GAS CARRIERS - DNVGL.com - Safer Smarter Greener ... GAS CARRIER Leading the way Leading the way GAS CARRIER 07 WORKING WITH DNV GL For decades, DNV GL has led the way in the gas carrier

SAFER, SMARTER, GREENER

GAS CARRIERSLeading the way – from concept to operation

Leading the way GAS CARRIER 03 02 GAS CARRIER Leading the way

DNV GL – leading the way DNV GL has over the years accumulated unique expertise in the gas-carrier segment. We have played a central role in developing both the membrane- and Moss-type cargo containment systems and are regarded as an important and ground-breaking player in the industry, bringing innovation and making new ideas come alive. As a recognized leader in the classification services sector, DNV GL is in the forefront of technical develop-ment, providing state-of-the-art class and advisory services.

Our goal is to be the best-performing and most qualified supplier of services to the gas industry, using our vast network of skilled personnel to help the industry improve its performance throughout the life cycle of its vessels.

04 DNV GL – your trusted partner

06 Working with DNV GL

08 Innovation

10 Pre-contract

12 Design and plan approval

14 Construction

16 Operation

20 Recycling

22 Research and development

24 History and innovation

26 DNV GL – global reach with local presence

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DNV GL – YOUR TRUSTED PARTNERFor today’s gas operators, safety, quality and opera-tional efficiency have always been first priority. LNG shipping has a very impressive and unprecedented safety record after more than 50 years of commercial operation. More than 80,000 cargoes have been lifted with no loss of cargo tank containment and, last but not least, no onboard fatalities directly attributa-ble to the crew.

Cargo owners also want to be sure that no shortcuts are taken that might threaten these fundamental goals. These priorities are supported by DNV GL’s stated mission: to safeguard life, property and the environment. Quality is the number one priority in DNV GL and is one of the reasons why we are a trust-ed partner for gas operators when it comes to safety and compliance.

We offer classification and related services in which we support gas owners in their critical efforts to perform in compliance with their charterers' expec-tations and requirements. Our goal is to stay in the forefront of technology innovation, responding to commercial market developments and the demand for efficiency and environmental and safety improve-ments.

DNV GL has extensive R&D resources and expertise to strengthen its technology and competence base. And with around 6,000 highly skilled employees active in the maritime segment of the company, we are in a unique position to support customers with premium, cost-effective classification and advisory services – anytime, anywhere.

For our customers, that means we have more survey-ors, a faster response time and more experts within business-critical disciplines than any other classifica-tion society.

Our expertise in the gas carrier segment cannot be measured simply by the number of ports where we operate or the number of vessels in our portfolio. Rather, our success is determined by the quality of the services we deliver to each individual customer. We believe that while the size of our organization represents a genuine benefit to our customers, our skills, dedication and understanding of the gas busi-ness are what differentiate DNV GL from competing providers of class services.

Collaboration for us means achieving goals together with our customers within areas like safety, the envi-ronment, efficiency and sustainable business results. We are committed to creating a deep and collective working atmosphere in which all parties are deter-mined to reach common objectives.

Today, DNV GL is a technology leader in the gas carrier segment. By developing rules and maintain-ing cutting-edge expertise, we remain committed to strengthening our peerless reputation in this dynam-ic segment. Looking ahead, DNV GL will continue to focus on ship safety, efficiency and environmental performance to help make your operations safer, smarter and greener.

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WORKING WITH DNV GL

For decades, DNV GL has led the way in the gas carrier segment, working in partnership with own-ers, shipyards, designers and suppliers to improve vessel performance. The foundation of our success has been our deep expertise combined with our understanding of customers’ needs and our techni-cal know-how.

Our ambition is to deliver a high-value service to your key challenges including:

■ Safety ■ Cost-efficient operations ■ Ship availability ■ Compliance with cargo owners’ requirements ■ Compliance with current international rules and port state requirements

■ Protecting brand integrity ■ Crew safety and competence development ■ New technology insight and regulatory foresight

Over the past few years, the gas carrier industry has faced significant challenges. To remain competitive, owners have focused on increasing efficiency and cutting costs without compromising on safety. While DNV GL’s core services remain classification and certification, we also offer a broad range of advisory services to help customers navigate the new market reality.

