Container ship update 1 2013 by DNV GL (old account)

South Korean 18,000 TEU designs

New OMT/SWS design reduces slot cost

Waigaoqiao goes for 18K TEU

container ship update

News from DNV to the container ship industryâ&#x20AC;&#x192; No 01 2013

Focus on Ultra Large Container Ships

cONtENts

South Korean 18,000 teu designs

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new oMt/SWS design reduces slot cost

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Waigaoqiao goes for 18K teu

photo: SWS

illustration: dnV

photo: iStock

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container ship update wE wElcOmE yOUr thOUghts! published by dnV Maritime and oil & gas, Market communications.

ULTRa-LaRGe COnTaIneR VeSSeLS – Can THe eCOnOMY OF SCaLe Be QUanTIFIed? ........................................... 4

Editorial committee: Jost Bergmann, container Ship Business director Vebjørn guttormsen, associate editor Knut døhlie, associate editor Magne a. røe, editor Marianne Wennesland, production design and layout: coormedia.com 1301-039

aRe THe TeRMInaLS ReadY FOR ULCVS – Indeed THeY aRe! ..... 6

front cover photo: aurélie amiot, www.aurelie-amiot.fr

SOUTH KORean 18,000 TeU deSIGnS ........................................... 10

please direct any enquiries to dnVupdates@dnv.com

neW OMT/SWS deSIGn RedUCeS SLOT COST ............................. 14

online edition of container ship update: www.dnv.com/containershipupdate

an ULTRa-LaRGe COnTaIneR VeSSeL FOR an UnCeRTaIn FUTURe ..................................................................... 20 WaIGaOQIaO GOeS FOR 18K TeU................................................. 24 an 18K TeU deSIGned TO dnV STandaRd ................................. 26 TWIn SKeG VeRSUS SInGLe SKeG On ULCS ................................. 30 Can YOUR COnTaIneR VeSSeL SUSTaIn WHIPPInG? .................. 34 IMPROVed COnTaIneR CaPaCITY THROUGH dIReCT CaLCULaTIOnS ............................................................................. 38

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EditOrial

Jost Bergmann container Ship Business director Jost.Bergmann@dnv.com

Name surname title mail address

Ulcs Of 18,000 tEU

Signature

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Is there a need for these huge ships in this day and age? There may be too many ships in the pipeline, so why should there be an interest in even more and bigger ships? The driving force is cost per TeU-mile, or in other words, economy of scale. Bigger ships are being deployed in all trade lanes if you compare figures from 2012 with those from 2008. However, bigger ships do pose some challenges. dnV logistics experts point to the criticality of the load factor – if you can’t fill the ship, you will operate at a loss. We have compared the critical load factor for the different ship size classes. niels Vallø gives an excellent review of the various ports and terminals around the world. Ports and terminals must cater for the bigger ships if this is going to work, and he concludes that many terminals are ready for them. In this issue, we bring you the latest in ULCS design, introducing the new 18K TeU from OMT and SWS as well as the latest status on 18K developments from HHI, dSMe and STx in South Korea. The OMT/SWS 18K has been designed by the experts from Odense Steel Shipyard who made the e-Class Series, in cooperation with Shanghai Waigaoqiao Shipyard. This yard has long experience in building large ships and is now able to offer a cutting-edge design for the container segment. The ship is presented in detail in the following pages. The technical challenges are being met in close cooperation with the dnV team, producing a cost-efficient and safe solution. Should this size of ship have one or two propellers? We discuss the pros and cons. Fuel efficiency and Capex are important factors. The space available for containers also plays a significant role, and the two alternatives are modelled in 3d to provide a reliable estimate. Gaute Storhaug writes about whipping on container ships for the layman. Whipping has received increased attention in recent years and designing to control the effects of the phenomenon is an integral part of the dnV container ship standard. I hope you enjoy this issue – please send your views to my e-mail address below.

Jost.Bergmann@dnv.com

container Ship update NO. 1 2013 |

Economy of scale

Ultra-large container vessels – can the economy of scale be quantiﬁed? After a period of rapid developments in the container-vessel sector, where yesterday’s deep‑sea vessels are today’s feeders, will the ULCS size and capacity peak at or around the 18,000 TEU level and the attention shift towards different optimisation parameters, or will the increase in size continue? Owners and operators alike are looking for decisive evidence in either direction: will ever larger vessels mean ever increasing efficiency gains? Text: Audun Grimstad and Eivind Neumann-Larsen, DNV

In all segments of bulk or commodity shipping, the focus will in principle be on economy of scale within the boundaries of physical and technological constraints – both for vessels and for the supporting infrastructure. In practice, however, the constraints and limitations posed by the other parts of the transport chain will restrict and check these developments; in a container shipping context this will typically be issues like the capacity of ports and terminals, shore cranes, hinterland infrastructure and the volume of cargo available for the trade in question. Port developments for mainlane trades (FEA – EUR and FEA – US) in general seem to be keeping up with the growth in vessel size, driven by a projected cargo volume increase and competition between ports. Assuming, then, that the system as a whole will cope with continued growth in vessel size, what will the slot costs per TEU be as the vessel size increases? In order to provide credible results, an analysis that aims to address this must recognise that a significant number of parameters govern the design and selection of vessels: a key challenge will thus be to reduce this complexity to a manageable set of data. In this respect, previous

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work in DNV on similar problems has provided us with some useful insight: if the focus is shifted from absolute numbers to relative performance, such studies often become much more applicable. In other words, the percentage difference is of much higher importance than the actual cost in USD. With this in mind, we wanted to investigate whether or not a clear trend would emerge with respect to cost/TEU for a range of four vessels (14K, 16K, 18K and 21K TEU) using a simplified and straightforward approach: DNV has developed a small application, the Container Cost Calculator (CCC), in order to calculate the slot cost for a container service. All vessel performance data were taken from DNV concept studies and projects and will thus not necessarily match existing vessels or published data. The CCC includes fairly detailed representations of the vessels’ speed-power-displacement relations (and hence also the FO consumption), in addition to port productivity, first costs (capital cost), operating cost elements (OpEx) and voyage-related costs and charges. The cost picture shown, again with a particular focus on relative costs, should thus be fairly true-to-life, although it will not

necessarily capture all the finer points related to the operation of a ULCS or container terminal. Even this simplified approach seems to be able to point to at least three interesting trends. Firstly, it is not surprising to find that the cost per TEU is strongly related to the vessel’s utilisation – as may also be seen from the figures. But it is of somewhat more interest to note that the difference in utilisation corresponding to a given slot cost is not very large between the vessels in our comparison. In other words, if the utilisation drops by only 3–5%, the cost advantage of a vessel that is “one size larger” will be evened out. Please note that the apparent gap between the 18K and 16K vessels is due to engine differences and subsequently a speed/power representation for 14K and 16K vessels that will tend to overestimate the slot cost slightly. Secondly, our findings show that the “slot cost parity” between a 14K and a 21K vessel corresponds to an up to 12% difference in utilisation; the difference will be reduced as utilisation rates fall. This means that you need as much as 5,000 additional TEUs per voyage for the 21K compared to the 14K vessel in order to have the same

EcONOmy Of scalE

Relative cost per TEU (slot cost) 150% 145% 140%

Relative cost per TEU

135% 130% 90.5%

125% 120%

96%

88%

115% 110% 105% 14k TEU 16k TEU

100% 95%

18k TEU 21k TEU

90% 85% 70%

80%

85% Utilisation %

90%

95%

100%

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figure 1 Slot cost (uSd/teu) for different vessel sizes and varying utilisation. data from different dnV projects and studies; minor inconsistencies may occur. actual curves calculated for 18 kn average speed. [dnV]

Vessel Size

Utilisation

slot cost. Of course, the top slice or potential for profit should not be forgotten – the larger vessel will have a great number of available slots that may be sold at a healthy profit. and thirdly, it appears that this trend will hold for all investigated ship sizes and speeds. Slow-steaming larger vessels thus do not appear to help much in this respect; the utilisation must still be kept almost as high as for the smaller vessels. In short, you will always need to fill up your vessel to be profitable, no matter what its size. In addition, the number of ports at each end of the deep-sea leg cannot be too high, as any potential gains in utilisation are rapidly consumed by extra costs and time. after all, the main advantages of the larger vessel lie in the long legs and lower fuel cost per TeU. In other words, it appears that the economy-of-scale effect is not necessarily as significant as has often been assumed. The natural conclusion that can be drawn from this is that you need to be absolutely sure that you can fill your vessel in order to justify investing in ever larger ships – the slot cost reduction will not make up for or hedge against a significant drop in utilisation. 

75%

14,000 TEU

16,000 TEU

18,000 TEU

21,000 TEU

100%

97%

91%

89%

95%

105%

101%

96%

94%

90%

110%

106%

101%

98%

85%

117%

112%

106%

103%

80%

123%

119%

112%

109%

75%

131%

126%

119%

116%

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figure 2: Slot cost equivalence table. [dnV]

data in the slot cost table will show the development of cost vs. vessel size along two different axes of comparison: if the table is read line by line, the slot cost for a given utilisation can be compared. for instance, looking at the 100% utilisation line, the table shows that the slot cost for a 21K teu vessel is 89% of the slot cost for a 14K teu vessel. if the table is read column by column, the slot cost increase for diminishing utilisation can be compared: for the 14K teu vessel, reducing the utilisation from 100% to 75% will increase the slot cost by 31%.

container Ship update NO. 1 2013 |

POrts aNd tErmiNals

are the terminals ready for ULCVs – indeed they are! over the past 25 years, the container business has been characterised by a constant drive towards greater economy of scale – and container vessels have grown in size since the first full container service was inaugurated. terminals across the globe are now ready to accommodate ultra-large container vessels. TexT: niELs vALLø, COnTPORT COnSULT

EcONOmy Of scalE

engine/technology to keep the costs per TeU transported down, including at low speeds.

