable of operating directly on natural gas, converting methane into hydrogen within the fuel cell itself. Unfortunately, while feasible, (many megawatts of power are currently generated worldwide by natural gas-fuelled fuel cells) the use of any fuel other than hydrogen means that the fuel cell becomes significantly larger and substantially more complex than the highly efficient hydrogen-oxygen-fuelled fuel cell and, in consuming hydrocarbon fuels such as natural gas, will produce some undesirable emissions. Arguably more significant, however, is that the overall efficiency of the power plant will be significantly lower than the efficiency delivered by the hydrogen-oxygen-fuelled fuel cell power plant. Such a reduction in efficiency means that early marine fuel cell power plants are likely to operate at efficiencies not dramatically greater than those achievable using conventional power generation technologies and well

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below the maximum theoretical efficiency of the fuel cell. The process and physical arrangements by which the energy is converted within the fuel cell are similar to those of a battery and are essentially the same regardless of the type of fuel cell. Two reactants, hydrogen and oxygen, combine within the fuel cell to produce water, releasing both electrical energy and thermal energy in the process. The reaction proceeds as long as hydrogen and oxygen, both of which are consumed within the reaction, are supplied to the fuel cell. The desire for particular operating characteristics and improved fuel cell performance has led to the development of several different types of fuel cell which are individually identified by the electrolyte material they use. All offer particular advantages when compared. However, of the five basic types currently under development, the high temperature solid oxide (SOFC) type, operating at temperatures between 700 and 1000 deg C, and, to a lesser extent, the low temperature proton exchange membrane type (PEMFC), are perhaps most suited to the marine operating environment. It is expected that performance will gradually improve, and the introduction of combined cycle techniques, combining fuel cells with gas turbines, will result in a substantial additional increase in the overall efficiency of the plant. In the longer term, however, it is the operating environment that is expected to change in favour of the fuel cell. Driven by concerns about the stability and, ultimately, the availability of fossil fuel supplies, it is hoped that ‘green’ hydrogen, generated using renewable energy ashore and consumed in hydrogen fuelled fuel cells on board ships, will provide the eventual solution. In such an ideal operating environment, the benefits of fuel cell technology will be fully exploited. Lloyd’s Register is currently working closely with industry as part of the EC METHAU project, the ultimate aim of which is to install and evaluate the performance of a methanol fuelled SOFC on board an operational PCTC [8]. 4. FACILITATING CHANGE 4.1 RULES, REGULATIONS AND GUIDANCE In order to support the marine industry in meeting the challenges of sustainable power generation and sustainable shipping generally, Lloyd’s Register has developed, and continues to develop, Rules and Regulations to facilitate the introduction of new technologies on board ships.

Where Lloyd’s Register has sufficient understanding, expertise and knowledge of the risks associated with the technologies proposed for installation on board Lloyd’s Register classed ships, application-specific Rules and Regulations are published accordingly. To facilitate the introduction of technologies for which Lloyd’s Register may not necessarily have sufficient understanding and knowledge to justify the publication of specific Rules and Regulations, a set of generic, systems engineering-based Rules and Regulations have been published. These allow Lloyd’s Register to assess the safety and reliability of such technologies, while allowing the industry the freedom to evaluate radically new solutions under seagoing conditions. 4.2 RULES AND REGULATIONS FOR ON-

SHORE POWER To facilitate the uptake of on-shore power, Lloyd’s Register has recently published application-specific Rules for On-Shore Power Supplies and currently supports the development of complementary international standards by TC18 of the International Electrotechnical Commission (IEC) in cooperation with the International Standards Organisation (ISO). Although the environmental benefits are many, the technical risks for the ships themselves and the safety risks for those who work on board and ashore need to be given equal consideration. Further, as such shore-side power systems proliferate, adequate standards are needed to ensure effective operation and compatibility between systems. The potential environmental benefits of on-shore power supplies should not take precedence over ship safety. The technical difficulties, hazards and potential for serious injury and damage introduced are not to be underestimated. The aforementioned Rules for On-shore Power Supplies were created to assist in addressing these hazards, along with a corresponding class notation, OPS. The requirements in the Rules and Regulations were developed in close consultation with a wide variety of industry stakeholders. 4.3 RULES AND REGULATIONS FOR

METHANE GAS FUELLED SHIPS To enable shipyards and owners to assess the class-related implications of a gas-fuelled ship, Lloyd’s Register has published its Provisional Rules for the Classification of Methane Gas Fuelled Ships. The development process has involved a wide cross-section of industry experts, including ship designers and engine builders. The requirements provide a structured approach for design and assessment. Ships complying with the requirements will be eligible for the assignment of a

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class notation, GF. The Rules have encompassed applicable requirements from current standards, including the draft IMO requirements, IACS Unified Requirements (UR) and Lloyd’s Register’s requirements for offshore installations. One of the key aspects of the Rules is the designation and assessment of hazardous areas and the location of machinery and equipment, consistent with current practice and terminology. Particular care is required in the design of ventilation and safety arrangements for safe and reliable operation of gas-fuelled machinery, and these issues are fully addressed in the Rules. The requirements cover all types of gas-fuelled machinery including both single and dual fuel engines, as well as gas turbine machinery and boilers. 4.4 RULES AND REGULATIONS FOR

MACHINERY AND EQUIPMENT OF UNCONVENTIONAL DESIGN

Reliance on in-service feedback, incidents and failures as a process for identifying the risks associated with new technologies is not realistic in today’s society. Equally unacceptable, however, is prohibiting or delaying the installation on board ships of the technologies desperately needed to meet the challenges of sustainable power generation while the regulators acquire the necessary knowledge and experience to develop prescriptive requirements for their design and construction. Accordingly, the requirements described in this paper outline the pragmatic, process-based, systems engineering approach taken by Lloyd’s Register to the assessment of the safety and dependability of systems, machinery and equipment, making use of new technologies and systems of unconventional design. As a means by which Lloyd’s Register may satisfy itself of the safety and dependability of engineering systems of unconventional design proposed for installation on board Lloyd’s Register classed ships, and for which Lloyd’s Register may very likely have no in-service experience, a set of process-based requirements has been developed based on established and internationally recognised systems engineering principles. In accordance with the aims of the IMO guidelines for Formal Safety Assessment (FSA), the requirements aim to ensure that risks to maritime safety and the environment, stemming from the introduction of new technologies, are addressed in so far as they affect the scope of ship classification. The requirements apply to machinery and engineering systems intended to be installed on board Lloyd’s Register classed ships and considered by Lloyd’s Register to be of an ‘unconventional’

design, and which, as a result, are not directly addressed by the extant Rules and Regulations. It should be noted, however, that the general requirements of the Rules and Regulations remain to be satisfied as applicable. The underlying principle behind the requirements is that formal controls are required to be employed for all development-related activities which include certain key systems engineering processes, including: • project management • requirements definition • quality assurance • design definition • risk management • configuration management • verification • integration • validation (certification and survey). Assessment by Lloyd’s Register involves examination of the procedures for the application of the processes, together with all records associated with their application. For each of the processes, the procedures and their associated records are to provide evidence as described here. 4.4 (a) Project Management A project management procedure is required to be established, documented and followed, in order to define and manage the key project processes. For the entire project, and each of the processes within the project, project management procedure documentation is to define the activities to be carried out, the required inputs and outputs, the roles and responsibilities of key personnel, the competence of key personnel and a schedule for the activities. 4.4 (b) Definition of Requirements A requirements definition procedure is needed to be established, documented and followed, in order to define the required functional behaviour and performance of the machinery or engineering system in the environments to which the machinery or engineering system are likely to be exposed, under both normal and foreseeable emergency conditions. Account is required to be taken of the requirements of all key stakeholders, including the shipowner, the ship’s crew, the shipyard, equipment suppliers and regulators. The requirements definition procedure documentation is required to specify the functional behaviour and performance requirements and is to identify the source of the requirements. Lloyd’s Register’s requirements include compliance with statutory regulations and Lloyd’s Register’s

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existing Rules and Regulations as far as they are applicable to the fuel cell system. Additionally, where internationally recognised standards, codes of practice or guidance, relevant to the design and construction of marine fuel cell systems exist, due account is to be taken of the provisions of such documents. Typical of such standards are the international standards IEC60092 – Electrical installations in ships – Part 101 Definitions and general requirements; and IEC60721 – Classification of environmental conditions Part 3: Classification of groups of environmental parameters and their severities – ship environment which together provide a relatively complete definition of the environment in which a new power generation technologies would be expected to operate. 4.4 (c) Quality Assurance A quality assurance procedure is required to be established, documented and followed, in order to ensure that the quality of the machinery or engineering system is in accordance with a defined quality management system. The specific quality controls to be applied during the project, in order to satisfy the requirements of the quality management system, are to be defined. The quality management system itself is required to satisfy the requirements of ISO9001:2000 – Quality management systems – Requirements or an equivalent acceptable national standard. 4.4 (d) Design Definition A design definition process is required to be established, documented and followed, in order to define the requirements for the design of machinery or an engineering system which satisfies the stakeholder requirements, the quality assurance requirements and complies with basic internationally recognised design requirements for safety and functionality. The design definition process is required to ensure that the design of the machinery or engineering system satisfies statutory legislation, classification requirements and international standards and codes of practice where relevant and is to take account of stakeholder requirements and the quality assurance requirements. Design definition procedure documentation is required to specify the design requirements, identify the source of the requirements and ensure that the requirements for the design of major components and subsystems of the machinery or engineering system can be verified before and after integration. 4.4 (e) Risk Management A risk management process is required to be established, documented and followed, in order to ensure that any risks stemming from the introduction

of the machinery or engineering system are addressed, in particular: risks affecting the structural strength and integrity of the ship's hull; the safety of shipboard machinery and engineering systems; the safety of shipboard personnel; the reliability of essential and emergency machinery and engineering systems and the environment. Consideration is required to be given to the hazards associated with installation, operation, maintenance and disposal, both with the machinery or engineering system functioning correctly and, following any reasonably foreseeable failure, taking account of stakeholder requirements and design requirements. Hazards are required to be identified using acceptable and recognised hazard identification techniques. The process is to ensure that risks are eliminated wherever possible. Risks which cannot be eliminated are to be mitigated as necessary. Details of risks, and the means by which they are mitigated, are required to be included in the operating manual. Guidance on selecting and performing the various risk assessment techniques is widely available, with certain techniques being more suited for particular applications than others, as indicated in the international standard IEC60300 Dependability management – Part 3-1: Application guide – Analysis techniques for dependability – Guide on methodology. The IMO’s Formal Safety Assessment (FSA) process serves as one such technique, as do those described in several international standards including: IEC61882 – Hazard and operability studies (HAZOP studies) – application guide; and IEC60812 – Analysis techniques for system reliability – Procedure for failure mode and effects analysis (FMEA). 4.4 (f) Configuration Management A configuration management process is required to be established, documented and followed, in order to ensure traceability of the configuration of the machinery or engineering system, its subsystems and its components. Items essential for the safety or operation of the machinery or engineering system, and which could foreseeably be changed during the life time of the machinery or engineering system are to be identified such as documentation, software, sensors, actuators, instrumentation modules, boards and cards. The process is required to take account of the design requirements and any items used to mitigate risks. Configuration management procedure documentation is required to ensure that any changes to configuration control items are identified, recorded, evaluated, approved, incorporated and verified. The international standard ISO10007 – Quality management systems -- Guidelines for configuration