Life-cycle supportDNV GL has the solutions and tools to help you man-age these and other issues throughout the life cycleof your vessels and ensure efficient operations with minimum downtime.

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RESEARCH AND DEVELOPMENT

PRE-CONTRACT DESIGN AND APPROVALINNOVATION CONSTRUCTION OPERATION RECYCLING


INNOVATION

LNGreen was a Joint Development Project between DNV GL, Hyundai, GTT and LNG ship-owner Gaslog.

■ The goal of the project was to develop an improved , more energy- and fuel-efficient, LNG carrier concept using the latest developed technology and within the bounds of existing shipbuilding methods

■ The developed concept can therefore be readily implemented in forthcoming LNG carrier orders

The areas of focus of our development were: ■ Hydrodynamic and hull optimization ■ Improved design of the containment system and tanks

■ Improved machinery configurations incorporating energy recovery technologies

The hull was optimized using CFD methods for multi-speed optimization, linked to a new tank shape that can minimize the amount of void space around the first cargo tank. In parallel, advances in the con-tainment system were applied to minimize boil-off.Our in-house modelling and simulation framework, COSSMOS, was used to assess various machinery configurations and energy recovery technologies with respect to energy efficiency, fuel costs and economics.

The use of trading route characteristics and intended operational profiles was a key element in our assessment.

The outcome of the project is an LNG carrier concept with:

■ 5% increased cargo capacity and a particularly low boil-off rate of 0.085% vol/day.

■ 8% increase in the overall efficiency and reduction in fuel-related costs through the improvements in hydrodynamic performance and optimisation of the machinery configuration

The above improvements have been achieved taking into account the complete integrated ship machinery system for the trading route and the vessel’s operat-ing profile characteristics. It should be noted that the baseline for our improvement analysis used DFDE (propulsion) and MARK III-Flex (Cargo Containment System).

The project demonstrated the value of robust deci-sion-making using advanced computer-based meth-ods that manage complexity in practice and can lead to tangible improvements in LNG carrier design.



LNG CARRIER OF TOMORROW – A JOINT DEVELOPMENT PROJECT

LNGREEN

5% 8%0.085%RESULTS

TARGETS

Increase of cargo capacity

Maximise hydrodynamic performance

Utilise twin-skeg hull form

Increase of overall efficiency and reduction of fuel costs

Increase overall machinery and system efficiency

Base case for comparisons is a DFDE LNGC, model-based assessment using COSSMOS

Achieved boil-off rate per day

Maximise cargo volume & minimise boil off

Utilise GTT Mk III Flex system


PRE-CONTRACT

Help to qualify novel containment systems DNV GL experts offers to support the technology development and justification of your design and can assist during the whole concept and design development phase, including:

■ Development and specification of the design basis and assessment methodology

■ Strength evaluation of the containment system, including ultimate strength, fatigue and crack propagation, depending on the type of contain-ment system

■ Production of documentation necessary for the formal qualification of the system, including the review for Approval in Principle (AiP) and General Approval for Ship Application (GASA)

Hull lines and propulsion optimization to maximize fuel efficiencyDNV GL’s fuel-efficiency hydrodynamics experts help customers to make hull design improvements to achieve enhanced performance. Naval architects and specialists use powerful and cost-effective analysis tools to create a basis for hull design optimization and support according to our customers’ needs. Our service offering includes:

■ Hull optimization according to the expected oper-ating profile, accounting for flexibility in operating drafts, trims and speeds

■ Using state-of-the-art hull design tools and compu-tational fluid dynamics (CFD) analysis in full scale to make modifications and evaluate the hull hydrody-namic performance and hull-propeller interaction

The benefits are reduced fuel consumption and a ship design better suited to the intended operations.