When the Maersk Line built the 15,000 TeU emma class in 2006, many in the industry were sceptical about the size, questioning the economy of scale – could these ships be filled/operated efficiently in service, etc. The sceptics were answered when the 18,000 TeU Triple-e series was ordered in February/June 2011 – 20 in total at a price of USd 190 million each. Fuel prices have almost doubled since the emma class came into service in 2006. Container volumes are continuing to grow at a rate of 4–5 per cent per year, albeit with different growth rates depending on the trade. Slow steaming is here to stay, giving an additional advantage to the ULCV, which is built with the latest main

frOm 15,000 tO 18,000 tEU The Maersk Line has ordered 20 ULCVs increasing in capacity from 15,000 TeU to 18,000 TeU. How can it do that if the terminals are not ready? Remember that the LOa of the 18,000 TeU Triple-e class is the same as that of the emma class – 400m! So the additional capacity – 3,000 TeUs – has been achieved by making the vessels one container position wider, from 22 container rows across on deck to 23 rows across, plus creating additional positions on deck. The scantling draft is the same for the two types – 16m.

frOm 22 tO 23 rOws ON dEcK! The terminals are being challenged by more ULCVs coming into service because they are forced to continue to invest huge amounts in infrastructure and equipment to make sure their customers – the shipping lines – do not run away to other ports/terminals. For ULCVs with an LOa of 400m, the shipping line will ask for the maximum number of gantry cranes able to reach 23 rows across on deck. Terminals consequently come under pressure to either rebuild/extend existing cranes or, when that is impossible, to buy new gantry cranes. new gantry cranes for 23 rows across are often both more expensive and heavier than existing cranes, so not only are terminals forced to invest

NiEls VallØ, cEO cONtPOrt cONsUlt

contport consult

• niels Vallø’s broad container-shipping expertise is based on 35 years of top positions in the Maersk line organisation, including postings abroad, as coo and as the architect behind what are today apM terminals. When the emma Maersk series was launched in 2006, he was responsible for ensuring that ports and terminals were ready for vessels of this size.

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• as managing director of contport consult, Vallø specialises in the global container terminal sector and is active within the field of new container tonnage. current activities include the marketing of new oMt designs, such as 18–21K teu ulcVs and a new panamax design for 2015 with overall length of 266 m and width of 49 m, giving a 13.5K teu capacity. • contport consult’s focus areas include the growth in container volumes as well as South american terminals and their fast-growing capacity for bigger vessels. the company has prepared studies on the next generation of container vessels – the 13.5K teu size.

Ports and terminals

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Terminals across the world are ready to accommodate ULCVs. Here Marco Polo, the world´s largest ULCV, in Hamburg.

in cranes, they are often also forced to improve the rails and superstructure (quay wall) supporting the cranes. The same challenges were a reality when the Emma class, with its 22 rows across, came out in 2006 and, due to careful planning, terminals were ready when these vessels came into service. The same will be the case for the 18,000 TEU size.

Trades for ULCVs The container shipping industry focuses on the Far East–Europe when it comes to the deployment of ULCVs for three main reasons: ■■ Huge volume of containers ■■ Well-developed container terminals with high productivity ■■ Efficient and cost-effective feeder network in both Europe and East Asia. The ULCVs could also be deployed between East Asia and the US West Coast

– the Pacific Trade – which is the world’s second-biggest in terms of volume. Owners have so far been hesitant to deploy ULCVs on Pacific trades, mainly due to the demand for a high sailing frequency combined with relatively low terminal productivity at US ports. Other trades are not yet ready for the 18,000 TEU size, although many terminals have the handling capacity, such as those in Cristobal, Balboa, Bahamas Freeport, etc. Cargo volumes are still insufficient for regular liner service using ULCVs on the US East Coast.

Yard capacity The high volumes of containers handled during an ULCV’s port call do indeed challenge the terminals when it comes to yard capacity. To ensure cost-effective yard operations, what is required is not only more space but also better handling equipment for higher stacking combined with improvements in IT systems. Some

terminals have easy access to more land, while other, often older, facilities with no additional land will invest in better yard-handling equipment to deal with the growth in the business.

Berth capacity The 400m-long ULCV challenges the terminals’ optimal berth utilisation, but experiences with the Emma class, and now also the CMA CGM Marco Polo class, show that proper berth-window planning combined with high schedule accuracy does allow the terminals to optimise their berth utilisation. The slow-steaming reality indirectly helps improve schedule reliability, as delays en route can often be rectified through speed, thereby meeting berthing windows.

Productivity The 400m-long ULCV combined with a high number of crane moves in each bay/ crane position opens up for a win-win

container ship update NO. 1 2013 |

Ports and terminals

Seattle Tacoma Oakland Los Angeles Long Beach

Norfolk Mobile Freeport Miami

ULCV READY TERMINALS ACROSS THE WORLD US West Coast US East Coast

Århus Rotterdam Felixstowe London Gateway Southampton Le Havre Zeebrugge Antwerp Valencia Algeciras Tangiers Barcelona Fos-sur-Mer

Gothenburg Gdansk Hamburg Bremerhaven Wilhelmshaven Genoa Cagliari Gioia Tauro Malta

Abu Jeddah

Christobal Balboa

Panama North European terminals Mediterranean terminals Middle East terminals East Asian terminals

situation for both the terminal and ship owner. When the terminal is able to place eight or ten cranes on the ULCV and work for several hours in the same bay due to the high container volume, the terminal’s costs per move fall while the owner gets fast operations; the hours saved can be spent at sea. It is hard to put concrete saving percentages on this productivity gain, as it depends on the actual stowage, the number of cranes on the vessel and the vessel’s onward schedule in terms of ‘using’ saved terminal time. But it remains a fact that ULCVs lead to improved productivity for the terminal and time saved for the owner of 3–5%.

Terminals ready for the 18,000+ size – longer vessels of 20–21,000 TEU Several terminal companies have already ordered and installed cranes able to handle vessels with 24–25 rows across on deck, i.e. 1–2 rows more than the 18,000 TEU size with 23 rows across. This is despite the fact

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will include cranes for the next generation of ULCVs. In East Asia, the main terminals already use the latest generation of gantry cranes. It should furthermore not be ruled out that ULCVs could grow to both 24 and 25 rows wide on deck, so it is interesting to note that some terminal companies are already preparing for future growth in terms of wider container vessels – 23–25,000 TEU! that the 21,000 TEU ULCV (still to be built) will most likely continue to have a width of 58.5m/23 rows of containers across, but with a length extended from 400m to 427m. The advantage of gantry cranes reaching 24 and 25 rows is higher productivity, as the trolley moves faster when it is not at the end of the crane boom on the outer row. Good examples are Wilhelmshaven in Germany, the new London Gateway terminal soon to open, and terminals in Felixstowe, Rotterdam and Algeciras, all of which have cranes that reach 24–25 rows across. Expansions in Gdansk, Gothenburg, Bremerhaven, etc.

How big a challenge is the gantry crane height? ULCVs require cranes to reach the tenth layer on deck, depending on the actual vessel draft combined with the height of the terminal above the water level plus fluctuations due to tide water. Often the container vessels are filled with empty containers on voyages back to East Asia, so they leave the last European terminal fully loaded and the first receiving terminal should naturally be able to work over the vessel using any gantry cranes. The terminals often have two to three

Ports and terminals

Tianjin Qingdao

ort Said Dubai u Dhabi

Shanghai-Yanshan Xiamen Khor (Al) Fakkan Shenzhen-Chiwan Jebel Ali Salalah

Dalian Busan

Yokohama

Kwangyang Osaka-Kobe Ningbo

Hong Kong

Port Kelang Tanjung Pelepas Singapore

Said, Salalah, Jebel Ali, Algeciras/Tangiers, Malta, Gioia Tauro, Singapore/Tanjung Pelepas, to mention the most important ones. Both extensive feeder networks and the combination of parent vessels’ main strings interchanging volumes will grow in importance. Liner operators will continue to base their calculations on either direct calls to a given port by the ULCV or a feeder solution. Who would have thought just five years ago that ULCVs would go into the Baltic and call at Gdansk – which today helps cover the Baltics. So the debate about using hub terminals/feedering versus direct calls will continue for years to come, and careful calculations will show the way forward.

16m scantling draft

tall cranes that start the top-tier operations, and other cranes can then get into action when their height fits the container layer. This is not ideal for operational efficiency, but reflects the fact that investments in cranes with both the right height and a big outreach are expensive and take time.

The fight for the best Berth Window Liner operators will continue to compete for the best berth window, i.e. the day of the week when most cargo is ready for loading (often a Saturday) or when it is optimal to discharge a huge volume so that it is ready at the inland points/ distribution centres on a Monday morning. Considering ULCVs require 8–10 cranes for efficient operations, few terminals can have two ULCVs lying alongside simultaneously. However, the big ports like Rotterdam, Algeciras, Hongkong, Yantian, Shanghai, Qingdao, Tanjung Pelepas, etc. either

have several big terminals or have already invested in berths/cranes and other terminal facilities so that they can take several ULCVs at the same time. Other ports/terminals still need to develop the required infrastructure in order to attract the ULCVs of the future. So the terminals’ ULCV capacity will necessarily have to be distributed throughout the week so that all seven days are used optimally – and cargo owners will be required to adjust their supply chains accordingly to achieve the right freight-rate level and transportation capacity.

Transfer Hubs are here to stay There will be a concentration of container volumes at the known hub terminals in order to ensure that the ULCV’s capacity is used optimally – facilities like Port

It is often discussed whether the deep drafts of, for example, a 16m scantling for an ULCV is problematic in relation to operating the vessel on a service string. Indeed, the deep drafts need to be taken into consideration, but often the design draft of 14m is the actual draft the vessel leaves the last loading port with, or 14–16m depending on the nature of the cargo carried. As long as the last loading port terminal and first discharge port terminal have a sufficient water depth, then in reality draft becomes a question of ensuring the right service rotation between ports. Looking at the East Asia–Europe trade, the cargo carried is relatively light westbound, and the vessels are rarely loaded to the marks when eastbound. Ports like Rotterdam, Algeciras, Tanjung Pelepas and Yantian are able to take vessels at their scantling draft, and several others on the way have similar good depths alongside the terminals, like Salalah, Port Said, etc. It should be mentioned that the river ports/terminals of Antwerp and Hamburg are already handling 16,000 TEU vessels, despite these ports’ well-known draft restrictions. The liner operators plan the rotation to fit the draft restrictions when these are an issue. 

container ship update NO. 1 2013 |

South Korea

South Korean 18,000 TEU designs Korea entered the world shipbuilding market during the shipbuilding boom in the 1970s. During the 1990s, Korean shipbuilders committed themselves to massive capital investments to increase capacity with the confidence that they could acquire competitive advantages over Japanese shipbuilders. Today, the top four container-ship builders are all South Korean and around 75% of all container ships above 7,500 TEU are built in South Korea.

Photo: STX

Photo: HHI

Photo: DSME

Text: Hwa Lyong Lee, DNV

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All the major Korean yards are now offering mega-size container ships in the 18,000 TEU range. We are pleased to introduce the latest developments in this size of ship from (left to right) HHI (Hyundai Heavy Industries), DSME (Daewoo Shipbuilding & Marine Engineering), and STX Offshore and Shipbuilding.