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management is available as a guide in the development of a configuration management process. 4.4 (g) Verification A verification process is required to be established, documented and followed, in order to ensure that subsystems and major components of the machinery or engineering system satisfy their design requirements. The process is to be based on one of, or a combination of, the following activities, as appropriate: design review; product inspection; process audit; and product testing. Verification procedure documentation is required to identify the requirements to be verified, the means by which they are to be verified, and the points in the project at which verification is to be carried out. 4.4 (h) Integration An integration process is required to be established, documented and followed, in order to ensure that the machinery or engineering system is assembled in a sequence which allows verification of individual subsystems and major components following integration in advance of validating the entire machinery or engineering system. The process is required to take account of the verification requirements. Integration procedure documentation is to identify the subsystems and major components, the sequence in which they are to be integrated, the points in the project at which integration is to be carried out and the points in the project at which verification is to be carried out. 4.4 (i) Validation (Certification and Survey) A validation process is to be established, documented and followed, in order to ensure the functional behaviour and performance of the machinery or engineering system meets its functional and performance requirements. The process is to validate stakeholder requirements, arrangements required to mitigate risks and the traceability of the configuration control items. Validation procedure documentation is to identify the requirements to be validated, the means by which they are be validated and the points in the project at which validation is to be carried out, including factory acceptance testing, integration testing, commissioning, sea trials and though-life survey. It may be said that the key processes described above are simply good engineering practice, much of which is, or ought to be, established practice in a sector as mature as the marine industry – a sentiment which is shared by the author. The requirements described above have been published by Lloyd’s Register as an additional chapter in the Rules and Regulations for the Classification of Ships [9].

To support the application of these Rules and Regulations, it is planned to develop application specific guidance. An early example of this will be for fuel cell systems providing electrical power for essential services, using knowledge gained through its participation in both commercial fuel cell demonstration projects and research and development projects, such as the EU projects METHAPU, FCSHIP and FCTESTNET. The publication of guidance rather than Rules and Regulations requiring verification allows Lloyd’s Register to pass on such knowledge for the benefit of the industry. At a point when Lloyd’s Register has sufficient knowledge and understanding of the risks associated with fuel cell technology application, specific Rules and Regulations will be published, as is done for conventional machinery and equipment. 5. CONCLUSIONS The energy demands on board a large modern ship make the challenge of sustainable shipping appear daunting. However, as can be seen, several near-term solutions would appear to have the potential to make a significant contribution to the sustainability of shipping. Together, these suggest that a dramatic reduction in both emissions and fuel consumption can be expected in the not too distant future. There are several other power generation scenarios in existence, not included in this paper, which could play an equal, or even greater, role in the provision of shipboard energy. However, there remains considerable debate as to their place in a sustainable society, whatever their role at this point in time. 6. REFERENCES 1. Renewable Energy & Energy Efficiency Partnership, Jan 2009 (www.reeep.org) 2. Z Bazari & G Reynolds, ‘Sustainable Energy in Marine Transportation’, IMAREST Conference, Sustainable Shipping, 1-2 February 2005 3. G Reynolds, ‘The Reduction of GHG Emissions From Shipping – A Key Challenge For The Industry’, WMTC, 2009 4. O Levander, ‘Cruising on gas into a cleaner future’, Wartsila Technical Journal, 01.2007 5. Lloyd’s Register, ‘Provisional Rules for Methane Gas Fuelled Ships’ January 2007 6. Wind Assisted Ship Propulsion project (WASP), Jan 2009 (www.greenwave.org.uk) 7. Lloyd’s Register, ‘Rules for On-shore Power Supplies’ July 2008

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8. Validation of renewable methanol based auxiliary power systems for commercial vessels project (METHAPU), EU 6th Research Framework Programme (www.methapu.eu) 9. Lloyd’s Register, ‘Rules for Machinery and Equipment of Unconventional Design’ January 2008

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PAPER 8

CONFIGURATION MANAGEMENT AS A RISK-BASED TOOL IN MANAGINGDEPENDABILITY OF COMPLEXSOFTWARE-BASED SYSTEMS

Bernard Twomey B.Eng., C.Eng., F.I.E.T., M.I.Mech.E. and

Renny Smith B.Sc., C.Eng., M.I.E.T.

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CONFIGURATION MANAGEMENT AS A RISK-BASED TOOL IN MANAGING DEPENDABILITY OF COMPLEX SOFTWARE-BASED SYSTEMS Bernard J Twomey and Renny Smith SUMMARY

The increasing reliance upon complex systems in marine operations brings a corresponding need to ensure that these systems are demonstrably dependable in use. Furthermore, in order to be truly effective integrated systems, they must be developed so that they function as a seamless whole, fulfilling operational needs. Ensuring that integrated systems are traceable throughout the system’s lifecycle has been addressed in numerous standards, but the application in the marine sector has been limited, resulting in significant financial loss to the client. This paper will emphasise the importance of shipowners’ configuration management (CM) during a system’s lifecycle and identifies the benefits of having a CM discipline in place to help manage the risks associated with software maintenance. Numerous standards have been produced to deal with configuration management and this paper will look at CM with regard to the International Standards ISO 17894 – General Principles for the Development and Use of Programmable Electronic Systems in Marine Applications and BS ISO 10007:2003 – Quality Management Systems – Guidelines for Configuration Management.

From the platform of these standards, the paper promotes good systems engineering practice in managing the risks associated with through-life software maintenance and seeks to rationalise the ideals with the current practices of the marine sector. In adopting the methodology, it is contended that the goal of effectively managing the automation systems now found in the marine sector can be realistically achieved. Key CM functions, such as CM planning, CM identification, change control, impact analysis and CM audit, and their respective roles for newbuild and existing ship implementation are described. In addition, this paper identifies some new opportunities in identifying future risks associated with obsolescence of programmable electronic systems.

NOMENCLATURE SCM Software Configuration Management CI Configuration Item CR Change Request SA Status Accounting IAF Implementation Approval Form STCW International Convention on Standards of

Training, Certification and Watchkeeping for Seafarers

1. INTRODUCTION

Configuration management was first developed by the United States Department of Defence in the 1950s as a technical management discipline. The concept has been widely adopted by numerous technical management models, including systems engineering, integrated logistics support, Capability Maturity Model Integration (CMMI), ISO 9000, Information Technology Infrastructure Library (ITIL), product lifecycle management, and application lifecycle management. Many of these models have redefined configuration management, from its traditional holistic approach to technical management. Some treat configuration management as being similar to a librarian activity and split change

control and change management into separate disciplines and some break out the traditional elements of revision control and engineering release into separate management disciplines. Others treat CM as an overarching management discipline. In many other sectors such as the rail industry, CM is a mature discipline and applied rigorously in safety related systems

Within the marine sector there is an expectation that the integrated software-based systems for a ship will be realised by using several manufacturers to provide the design solution that will ’hopefully’ meet the owners specification.

Each manufacturer will have its own quality management procedures for the development of software-based systems, and these will be part of the classification approval process [1] [2]. Where standards such as ISO 17894 [3] are specified, they contain requirements for configuration management.

Naval and passenger ships have traditionally been at the leading edge of many new developments, though the availability of computer technology and component-based development has led to software-based systems appearing on virtually all ship types.

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As a result, the safety operation of ships is becoming dependent to varying degrees on these systems. Increasing reliance on complex, highly integrated computer-assisted systems presents a problem for most maritime stakeholders. The combination of complexity, use of computer hardware and software, and practices in the purchase, operation and maintenance of computer-based systems leads to a range of potential defects that cannot be guarded against by current marine procedures. Few ships’ engineering staff have an understanding of the implication of software being present in the equipment, and the interaction between the sub systems to ensure the system functions as an integrated whole. Consequently, the modern seafarer is becoming reliant on the correct operation of the system to ensure the safe operation of the vessel. To ensure systems continue to meet technical and business needs it is usual for software systems to be modified; this modification is referred to as software maintenance. According to Martin and McClure [4]

software maintenance must be performed in order to: • correct errors • correct design flaws • interface with other systems • make enhancements • make necessary changes to the system • improve design. In marine applications we also need to consider obsolescence as a cause for maintenance, which would require the introduction of new technology that may be required to interface to older systems and software platforms. To ensure the systems continue to meet the operational requirements of the owners, consideration should be given to managing these changes throughout the system lifecycle; failure to do so has resulted in significant financial loss and the potential for physical or environmental damage. 2. CM AS A PRACTICAL RISK REDUCTION

TOOL Very few operators have processes in place to properly control the changes to embedded software in their equipment and systems and reliance is placed on the manufacturers and Original Equipment Manufacturers (OEMs) to provide this process. It is not sufficient to simply track the modification request; the software product and any changes made to it must be controlled. This control is established by implementing and enforcing an approved Software

Configuration Management (SCM) process. For this process to work, management must support the concept of software configuration management. The SCM process is implemented by developing and following a configuration management plan which includes all system documentation, base line software in the systems and procedures for managing software changes, thereby providing tools for the ships’ staff to manage changes to their systems. A fundamental tool to support SCM is impact analysis, through which the effect of change within the system and on interrelated systems is analysed and the risks associated with the change are assessed. Software Configuration Management is therefore seen as a risk mitigation tool that will enable owners to successfully identify and manage their risks throughout the system’s life. SCM is part of the software maintenance process. In order to give the context of SCM, further discussion of maintenance follows. 2.1 WHY IS THERE CONFUSION ABOUT

SOFTWARE MAINTENANCE?

Software maintenance is a much maligned and misunderstood area of software engineering. Although software has been maintained for years, relatively little is written about the topic of maintenance. Funding for research about software maintenance is essentially non existent [4], thus, the academic community publishes very little on the subject. Practitioners publish even less because of the corporate fears of giving away their ’competitive edge’. There are a few text books on software maintenance but these are outdated. Periodicals address the topic infrequently and this lack of information contributes to the misunderstandings and misconceptions that people have about the subject.