Concept development ■ Operating profile development ■ Determination of the ship’s main particulars ■ Support for specification development ■ Strength analysis of LNG tank systems ■ Support for the design of novel containment systems

■ Assessment and selection of machinery configura-tions

■ Hydrodynamic benchmarking and verification studies for new gas carrier designs

■ Assessment of a concept’s fuel-efficiency improvement potential

■ Hull lines and propulsion optimization to maximize fuel efficiency

■ Model test support ■ Predictions of propulsion power requirement and fuel oil consumption

DNV GL's COSSMOS modelling and simulation computer toolDNV GL invests heavily in R&D, Joint Industry Projects and the development of rules and new services to ensure safe and cost-effective operations. Recent developments include our in-house machinery and systems modelling and simulation computer plat-form - COSSMOS. Our key machinery experts model, simulate and optimize integrated ship systems with respect to energy efficiency, emissions, costs and safety, based on the operational profile and trading route. COSSMOS has been successfully used to con-

duct quantitative comparisons of different solutions and support complex decision-making.

Application areas for gas tankers include: ■ Techno-economic comparisons of configuration and optimization alternatives

■ Waste heat and energy recovery feasibility & in-vestment analysis

■ Reliquefaction plant selection and optimization ■ Multi-point engine/propeller matching ■ Assessment of power management strategies and optimization

COMPONENT MODELS LIBRARY GRAPHICAL ENVIRONMENT TO SYNTHESISE SHIP MACHINERY SYSTEMS

MODEL-BASED STUDIES

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DESIGN AND PLAN APPROVAL

Setting the standard in the development of gas carrier designDNV GL is in the forefront of the development of gas carrier design. The marked has changed from the tra-ditional gas carrier trading routes to a more complex LNG and LPG business in the world today. DNV GL has been assisting and supporting the development by issuing rule standards for e.g. Gas bunker ships, Floating Storage Units (FSU), Floating Storage and Regasification Units (FSRU). Also the developments of gas burning combustion engines, new concepts for re-liquefaction of LNG boil-off and oxidation of boil-off vapours have been supported by issuing prescriptive classification standards.

The need for cleaner energy on shore has caused the fleet of FSRU’s to continue to expand. Since 2008, DNV GL has had dedicated rules which address the increased challenge of additional hydrocarbons under pressure on open deck and how to handle this safely. These rules include detailed requirements covering the entire gas circuit from the supply of the liquefied gas (mainly LNG for the time being) to the FSRU, storage, supply the regasification trains where the liquefied gas is pressurized, vaporized and then in the end export high pressure gas directly to a pipe grid. These vessels will have the mandatory notation REGAS.

The increased number of gas fuelled ships has cre-ated a need in the marked for liquefied gas bunker solutions.

One of the solutions will be use of dedicated Gas bunker ships for supplying gas fuelled ships in a safe and efficient predicate way. The current codes IGC Code and IGF Code does not address this very important issue in detail and therefore DNV GL has now developed rules to meet the industry need for

standards. Ships built in compliance with these rules will be assigned the class Gas bunker.

The shift from steam to new propulsion alternatives continues and DNV GL has firsthand experience re-lated to medium and high pressure gas fuel systems and how to class such installations. A gas carrier with gas-fuelled installation will be given our register notation GF.

An alternative to transporting LNG is transport of Compressed Natural Gas CNG DNV GL rules are available for classification of such ships. A CNG carrier will have the mandatory notation tanker for compressed natural gas.

Knowledge hubs and plan approvalDNV GL’s maritime knowledge hubs for gas carriers are located in Oslo and Hamburg, where leading technical experts in the segment are ready to assist as needed. The organization also has plan approval offices in China and Korea. This provides customers with “one stop shop” services covering all relevant disciplines. Strong, long-term relationships with the industry’s leading shipyards and designers put DNV GL in a good position to support customers during the design and plan approval process.

Design supportDNV GL offers value-added advisory services in vari-ous disciplines and competence areas to supportowners, shipyards and designers during the design process and also to assist on novel design.