From mid-2000, Korean shipbuilders reconsidered their business strategy to cope with China’s remarkable growth and implemented segmentation strategies focusing on sophisticated ships to avoid severe price competition. South Korea is now the global leader in the production of advanced high-tech vessels such as supertankers, LNG carriers, drill ships and largesized container ships. High energy prices and the introduction of new emission regulations, such as

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the IMO Energy Efficiency Design Index (EEDI), have set a new standard for ship design, with owners focusing much more on fuel efficiency when ordering new vessels. This paradigm change for the industry has given Korean yards great opportunities to secure newbuilding projects thanks to their recognised/prevailing technology for fuel efficient designs. In 2011, DSME entered into a contract with the A. P. Moller-Maersk Group to build 20 Triple-E class 18,000 TEU

container ships. Triple-E class ships are the biggest container ships built until now, and have redefined the concepts of economies of scale and slot cost efficiency. All the major Korean yards are now offering mega-size container ships in the 18,000 TEU range and we are pleased to introduce the latest developments in this size of ship from HHI (Hyundai Heavy Industries), DSME (Daewoo Shipbuilding & Marine Engineering), and STX Offshore and Shipbuilding. 

South Korea

Daewoo Shipbuilding & Marine Engineering – Ultra-E 18,000 TEU class In the past, container-ship design was mainly concentrated on how to transport cargo rapidly, whereas nowadays optimisation is the new focal point. DSME has incorporated different design features into its vessels, taking each client’s preferences and the operational features, including optimum cargo handling, into account.

Illustration: DSME

Text: Odin Ohyig Kwon, DSME

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DSME Ultra-E 18,300 TEU.

The world’s 20 largest container ships of 18,000 TEU are being built for AP Moller at DSME’s Okpo yard. Based on the experience and knowledge gained from this mega project, DSME has also developed an 18,000 TEU ship with a single-screw design. The single-screw version has a DSME full-spade rudder and a fixed-pitch propeller directly driven by a slow-speed diesel engine. A pre-swirl stator, designed by DSME, is to be installed in front of the propeller as an energy-saving device. The propulsion machinery is located semi-aft and all the living quarters, including the navigation bridge, and fuel tanks are to be located amidships while two bow thrusters are to be arranged for port manoeuvring. The vessel is designed with a continuous upper deck without forecastle, an aft sunken deck, a raked stem with bulbous bow and a transom stern with an open water type stern frame. The vessel is to be built in general as a double-skinned construction with 11 cargo

holds, 24 bays holding 40 ft containers and 21 hatches. Containers on deck are generally to be carried in 23 rows and up to 10 tiers. A three-tier lashing bridge is to be installed on the upper deck. DSME has developed the following further specialised 18,000+ TEU container ships: ■■ Triple-E 18,300 TEU CTN/twin propulsion: to be delivered around June 2013. ■■ Ultra-E 18,300 TEU CTN /twin propulsion: more economic due to FOC reduction (-10%) ■■ Eco-friendly 18,300 TEU CTN/LNGfuelled: DF ME-GI engine with DSME FGS system 

Deadweight at Ts:

Complement Crew: Main Engine Type: Nominal rating: MCR:

approx. 405.0 388.9 59.0 30.3 14.6 16.0 73.0

m m m m m m m

10,200 m3 900 m3 65,000 m3

31 persons + 6 Suez crew MAN B&W 12S90ME-C_x.x 90% approx. 57,700 kW x 84.0 rpm

Power supply Diesel generators: 2 x 4,300kW, AC6,600V, 60Hz +2 x 3,800kW, AC6,600V, 60Hz Emergency generator: 1 x 500kW, AC450V, 60Hz Service Speed:

23.0 knots

Fuel Oil Consumption of main engine DFOC at NCR: approx. 198 MT Cruising range:

Main Features Main particulars Length over all abt.: Length between perp.: Breadth: Depth: Draught, design: Draught, scantling: Air draught above baseline:

181,400 MT

Tank Capacities (approximate) Heavy fuel oil: Diesel oil: Ballast water:

approx. 23,500 nautical miles

Container Capacities On deck: approx. 10,600 TEU In hold: approx. 7,600 TEU Total: approx. 18,200 TEU Rows in hold/on hatches: 21/23 Tiers in hold/on hatches: 11/10 Reefer positions (in hold/on deck): 100 FEU/900 FEU Homogeneous loading: 14,050 TEU @Homo. 10MT

container ship update NO. 1 2013 |

South Korea

Hyundai Heavy Industries – 18,000 TEU class The HHI 18,000 TEU Class container ship is the largest container vessel ever developed by HHI. The vessel is based on HHI’s advanced ship-building technology and experience. A single-skeg hull form has been adopted and optimised for various operating draughts and speeds, reflecting various clients’ needs.

Illustration: HHI

Text: Jeiwoo Jang, Hyundai Heavy Industries Co., Ltd.

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HHI 18,700 TEU.

Main design features To achieve the utmost propulsion efficiency, the vessel is fitted with a Vs (variable section) propeller and X-twisted full spade rudder developed by HHI. In addition, energy-saving devices are applied to further improve the water flow to the propeller and rudder. The vessel is equipped with the latest electronically controlled main engine and optimised to minimise FOC and CO2 emissions (EEDI) and allow economical operations. The WHRS (Waste Heat Recovery System) and shaft generator (PTO, power-take-off) are equipped to reduce the overall fuel oil consumption of the main engine and auxiliary engines in normal operating conditions. In addition, LNGfuelled propulsion and SCR (Selective Catalytic Reaction) can be adopted as an optional environmentally friendly design to reduce NOx and SOx emissions. 

12 | container ship update NO. 1 2013

Main features Main particulars Length over all abt.: Length between perp.: Breadth: Depth: Draught, design: Draught, scantling: Air draught above baseline:

Max. 400m 383m 58.6m 30.6 m 14.5m 16m 71.2m

Deadweight Deadweight at Td: Deadweight at Ts:

170,900 mt 200,000mt

Tank Capacities Heavy fuel oil: Diesel oil: Ballast water:

10,100 m3 600 m3 50,500 m3

Complement Crew: 28 Main Engine Type: Nominal rating MCR/NCR

12S90ME-C9.2 55,780 x 84.0

Power supply Diesel generators: 4,320/3,840 (kw) x 3/2(sets) Emergency generator 200 (kw) x 1(set) Service Speed Speed max Service Speed:

22 knots

Cruising range:

22,000 NM

Container Capacities On deck: 10,499 TEU In hold: 8,192 TEU Total: 18,691 TEU Rows in hold/on hatches: 21 / 23 Tiers in hold/on hatches: 11 / 10 Reefer positions (in hold/on deck) 1,000 FEU on deck/hatch covers Homogeneous loading: abt. 13,478 TEU at scantling draught (Based on 14T/TEU, full consumables, 8’6”, 45% VCG)

sOUth KOrEa

STx Offshore and Shipbuilding – 18,000 TeU class StX offshore & Shipbuilding co., ltd. has developed an 18,000 teu ultra large container vessel in compliance with the cSS code and advanced green technologies. StX developed the world’s largest 22,000 teu class container vessel using both twin and single-screw designs and its performance was verified through model tank tests in the recognised european model basin about five years ago, as a pioneer in the development of the largest container vessels.

illustration: StX

TexT: younG-dAL cHoi, STx OFFSHORe & SHIPBUILdInG CO., LTd.

››

StX 18,300 teu.

The 18,000 TeU has been designed to meet the market trends towards reducing the client’s costs and meeting the environmental requirements for nOx & SOx emissions. The hull form is optimised for multi-drafts over a speed range of 18 ~ 23 knots and fitted with advanced green technologies such as a nWCT (new Wide Chord Tip) propeller developed by STx, a twisted leading-edge rudder and ring-type wake-equalising duct. Waste heat recovery system, ballast water treatment system and shaft generator are also included. The vessel can also be delivered with an LnGfuelled propulsion concept. The accommodation is aerodynamically designed to minimise air resistance and the bulwark height is larger than on other normal container vessels to prevent damage to mooring equipment by green-water. The ship/bulwark height will make operations safer and reduce the cost of maintenance work. 

maiN fEatUrEs Main particulars length over all abt.: length between perp.: Breadth: depth: draught, design: draught, scantling: air draught above baseline: Deadweight deadweight at td: deadweight at ts: Tank Capacities heavy fuel oil: Marin gas oil: Ballast water:

Fuel Oil Consumption of main engine dfoc at ncr: 183.32 t/day (Bf 3) 401.6 384.6 59.0 30.1 14.5 16.0 68.6

m m m m m m m

170,000 tons 200,000 tons

28+6

Main Engine: type:

STX MAN 11S90Me-c9.2

Service Speed Service Speed:

Container Capacities on deck: in hold: total: rows in hold/on hatches: tiers in hold/on hatches: reefer positions (in hold/on deck): homogeneous loading:

24,200 n.M 10,610 teu 7,670 teu 18,280 teu 21/23 11/10 1,000(0/1,000) 13,358teu (at 14ton hoMo. loading)

9,700 m3 400 m3 70,000 m3

Complement crew:

Power supply: diesel generators: emergency generator:

Cruising range:

STX MAN 8L32140x4sets each 3,850kWx720 rpm 350 kw 22.00 knots

container Ship update NO. 1 2013 |

OdENsE maritimE tEchNOlOgy

Competitive advantages of ULCS

new OMT/SWS design reduces slot cost in a market characterised by overcapacity, low margins and price pressure, reducing the slot cost is a determining factor for floating your boat. drawing on experience gained from designing the Maersk e-class, danish design firm odense Maritime technology (oMt) is seizing asian newbuilding opportunities to further enhance the quality of its designs. ceo K책re groes christiansen and director of projects erik hansen discuss their new 18K teu design and its impact on slot costs as well as the competitive advantage of ultra-large container ships (ulcS). TexT: mAriAnnE wEnnEsLAnd, dnV

14 | container Ship update NO. 1 2013

illustration: dnV

OdENsE maritimE tEchNOlOgy

container Ship update NO. 1 2013 |

co. Schiller, Schiller & photo: oMt/leif

photo: oMt/Martin lund me, lundme photogra phy

OdENsE maritimE tEchNOlOgy

››

oMt ceo Kåre groes christiansen.

oMt director of projects erik hansen.