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2.2 WHAT IS SOFTWARE MAINTENANCE? What then is software maintenance? And where does it fit into the lifecycle? Here are some generally accepted traditional descriptions of software maintenance: • “…changes that have been made to computer

programs after they have been delivered to the customer or user.” [4]

• “…the performance of those activities required to keep a software system operational and responsive after it is accepted and placed into service.” [6]

• “Modification of a software product after delivery to correct faults’ to improve performance or attributes, or to adapt the product to a modified environment.” [6]

• “…software product undergoes modifications to code and associated documentation due to a problem or the need for improvement. This objective is to modify existing software product while preserving its integrity.” [7]

The common theme of the above descriptions is that maintenance is an ‘after the fact’ activity. Based on these definitions, no maintenance activities occur during the development process. Maintenance occurs after the product is in operation. 2.3 WHAT IS THE IMPACT OF NOT

MANAGING THE RISK? A recent incident that took place on an LNG vessel resulted in significant financial loss to the owners. The report from the OEM (below) highlighted the fact that the owners were reliant on the manufacturer’s SCM procedures being applied. The result of this failure was the ship coming off hire at considerable cost (millions of dollars) to the owner. “The upgrade of the reliquifaction software was requested by the shipowner in conjunction with the reliquifaction process system supplier. It is very important to understand that the upgrade was not a standard operational procedure and requires secure high level access to the software based system and detailed planning and documentation…prior to import of new software pre system configuration status audit was not undertaken to establish a firm base line. Pre works backups were not made, import procedures were not fully documented and associated technical risks not advised to the ship owner.” Unfortunately, reports of this nature are becoming more frequent due to the increase in software-based systems being installed in marine applications.

Upon investigation, it was found that these incidents could have been avoided if the shipowner had a SCM process in place to identify and manage the risks associated with the upgrade. In land-based applications, there are numerous reported failures due to software upgrades:

• PayPal based in San Jose, Calif., and owned by eBay Inc., is the major online payment system for eBay auctions as well as smaller e-commerce sites. In 2004, the company suffered intermittent outages. AlertSite Inc. reported that PayPal was available only 35 percent of the time. Keynote Systems Inc. also was unable to connect to the site from 10 locations nationwide. PayPal is blaming the outages on the software update, and officials did not know how many of its 50 million user accounts were affected.

• During the Thanksgiving holiday weekend in 2001, Amazon.com suffered a series of outages, due to a software upgrade which cost the retailer an estimated $25,000 per minute of downtime.

We have to accept that certain operators don’t know what software is in their system and the training requirements of STCW [8] fall far short of providing adequate training for the operators to address the complexity now found on modern vessels. The Marine Accident Investigation Branch (MAIB) report [9] on the MV Prospero, another vessel suffering an incident caused by software modifications, identified that the basic elements of STCW training for engineering officers is unlikely to equip them to deal with modern technology. 2.4 ESTABLISHING CONTROL The approach described for managing software change and introducing SCM into an organisation has been trialled and implemented by a number of ship owners. Each organisation has adapted the procedures to take into consideration their own risk identification processes and management structure,. The benefit of this approach has been a SCM procedure that is tailored for each organisation and aligns with their existing processes. 2.4 (a) Ships' Configuration Management

Procedure This process, based on BS ISO 10007:2003 [10], applies to specified programmable electronic systems on board a vessel and requires information to be provided by systems suppliers, but the procedures do not apply to the configuration management used by suppliers.

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The Configuration Management of software, firmware and configuration data is achieved by controlling the media upon which they are held. Typical examples of the type of systems used on board are: computer files for personal computer based systems; electronic memory devices, such as EPROM; embedded electronic cards; and removable magnetic and optical media. While the procedure can be applied across the whole fleet, each ship has a ship-specific Configuration Management Plan, which is used to document the local arrangements for the implementation of the procedure. For newbuild projects, the configuration management process for a particular ship’s system should ideally be brought into use when one or more of the following criteria has been met: • The ship’s system is first integrated with other

ship’s systems. • The ship’s system is brought into operational use. • The approval for the ship’s system has been given

using the New System Development. During the implementation phase, suppliers may make changes to their systems under their own configuration management systems without invoking the ship’s configuration management processes , provided the systems are not integrated with other systems and have not been put into operation. In practice, because shipowners do not have responsibility for, or formal control over, systems on board ship until formal hand over, it is not possible to mandate the ideal configuration management processes for newbuild projects. The actual configuration management arrangements that can be achieved for specific newbuild projects will be recorded in a newbuild Configuration Management Plan for the ship. Shipyards will not accept a manufacturer’s SCM procedure being imposed on the whole project, so it is important that the shipowner specifies SCM requirements at the contract stage with clearly defined deliverables at the time of delivery of the vessel or system. As a minimum, the shipowner should: • define the version control information that it

requires from system suppliers • define and implement the activities necessary for

it to have confidence in the configuration information that will be provided when systems are eventually handed over, activities which should include: defining the configuration management information required from the

supplier, oversight activities, and the configuration audit process

• seek the version control information previously defined from system suppliers before accepting the handover of the vessel.

When a ship is commissioned into service (handover of the ship) the New Build Configuration Management Plan for the ship will be replaced by the ship’s In-Service Configuration Management Plan. Configuration Management is only one of the processes required for the proper management of new and changed systems on a ship. The other processes, such as systems engineering, contract, commercial, and project management processes are normally not addressed by this procedure. It is also assumed that there will be co-operation between, and co-ordination of, the different process activities, and that the outputs from the configuration management process will be used to support some of the other processes. For instance, the output from the impact analysis, which is a key part of the configuration management process, could be used as an input to the risk assessment process that should be performed as part of the best practice processes for the development of programmable electronic systems in marine applications, as specified by ISO 17894 [3]. The procedures are normally written in a style which assumes that equipment is installed on board ship and that the necessary configuration management information is available and within the ship’s configuration management system. For existing ships, which have not implemented this procedure, a separate document that plans and controls the introduction of the procedure will be required. The basic configuration management model used in this procedure is represented diagrammatically by Figure 1.

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Figure 1: Configuration management model Items that are required to be held under configuration control are referred to as configuration items (CIs). The model assumes that: • all CIs are defined and recorded in a database • all documents and records related to the

configuration items are in existence and available • staff with the competence and authority to assess

and approve requested changes are available. 2.4 (b) Documenting Proposed Changes The decision to invoke SCM for a particular change needs to be evaluated in accordance with clearly defined and agreed criteria as not all changes need the level of rigour required by these procedures ( changes such as set points and hysteresis, for example, which are tuneable parameters that are provided to be able to be changed by ships’ staff). For these arrangements, alternative mechanisms to the configuration management procedure need to be in place to ensure the initial or default state of the parameter is defined and recorded and that, when changes are made, these are recorded and communicated to other staff using the system/equipment. The limits of allowable change should be defined and staff should be aware of the limits of changes.

Before a change is formally raised as a ’proposed change’ and subsequently processed in accordance with this procedure:

• a change request shall be produced, and

• an initial analysis of the impact of the change shall be performed.

The scale of the risk associated with a change shall be taken into account when specifying the proposed list of deliverables on the Change Request (CR); less complicated changes such as changes to application data may be performed by local agreement with ships ‘staff with minimal planning documentation, whereas replacement of equipment to prevent obsolescence, would need stringent and detailed planning.

The model shown in Figure 2 outlines a process for managing software maintenance. There are three key areas for consideration: the data required to identify and control the change; the stakeholders’ responsibilities; and guidance to ensure the risks associated with software maintenance are successfully managed.

Figure 2: Documenting proposed change

2.4 (c) Approving Preparation of the Change

(Figure 3) The next stage in the process is approval of the Change Request. Approval responsibility for a CR shall be assigned to a competent person based on the results of the risk assessment performed at the time of preparing the documentation for the change. In this example, we have chosen the Chief Engineer, but this can be modified to deal with companies’ specific processes.

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The approval process shall be conducted in a way that ensures that the CR and supporting impact analysis are reviewed by persons competent to assess the information being presented. If the review of a change request raises doubts about the adequacy of the available information relating to the change, consideration should be given to performing a risk assessment of the proposed change before approval. When a decision has been reached, the approval authority shall record it on a Preparation of Change Approval Form, together with any additional information, including: the reasons for rejection; the reasons for returning the Change Request; and an explanation of what needs to be done before approval can be given, or any conditions that apply to the approval. Copies of the CR, impact analysis, supporting information, and Preparation of Change Approval Form, shall be provided to shore staff, based on the results of the risk assessment performed at the time of preparing the documentation for the change.

Figure 3: Approving preparation of the change

2.4 (d) Preparing Change/Develop New System

(Figure 4) Once the approval has been given to develop a change, or a system for a new ship, action shall be taken to prepare all necessary systems, equipment, products, processes, documentation and records in accordance with the details specified in the Change Request/New System Development Approval Form.

The level of management and oversight activities to be performed by the provider of the system and the shipowner’s staff, or their agents, shall be agreed, as appropriate to the scale of the change/development and the level of risk involved. The arrangements shall be recorded as appropriate, typically in one of the deliverables proposed in the Change Request/New System Development Approval Form, such as a project or quality plan.

This part of the process introduces requirements for the supplier to develop the approved change/new system and all agreed deliverables in accordance with the approved CR.

During their production, the implementation stage documents, such as Installation, Testing and Commissioning Plans, shall be agreed with the ship’s staff to ensure that:

• adequate provision is made for the operation of the ship during the implementation stage

• fallback and transition strategies have been prepared and are adequate

• the testing provides sufficient coverage to demonstrate the success of the changes/development.

On completion of the development activities, but before installation, the Chief Engineer shall inform the approval authority of the status of the development and arrange for the approval authority to assess the readiness of the change/development for implementation.

Problems that arise during this phase which may require a change to be made to the functional, performance, or contract requirements of the system being changed or developed, shall be treated as a change and shall be managed using this procedure.

For newbuilds, where the shipowner has no formal responsibility or control over suppliers, attempts should be made to influence them to adopt or co-operate with the shipowner’s process on a voluntary basis.

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Figure 4: Prepare change/develop new system 2.4 (e) Approval for Implementation

(Figure 5) On notification that the development activities are finished, the approval authority shall make arrangements to assess the completeness and readiness of the change/development for implementation on ship.