Advisory, training and software services ■ Global ship structure analyses, including rule com-pliance and weight optimization

■ Strength and fatigue analyses ■ Noise and vibration analyses ■ Hydrodynamics analyses ■ Machinery system analyses ■ Training courses for newbuildings and design ■ Specification reviews

Typical gas related notations for LNGC with Gas Fuelled installation

■ Tanker for liquefied gas, Ship type 2G (-163°C, 500kg/m3, 0.25 bar) GF



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CONSTRUCTION

There, where you need usDVN GL has a strong presence in all major shipbuild-ing regions. Due to its large portfolio of gas carrier newbuildings, DNV GL has not only established strong, long-term relationships with owner represent-atives, shipyards and designers, but also has experts covering a broad range of topics available on site around the world.

DNV GL has also developed highly effective project management tools. The organization assigns a highly experienced project manager to act as a single point of contact and coordinate all DNV GL on-site team

activities. Our multidisciplinary technical expertise covers fields such as electrical and automation systems, machinery, pressure vessels and welding.

Traditional DNV GL services during the construction phase are related to classification and certification. In addition, DNV GL can assist owners, yards, designers and suppliers with tailored advisory services.

Advisory services ■ Shipyard and supplier assessment ■ Project management support ■ Support to hull lines and appendages optimization ■ Performance verification, e.g. sea-trials and Build-2Design service

Class services ■ Shipyard assessment according to the IACS UR Z23 and Yard Fitness Programme

■ Certification of workshops, welders and NDT ■ Scheduled and non-scheduled class and statutory inspections

■ Verification of tests and trials ■ Issuance of class and statutory services

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OPERATION

Your global resource for ships in operation Quality and safety at reasonable cost are key success criteria in the gas carrier segment, forcing ship-owners to review how they operate their fleet and to always seek potential improvements.

Shortcomings in quality and compliance will put ships out of business so, if challenges do arise, it is essential to resolve them as quickly as possible. DNV GL is involved daily in answering customers’ techni-cal questions and resolving port-state-control and vetting issues to keep customers’ ships in business with as little as possible downtime.

DNV GL has taken a leading position in working with owners and operators to help manage these issues. We offer comprehensive 24/7 back-office support to surveyors and owners worldwide through our DATE (Direct Access to Technical Experts) service.

DNV GL also offers an Emergency Response Service (ERS) that provides prompt access to shore-basedexpert assistance to assess the damage stability and residual strength of a vessel in distress. ERS is a fast,reliable, around-the-clock professional assessment of a ship's condition in an emergency situation.

DNV GL advisory and class services empower opera-tors to improve efficiency and reduce costs or to see new business areas for their ships. DNV GL can help ship-owners to optimize machinery installations and provide input on potential new cargoes, potential conversions of regasification ships (FSRUs) and many more issues.

We also have a streamlined process for transferring class. Our local DNV GL office is always standing by to plan the practical aspects of the class transfer with you in order to ensure a smooth transition with the minimum disruption to your operations.

Life extension/conversion studiesSurveys and technical studies of vessels indicate that LNG carriers have a potential for use far beyond the lifetime anticipated at the time of newbuilding. Older vessels may be attractive for continued operation as LNG carriers or for conversion to carriers for other liquefied gas cargoes or FRSUs/FSUs. Nevertheless, the authorities, charterers or new owners may require documentation of the vessel’s condition and its ability to serve its intended purpose in the future. A typical scope includes:

■ A review of the relevant design, maintenance and trading history documentation

■ Structural strength and fatigue analyses of the hull, cargo containment system and its supports, con-sidering the actual trade and future operations

■ Onboard inspections to verify the actual condition of the hull, machinery and electrical systems

■ A life extension/conversion assessment including recommended actions

■ Issuance of life expectancy statements

FSRU conversionIt has been proven attractive to convert older LNG carriers to FSRUs. This requires qualification of the vessel for the new application and risk management of the operation. DNV GL has long experience with LNG vessels and different tank designs. A typical scope for a Moss-type FSRU conversion may include:

■ Relevant condition-assessment activities ■ Sloshing load assessment for partially filled tanks considering the vessel’s intended operation

■ Structural analyses (ultimate strength and fatigue) of the hull and affected areas of the tank, including the tower and tower connections for the intended FSRU application

■ Crack propagation and leak rate assessment to justify the capacity of the partial secondary barrier