(OMT) is a spin-off from a.P. Møller’s former shipyard Odense Steel Shipyard (OSS). For more than 20 years, OSS designed and built all new generations of container ships for the Maersk Line. This included the Maersk e-Series, which until 2012 had the world’s largest container ship in operation – the emma Maersk. When Odense Steel Shipyard (OSS) was shut down, its most experienced personnel

illustration: dnV

The new 18K TeU, designed by OMT in cooperation with Shanghai Waigaoqiao Shipbuilding Co. Ltd. (SWS) and to dnV standards, has the precision and flexibility to meet a range of future scenarios. This includes solutions addressing the uncertainty related to fuel costs, speed and utilisation. established in 2010, danish ship design company Odense Maritime Technology

››

18,000 teu designed by oMt in cooperation with SWS to dnV standards.

16 | container Ship update NO. 1 2013

formed OMT and entered the market as a design firm. “To us, it made sense to continue design work and development activities here in europe, where many of the technology companies and end customers are still located,” says OMT CeO Kåre Groes Christiansen. He explains how moving new building to asian yards has provided them with new opportunities to further enhance quality. “When building ships in northern europe, it was sometimes necessary to compromise on some of the design features which involved a lot of man hours and high costs. With the Chinese cost structure, we can afford to specify a higher quality. This allows us to present the end customer with a ship of higher quality than we could have built here.” rEducEd sLot cost The OMT/SWS 18K TeU’s optimised hull form and consequent fuel efficiency are main components in the positive spin of its slot-cost equation. “We put all our experience from the designing, building and operational phases of the Maersk e-Class into developing this 18K TeU,” says erik Hansen, OMT

Odense Maritime Technology

Director of Projects. “Then we involved DNV’s Advisory Services and MARIN Maritime Research Institute (NL) to further develop the hull form.” Christiansen points out that DNV putting on its advisory hat and providing options and suggestions added great value to the design process. “A classification society sits on a lot of knowledge which, used in the right way, is very valuable when designing new vessels,” he says. Extensive CFD analysis and model testing was carried out through close cooperation between the three parties. The end result was a hull optimised for 14–18 knots. “Should the market, contrary to expectations, take a turn away from slow steaming and back towards water-skiing speed, then the 18K TEU can obviously handle a higher speed than that which it is optimised for,” says Christiansen. However, he is confident that these vessels will not operate at more than 23 knots. Amongst other 18K TEU design features reducing the slot cost is the use of antirolling tanks. A challenge with wide beam ships, like the OMT/SWS 18K TEU, is the

increased GM value resulting in more severe transverse accelerations. This reduces the ship’s loadability. The anti-rolling tanks reduce GM and allow for heavier containers to be placed higher up in the stack on wide beam ships. A single-skeg propeller has been chosen for the 18K TEU in the standard configuration. The decision was based on an extensive OMT study of propeller efficiency vs. cost benefit. According to this, a single-skeg solution will be profitable with a 7–8-year horizon. Owners with a longer time horizon can chose to go for a twin-skeg solution, with higher CapEx and reduced VoyEx. Production-friendly plated bulkheads OMT’s plated bulkheads are one of many design features derived directly from the years of close cooperation with the Maersk Line. Experience shows that this solution is more production friendly than pillar bulkheads. “The plated structure makes it easier to align the cell guides for such large vessels,” says Erik Hansen. “They also enable better ventilation of holds during operations. All in all, we feel

Odense Maritime Technology (OMT) Established in 2010, Danish ship design company Odense Maritime Technology (OMT) is a spin-off from A.P. Møller’s former shipyard Odense Steel Shipyard (OSS). For 20–25 years, OSS designed and built all new generations of container ships for the Maersk Line. This included the Maersk E-Series, which until 2012 had the world’s largest container ship in operation – the Emma Maersk. The OMT/SWS 18K TEU: On 1 February 2012, OMT signed a cooperation agreement with Shanghai Waigaoqiao Shipbuilding Co. Ltd. (SWS) to develop a new 18K TEU design. This ship is optimised for 14–18 knots/slow steaming and has a top speed of 23 knots. DNV’s key deliverables: The OMT/SWS 18K TEU is designed to DNV standards. In addition, OMT has worked closely with DNV Advisory on hull optimisation and structural analysis in order to ensure a fuel efficient and safe design.

container ship update NO. 1 2013 |

Odense Maritime Technology

OMT/SWS 18,000 TEU model.

the plated bulkheads provide better quality to our final product.” Fit for future scenarios OMT’s philosophy is to ‘design for uncertainty’. “We want to provide owners with the necessary flexibility without compromising on the quality of the original design,” says Christiansen. “Our focus is on creating an investment which remains competitive throughout its lifetime, so that the owners don’t end up with an obsolete asset.” The scalable 18K TEU is designed with the option of being lengthened through adding an extra bay, either initially or through retrofitting. Equipped with exhaust gas scrubbers and oil tanks for various types of fuel, including low sulphur, the OMT/SWS 18K TEU meets future ECA requirements. The ship is furthermore designed with a ballast water treatment system and is LNG ready. “We want to provide our end customers with an asset of long-lasting value. The LNG infrastructure is not yet mature, but that could change and the cost of LNG could outcompete that of heavy fuel oil,” says Christiansen. “If or when that game is on, our vessel can be retrofitted for LNG operation.”

18 | container ship update NO. 1 2013

OMT estimates the maximum container ship size for the near future to be around 21K TEU. Larger ships would require major investments in terminals and related infrastructure. Other limiting conditions are the dimensions of channels and straits, as well as the already reached limit on stacking weight; today’s containers are already carrying the maximum load that they are designed for. Why contract new and larger container ships in a market with excess capacity? In Christiansen’s opinion, the real question is whether or not the capacity available is the right one. He believes the demand for efficient and clean containerised transportation will remain high, and stresses that further efficiency gains per transported container will continue to be an important driver for global trade. “Reducing the energy consumption per cargo unit is an environmental and financial driver,” he says. “In the end, slot cost is the name of the game in this highly competitive situation. Through investment in ULCS, owners and operators gain a necessary competitive advantage.” 

Illustration: DNV

››

OdENsE maritimE tEchNOlOgy

››

oMt/SWS 18,000 teu model.

container Ship update NO. 1 2013 |

OMT/SWS 18,000 TEU

An ultra-large container vessel for an uncertain future The 18,000 TEU from Odense Maritime Technology (OMT) and Shanghai Waigaoqiao Shipbuilding Co. Ltd. (SWS) has been designed to meet the owner’s need for a cost-efficient and flexible container ship that remains competitive throughout its lifetime. Despite a slowdown in world trade, the global economy continues to grow and the demand for efficient and clean containerised goods transportation is likely to remain high. Larger vessels have lower building and voyage costs, resulting in a more attractive slot cost. The 18,000 TEU from OMT and SWS provides a flexible solution that deals with the uncertainties related to the fuel cost, transit speed, utilisation and environmental footprint. Text: Erik Hansen, OMT

45' CONTAINER.

55 55

23 (21R)

23 (2

23 R

No. OF 40' CONT. ACROSS

23 No. OF 20' CONT. ACROSS No. OF REEFER ACROSS

23 21

VOID FO

8520

770

22680

800

770

2030 12560

800

770

2030 12560

37270

1015

800 2030

12560

1015

770

1015

800

1600 8520

21 (11R)

21 (1

21 (11R)

21 WB 21

K AN 21 WB 21 (11R)

21 EEL H

21 (11R)

21 EEL H

21 (11R)

21 EEL H

21 (11R)

21 (1

21 (11R)

19 (1

19 (11R)

17 (1

FLAT OF

SIDE

VOID

900

51860

800

1800

770

2700

12560

12600 68250

80850

800

770

2030 12560

108000

800

770

800

770

2030 12560

800

770

2030 12560

122590

137180

2030 12560

93410

WB 1015

5280

WT. DOOR

1015

800

770

2030 12560 151770

800

770

166360

800

770

2030 12560 180950

195540

35390

››

MOORING FOR BUNKER BARGES

PILOT ACCESS PILOT LADDER SB/PS

General arrangement.

WT. HATCH (600x600) EACH BDH SB/PS

20 | container ship update NO. 1 2013 WT. HATCH - EM. EXIT (600×800)

FOR CASING AND MACHINERY ARRANGEMENT SEE DRW. : M106-101-100-000 SHEET 3

800

770

2030 12560

MOORING FOR BUNKER BARGES

21 (1

2030 12560

21 (1 WB

800

770

2030 12560 210130

2030 12560 224720

1015

TRAFO

1015

TRAFO

1015

TRAFO

1015

13 VOID

WT. HATCH

1015

6000

TRAFO

1015

#86 +10000 CASING

OMT/SWS 18,000 TEU

Main particulars Length over all, abt. Breadth, moulded Depth to Main Deck Air draught above baseline Draught, design Corresp. Deadweight Draught, scantling Corresp. Deadweight Complement (normal + Suez)

Hull design ■■ The 18,000 TEU is available in two options: 1) The single-skeg option is the right choice if the owner wants the lowest possible CapEx and OpEx cost per container slot, and 2) The twin-skeg solution is the right choice if the lowest possible VoyEx cost per container is required. ■■ The hull lines are optimised to provide high efficiency over a wide speed and draft range. The block coefficient has been selected in such a way that the vessel can be optimised within the 14–22 knots range. However, the owner has to make a choice regarding the shape of the bulb design. The vessel is delivered with a bulb optimised for an operational profile with speeds in the 14–18 knots range or with typical speeds in the 18–22 knots range. Whatever the owner decides, the ship has the option to retrofit the bulb at a later stage. ■■ The hull design is also available in two lengths. In the base configuration, the design has 18,000 container positions. However, the vessel is designed with a built-in option to extend the design at a later stage. ■■ The design minimises the need for ballast water during operations. This is a CapEx/VoyEx trade off. It makes the design more expensive to build for the yard, due to the extra steel, but the additional cost is money well spent for the owner. ■■ In the design of the steel structure, the focus has been on simplicity. For example, a plate-style bulkhead has been selected. The beauty of this solution is that it is simple to manufacture and allows the flow of ventilation air between the two cargo holds to be controlled. ■■ Slim guides have been selected to reduce the width of the vessel by more than 0.8m. ■■ Optimised for a large percentage of high cube containers without losing container slots in the holds.