When a decision has been reached, the approval authority shall record it on an Implementation Approval Form (IAF) (to be developed by the shipowner) together with any additional information, including, the reasons for the return (non approval) of the IAF and an explanation of what needs to be done before approval can be given, or any conditions that apply to the approval. Clarification should be sought from the suppliers in areas of uncertainty to ensure there is full understanding of the risks. After clarification, re-approval may be necessary before implementation takes place.

If it is considered necessary for a configuration audit to be performed this shall be specified on the IAF.

For newbuilds, where the shipowner has no formal responsibility or control over suppliers, the process defined in this section should be applied, as far as practicable, given the limitation of available data and documentation.

GuidanceData Required

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Figure 5: Approval for implementation 2.4 (f) Implementing Changes The software implementation shall be installed, tested and commissioned in accordance with the plans produced during the development phase.

Installation, testing, and commissioning requires a high degree of communication and co-ordination between ship's staff, the shore-based ship’s team, potential multiple suppliers and installation organisations, and other agencies such as classification societies. The activities should be closely overseen and managed by the ship’s staff to ensure that configuration management good practice is maintained, particularly in respect of on-ship changes.

Temporary changes outside the formal configuration management process should be exceptions and only allowed with approval from the Chief Engineer

The supplier/installer shall co-ordinate its activities with ship’s staff to ensure that the revision status of all systems, equipment, and products is known to the ship’s staff and suppliers of other interfacing systems which are being implemented at the same time. This should allow the ship’s staff to use the operational and maintenance procedures appropriate to the current status and minimise incompatibility of integrated systems.

During the implementation phase, suppliers may make changes to their systems under their own configuration management systems without invoking

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the ship’s configuration management processes , provided the systems are not integrated with other systems and have not been put into operation.

All systems shall be put under the ship’s configuration management procedure before being brought into operational use or integrated with other systems.

Typically, as it is difficult to maintain good configuration control during this phase, it is recommended that a member of the ship’s staff is assigned to monitor what changes are made and to promote good configuration management practice (this role need not be an exclusive one and could be one of a number of roles held by the staff member).

Following each discrete stage of implementation (if there is more than one) the CI Status Database shall be updated to ensure that the integrity of the database, with the installed equipment, is maintained throughout the implementation activities.

If a configuration audit has been specified in the IAF, the performance of the audit shall be co-coordinated with the implementation activities to ensure that the audit records show the final status of the systems after changes have been finalised.

On successful completion of the implementation, and any remedial action, copies of all changed or new software, firmware and configuration data should be made and held as archive versions on ship and by the relevant manufacturer or supplier. The Chief Engineer shall be responsible for the management and documenting of archiving and backup.

When the implementation has been completed to the satisfaction of the installer and the ship’s staff, the Chief Engineer shall be informed.

Problems that arise during this phase, which may require a change to be made to the functional, performance or contract requirements of the system being changed or developed, shall be treated as a change and shall be managed using this procedure.

For newbuilds, where the shipowner has no formal responsibility or control over suppliers, attempts should be made to influence the suppliers to adopt, or co-operate with, the process defined in this section on a voluntary basis. As a minimum, version control information for all systems should be sought before accepting handover of the vessel.

Figure 6: Implementing change

2.4 IMPACT ANALYSIS Impact analysis is the analysis of the effects of a proposed change on existing ships’ systems. The term ‘ships’ systems’ is used in the widest sense to include equipment, processes and people1.

1 systems, which may include such things as:

• electrical systems • propulsion systems • monitoring, alarm and control systems • hotel equipment and services.

These physical systems will include electrical, electronic, mechanical, hydraulic, programmable and data configurable subsystems, and components. In order to use the equipment effectively and correctly, processes are developed and implemented. These are typically recorded in a suite of operating procedures and maintenance procedures. At the highest levels of the operating procedures, such as hotel services, the link with the physical equipment might not be explicit. However, failure of the hotel services infrastructure, such as the hotel computer systems, public address, or fire detection systems, will all have an effect on the operational procedures used to manage the guests. The people element of a system concerns the competence of the staff to operate and maintain equipment and implement processes effectively and correctly. Competent staff are established by:

• the selection of people with adequate education and the correct underlying skills, knowledge and personal characteristics for the functions they are required to perform

• training staff in the processes and procedures to be used for the functions they perform

• monitoring performance of staff and providing additional training, education and experience as required.

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For any software change, it is usual, and expected, that the supplier analyses the effect of the proposed change on the complete software to ensure that there will be no unintended effects of the change. The analysis guides the way the changes are implemented and tested.

Similarly, at a system level, the effects of proposed changes on the other parts of the system, whether equipment, process or people-related, should be considered.

The responsibility, and skills necessary, to perform the impact analysis on the internals of a software system lie with the supplier and are not included in this paper.

Analyses of the effects of software changes on ships’ systems is the subject of this paper. Change sponsors are given responsibility to ensure that analyses are performed, but to do so they might need the support of people with knowledge and experience from the ship’s staff, the shipowner’s shore-based staff, and suppliers of other systems.

Impact analysis involves considering the effect of the change proposed on all elements of the ship’s systems in detail. Ultimately, it is the approval authority for the change who decides whether sufficient analyses have been performed. His or her decision should be based on the criticality to the safe, effective and profitable operation of the ship, of the system being changed and the other systems affected by the change. The analyses should continue until it is considered that the risks of not having identified problems associated with the change are tolerable.

2.5 BENEFITS The key theme of this paper has been the mitigation of risk associated with software maintenance by implementing SCM. The most obvious benefit of mitigating software maintenance risk is the correct and continued operation of the systems containing software. While the operation of systems and equipment might be the primary focus of the ship’s engineering staff, management sees other benefits from implementing SCM.

As discussed earlier in this paper, the failure of software to operate correctly can have very expensive consequences when the operation of a vessel is affected. The mitigation of risk through SCM, with the resulting improvement in the success of software maintenance, is therefore an important contribution to minimising cost of ownership.

Generally, implementing SCM returns the control of software-based systems to shipowners, specifically removing the consequences of unilateral and poorly considered changes by suppliers. By taking up the

control provided by SCM, shipowners will be better able to understand the implications of software maintenance being carried out on their behalf by suppliers and contractors.

SCM also helps demonstrate due diligence, with regard to control over software maintenance, helping to address questions that are starting to be raised by: national authorities such as the Maritime and Coastguard Agency (MCA) and the United States Coast Guard (USCG); accident investigation boards such as the Marine Accident Investigation Branch (MAIB) and National Transportation Safety Board (NTSB); and legal companies who may question a shipowner’s SCM processes in the event of an incident. A number of shipowners have linked SCM procedures to their planned maintenance system and, through this process, are tracking obsolescence in their installed systems. This approach provides a significant benefit by enabling them to form and implement an appropriate obsolescence strategy. 3. CONCLUSIONS

Not managing the maintenance of software-based systems properly can have serious consequences, both in terms of operational control of ships and consequential financial losses. SCM is an important tool that can be used to mitigate some of the risks associated with software maintenance. The resulting benefits include: optimising the availability of software systems; minimising the cost of ownership; returning control of change to the shipowner; and demonstrating due diligence to national authorities. The procedures described in this paper are expected to be tailored to the specific needs of shipowners, taking into consideration their current organisational structure, existing risk mitigation practices and the competence of the ship’s staff. The implementation of SCM procedures will help ensure that shipowners can fully understand the implications of the software maintenance being carried out and have control over their systems.

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4. REFERENCES 1. Lloyd’s Register Rules and Regulations for the

Classification of Ships, Part 6, Chapter 1 2. Lloyd’s Register Rules and Regulations for the

Classification of Naval Ships, Vol 2, Part 9. 3. ISO 17894 General Principles for the

Development and Use of Programmable Electronic Systems in Marine Applications, 2005

4. J Martin and C McClure. Software Maintenance: The Problem and its Solution. Englewood Cliffs, NJ: Prentice-Hall

5. TM Pigoski, Practical Software Maintenance, ISBN 0471170011

6. IEEE 1219: Standard for Software Maintenance: 1998

7. ISO/IEC 12207 Systems and software engineering -- Software life cycle processes, 2008

8. International Convention on Standards of Training, Certification and Watchkeeping for Seafarers STCW, 1995 Amendments

9. MAIB Report no 24/2007. Published 21 December 2007

10. BS ISO 10007:2003, Quality management systems -- Guidelines for configuration management

11. ISO/IEC 90003, Software engineering – Guidelines for the application of ISO 9001:2000 to computer software

12. RTCA/DO-178B, "Software Considerations in Airborne Systems and Equipment Certification," December 1, 1992.

13. Boeing Co, ‘ The impact of configuration management during the software product's lifecycle’, Digital Avionics Systems Conference, 1999. Proceedings.

14. DOD-STD-2167A, "Military Standard Defense System Software Development," AMSC No. N4327, February 29, 1988.

15. AC Messer, System Integration and Complexity: managing dependability. Lloyd’s Register.

16. MIL-HDBK-61A(SE) Configuration management Guidance, 7 February 2001

17. ANSI/IEEE Std 1042-1987 IEEE Guide to Software Configuration Management, IEEE Standards Board, September 10, 1987

18. IEEE Std 828-1998, IEEE Standard for Software Configuration Management Plans, 25 June 1998

19. California power outages suspended--for now, by Rachel Conrad, CNET news.com, January 18, 2001 http://news.com.com/2100-1017-251167.html

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PAPER 9

THE INFLUENCE OF SHIP UNDERWATER NOISE EMISSIONS ON MARINE MAMMALS

John Carlton D.Sc., B.A., C.Eng., M.I.Mech.E., M.R.I.N.A.,

M.I.Mar.EST. and Emma Dabbs

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THE INFLUENCE OF SHIP UNDERWATER NOISE EMISSIONS ON MARINE MAMMALS John Carlton and Emma Dabbs SUMMARY Recognising the concerns that have been developing in various parts of the world, Lloyd’s Register has, in recent years, undertaken research into the effects of radiated underwater noise emissions from merchant ships on marine mammals. This debate is now planned to commence within the IMO arena. Given this developing background, the paper discusses some of the initial findings of Lloyd’s Register in relation to the physiology of marine mammals in the context of ships’ far field noise emissions in order to assist in forming a basis for future discussion. 1. INTRODUCTION In recent years, a number of conferences and research initiatives have been undertaken in various parts of the world directed towards arriving at an enhanced understanding of the behaviour of marine mammals in relation to disturbances to the environment caused by shipping activity. In keeping with these initiatives, Lloyd’s Register has, over the last five years, been undertaking a continuing study into the affects of the marine industry on the behaviour of marine mammals with particular reference to the influence of noise emissions from ships on their hearing, communication and navigational abilities. In the 58th session of the Marine Environmental Protection Committee of the International Maritime Organisation, a proposal (58/19) for a work programme was tabled by the United States of America. The programme is directed towards promoting action to minimise the incidental introduction of noise from commercial shipping operations into the marine environment, in order to reduce potential adverse impacts on marine life. The proposal claims that a significant proportion of the anthropogenic noise input into the oceans is attributable to the increasing number and size of commercial ships operating over wide-ranging geographical areas of the world. Moreover, it is claimed that the noise generated by these sources has the potential to disturb the behaviour and critical life functions of marine animals. Within the deep ocean environment there is evidence to suggest that noise levels have increased in recent years. Hildebrand reports [1] that from measurements made at the San Nicolas SOSUS Array in the Pacific