■ Safety, risk and reliability studies such as HAZID, HAZID, QRA, Fire Safety, Port Manoeuvrability Simulation, Navigational Risk and RAM (Reliability, Availability, Maintainability)

■ Winterization and Cold Climate studies

Retrofit – bulb optimisationMost vessels operate at conditions that are different from their contract condition, i.e. design draught and design speed. In DNV GL’s experience, the savings potential of a bulb retrofit is often significant when the distance between the contract and actual operat-ing conditions is large. In off-design conditions, e.g. lower speeds, the bulb can create an adverse wave system that increases the resistance, power demand and thus fuel consumption.

DNV GL has long experience and efficient tools and processes for re-designing the bulbous bow region in close contact with the customer.

The bulb is optimized to fit the actual and expect-ed operating conditions using computational fluid dynamics (CFD).

The benefits are reduced fuel consumption (3-10%) and a flexible bulb design fit for actual operations.

Vetting advisoryThe liquid cargo owners’ vetting regime is continu-ously increasing and it is becoming harder for ship owners to stay updated on the latest developments, to demonstrate compliance with the requirements and to effectively take the correct actions.

As the vetting inspections are increasing in frequen-cy, they make high demands on the superintendents and crew. DNV GL offers vetting advisory services to ship owners and operators to further improve their vetting performance and optimize the time and cost of vetting inspections. Our services include:

■ Pre-vetting inspections ■ Vetting training for crews and superintendents ■ A systematic approach to control the vessel’s condition

■ Preparations for the latest developments in the vetting regime

Analysis and benchmarking using a vetting-finding database

Retrofit – machinery optimisationNew regulations, fuel economy and technological developments are drivers for improving the machin-ery and systems on existing vessels. DNV GL has experts and tools to help its customers optimize and analyse the design and performance of ship systems and components. Services include:

BULB OPTIMISATION

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Advisory, training and software services ■ Energy and fleet management advisory ■ Fleet performance management, benchmarking and optimization

■ Maintenance and hull lifecycle management ■ Damage root-cause investigation and troubleshooting

■ Technology qualification of novel design ■ Training courses for safe, efficient and compliant ship operations

■ Life-extension studies ■ Conversion of LNG carriers to FSRUs ■ Vetting advisory ■ ECO Retrofit bulbous bow, propeller, propulsion improvement devices

■ ECO Retrofit machinery and systems ■ Trim optimization ■ Performance management through ECO Insight

Class services ■ Ship classification, such as periodical and unscheduled inspections and docking support

■ Vetting support ■ PSC support ■ Emergency Response Service

■ Evaluation of the fitness for purpose and benefits of, as well as the risks involved in, new designs or changes to existing designs or operations

■ Analyses of different machinery setups for a wide combination of loads and temperatures to find the right engine system arrangement for the intended transport demand. Focus areas may be: - Cooling water system - Ventilating system - Ship-specific energy systems - Reliquefaction

Shaft alignment support in newbuilding, conversions and troubleshootingDNV GL’s unique strength is to combine a theoret-ical approach with practical experience and onsite measurements or damage investigations. Our deep knowledge in propulsion systems and components, together with its modelling expertise for shaft align-ment, CFD, FEM and tribology, makes DNV GL a total supplier of design assistance, design verification, measurements and troubleshooting.

■ Service offering for new designs: - Shaft alignment and whirling analyses - Analysis of propeller excitation forces - Hull deflection FEM analyses - Alignment procedure and verification of the alignment

■ Service offering for conversion, repair and trouble-shooting projects: - In-situ measurements (jacking loads, deflections, gap/sag, laser measurements) - Proposed new alignment for the shaft line - On-site bearing damage investigations - In-situ supervision and advice

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RECYCLING

The International Maritime Organization (IMO) has developed a standard for ship recycling (the Hong Kong Convention). While it may take time for the Convention to enter into force, many prudent owners are already taking steps to ensure that ship recycling is done in a safe and environmentally friendly man-ner in anticipation of ratification by member states.