Tank Capacities Heavy fuel oil (100%) Diesel oil (100%) Ballast water (for ballast condition) Ballast water high tanks

399.2 58.5 30.2 73.2 14.0 153,500 16 192,100 29 + 6

m m m m m t m t

13,000 350 42,800 9,300

m³ m³ m³ m³

Class DNV @1A1 Container Carrier, Nauticus (Newbuilding), SafeLash, DG-P, NAUT-OC, COAT‑2, E0, BWM-T, Clean, ECA (Sox-A), TMON, BIS, Recyclable (or similar ABS, LR, GL) Engine plant Main Engine MAN S90ME-C9.2-TII (de-rated) or equivalent Power Supply Diesel Generators

4 x 3,700 kW

Container Capacities Rows across max. in holds/on hatches 21/ 23 Stack weight in holds 20’/40’ 162 / 325 t Stack weight on hatches/deck 20’/40’ 81 / 160 t Average stow. of 14 tons/TEU 12,364 TEU Average stow. of 9 tons/TEU 17,998 TEU Cargo intake at design draught 139,000 t Positions Iso ( 8½’ ) On deck (tiers-pos) 10-10,528 TEU Below deck (tiers-pos) 11- 7,930 TEU Total, appr. TEU 18,458 TEU Reefer Positions (33% in holds, watercooled) 994 FEU Revision

IMO VISIBILITY IMO VISIBILITY

23 (21R)

23 R

21 DE

21 FLAT OF SI

21 WB

TRAFO

17 (11R)

11R)

15 (11R)

11R)

13 (11R)

VOID 5

11R)

13 (11R)

11R)

239310

1600 10000 250910

2030 12560 265070

2030 12560 279660

800

770

2030 12560 294250

800

770

2030 12560 308840

800

770

2030 12560 323430

1015

770

1015

800

1015

770

800

770

2030 12560 338020

770

352610

725

1600 12560 368800

500

152

152 55

55 55

50 50

BOWTHRUSTER COMPARTMENT

800

383000

172

Cruising range at medium service speed, 15%SM, Tdesign and all electr.load w/full load of reefers + shaft generator + four days. 58500

All information are subject to further detail design and model test results.

FOR ACCOMMODATION ARRANGEMENT SEE DRW. : M106-101-100-000 SHEET 2

500 55

50 172

Average stow of iso containers are calculated at even keel, scantling draught, cont.VCG 45%, no ballast water.

VOID

2030 12560

23 kn 26,000 NM 55

2438

VOID

800

1015

770

1015

800

1015

800

1000

VOID

55 55

Lashing bridges, two tiers high, arranged at all bays. Special horizontal and sloped lashing.

CHAIN LOCKER

container ship update NO. 1 2013 |

STORES HATCH 1000×1400 SUEZ HATCH

NGLE 5°

1600 12560

800

770

VOID

Illustration: OMT/SWS

FOR ACCESS CORRIDOR - SEE DRW.: 106-101-000 SHEET 2

LINE T: 14.00 m

Remarks The vessel has been designed for minimum use of ballast water in normal operating conditions.

800

LINE T: 16.00 m

2591

2896

2896 2896 2591

109 t/day (ISO)

Comme

Initials

145

1015

21R)

Performance Consumptions at 18 knot: Service speed (15%SM,Tdesign, 90% MCr) Cruising range

Date

50 50

50 172

Revision

Date

Initials

Comment

55 55

55 500

152

500

55 55

145

2896

2591

2438

50 50

172

50 50

172

50 172

Illustration: OMT/SWS

2896 2896 2591

58500

››

Midship section.

Machinery and systems ■■ The propulsion-system configuration is critical for the total fuel consumption. A number of engine configurations have been prepared for this design. All the configurations come with a number of retrofit options to provide the required flexibility. ■■ The machinery and systems are optimised for the most likely operating profile within a speed range of 14–20 knots. However, the propulsion configuration may later be retro fitted for a higher speed if the market changes. ■■ Energy-saving technology with a payback period of less than six years is embedded as standard: – An exhaust gas waste heat recovery system to generate steam from the heat in the auxiliary diesel generator during a stay in port. Less fuel is burned in the oil-fired boiler. – A shaft generator. The main engine is a more efficient power plant than a diesel generator. The design therefore

IMO BLIND ANGLE 5°

OMT/SWS 18,000 TEU

VOID

22 | container ship update NO. 1 2013

VOID

contains a shaft generator to provide power for reefer containers. ■■ Energy-saving technology with a payback period of more than six years is offered as a newbuilding option or can be retrofitted. ■■ The design is prepared for waste-heat recovery. ■■ “LNG-ready” design. The design can be LNG powered from the start. Alternatively, a decision regarding LNG can be postponed until the business case for LNG is more certain than it is today. The design is therefore prepared for a later LNG retrofit. ■ ■ “Scrubber-ready” design. As an alternative to LNG, the WB design is also prepared for a scrubber retrofit. The Cdecision regarding a scrubber can be postponed until the business WB case for a scrubber versus LNG is more certain than it is today. FO

VOID

Illustration: DNV

OMT/SWS 18,000 TEU

››

Cut-through section showing support bulkheads. The bulkheads are arranged with flat panels to facilitate alignment of cell guides.

Efficient Operations ■■ The design has been fitted with an optimised lashing arrangement and anti-rolling tanks. This will give the operator a high degree of flexibility in loading containers and, as a result, the operator will have actual payload in more containers on the hatches. For the same reason, the hatches have been designed to allow a higher stack weight. This will have an effect if the slot cost index is calculated based on the number of payload containers and not just nominal container slots. ■■ Senior captains have been involved in order to develop an optimised and compact mooring arrangement. ■■ OMT is committed to ensuring that owners get the expected benefits during operations. A good design is not always enough. Proper implementation in daily operations is also required. In order to reduce fuel consumption during operations, the crew needs to use the various systems

installed in an optimum way. OMT has developed a software tool that can help the crew optimise the use of the main engine, waste heat recovery system and diesel generator based on the actual route and time schedule.

container ship update NO. 1 2013 |

Shanghai Waigaoqiao Shipbuilding

Waigaoqiao goes for 18K TEU Shanghai Waigaoqiao Shipbuilding Co., Ltd. (SWS) is one of China’s leading shipbuilding companies, with vast experience from the tanker and bulk segment and 33 very large crude carriers on its list of merits. In 2012, the company entered into cooperation with Danish design firm OMT to develop an 18K TEU ultra-large container ship. Chief Engineer Tao Ying discusses market trends and the role of SWS and China in the world of ultra-large ships.

Illustration: DNV

Text: Yin Hong Bo Hubert and Pål Wold, DNV

››

OMT/SWS 18,000 TEU.

SWS has a strong position outside the ultra-large container ship segment. Which do you think will be the key success factors when developing the ULCS newbuild activity at SWS? We understand how important it is to be prepared on the ship technical side. We have been visited by many owners and they all say that we are ready and have the capacity to build ULCS. Our track record for large ships in the tanker and bulk segments is well known in the industry. However, since we lack a track record for container ships, we really just need to have the opportunity to prove ourselves and a

24 | container ship update NO. 1 2013

‘brave’ owner would be welcomed. But we really believe it is just a matter of time before orders start to come in.

ULCS sizes in order to have a larger design portfolio.

The 18K design has been developed in cooperation with OMT. What has this experience been like for you?

Building bigger ships represents technical challenges. What in your view are the most prominent ones? How can these challenges best be tackled?

We’re pleased with the cooperation with OMT. It has been very good for our technical staff to get fresh input from a wellestablished designer. By working closely with OMT technical experts, we have received valuable input on design trends. And we’re working together not only on the 18K TEU design but also on other

We see no obvious challenges. The CSSC group has already both design and building experience for ULCS, and as a member of this group we have access to this knowledge and dialogues have already been established. Hence, we are technically prepared. Our focus is on the building period.

shaNghai waigaOqiaO shiPBUildiNg

years are more active now. For owners with older and less fuel-efficient ships, times will be harder and they will soon be forced to make a choice about their newbuilding plans.

››

chief engineer tao ying, Shanghai Waigaoqiao Shipbuilding co., ltd. (SWS).

some designers claim ‘fuel efficiency’ to be the key driver when developing new designs. how do you see this trend in the future? We fully agree that fuel efficiency is very important for the new ULCS designs. High fuel costs are still expected in the future and in addition we need to consider the environmental impact. The owners’ focus will be very much on saving costs in order to be competitive in the future. One way is to optimise the design itself (i.e. optimising the hull, propeller, etc), but another important way to save cost is slow steaming. The combination would result in a very low cost per transported TeU for the owner. a ‘two-tier market’, where new fuelefficient designs yet to be delivered will compete with the recently delivered designs, may be part of a future scenario. how, in your opinion, will container ship owners adjust to this new reality? The two-tier market is a dilemma for the owners and not just those in the container segment. It is a difficult decision for owners – to order or not? newbuildings would be more fuel efficient, but what are owners to do with their existing fleet? We see that owners who did not order in the boom

The trend of increasing ship size applies not only to container ships, but to all ship segments. Larger ships always have an advantage over smaller ships regarding the unit cost of transportation. and with slowsteam operations, larger ships are even more beneficial than smaller ones. how do you see the container newbuild market developing in the coming years? We are now studying the container ship market and foresee some positive trends for newbuildings. However, it will not be like the boom of some years ago. The outlook for newbuildings in the ULCS segment is especially promising. newbuilding prices are now near the bottom, so the timing for placing orders is good, particularly for owners who are in a strong financial position and can get bank credit finance. In addition to low newbuilding prices, owners today get fuel-efficient ships which will put them in an advantageous position and push old tonnage out of the market. Korea is presently the biggest builder in the Ulcs segment. how do you see china’s role in the future? For the time being, Korean yards are leading in the ULCS segment. However, we are working hard to close the gap. The biggest advantage the Korean shipyards have is their building efficiency, which means they can deliver ships more quickly. This challenge is really one that we focus on. However, on the ship-technical and fuel-efficiency sides, we see no obvious obstacles. 

photo: SWS

why do you think it is important to focus on the very big container ships?

shaNghai waigaOqiaO shiPBUildiNg cO., ltd. founded in 1999, Shanghai Waigaoqiao Shipbuilding co., ltd. (SWS) is a subsidiary of china cSSc holdings ltd., a listed company owned by the china State Shipbuilding corporation (cSSc). the company focuses on shipbuilding and offshore engineering and, on the maritime side, has so far delivered 121 bulk carriers, 65 oil tankers and 33 very large crude carriers (Vlccs). Since its formation, SWS has stated its goal of creating a green brand and building world-class products. examples include the popular 170,000 dWt-class green capesize Bulk carrier developed by the company. the company has about 650 employees doing design and engineering work. SWS originally specialised in building large bulk carriers and tankers, but has recently also built fpSos, drilling rigs, jack-ups and drill ships. SWS promotes the spirit of ‘study, innovation, solidarity and excellence’ and the value of ‘common development of the employees and the company’.

container Ship update NO. 1 2013 |

18,000 TEU design

An 18K TEU designed to DNV standard – a safe, reliable and efficient design The OMT/SWS 18,000 TEU design has been evaluated against the highest design level in the new DNV standard to ensure that all critical structural details are adequately designed to meet stringent fatigue and strength requirements. DNV Maritime Technical Advisory Services has also assisted OMT in the optimisation of hull lines in order to develop a fuel-efficient design and has carried out extensive calculations to assess the vibration level on the ship. Text: Serge Schwalenstocker, Tormod Landet, Eileen Mandt, He Jiang and Vebjørn J. Guttormsen, DNV

DNV has invested heavily in R&D and the development of rules and services related to the container sector. In 2011, DNV released a new set of rules and supporting software tools for container ships.