Ocean this increase has been of the order of 3 dB over the decade to 2004. This paper presents, in outline form, some of the findings from the continuing Lloyd’s Register study into this issue. In so doing it concentrates on the frequency ranges used by marine mammals and the noise emissions from ships. 2. THE SHIP PROPULSION PROBLEM Some years ago [2], comparative noise emissions were qualitatively studied. It was demonstrated that the sources of self-noise at a single frequency, measured at the sonar dome of a naval ship running at full speed, were, in descending order of importance: • propeller cavitation • the ship’s boundary layer • machinery sources • electrical noise. This ranking was preserved until about the mid-speed range when the dominant noise source became the machinery noise. Merchant ship propellers tend to be designed to maximise the propulsion efficiency within certain constraints. These constraints vary with ship type and operational profile. In particular, the major conflicting propulsion constraints are propulsion efficiency and cavitation development in the context of vibration, noise and erosion of either the ship’s propeller blades or the rudders which operate in the propeller slipstream. The radiated pressure field derived from marine propellers comprises a combination of harmonic and broadband emissions, the

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latter occurring at the higher frequency ranges and sometimes in the lower ranges in the vicinity of the first few blade rate harmonics. This pressure field, in whatever combination of harmonic and broadband components, is derived from the propeller developing rapidly changing cavitation structures when working in a spatially and temporarily varying ship wake field. At the propeller design stage, the designer endeavours to produce a radial and chordally varying loading distribution, which itself is a variable as the propeller rotates, in order to minimise the propeller’s influence on the hull structure or passenger and crew comfort. At present, in all but a few ship types in the merchant sector, the external radiated noise emissions are of lesser interest than the noise and vibration transmitted into the ship. The exceptions to this are, typically, marine research ships and some fishing vessels where the far field radiated noise signature is critical to the ship’s performance. The noise signatures emitted by ships are variable. They vary, among other factors, with the type and age of the ship, the ship’s speed and the type of propulsor deployed. Figure 1 shows the upper and lower bounds of typical emitted noise spectra derived from a variety of source measurements for a range of ship types, sizes and ages over the last two decades.

Figure 1: Bounds of ship noise spectra (15 ships) The actual signature produced by a ship varies considerably with the power absorbed by the ship and the propeller type. This in turn influences the flow and cavitation development over the propeller blades. In the case, for example, of a large cruise ship the overall sound level of the ship may increase by between 6% and 12%

when the ship increases its speed from 10 to 20 knots. This resulting emitted signature is a combination of the emissions from the diesel generators, electric propulsion and the propulsors. Within the literature, propeller singing is often cited as a source of noise emission from ships. In the occasional instances when singing is encountered, the phenomenon is caused by the shedding of vortices from the tip and outer trailing edge region of the propeller blades, which may then excite high frequency blade resonances [3]. Singing, however, is normally so annoying to the ship’s crew that at the next dry-docking, or indeed at a special docking if the noise is too intrusive, minor modifications are made to the propeller blades’ trailing edges in order to cure the source of the noise emission. 3. MARINE MAMMALS Marine mammals evolved from land animals, making the transition from land to water approximately 55 million years ago and adapting to exploit deep oceans over a period of 15 million years. The evolutionary process brought about adaptations to their respiratory and auditory systems, limb structure and additional specialisms to other body parts. There are three orders of marine mammals: Cetacea, Sirenia and Carnivora. The first two are exclusively marine mammals and the third includes some groups that live on land and in water, such as polar bears, and others that live only on land, such as dogs.

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3.1 CETACEANS The living cetaceans, which are all carnivorous, are extremely diverse. However, there are two main groups and these are the Toothed whales (Odontocetes) and Baleen whales (Mysticetes). 3.1 (a) Toothed Whales Toothed whales are the most numerous members of the cetacea. They comprise all dolphins and porpoises, and the Sperm, Killer, Pilot, Beluga, Narwhal and Beaked whales. They are different from Baleen whales in that they have teeth, have only a single blowhole and are mostly smaller with the sperm whale being the largest at

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around 18m. Toothed whales actively hunt prey, often using echolocation for this purpose. 3.1 (b) Baleen Whales Baleen whales are less diverse than the Toothed whales, encompassing Bowhead, Right, Blue, Fin, Sei, Bryde’s, Minke, Humpback and Grey whales. Unlike the Toothed whales they have two blow holes, baleen plates and are generally much larger in size. These baleen plates or ‘whalebone’ are made of keratin and arranged like densely packed combs creating a filter to sift zooplankton and small fish from the seawater. 3.2 SIRENIANS The order Sirenia includes the only herbivores of the sea: the Manatee and Dugong. As their colloquial name ‘sea cow’ would suggest, they are bulky, rotund and rather slow-moving. They live in shallow, warm or tropical, coastal or river waters. 3.3 PINNIPEDS Pinnipeds are part of the order of carnivores. They are from a less ancient lineage than the cetacea and sirenians, and are hence less specialised for deep water living. The main three families are: True or Earless seals (Phocids), Fur or Eared seals and Sea lions (Otariids) and the Walrus (Odobenids). 3.3 (a) True Seals True seals are more specialised for water than Fur seals and Sea lions: they have no external ear flaps, are more streamlined and tend to be larger than otariids. However, they are much clumsier on land, generally lurching and bouncing ungracefully along because their hind limbs are unable to rotate forward under their bodies. 3.3 (b) Fur Seals and Sea Lions A defining characteristic of the otariids is the presence of small external ears. Additionally they generally have thicker fur, less blubber and longer necks than the Phocids. They are much better suited to life on land, being able to use their rear flippers to walk and lift their bodies clear of the ground. Consequently, they tend to spend a greater proportion of their time on land

than the Phocids, especially when they are with pups. 3.3 (c) Walrus The Walrus family shares some characteristics with both phocids and otariids; nevertheless they are immediately identifiable from their huge tusks, whiskers and bulk. They have no external ears, but walk on their hind flippers and spend significant periods of time on ice. 3.4 OTHER MARINE MAMMALS Sea otters and polar bears are also marine mammals, but are not considered further at the moment. 4. MARINE MAMMAL PHONATION The term ‘phonation’ is used to describe the sounds produced by marine mammals, since some marine mammal sounds are not produced in the larynx, in the way that humans produce speech. When discussing the influence of radiated sound from shipping activity on marine mammals, it is essential to have an understanding of how marine mammals hear. This is in order to consider how noise might be perceived by them or, conversely, might damage their hearing systems. Moreover, having insights into why it is important for marine mammals to hear enables us to understand how an inability to hear might affect them. For most marine mammals, hearing and sound is important for a number of reasons: • avoidance of predators • communication and social behaviour • echolocation • foraging for food • navigation • overall awareness of their environment • parental care • reproduction. Marine mammals have the basic same ear structure as terrestrial mammals, although this has been adapted to suit an aquatic environment. Additionally, the brains of these marine mammals are thought to process the sound in the same way as humans.

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It should, however, be noted that the ears are not the only potentially delicate structures in marine mammals that could be impacted by sound. Fundamentally, any airspace in the body may be susceptible to pressure and acoustic effects. While the ear is an obvious candidate, other air-spaces such as the lungs, airways and sinuses need also be considered. For example, acoustically induced resonance in the lungs of human divers can be potentially harmful and this has been demonstrated at frequencies of around 70 Hz. Additionally, in Cetaceans it is likely that there is more than one pathway to the inner ear. There is substantial evidence to suggest that high frequency sounds are channelled through sound conducting tissues located in the lower jaw of Odontocetes, especially for echolocation tasks. The lower jaw bones typically contain mandibular fats, which are good conductors of sound and well impedance matched for the task underwater. However, lower frequency sounds probably follow the more conventional route of transmission into the

Figure 2: Example of a balaenid phonation from a Right whale call [6] middle and inner ear. Figures 2 and 3 illustrate the principal types of phonation from marine mammals: the first is for communication, while the latter is for echolocation purposes. In both spectra it is seen that there is a considerable quantity of data at differing frequencies. 4.1 ODONTOCETES Toothed whales, dolphins and porpoises are mostly sociable. They travel and feed in groups, often co-operating to maximise feeding potential. Dolphin phonations have been the most comprehensively studied.

They produce complex ‘whistles’ at around 10 kHz for communication purposes and ‘clicks’ at 100 kHz for echolocation, by which they navigate and detect prey.

Figure 3: Idealised Sperm whale click and frequency spectrum based on experimental data [6] Whistles are also used as signature calls so that the mammals can identify each other, a function that is especially important between mothers and calves. This is the general pattern of phonation for Odontocetes, with a few exceptions: • Porpoises produce even higher

ultrasounds, around 130 kHz and some species have not been proven to whistle. Some porpoises produce low frequency clicks (~2 kHz) for communication instead.

• Sperm whales only produce clicks, with most sound energy around 3 kHz and 10.5 kHz.

• Killer whale phonations are of a lower frequency: their whistles are around 10.5 kHz and their pulsed calls are mostly around 4 kHz, but can vary from 500 Hz to 25 kHz.

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4.2 MYSTICETES The larger Baleen whales typically produce relatively low frequency (~20 Hz to 1000 Hz) continuous tone or sweeping ‘moan’ phonations, with some species producing infrasonics: frequencies that are too low for humans to hear. Many sounds are quite simple, apart from when Humpback and Bowhead whales sing: in these cases frequencies may extend above 1 kHz. The songs are produced by solitary males as reproductive displays and travel long distances underwater [4]. While recognising that these sounds are low frequency and therefore travel long distances though the ocean, this may suggest that the hearing mechanism of these, and perhaps other, mammals is particularly sensitive. There has been no conclusive evidence that Baleen whales echolocate, although there is speculation that the reverberation of their low frequency calls from the sea bed provides them with a picture of their environment, such as ice or islands, thus helping them to navigate [4, 5]. 4.3 SIRENIANS It is unknown how important sound is to the lives of Manatees and Dugong; they are usually very quiet except for calls between mother and calf and to signal danger. Recorded calls have been in the general range 1 kHz to 10 kHz. 4.4 PINNIPEDS Pinnipeds produce phonations above and below water. Pinnipeds that mate on land tend to be more vocal on land and limited to clicks and barks in the frequency range 100 Hz to 4 kHz underwater. In contrast, the True seals that mate underwater produce a greater range and variety of phonations underwater from grunts below 100 Hz to clicks, which may be for echolocation, up to 150 kHz. It is known that all Pinnipeds use sound to establish and maintain the bond between mother and pup and acoustic contact is especially important when the two become separated [4].