DNV GL offers a variety of class notations that help ship owners specify certain minimum standards related to the use and documentation of hazard-ous substances on board throughout the entire life cycle of a vessel. Many owners and yards are already

preparing to comply with the Inventory of Hazardous Materials (IHM), a key provision of the Convention. In support of these efforts, DNV GL has developed the IHM Green Server, which is specifically designed to help owners keep IHM documentation updated throughout the vessel’s life cycle, thus providing relevant information when the vessel is due to be recycled.

DNV GL offers advisory services to help stakeholders collect information, develop plans and documents for recycling, and assess recycling facilities.

Advisory ■ IHM/ HAZMAT survey ■ IHM development for newbuilding or existing ships ■ Adaptation of management systems ■ Assessment of recycling facilities

Class/certification ■ Class Notations

- EP-D/ EP-O/ CLEAN/CLEANDESIGN - RECYCLABLE - IHM certification



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RESEARCH ANDDEVELOPMENT

Solutions for a changing industry Operating a successful fleet of tankers in the future will require the adoption of new technologies and innovative solutions. Those players willing to invest in new technologies are likely to achieve a strong competitive advantage in the years ahead. Energy efficiency, operational flexibility and not least the best fuel strategy to meet future emission require-ments are key areas which are highly relevant to the gas carrier segment.

DNV GL allocates a significant part of its yearly reve-nue to projects bringing innovation to the maritime industry, as well as to projects that help maintain our position as a leader in selected technology fields.

In addition to being in the forefront of rule development, DNV GL is a recognised industry leader in research and development, often working with other stakeholders in Joint Industry Projects. With concept studies like Triality, Best Plus and

LNGreen, DNV GL has taken the lead in developing new concepts, employing both available and emerging technologies. Another recent example on research and innovation in DNV GL is the development of COSSMOS (Complex Ship Systems Modelling & Simulation). COSSMOS is a software tool for optimising the design and operation of energy-intensive systems such as ship machinery power plants. The tool is especially suitable for analysing the complex arrangements of steam/boiler systems and waste heat recovery systems providing good decision support during the design phase.

DNV GL contributes expertise to the development of emerging maritime technologies and works together with other industries to develop solutions for gas carriers. In addition, we offer acknowledged processes for qualifying new technology and assist in bringing safe, commercially viable and efficient solutions to the market.

Next-generation innovations in tankers ■ Concept designs including Triality, Best Plus and LNGreen

■ COSSMOS

■ LNG Ready ■ ECO Assistant ■ ECO Insight

The COSSMOS platform has been success-fully applied in a series of projects showing significant potential fuel savings.



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HISTORY AND INNOVATION

The LNG story - unleashing our innovation The bulk seaborne transport of liquefied gas is older than often realised. The first dedicated liquefied gas tanker, Herøya, was built to DNV class in 1949 at the Horten yard in Norway. She had pressurised cargo tanks for the transport of LPG and ammonia. DNV thus became involved in setting safety standards for this type of ship at a very early stage, and in 1962 was the first classification society to publish compre-hensive rules for gas carriers.

One of the most severe challenges when design-ing liquefied natural gas (LNG) carriers is the low temperature of the cargo, minus 162°C. This makes most of the materials commonly used in shipbuilding unsuitable for cargo containment. The low tempera-ture calls for special design measures to ensure the safety of such vessels.

Membrane tanksDNV’s first involvement with LNG carriers was in de-veloping a membrane-type tank system in a project with Norwegian ship owner Øivind Lorentzen and the Bennet Group of Dallas in 1959-62. A number of designs were considered, including the waffle-type membrane tank invented by DNV. A 32m³ test tank was constructed in 1962 and tested successfully using liquid nitrogen.

However, this tank system was not developed further by the original project group. The patent rights were transferred to a French company, Gazocean, which developed the system into the Technigaz Mark family of LNG containment systems. Membrane tanks that have a thin layer (membrane) supported, through their insulation, by the adjacent hull structure and are designed to minimise the effect of thermal contrac-tion without undue stress. A secondary barrier is able to contain the cargo for at least 15 days should the primary barrier leak.