Hull optimisation DNV has worked on the hydrodynamic performance of the 18,000 TEU ULCS design in cooperation with OMT, SWS and MARIN. DNV supported MARIN’s hulloptimisation work by providing analysis results and suggested modifications, while MARIN executed the hull-shape modifications based on a combination of its own and DNV’s analysis results and suggestions. As for the rest of the container industry, the mega carriers are expected to operate at lower speeds in the years to come. An operating profile with speeds ranging from 14 to 22 knots combined with a range of drafts was used for the optimisation. At the same time, the vessel should be able to reach a top speed of 23 knots.

26 | container ship update NO. 1 2013

The block coefficient (Cb) study Prior to detailed hull optimisation, a study on the optimum Cb was conducted to see the effect of varying the ship fullness. A high Cb will allow for a higher container intake but will also require more power to propel the ship. The power per TEU was calculated with Cb variations of between 0.66 and 0.70. It is evident that a higher Cb would give higher resistance but, at the lower speed at which we expect the vessel to operate, the penalty is smaller than the gain coming from the added intake capacity. At speeds of 18–19 knots, the added power per TEU is in the range of 5–6% for a block of 0.66 instead of 0.70. See Figure 1. Hull-line optimisation With the given Cb and main dimensions, the hull was further optimised by using advanced Computational Fluid Dynamics (CFD) to find a hull form with minimum resistance to fulfil the operating profile. A 3D RANS CFD was used to study the physical

effects occurring at five selected operating points. The wave profile, wave cuts and pressure distribution were then used to determine suggested modifications to the hull shape in order to reduce unwanted physical effects. Special attention was given to the fore ship and how the water will meet and flow along the bow. Experience from previous projects has shown that huge fuel savings can be achieved by improving the bulb design to reflect the new slow-steaming environment. See Figure 2.

Load and response a nalysis DNV has applied the Level 3 containership analysis methodology from DNV Classification Note 31.7 to verify the OMT 18,000 TEU container-ship design. Level 3 is a comprehensive analysis level including global FE analysis with direct calculated wave loads. The aim of the analysis is to ensure that all critical structural details are adequately designed to meet fatigue and strength requirements. See Figure 3.

18,000 TEU design

Figure 2: A lowered bulb with more volume was proposed in order to improve the efficiency at low draft and low speed.

The main tasks in the Level 3 analysis are: ■■ Finite element modelling of the whole ship (global model) and specified local details where experience shows that failures related to ultimate strength (yield and buckling) or fatigue strength (cracks) typically appear ■■ Hydrodynamic analysis to obtain real ship-specific sea pressures and accelerations ■■ Ultimate Limit State (ULS) analysis to find any areas where the calculated stress exceeds the allowable stress during the lifetime of the vessel ■■ Fatigue Limit State (FLS) analysis to find any areas that have a high probability of experiencing fatigue cracks during the lifetime of the vessel

Relative diff. powering per TEU – OMT70 8% 7% 6% 5%

Relative [%]

››

OMT 66

3% 2%

OMT 68

OMT 70

Direct calculated wave loads and response Based on direct hydrodynamic analyses, two loading conditions were selected in order to find the maximum still water midship hogging moment and the highest torsional moment. A typical deformation plot for the

–1% 18

18.5

19.5

20.5

21.5

Speed [knots]

››

Figure 1: Relative increase in power per TEU compared to a Cb of 0.70.

container ship update NO. 1 2013 |

18,000 TEU design

››

Figure 3: Global final element model.

››

Figure 4: Maximum hogging condition.

maximum hogging condition can be seen in Figure 4. The maximum combined hull girder stresses are then calculated in order to examine the hull structural response and acceptance according to DNV’s requirements for buckling, yield and fatigue. Detailed analysis for selected details Special attention is given to areas which are highly utilised and where the probability of failure is high, such as the coaming and hatch corners. Girders and other structures in the bottom can typically also experience problems. The Level 3 analysis puts a special focus on these areas, including fine-mesh

28 | container ship update NO. 1 2013

models to accurately capture the strains and stresses experienced by these highly loaded details. Novel design approach The highest Level 3 analysis is recommended for novel designs where experience from ships in operation is limited. By running a full stochastic analysis, all relevant ocean waves are included, giving a better picture of the vessel’s capacity than a simplified approach. The cost of running such an analysis is obviously higher than a traditional rule-load analysis, but this is a relatively small investment compared to the cost of potential problems that can occur at a later stage.

Nauticus (Newbuilding) The 18,000 TEU has also been reviewed against prescriptive requirements of the DNV Rules. A ½+1+½ container-hold analysis has been carried out for typical structures in the midship area, in accordance with Nauticus (Newbuilding) requirements. The typical structural arrangement for container ships is to have a watertight transverse bulkhead for each two 40-foot-container lengths. In the middle, a non-watertight support bulkhead is arranged designed as a truss system with vertical girders arranged as pillars connecting the double-bottom structure to the cross-deck structure and horizontal stringers are arranged to stabilise the truss system.

Images from DNV Sesam Structural Model

18,000 TEU design

››

Figure 5: Plate-type support bulkhead.

››

Figure 6: Typical global torsional vibration mode.

With increased support-bulkhead dimensions, it will be more difficult to control cell-guide alignment during construction. A plane-type non-watertight bulkhead has therefore been introduced by OMT/ SWS to make a more production-friendly design. See F igure 2 for an illustration. With a plane-type support bulkhead, the connection of the bulkhead to the double bottom structure will also lead to fewer hard points with high-stress concentration. See Figure 5.

Favourable design for noise and vibrations Noise and vibration problems are often observed on big container ships. Both

propeller and main engine excited vibration may result in problems due to high power and speed. In order to ensure a favourable design, DNV has conducted extensive calculations of the vibration level on the OMT/SWS 18,000 TEU container ship. With the superstructure located well away from the excitation sources, the crew members may look forward to a comfortable “cruise”. The global vibration analysis carried out shows that vibration levels comfortably within the vibration limits of DNV Comfort Class may be expected on board. The long distance between the major noise sources and the accommodation also indicates a pleasant noise situation in the living

quarters, although no detailed noise study has been carried out. A Finite Element Model of the complete vessel has been utilised for a natural frequency and forced response analysis. Engine forces and moments together with the pressure forces from the propeller were applied in the aft ship. The six-bladed propeller (ensuring excitation frequencies above the fundamental hull-girder vibration modes), combined with the favourable location of the superstructure, results in comparatively low calculated vibration levels in the accommodation areas. See Figure 6. 

container ship update NO. 1 2013 |

Twin skeg versus single skeg on ULCS

Twin skeg versus single skeg on ULCS During the autumn of 2012, DNV conducted a cost benefit analysis of a twin skeg solution versus a single skeg solution for an 18,000 TEU ULCS. Based on an assessment of the impact on required power, it was found that a reduction of 6% in required power is achievable. Text: Serge Schwalenstocker, Jaeouk Sun & Anders Thoresson, DNV

The study has shown that the most important factor determining the payback time for a twin skeg solution is the average speed at which the vessel is expected to operate. In the current slow-steaming regime, a twin skeg solution will have a payback time of more than six years. However, if the average speed on the FE-NE route is increased to e.g. 20 knots, the payback time is reduced to four years. Why twin skeg? Container ships are gradually increasing in size to take advantage of economies of scale. This has led to the development and ordering of vessels up to 18,000 TEU. The increase in size leads to demands for even larger machinery and greater power output to the propeller. The high loading of propellers leads to reduced propulsive efficiency and also increases the risk of excessive cavitation and of vibrations. A way to remedy these factors is to consider a twin screw solution fitted with a twin skeg. So far “all” container vessels up to 15,000 TEU have been single screw vessels. But with the Maersk Line’s order of a Triple E, we saw the introduction of a twin screw solution for a ULCS. However, as a result of the financial crisis and overcapacity of container ships, a significant reduction in average speed has been seen in the container trade during the last 2–3 years. This has the opposite

30 | container ship update NO. 1 2013

effect on the amount of power delivered to the propellers, and we are seeing reductions in installed power on ULCS. The increased vessel size and power indicate that a twin screw solution is needed, but on the other hand a reduction in speed indicates that it may not be needed. For this reason, DNV conducted a research study comparing the performance of a twin skeg versus a single skeg propulsion system for an 18,000 TEU ULCS in the autumn of 2012. Key areas to consider A comparison of a twin skeg to a single skeg needs to encompass all the key areas that would be affected, both technical and financial. This includes the impact on hull resistance, hull efficiency, propeller efficiency, machinery efficiency, cargo slot impact, added CapEx and OpEx. Case vessels and route An 18,000 TEU container ship operating in an FE-NE route was used as the basis for the study. The ship is able to reach speeds of 22 knots, but will operate at lower speeds. The length, beam and draft are maintained constant for the sake of comparison. See Figure 1. Impact on resistance Adding a skeg to the aft of the vessel is expected to have a negative impact on the vessel’s resistance. At this stage, two basic hull designs were

developed to assess their relative resistance. The main contribution to a change in resistance comes from the added wetted surface. Several other components may also cause a change in the resistance. But the careful design of the twin skeg aftship is expected to minimise other effects, and these are as such considered to be secondary effects. A twin skeg solution will also move the LCB further aft, which one would expect to reduce wave-making resistance. But, in this case – a vessel of approximately 390 metres sailing at 20 knots – the wavemaking resistance is in the magnitude of 5–10% of the total resistance. As such, the impact of moving the LCB aft is expected to be negligible. It does, however, open up for changes in the foreship volume distribution which could have a positive impact, but this has not been investigated in this study and the foreship shape has been kept identical. Based on this assessment and measurements of the basic hulls, a 4.9% increase in resistance is found for the twin skeg solution. This added resistance is constant over the entire speed range. Hull efficiency Traditionally, converting to a twin skeg solution has a large impact on propulsion characteristics, and in particular on wake and thrust reduction. All empirical formulas also indicate this. However, one major difference when

Twin skeg versus single skeg on ULCS

Figure 1: Aft ship lines for a single skeg and twin skeg design.