5. RELATIONSHIP BETWEEN SHIPS’ RADIATED NOISE EMISSIONS AND MARINE MAMMALS

It is relatively easy, with the aid of hydrophones, to measure the apparent range of communication between marine mammals of the same species. What is uncertain is the actual breadth of the hearing of each of the species and whether within that broader range distress can be caused by being subjected to certain frequencies and noise amplitudes. It is known that in certain circumstances marine mammals are reluctant to approach certain large ships too closely, but whether this is because of distress caused by noise or a natural reluctance to come too close to another large moving maritime object is again unclear. While little is known about the auditory thresholds and audiograms for the larger mammals, a body of information is available for the small marine mammals since these can be handled and subjected to experimentation more easily. Figure 4 is typical of the data available in the form of an audiogram for a dolphin [6].

Figure 4: Example of a dolphin audiogram with a coloured sensitivity map The audiograms for those species already studied are typically non-linear with respect to frequency, as seen in Figure 4. In marine mammals the audiogram is typically U-shaped, implying that at the upper and lower frequency ends of the hearing range hearing is less sensitive than in the middle of the frequency range. Indeed, such a hearing sensitivity is similar to that of humans, characterised by the A-Weighted hearing scale. Indeed, such a finding is not surprising due to the similarity of the ear

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structure for both humans and marine mammals. In the case of the marine mammals studied to date, this general pattern seems to hold true, although frequency and sensitivity ranges vary between the various marine mammal frequencies.

Figure 5: Overall communication and echolocation frequency ranges associated with each species When compiling the known data on the Toothed and Baleen whales, Pinnipeds and Sirenians it is clear that there is an abundance of communication and navigational signals produced by these mammals within the frequency range 100 Hz to 100kHz with, in the case of the Baleen whales, frequencies down to 10Hz. Figure 5 shows the overall frequency ranges which encompass both the communication and echolocation signals from each species. When studying this figure it must also be noted that the mechanisms for emitting and receiving the various types of signal are likely to be different and, moreover, there is likely to be an interval within the spectrum between the two types of signal. While within each of these ranges associated with the various species, some estimate can be made for regions of particular sensitivity from the available audiograms, such a broad range clearly encompasses the frequency ranges emitted by ships. As was noted in Figure 1, where full scale noise data bounds in the frequency range 100 Hz to around 1250 Hz were shown, the true extent of the noise spectrum from a propeller is considerably greater and extends up to 100 kHz and beyond, although with reduced noise levels. Additionally, propulsors emit low frequency noise down to the first blade rate frequency and lower. While these frequencies are below the threshold of human hearing they

can border on the lower end of the frequency ranges used by Baleen whales. In terms of the contribution of cavitation to these noise emission spectra, a significant amount of work has been undertaken in recent years, both in naval and merchant ship communities. Each type of cavitation has a characteristic noise signature associated with it, depending upon the cavity dynamics that are involved. For example, in the case of sheet cavities the decay of the primary structures into vortex structures and then, subsequently, into systems of micro-bubbles produces characteristic signatures, probably through synchronised collapse of all or part of the system of bubbles – the actual mechanism being far from fully understood at the present time. While there is much that can be learnt from naval practice in the design of quieter merchant ship propellers, it must be recognised that there is a fundamental difference in the design philosophy of both types of ship. In the former case, the concept of cavitation inception speed features prominently when the propeller is designed to operate in a sub-cavitating mode up to a certain ship speed, typically, 10 or 15 knots depending on the naval requirement. To achieve this, several iterations of the design process, including cavitation tunnel testing, are normally required. In the case of the merchant propeller, consideration of propulsion efficiency is dominant and the presence of cavitation is accepted provided that it does not promote either significant ship internal vibration or erosion of the propeller blades or rudder. Nevertheless, the cavitation structural dynamics on the propeller blades and in the slip-stream, which will influence the radiated hull surface pressures and the erosive potential of the cavitation, will also have a significant effect on the far field noise emissions. As such, there is likely to be some synergy in these merchant ship cavitation influences.

0 20 40 60 80 100 120 140 160

Frequency Ranges (kHz)

Odontocetes (General)Porpoises

Sperm WhalesKiller Whales

MysticetesSirenians

Pinnipeds (General)True seals

Considerable further work is required, at full scale on the observation of the cavitating structures on ship’s propellers since, due to scale effects, these structures generally vary from model scale predictions. Such studies need then to be related to the noise emissions measured using sonar buoys or sea-bed arrays: one means of doing this could be in association with boroscope observations of the propeller behaviour [7].

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6. CONCLUDING REMARKS This short overview has drawn on some of the ongoing research work that Lloyd’s Register is undertaking on the interaction between ship operations and marine mammals. In giving an overview of the work carried out it is clear that considerably more study is needed by the marine engineering and biological communities in order to understand the true extent of the problem. Such initiatives are required particularly in the following areas: • characterising the noise emissions from

different types of cavitation generated by merchant ships’ propellers at their various ranges of operating conditions

• methods of de-coupling machinery noise from merchant ships in order to attenuate noise transmission into the sea

• understanding the response to noise spectra of the larger marine mammals, particularly in relation to relative extents of the phonation to hearing frequencies

• understanding more clearly the noise transmission paths in marine mammals

• the physical and behavioural response of marine mammals to ship noise emission stimuli.

7. ACKNOWLEDGEMENTS The authors are most grateful for the initial work done within this Lloyd’s Register research programme by Dr John Goold who stimulated many of the ideas contained here and who laid the foundations of the study. Thanks are also due to Caroline Johnson who has made valuable contributions to the work. 8. REFERENCES 1. Hildebrand, J. Large Vessels as Sound Sources I: Radiated Sound and Ambient Noise in Nearshore/Continental Shelf Environments. NOAA Vessel-Quieting Symposium, May 2007. 2. Sabathé, P. and Guieysse, L. Aquoustique Sous-Marine, Dunod, Paris, 1964. 3. Carlton, J.S. Marine Propellers and Propulsion. 2nd Edition. Butterworth-Heinemann. 2007. 4. Richardson, W.J., Greene, C.R., Malme, C.I. and Thomson, D.H. Marine Mammals and Noise, 1995.

5. Nachtigall, P.E. Marine Mammals, Hearing and Sound. Advisory Committee on Acoustic Impacts on Marine Mammals. 6. Goold, J. Underwater Acoustic Sensitivity of Marine Mammals, Lloyd’s Register Internal Research Paper, 2006. 7. Carlton, J.S. and Fitzsimmons, P.A. Cavitation: Some Full Scale Experience of Complex Structures and Methods of Analysis and Observation. Proc. 27th ATTC, St John’s Newfoundland, August 2004.

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PAPER 10

THE ASSURANCE OF SAFETY IN THE MARINE ENVIRONMENT

Vince Jenkins B.Sc., C.Eng., M.I.Mech.E.

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THE ASSURANCE OF SAFETY IN THE MARINE ENVIRONMENT Vince Jenkins SUMMARY Lloyds Register’s mission is to ‘secure for the benefit of the community high technical standards of design, manufacture, construction, maintenance, operation and performance, for the purpose of enhancing the safety of life and property at sea, on land, and in the air', and to 'advance public education within engineering and technological disciplines'. This paper explores how we are fulfilling our mission today in three specific areas: embracing a robust approach to alternative design solutions; realising the benefits of our Naval Rules becoming more objective-based; and ensuring that the simple safety basics of design and operation are not forgotten. 1. INTRODUCTION News can now be delivered instantly in many different ways no matter where you are in the world, be it in the middle of the Pacific or at the top of Everest. Those responsible for running private or publicly owned companies drive performance with the relentless pursuit of efficiency and profitability. These two key fundamentals – instant access to information and the quest for performance – have had a considerable influence on the general public’s tolerance for mistakes. As an example, fifteen years ago a company could have made three bad decisions and probably still have stayed in business. Today, one bad mistake means a company will most likely fail. This simple fact affects most industries globally and defines the commercial environment in which the marine industry finds itself today. The marine industry has undergone its own significant changes in the five years to the second quarter of 2008, and has grown by an unprecedented amount. In responding to the growth in the global economy, average ship numbers have increased by approximately 30%, while various ship type sectors have seen between 10 to 55% growth. The container ship sector saw a growth of more than 200% in dwt. At the same time, we have seen a considerable increase in the complexity and size of vessels, a few examples of which are: • container ships in excess of 12,000TEU • 266,000 cubic metre LNG vessels • passenger vessels capable of carrying in excess

of 5,600 people • a significant increase in the use and complexity

of shipboard automation and IT infrastructures • podded propulsion • high voltage propulsion systems • cruise ships with ice rinks • designs which include kites to supplement

propulsion, in order to increase efficiency and reduce environmental impact.

At the same time, the industry has struggled to find the officers to cope with this huge growth. The result has been that the average experience and competence level of officers has not been enhanced. A career at sea continues to be close to the bottom of peoples’ long term career choices, which further compounds the problem. Anecdotal evidence suggests that officers, for example, no longer look to the sea as a life long career, but instead as a ten year period during which they can make a lot of money to establish a future business back in their homeland. The aforementioned is happening at a time when the value of ships and cargo has increased significantly: large container ships, for example, have been rumored to be worth US$1.5 billion fully loaded. It has not just been the ship operators and owners who have found quality manning difficult to maintain; most organizations which operate within the industry have struggled to fill the necessary places. For instance, classification societies have had to work very hard to find the numbers of experienced surveyors needed to support the huge growth in newbuild yards. Charterers, P&I, insurers and component manufacturers, among others, have all struggled with maintaining competence. The first half of 2008 saw growing concerns with regard to a change in incident statistics. The IUMI (International Union of Marine Insurers) 2007 shipping statistics report released in March 2008 had some alarming headlines, as the following two extracts show[1]: • “…Since last report (March 2007) the number

of total losses for the 2006 year have significantly increased from 67 to 92 – we anticipated more reports during 2007 but this 37% increase is probably unprecedented…”

• “...The serious partial losses continue to increase dramatically, there has been a strong upward movement since 1998 where 247 serious incidents were reported with 727 reported in 2006 (a 6% increase since last reported) and a staggering 914 so far for 2007. A 270% increase in one decade…”

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The industry is witnessing an increase in incidents which are becoming increasingly expensive, as reflected by IUMI’s report. The IUMI report covering 2008 will make interesting reading. Operators have clearly wanted to capitalise on the business opportunity that the last five years has presented, while the public and business tolerance for mistakes has continued to reduce. Have our systems to control the risks which the industry faces been adequate? While the last six months have seen a dramatic change of fortune for the global economy and the marine industry, it could be argued that the following two questions are even more important for the industry now and in the future: • Given the need to provide year on year

company growth, have the simple basics of design and operational safety been maintained or sacrificed for profit?