Spherical tanksThe Moss spherical tank design was developed by the Kvaerner Moss Group in Norway between 1969 and 1972, with a significant contribution from DNV. The spherical containment system had already been pur-sued as one of the alternatives studied in the 1959-62

project with Øivind Lorentzen, and he ordered an LPG vessel to this design - the Mundogas Brasilia deliv-ered by Fredrikstad Yard in Norway in 1961.

The basic design criteria for LNG ships were formu-lated by DNV in its 1972 rules, setting the standard for the subsequent development of the 1976 Inter-national Gas Code for both spherical and prismatic tanks. To confirm compliance with the design criteria, DNV undertook research on sloshing loads due to liquid movement inside the cargo tanks, crack propa-gation, fatigue characteristics and buckling strength. In the early 1990s, the tank and skirt buckling criteria were reassessed and converted to a modern lim-it-state format based on new research and structural reliability analysis.

The basic design condition is the “leak before fail-ure” principle, which means that, from the time when it is detected, a crack in the tank should propagate at a slow and predictable rate under the worst antici-pated loading conditions, leaving adequate time (at least 15 days) for the vessel to unload its cargo safely before the crack reaches a critical size.

Designs for an expanding LNG marketThe classification of new ship designs calls for active involvement in the development process and in formulating a technical basis for the design. DNV closely studies new tank designs, both independent and membrane types, together with designers, op-erators and shipyards and carries out model testing of sloshing loads and also investigates the strength of insulation systems through materials testing and numerical analysis.

Floating storage and regasification units (FSRUs)Importing LNG has become an interesting energy strategy for very many countries. This is related to issues such as the availability and cost of natural gas, replacement of fuel oil consumption for cost and en-vironmental reasons, flexibility and security of supply for seasonal demand, and reduction in dependence on a single gas pipeline supplier. A large number of the import terminals currently being discussed will involve an FSRU solution for cost, scheduling and permit reasons.

At present, the most common concept involves berthing an FSRU alongside either a dedicated jetty or a quayside. We have also seen that some custom-ers want the vessel to function as an FSRU for a peri-od and then to operate for a while as a gas carrier.More than half of the FSRUs in operation or on order are classed by DNV GL.

Compressed natural gas (CNG)As much as half of the offshore gas discovered worldwide may be stranded – located in small fields beyond the economic reach of pipelines – or found as associated gas in oil reservoirs.

Associated gas is usually considered as a non-com-mercial asset and either flared (producing green-house gases) or re-injected into the reservoir, with

the risk of impairing the well's long-term oil-pro-ducing capacity. If it could be commercialised by transporting it to land at an ambient or semi-chilled temperature and under high pressure in a CNG carri-er, this would at the same time permit cost savings in liquefaction, storage and regasification facilities and allow the gas to be discharged directly into the land-based gas grid. Studies show that such CNG carriers can be an economic alternative to LNG and pipeline transport over distances of 500–3,000 nautical miles.

CNG technology can bring stranded and associated gas to market and enhance the value of existing gas finds. DNV has been closely involved in the develop-ment of CNG ship-design concepts, and in 2004 was the first classification society to issue a complete set of rules for CNG carriers.

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DNV GLDriven by its purpose of safeguarding life, property and the environment, DNV GL enables organisations to advance the safety and sustainability of their business. DNV GL provides classification and technical assurance along with software and independent expert advisory services to the maritime, oil & gas and energy industries.

It also provides certification services to customers across a wide range of industries. Combining leading technical and operational expertise, risk methodology and in-depth industry knowledge, DNV GL empowers its customers’ decisions and actions with trust and confidence. The company continuously invests in research and collaborative innovation to provide customers and society with operational and technological foresight. DNV GL, whose origins go back to 1864, operates globally in more than 100 countries with its 16,000 professionals dedicated to helping their customers make the world safer, smarter and greener.

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GAS CARRIERS - DNVGL.com - Safer Smarter Greener ... GAS CARRIER Leading the way Leading the way GAS CARRIER 07 WORKING WITH DNV GL For decades, DNV GL has led the way in the gas carrier