Wake fraction / Thrust reduction / Hull efficiency

››

Optimum propeller diameter

w Twin skeg

ETA EtaH

Twin skeg

Dopt

1.2*D 1.1*D

D RPM

ULCS

Aftship fullness

››

Tanker

Figure 2: The effect of hydrodynamic properties on a twin skeg slim line ship and a full body ship.

investigating this is the size of the vessel and the skeg fullness of a ULCS. For a tanker or bulk carrier, going from a single to twin skeg would reduce the hull efficiency due to the reduction in skeg fullness. For a ULCS, the move from single to twin skeg does not have a significant impact on the skeg fullness, since the single skeg has an inherently slender shape. Hull efficiency is made up of the relationship between the wake fraction (w) and thrust reduction (t). Large single skeg container vessels have a low w and

››

Figure 3: Propeller efficiency as a function of diameter and RPM.

t and will not experience any significant reduction in these, so the change in their relationship will be negligible. See Figure 2. Again, this requires the careful design of the aftship, since a bad design could potentially severely reduce the hull efficiency of a twin skeg solution. Machinery A switch from single to twin propulsion lines will require two engines equalling approximately 50% of the single propulsion line solution. For this study, a MAN B&W 12S90ME was chosen for the

single skeg solution and a twin MAN B&W 7G80ME was chosen for the twin skeg solution. Recent developments within this area have resulted in engines that are able to deliver high output at increasingly low RPM, with the MAN B&W G engines and Wärtsilä X engines being the most commonly used engines for such properties. To enable higher propeller efficiency, the main parameter is the diameter. A larger diameter gives higher efficiency if the RPM is reduced at same time. Therefore, the development in engine technology

container ship update NO. 1 2013 |

Twin skeg versus single skeg on ULCS

is an enabler for increased propeller efficiency. Propeller Since a large propeller diameter will give high propeller efficiency, we have kept the diameter when going from single to twin screw system. By keeping the diameter, the propeller disc area will be doubled and the propeller loading (thrust per disc area ratio) will be halved. The low loading of the propellers is the reason for the increased efficiency. To obtain the full benefit from the big diameters, there are other parameters that have to be changed. For a given propeller diameter and power, there is an optimal RPM in respect of propeller efficiency. This optimal RPM will decrease with decreased power. Another parameter that has an impact on the optimal RPM is the number of blades. A lower number of blades gives an increased optimal RPM. See Figure 3. By choosing the engines with the lowest RPM and reducing the number of blades, our case ended up with a large increase in propeller efficiency. The B-series was used for the optimisation and selection of propellers. Further work on the propeller designs would increase the propeller efficiency. However, that is the case for both the single and twin propellers, so the relative performance would not see any significant change. The following main characteristics were found based on the B-series propellers: Single skeg Twin skeg Diameter 9.8 m 9.8m Number of blades 6 4 RPM at service speed (20 knots) 70.4 60.4 Area ratio 0.78 0.48 Open water efficiency 0.61 0.68 (11% improvement)

Based on this, an improvement in open water efficiency of 11% was found. This is achieved due to the reduced loading, RPM and number of blades. Since the propellers will follow their respective propeller curve, the relative impact will be constant across the entire speed range.

32 | container ship update NO. 1 2013

››

Figure 4: Twin skeg (left) and single skeg.

Cargo capacity By going from one long twelve-cylinder engine to a twin engine solution with seven cylinders in each engine, the length of the machinery room can be reduced by approximately one container bay. This opens up for a redistribution of cargo bay slots, allowing more cargo slots within the hold in the case of a twin skeg solution. In sum, the required engine room volume is increased with a twin engine solution, but the hull volume may be utilised more effectively. A study of slots within the cargo hold was made based on the selected engines to investigate the change in cargo slots. The aftship profile is kept identical for the two designs, and as such only the cargo bays surrounding the engine rooms are of interest. Based on our analysis, there is a gain in cargo slots forward of the engine rooms and a loss of cargo slots aft/side of the engine room. But in total we see a gain of 140 TEU cargo slots in the cargo hold if a twin engine solution is chosen. See Figure 4.

Financial scenarios The study revealed that there are three main drivers to the payback time of a twin skeg solution; added CapEx, average operating speed and income from added slots. Based on this, variations have been developed and are presented in Figures 5–7. Moving to a twin skeg solution has a significant impact on the CapEx. Based on input from yards and owners, added CapEx of USD 7–11 million has been found to be what one would expect. In addition, a twin propulsion line will impact on the OpEx by increasing the maintenance costs and the need for added crew due to the twin engines’ maintenance requirements. It is evident that there is a large spread in the payback time due to the uncertainty related to the key factors. Which case one chooses depends on the individual’s belief in the market in the coming 10–20 years. But, when looking at what we believe to be the most likely scenario, a payback time of six years is expected for a twin skeg solution. 

Twin skeg versus single skeg on ULCS

$10,000,000 $8,000,000

Discounted cash flow

$6,000,000 $4,000,000 $2,000,000 Years

$0 –$2,000,000

–$4,000,000 –$6,000,000 –$8,000,000 –$10,000,000 DNV base case scenario

››

DNV base case no slots

Figure 5: Slot cost sensitivity.

$20,000,000 $18,000,000 $16,000,000 $14,000,000 $12,000,000

Discounted cash flow

$10,000,000 $8,000,000 $6,000,000 $4,000,000 $2,000,000 Years

$0 –$2,000,000

–$4,000,000 –$6,000,000 –$8,000,000 –$10,000,000

Economic scenarios • Fuel price USD 600 or 700 • Average round trip speed 16 kts and 20 kts • Added investment USD9.0M • Added OpEx 250,000 USD/year – Maintenance 200’ USD – 1 crew 50’ USD • Cargo hold load factor 80% • Slot value 1,200 or 1,500 USD/loop

–$12,000,000 DNV base case scenario

››

DNV economic boom

DNV economic downturn

Figure 6: Revenue sensitivity.

$12,000,000 $10,000,000 $8,000,000

Discounted cash flow

$6,000,000 $4,000,000 $2,000,000 Years

$0 –$2,000,000

–$4,000,000 –$6,000,000

Base case • Fuel price USD600 • Average roundtrip speed 18 kts • Added investment USD 9.0M • Added OpEx 250,000 USD/year – Maintenance 200’ USD – 1 crew 50’ USD • Cargo hold load factor 80%/0% • Slot value 1,400 USD/loop

Investment cost variation • Fuel price USD 600 • Average roundtrip speed 18 kts • Added investment USD 9M, 11M • Added OpEx 250,000 USD/year – Maintenance 200’ USD – 1 crew 50’ USD • Cargo hold load factor 80% • Slot value 1,400 USD/loop

–$8,000,000 –$10,000,000 –$12,000,000 –$14,000,000 DNV base case scenario

››

Figure 7: CapEx sensitivity.

DNV High CapEx case

DNV Low CapEx case

Financial basics • Rate 10% • Fuel cost adjusted yearly by EIA oil price evolution • 270 sailing days per year • 5 FE-NE roundtrips per year

container ship update NO. 1 2013 |

springing and whipping

Can your container vessel sustain whipping? Wave-induced vibrations in hull girders were first reported in 1884. For more than a century, seamen have experienced that their ships occasionally shudder or shiver in waves. This happens especially when heading into the waves. Today, this is still not handled explicitly in ship design rules and the question is: how do these vibrations (whipping and springing) affect fatigue cracking and the risk of hull girder collapse? Some may say that the effects are covered by the safety margin and choose to ignore it. A relevant question is: can your container vessel handle the whipping it is being exposed to? Text: Gaute Storhaug, DNV

What is springing and whipping? A common term for springing and whipping is hydroelasticity. This term was introduced in 1959 and refers to the structure being elastic and the hydrodynamic loading being affected by the structure not being rigid. In other words, there is a mutual interaction between the wave loads and the structural response. The structure responds to waves by deforming and/or vibrating. Both effects are hydroelastic, while only the latter is referred to as either springing or whipping. The former effect is neglected in loading computers, which may explain why the draft in still water at forward and aft perpendicular can be correct while there is a deviation amidships. The vessel is quite simply bent! This effect also occurs in waves, even when there are no vibrations present. The hydroelastic effects are difficult to handle in codes/numerical tools and the best tools are not very reliable or efficient in use, which may explain why effects like springing and whipping have not yet been implemented in ship design rules. Since 1994, a conference devoted to this topic has been arranged every three years. The latest was arranged in Tokyo in September 2012 (www. hyel2012.com). This has been a conference for the world’s leading experts, but the industry is participating more and more.

34 | container ship update NO. 1 2013

Whipping is caused by wave impacts, a general term covering several excitation components, one of which is slamming. For a tanker and bulk carrier, slamming is not the dominant source of vibrations, but bow flare slamming is well known on container vessels (bow flare: the non-vertical sides of the bow, where the hull hangs out above the water line because of the desire for a broad deck area for the containers). The slamming can be observed by a lot of water spray occurring, especially when the vessel is heading into steep waves. Stern slamming may also occur and has caused local damage due to high localised pressures, but it mainly occurs in stern to beam seas at low to zero speed. The whipping is felt on board as sudden vibrations that last for about two seconds on a 300-metre vessel and decay slowly due to damping (dissipation of energy). On the bridge, this can also be felt as an aft-forward vibration, because the tall superstructure is attached to the hull girder at about the aft quarter length, where the vibration shape results in more rotation than vertical motions (see Figure 1). On a container vessel, the whipping can occur in bow quartering to head seas with similar magnitudes and it tends to increase at higher speeds and in steep sea states. Springing is caused by oscillating loads along the hull, where the meeting

frequency of the hull coincides with the lowest natural frequency (springing frequency) of the hull girder, corresponding to the 2-node vertical shape in Figure 1. This is referred to as linear springing and gives resonance (like when a washing machine shakes when the rpm exceeds its natural frequency). For a vessel sailing in head seas at 20 knots, it is waves with a period of about four seconds which linearly excite these resonance vibrations. These are small waves in the order of 0.5–1.0 metres high, which are “ripples” for a large container vessel. There is also nonlinear springing occurring due to bow reflection (important for tankers and bulk carriers), the ship sides not being vertical and the bulb. The most important nonlinear effect is caused by sum frequency effects, i.e. by waves with an encounter frequency which is half of the springing frequency. These waves may have a period of 6–7 seconds and be 1–1.5 metres high. They have more energy than the wave-exciting linear springing. The parameter that limits the resonance vibration in springing is damping, which is much higher on container vessels than on tankers and bulk carriers. The springing vibrations are thereby relatively low and not the main concern for container vessels. The damping is affected by the containers on board and is thereby greater for a large container vessel than for a small one.

springing and whipping

››

Figure 1: The governing vibration shape (2-node vertical), with vertical motion along the hull but also aft-forward at the superstructure. The vibration shape causes an additional bending moment which is maximum amidships.