• What framework, which will ensure continued profitable trading, is required for safe design and operation in the industry today?

2. THE PRESSURE TO PERFORM The demands of the market for continuing higher company performance – year on year growth in market size and increased profitability, for example – are relentless. If you are the CEO of a ship operator you need to deliver. The industry has significantly changed how it operates over the last 30 years. The merchant marine I joined as a young hopeful cadet in 1976 is a very different industry to that which exists today. Removing the fat from an industry is a necessary part of business and process improvement. One view, however, is that ship operation has been very lean, with little or no fat, for many years now. This is particularly so for the pure ship managers who do not have another profitable business, such as Shipowning, to support their ship management. In the last 12 to 18 months, Lloyd’s Register has seen an increasing number of examples of operators either cutting the maintenance budget dramatically, or not having sufficiently competent crew to maintain their vessels correctly. While significantly reducing effective maintenance has no immediate effect, the implications and results do reveal themselves over the course of a number of months. The same fundamental issues of either loss of capability or cutting costs and losing capability are being witnessed within the component manufacturers’ and suppliers’ sectors. While this could have significant business implications in the merchant marine, it could be catastrophic for the military with regard to vessels such as submarines.

A number of notable incidents occurred in 2008 which must raise concerns over the complexity of the vessels now being designed and whether sufficient systems’ engineering is being applied to their design and layout. The cost of such incidents is alarming owners, insurers and P&I clubs. There have been anecdotal reports of the pressure to perform having even reached the point at which a Master’s judgment can be overruled by commercial decisions. Not only is it a very short term view, but it also risks bringing the industry into disrepute. There are still many very responsible shipowners and operators in the industry. There are, however, those companies that deliver a positive safety message at a senior level, but the message is lost through failure to implement policies and follow through. So while the company policy might be ‘safety first’, it is simply not believed or not re-enforced adequately in the company’s actions and management systems. It is an unfortunate failing of humans that we are very capable of seeing the tangible and advantageous elements of a proposal (typically, the financial benefits), but we are not so good, or perhaps not so willing, to think about the disadvantages or risks involved in the same proposal. Has the huge profit potential of the last few years, and the knowledge that it will not last for ever, simply accentuated the financial advantages of the business, while the significant disadvantages of high risk strategies have not been understood? Has this tendency for high risk strategies now subsided in the credit crunch times of 2009, or have we become used to operating in this way? Have we even realised that some strategies have been increasingly high risk, such as reducing maintenance, or failing to take a systems approach to the increasing complexity of vessels? 3. THE ABILITY TO CONTROL YOUR OWN

DESTINY At the heart of any classification society are its Rules for classifying ships. Classification Rules are based on centuries of experience, and embody a huge amount of accumulated knowledge. The role of classification societies has changed over the 250 years they have been in existence. Perhaps it is useful to revisit where they came from and what classification includes? The insurers of the 18th Century were suffering significant losses, due to the unseaworthy designs of much of the tonnage they were covering. Something had to be done. An independent body,

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which had a set of rules which would ensure a vessel was seaworthy, was required. Classification was born, and while Lloyd’s Register was the first in 1760, each significant maritime nation had their own classification society within a century. As a result, classification was originally about ensuring structural strength and stability, i.e. a seaworthy hull (the term seaworthy is used in a more general way here, rather than its legal definition). In the 18th and 19th centuries, the skill and competence of the Master was recognized in ensuring the seaworthiness of a vessel; the classification of the vessel would change as the Master changed. It is important to note that today classification rules relate purely to hardware. While maintenance will ensure a vessel is kept in good order and ‘in class’, classification Rules rely only on physical hardware and not on human intervention. The role of classification societies today, however, has moved beyond independently assuring structural strength and stability. Representing flag administrations and supporting ship operating companies in meeting international legislation is all part of the role of classification. Therefore, most classification societies have two forms of support to the industry: regulatory compliance; and services beyond regulation. Lloyd’s Register is also heavily involved with the military, providing military ship classification and other support services. 20 years ago, almost all ship operators would have made their own decisions which had any bearing on their business, based on a rational understanding and assessment of the facts as they stood, with their own experienced and professional staff. It has been noticeable, however, over the last 10 years that a number of ship operators have turned to classification societies with one question: “What would you do in our position?” Such a position is understandable when it is in reference to a requirement of regulation, but all too frequently the question is asked when it is not a matter of regulation. Is it a loss of capability that is pushing operators to hand over decision making to other notable bodies? An alternative view might be that the industry has had so much legislation introduced recently, combined with an increasing litigious environment, that owners see the only safe way forward as implementing what other notable bodies suggest. It is hoped that, in the event of litigation, this gives them a more robust defense. The simple principle that is often forgotten is that it is the operator who is the one responsible for his actions, and the operator who is responsible for considering any advice before he implements it. Often, putting ”my lord” or “your honor” on the end of a justification brings a certain clarity to the decision being taken,

since one day an operator may find him or herself in court explaining the decisions. Clearly, this does not apply to all companies, but the reason for the increasing tendency of companies to look to others to make decisions may be a combination of both a reduction in capability and fear of litigation. 4. CLASSIFICATION RULES Classification rules are a set of design standards which ensure a vessel has structural strength, adequate propulsion capability and stability. They tend to be reactive; by their very nature, they can only respond to developments, such as the manufacture and use of stronger materials, which require revised rules. In this way, they support new developments, but they cannot lead development. Classification rules are also applied to all ships for global trade. They are generic rules, and cannot account for individual situations (although areas with extreme weather conditions have been used as the foundation for development – a particular area of the North Atlantic, for instance). There are a few situations when the extremes of an operational environment are considered, such as when operating in ice, a situation for which ice rules have been developed. These rules, however, apply to all vessels operating in ice and are generic. As a result, classification rules are limited to how they can address a specific challenge and reliance is placed on the designer or operator to move beyond classification requirements to address their specific issues. Is this limitation fully understood by the industry? To partly explain this concept a little further let us look at the example of pressure vessels. Many decades ago, industrial fatalities included deaths due to pressure vessels exploding. This was either due to over-pressure, or failure of the pressure boundary at normal operating pressure. Over-pressure incidents have principally been managed by fitting relief valves on pressure vessels, i.e. two relief valves set at somewhere between 105% to 120% of operating pressure. This mitigates the likelihood of an over pressure excursion. However, there are some assumptions or facts about which we need to remind ourselves. The relief valves could still fail, but the probability of a pressure vessel failure has been reduced considerably by the use of pressure relief valves. Now, imagine two factory sites involving an identical chemical process, with very hazardous pressurized liquids passing through three large pressure vessels. The first site has been in the same place for many decades, and a town has grown up around it. The three large pressure vessels are sited against the

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factory boundary wall. The factory wall is adjacent to a main street in the town, with a bus stop outside the factory wall. There is a school not far from the factory, and many 10s of children use this bus stop each day to get to and from school. The second site is a new site which has been built out of town. It has the same process plant with the same three pressure vessels placed adjacent to the factory boundary wall. There is a field of wheat next to the factory boundary wall. Failure of the over protection system and the resulting energy release, while having the same incident initiators, will have a totally different final consequence – damage to a field of wheat in one case, but potential multiple fatalities in the other. It is not possible to be assured that prescribed standards, on their own, control the risks associated with a specific situation or application, as this case demonstrates. This is because risk is comprised not just of the hazard but also of the consequences of the event. Hence, prescribed standards can only ever be best general guidance, subject to the consideration of the specifics of a particular case. Classification rules have, in the past, been heavily prescriptive. That is the nature of design rules. The marine industry feels comfortable with prescription and has increasingly pursued this route in all its regulation. It is not unusual to find that shipbuilders want to be told exactly what they need to do to comply with the rules. Therefore most classification society rules have developed over many centuries to become prescriptive. In many cases, the objective of a particular rule may have been lost. There have been two recent developments which are changing the nature of classification rules: these are the development of rules for military ships and the increasing use of novel designs and their approval. 5. MILITARY CLASSIFICATION First let us consider military classification. There are some key differences between the merchant marine and the military. Within the merchant marine, using classification rules is a requirement of SOLAS. There is no such requirement for the military since they elect to meet the spirit and in many cases the letter of SOLAS. The military has, however, found that classification provides many cost effective benefits, and has started to classify its vessels since the late 1990s. It is interesting to note that most nations with a strong naval presence now use classification rules to one degree or another. The military however have to work within the constraints of:

• making changes to an existing ship, not originally built to a classification regime, or

• the operational requirements of a new vessel which conflict with the prescriptive requirement of a classification rule.

When such examples occur, the discussion that ensues with regard to not meeting the specific classification requirement has encouraged Lloyd’s Register to focus on the fundamental objectives of the rules in terms of assuring structural strength and stability. A recent example is the sizing of ballast tank vent pipes. The objective of the rule is to ensure that a ballast tank cannot be over pressurized and damaged. The vent piping size for one particular ship was only 85% of the prescriptive requirement set in the rule. An analysis was undertaken of the specifics of this particular ship, including the high standards of crew training and management systems. The analysis concluded that the ballast tank could not be overpressurised, and subsequently the design met the classification objective. The voluntary nature of the military’s use of classification rules has resulted in the need for an even greater dialogue to ensure that the classification function is fulfilling its mission with the navies of the world. 6. NOVEL OR ALTERNATIVE DESIGN New technologies and designs are being introduced at an increasing rate. Often the designs are novel, one off, or pilot solutions. Developing specific rules for such situations is often not appropriate. Clients, however, require classification of such novel solutions in order to trade legally. The IMO is also keen to provide a framework to allow for novel designs to be introduced, and has broadened the provision within SOLAS to allow for alternative design solutions to be allowed which meet the objective of the law, but not necessarily the specifics of the rule [2]. Specifically, this applies to: • Section II-1 Construction – Structure,

subdivision and stability, machinery and electrical installations, Parts C Fire Suppression; D escape; and E Operational Requirements.

• Section III Life-saving appliances and

arrangements Clearly, without specific rules to design to, the assessment of the proposals in meeting the design objective has to be conducted in a different manner. How this will be achieved will vary.

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6.1 IMO AND SOLAS The requirements of SOLAS are incorporated into classification rules, hence Lloyds Register has to address this issue from a classification perspective. Additionally, we may be acting on behalf of a flag state as a recognized organisation. The IMO requires a risk-based justification to accompany the design, to demonstrate design equivalence. There is considerable detail to this and the subject would fill a paper on its own. The fundamentals however are that criteria have to be developed which will show equivalence. 6.2 NEW OR NOVEL DESIGN SOLUTIONS In the past when a novel design has been presented, an expert judgment has been formed on its acceptability and equivalence. One of the challenges of expert judgment is that it is often neither repeatable nor documented. The criteria applied are not transparent and will vary from one expert to another. Lloyd’s Register requires criteria and standards to be applied consistently. Expert judgment combined with transparent and consistently applied criteria is very powerful. This may seem to be very simple, and, in essence, it is. It can, however, be quite difficult to establish the fundamental objective, in such a way that a novel design can be assessed for demonstrating equivalence. Systems engineering could be considered in the same way, by asking: “What are the objectives we have for this system and what do we need as outputs?” The future of most legislation, be it classification rules or flag state requirements will consist of two parts: • the objectives of the regulation or rule, and • a prescribed solution which could be used to

meet the objective 7. CONCLUSIONS Today’s business environment is very different to that of 10 to 15 years ago. There is far less tolerance of mistakes by society and business. News of failure can be global in an instant. The pursuit of year-on-year growth is relentless and, combined with the huge growth in the industry, this has meant that competence and experience throughout the marine industry have reduced. Some of the steps being taken to deliver growth and profit have been at the expense of both safety and the bottom line.

The industry appears to be entering a period when companies are developing an appetite for much higher levels of risk and the rewards that may result. There is a danger that the safety/commercial balance is shifting too far because pure compliance is not a guarantee of safe performance. There are other companies that seem reluctant to take decisions, either through lack of capability or fear of litigation. They rely on being told what to do by notable industry bodies. To cope with the rate of change in technology and the overall faster pace of both the military and merchant marine world, Lloyd’s Register is ensuring its core service of classification is transparent and flexible. This will help ensure that the support that the industry needs in new, novel or the military situations is provided. It will also help ensure that our own approval process is robust and transparent. Classification societies and industry have to embrace risk-based and objective-based approaches, supported by robust criteria and transparent use of expert judgment. 8. REFERENCES 1. IUMI 2007 Shipping Statistics – Analysis

(Total Losses Sharply Up and Major Partial Losses Continue to Rise) March 2008

2. Guidelines on Alternative Design and

Arrangements for SOLAS CHAPTERS II-1 AND III MSC.1/Circ.1212 dated 15 December 2006.

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AUTHOR BIOGRAPHIES

Vaughan Pomeroy M.A., C.Eng., F.I.Mech.E., F.I.Mar.EST.,F.R.I.N.AVaughan Pomeroy is Technical Director of Lloyd’sRegister, responsible for Concepts and Studies, ExternalAffairs, Strategic Research and Technical Policy. Hejoined Lloyd’s Register in 1980, initially to work onengineering research and specialist projects, afterworking in the aircraft industry and with mechanicaland electrical engineering consultants. He has heldmanagement positions within Lloyd’s Register since1987. During this time, he has been responsible formarine machinery, pressure equipment and, from 1992,on appointment as Deputy Chief Engineer Surveyor, allHQ engineering activities. After a short spell managingLloyd’s Register’s Marine Consultancy Services, he tookover responsibility for the organisation’s marineresearch and development programme and thedevelopment of its global naval business. He is aChartered Engineer; a Vice President and Fellow of theInstitute of Marine Engineering, Science andTechnology; a Fellow of the Institution of MechanicalEngineers; a Fellow of the Royal Institution of NavalArchitects and a graduate of the University ofCambridge.

Robert Smart B.Sc., C.Eng., M.R.I.N.A.Robert Smart is Head of External Affairs for Lloyd’sRegister. In this position, he is responsible for liaisingwith international, governmental and non-governmental bodies such as IMO, IACS, and ILO.Robert has been with Lloyd’s Register for 14 years,during which time he has held a variety of positionsfrom Plan Approval Surveyor (fire and safety) toManager of Structures and Statutory Services. Beforethis, he spent five years as a Naval Officer and fouryears involved in marine consultancy work. This waspreceded by three previous years at Lloyd’s Register andsix years with the UK’s Ministry of Defence, duringwhich time he obtained his degree from Newcastle-upon-Tyne University in Naval Architecture andShipbuilding.

David Howarth B.Met., C.Eng., F.I.M.M.M., F. Weld.I.Graduating in Metallurgy from Sheffield University,David Howarth joined Lloyd's Register in 1985. He hassince been involved in all aspects of Lloyd’s Register'smaterials work and also represents Lloyd’s Register onseveral national and international committees. He wasManager of the Materials department from 1992 until2004, when he was appointed as Global TechnologyLeader – Materials and NDE. He now has a strategicglobal technical responsibility for materials, metallurgy,welding and NDE issues relating to Lloyd’s Register’smarine activities.

Alex Johnston C.Eng., F.R.I.N.A.Alex Johnston currently holds the position of GlobalTechnology Leader – Hull Structures within Lloyd'sRegister. He is responsible for providing technicalleadership in the maintenance of consistent standardson hull plan approval worldwide and ensuring a highlevel technical approach is achieved. He has been withLloyd’s Register for 28 years and, following some yearsin the shipbuilding industry, started his career in thePlan Approval department in London in 1981. In 1989,he was transferred to Busan, South Korea, where heremained for 12 years, During this time, he was head ofthe Korea Plan Approval department. He now workswithin the international shipping community to furtherLloyd's Register’s technical standards and is a member ofvarious international forums. He provides advice to theMarine business on future strategy and maintains aglobal view of the hull structure technical issues andknowledge networks which affect the organisation. Heis a Chartered Engineer and a member of the RoyalInstitute of Naval Architects.

John Carlton D.Sc., B.A., C.Eng., M.I.Mech.E., M.R.I.N.A.,M.I.Mar.EST. Following training as a mechanical engineer andmathematician, John Carlton served in the Royal NavalScientific Service undertaking research into underwatervehicle hydrodynamic design and propulsors. Five yearslater, he joined Stone Manganese Marine Ltd atGreenwich as a propeller designer and research engineer.He joined Lloyd’s Register in 1975, working first in theTechnical Investigations department and transferring, afternine years, to the Advanced Engineering department as itsDeputy Head. He later moved to the newly formedPerformance Technology department where he initiatedand led several research and development activities. In 1992, he returned to the Technical Investigationsdepartment as Senior Principal Surveyor and Head of Department. In 2003, John was appointed GlobalHead of Marine Technology and Investigation forLloyd’s Register and heads up the Concepts and StudiesGroup. He has twice won both the Denny Gold Medaland the Stanley Grey Prize of the Institute of MarineEngineering, Science and Technology (IMarEST) and isVisiting Professor at the School of Engineering andMathematical Sciences at City University, London.

Andrew Smith B.Sc., C.Eng., F.I.Mech.E.Graduating in Engineering from Hatfield University,Andrew Smith joined Lloyd's Register in 1975. He hassubsequently been involved in all aspects of Lloyd’sRegister's engineering plan approval activities andrepresents the organisation on committees and IACSworking groups. He was Manager and PrincipalSurveyor of the Engineering Systems department from2004 until 2008, when he was appointed GlobalTechnology Leader – Engineering Systems. He now has a strategic global technical responsibility for engineeringissues within Lloyd’s Register’s Marine business.

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Ed Fort B.Sc.Ed Fort trained as an electronic engineer and currentlymanages the Engineering Systems Subject Matter Teamwithin Lloyd's Register's Marine Product Developmentdepartment. He completed his marine engineeringcadetship with Mobil Shipping Co. Ltd in 1982, afterwhich he served on board oil and petroleum productstankers within the company’s fleet. In 1984, he movedto the European Space Agency’s technology andresearch centre (ESTEC) in the Netherlands, eventuallyassuming responsibility for the testing of space craftpower systems. During this time, he was involved in theevaluation of European and Russian alkaline fuel celltechnology in support of the European space agency’sHERMES space shuttle programme. In 2002, he joinedthe Research and Development department at Lloyd’sRegister, following a period in industry with the fuel cellmanufacturer Zetek Power plc and marine consultingengineers Wavespec Ltd. With more than 18 years’experience in fuel cell power generation technology, he has represented Lloyd’s Register on various EuropeanUnion marine fuel cell projects, including FCSHIP,FCTESTNET and METHAPU.

Bernard Twomey B.Eng., C.Eng., F.I.E.T., M.I.Mech.E.Bernard Twomey completed his apprenticeship in 1976,before spending twelve years in the merchant navy, twoyears of which were as an engineering superintendent.He then attended Loughborough University, graduatingin 1993 with a degree in Electro-Mechanical PowerEngineering. He joined Lloyd's Register in the sameyear, and is now the Global Technology Leader forElectrotechnical Systems. Bernard is a member of the BSI GEL 65 System Considerations Panel and is CourseDirector for the Lloyd’s Register/Cranfield Universitytraining course in Marine Engineering Systems.

Renny Smith B.Sc., C.Eng., M.I.E.T. Renny Smith is a Senior Consultant (Software Assurance) within Lloyd’s Register Rail. He is anexperienced software safety audit and assuranceconsultant who has extensive experience of softwarefor major transportation infrastructure projects,including Channel Tunnel, Hong Kong’s new Chep Lap Kok airport, and light and heavy rail in Asia and the UK. Recently, he has been involved in thedevelopment of Lloyd’s Register’s Dependable Systemsservices and has delivered some of these services,including development of configuration managementprocedures, to several major shipping companies.

Vince Jenkins B.Sc., C.Eng., M.I.Mech.E.Vince Jenkins is the Global Marine Risk Advisor withinLloyd’s Register’s Technical Directorate. His early yearswere spent as a seagoing engineer with Cunard, beforegraduating in Mechanical Engineering. He then spent11 years in the nuclear industry, which introduced himto nuclear submarine technology and its challenges.Following this, he joined DNV where he worked forover 10 years. At DNV, he was involved in deliveringMarine consultancy assignments and developing theorganisation’s capabilities in that area. Vince joinedLloyd’s Register in January 2008.

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