Figure 2: Vibration cycles superposed on wave response frequency cycles (WF). In this case, a whipping event occurs in sagging (negative values) at about 2,885 seconds and the vibrations decay due to damping. The vibrations are still present in hogging.

150 100

DLP [MPa]

Total WF

0 –50

–100 –150 2,870

How do springing and whipping affect fatigue cracking and the risk of collapse?

2,890 2,900 Time [s]

2,910

2,920

››

Figure 3: Wave frequency response (WF) and vibration response (HF) occurring at very different frequencies for a small vessel. [rad/s] is 2⋅π times the frequency in Hz.

250 SS2(ωe)

For both springing and whipping, the 2-node vertical vibration mode is governing (see Figure 1), but for larger container vessels the torsional or mixed torsionalhorizontal bending shape may also be associated with low natural frequencies in the order of 0.5–1.0Hz (1–2 seconds). These may also be excited but, because of the containers on board, the damping for these vibration shapes is even larger and the resonance vibration is not a significant issue. For this reason, whipping is perceived as the important vibration effect on container vessels.

2,880

200 150 100 50 0 0

WF response

ωe [rad/s]

HF response at 1.1Hz

Broad band process à Cycle counting by Rainflow counting When it comes to fatigue cracking, the high-frequency vibration cycles from springing and whipping occur simultaneously and are superposed on the wave response frequency cycles (see Figure 2). The frequencies related to the wave response refer to a band between 0.05 and 0.2Hz (5–20 seconds) and the band for the vibrations is between 0.5 and 1Hz. Fatigue damage may be calculated separately for each of the frequency bands by assuming a narrow band process (it is like a radio; each channel is related to a certain frequency band and vibrations occur at one frequency band and wave response

cycles at another). However, the sum of all this damage is less than the real fatigue damage. This is because many of the vibration cycles are superposed on the wave frequency cycles. The combined process is said to be broad banded and Rainflow counting is a recognised and widely used method to calculate the fatigue damage from broad-banded processes (see Figure 3). This method calculates all the small and large cycles contributing to the fatigue damage and is used on the time series of

stress, which is measured by, for instance, a hull monitoring system on board or model tests or produced by numerical simulations. It turns out that the vibrations on top of the wave response cycles contribute most to the vibration damage. For example, if the wave response cycles give an amplitude of 10 and the vibration cycles give an amplitude of only 10%, i.e. 1, then the combined amplitude is 11. The fatigue damage goes with the loading to

container ship update NO. 1 2013 |

springing and whipping

the power of 3.5, so the increase in the fatigue damage is then (11/10)^3.5=1.40. Hence, the small vibration cycles, giving a 10% increase in the amplitude, lead to a 40% increase in the fatigue damage. This 40% increase is referred to as the vibration damage. The small 10% amplitude vibration cycles on their own do not result in significant vibration damage. Considering all the sea states encountered by a vessel, frequent small “storms” (Beaufort 5 and 6) contribute most to the fatigue damage. Most of the fatigue damage comes from head and bow quartering seas. These are not encountered every day, but typically 1–2 times per six-week period. Whipping and springing are typically present when the vessels encounter these “storms” in head to bow quartering seas. The vibration damage may contribute 20–70% to the total fatigue damage of fatigue-sensitive details depending on the trade and ship design. An example is shown in Figure 4. Recent research suggests that the Rainflow counting method can occasionally be conservative, and that the large whipping cycles may be more important than the smaller springing cycles. The research is not conclusive and will be continued, as it is not desirable to overestimate the fatigue damage in general and the vibration damage in particular. When it comes to the risk of collapse, the springing cycles may be neglected, but the large whipping cycles are superposed again on the wave response cycles. For container vessels, the whipping occurs in head and bow quartering storms when the bow dives into steep wave crests. The whipping starts in the sagging cycle, but due to the low damping the whipping vibrations have only decayed slightly (10–20%) when entering the hogging wave response cycle (see Figure 2). Often extreme storms with a significant wave height of around 15 metres are considered in the design work. These are rare and have so far not been reported from measurements, but could be encountered if the vessel is not doing any routing to avoid it. The vessel speed in these storms

36 | container ship update NO. 1 2013

Vibration damage

Wave damage

0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 1

››

Figure 4: Fatigue damage as a function of heading from head (1) to stern (6) seas with 30-degree steps for a Panamax vessel. The vibration damage (red) is disregarded in design. The fatigue life was about 15 years for this vessel in its trade.

is low and assumed to be close to zero knots. In reality, captains try to avoid storms with significant wave heights of more than seven metres in the North Atlantic and, in general, they start routing to avoid storms with significant wave heights of more than five metres as the forecasts contain significant uncertainty. From model test and full-scale measurements, it seems that sea states with significant wave heights of 6–9 metres in head seas or bow quartering seas at high forward speed, sometimes up towards 17 knots (depending on the vessel), are in reality the worst sea states. The whipping and relative motion (between vessel and water surface) in the bow part increases significantly with increased speed. A rule of thumb is that the whipping response increases with the square of the speed, hence going from ten to twenty knots may increase the whipping four-fold. The whipping may be perceived as quite dramatic on the bridge and horizontal accelerations have been measured suggesting that people on the bridge may

fall if not grabbing on to something. For this reason, the captain also reduces the speed voluntarily. Still, combined wave and whipping loading well above design levels has frequently been measured (annually), including on the Asia–Europe trade, where a limited number of storms are encountered. This is causing concern because the larger container vessels often operating on this trade have more flare and higher speed capability than Panamax vessels operating in the Trans North Atlantic trade. Assuming that the whipping contributes to collapse, the safety margin for collapse may be significantly reduced compared to the design values. The increase in the dynamic loading due to whipping compared to design values may be anything from 1.3 to 2.3 depending on the design and trade (even tankers may have 1.3). An example of a vessel with a high strength but low amount of whipping is shown in Figure 5. However, it is not yet confirmed that whipping effectively contributes to collapse, even though this is commonly

springing and whipping

Whipping

WBM

SWBM

16,000 14,000 12,000 10,000 8,000 6,000 4,000 2,000 0

Load

Capacity

››

Figure 5: A small vessel with low service speed and small bow flare angle. Over five years, the collapse capacity exceeds the measured loads by 41%. On the load, the still-water hogging moment is superposed with the wave hogging moment and the whipping in hogging.

assumed today. The whipping half cycle in hogging has a duration of about one second (see Figure 2). Is this sufficient time to cause progressive collapse failure as happened on the MSC Napoli? It should, however, be remembered that the still-water loading condition is static and the vessel is thereby in hogging condition already. The wave loading may then result in an additional dynamic hogging cycle with a period of about 5–10 seconds (see Figure 2). The vessel is thereby already highly loaded in hogging condition. The question is then if the whipping cycles superposed may trigger the collapse even though it is not fully effective. In addition, the whipping cycle repeats a few times during this hogging peak. This behaviour is complicated, and proper dynamic collapse assessment has not yet been carried out to confirm the change in collapse strength due to whipping loading or the effectiveness of the whipping cycles in collapse. This research will probably continue to be a challenge over the next decade, but is it wise to wait for the answer?

How to handle this in design and operation? DNV has three approaches to evaluate the risk of fatigue and collapse due to springing and whipping in designs. In the early design work, empirical relations for fatigue and extreme loading have been established based on model tests and full-scale measurements, and the vibrations are superimposed on the vertical bending moment only. Collapse assessment in torsion and vibrations in torsion are considered less relevant and neglected. When it comes to the effect of vibration, the flare shape is most important, thereafter the speed and finally the vessel length. The vessel length refers to the flexibility of the vessel, i.e. the natural frequencies of the vessel, and it is a misunderstanding that only size matters. We have seen that some of the most challenging vessels are not the u ltra‑large container ships, but ships already sailing between Asia and Europe as well as in the North Pacific.

The Panamax vessels with long experience are the best. For design verification, model tests and numerical calculations can be carried out. The former is more accurate and the latter should be carried out with care. In both cases, it is regarded as necessary to consider real experience and not only some artificial or rare design events which may occur on tankers and bulk carriers. The consequence depends on the ship trade and ship design. The trade is incorporated by considering the trade-specific wave environment using, for instance, the DNV tool RoutSim (accounting for whipping and springing is currently voluntary, so there is no need to consider the North Atlantic if the vessel is designed for the Asia–Europe trade). In operation, the best way of handling the whipping and springing is by hull monitoring. DNV has a classification notation which works well for container vessels and this is referred to as HMON(), where the brackets include the list of sensors installed. There are associated DNV rules covering requirements as to components, documentation, installation and maintenance. It is important only to use r ecognised suppliers with approved systems, as the standard varies and many suppliers offer systems that have not been approved. It is also important that the data is a utomatically processed on board and stored so that it can be further used by the ship owner/operator onshore. These systems have already proved their value by the captain managing not to exceed design values. In addition, the same systems can confirm to the captain that he can go at higher speeds without overloading the vessel and thereby reach port in time. Along with routing systems, hull monitoring systems are considered a state-of-the art bridge system which may become mandatory in the future. They work for hull loading, but can include so much more, e.g. maintenance planning, fuel monitoring, shaft monitoring and input to secure containers and reduce lashing requirements for short sea shipping. 

container ship update NO. 1 2013 |

cONtaiNEr caPacity

Improved container capacity through direct calculations dnV is now introducing a new service that improves the competitiveness of container ships by allowing heavier containers on deck. this applies to both newbuildings and existing vessels. TexT: rAGnAr EimHJELLEn, dnV

This may be done by calculating individual and ship-specific accelerations using wave load analysis. establishing accelerations using wave load analysis will also represent a more precise engineering level, as the Ruledefined accelerations apply to all container ship hull forms. dnV is now offering a service that calculates individual accelerations. On dnV-classed ships, the container stowage and lashings are to be approved in accordance with Classification note no.

32.2 Container Securing. We will allow the containers to be secured based on individual accelerations provided these accelerations are calculated in accordance with an acceptable method. We are currently updating our Class note no. 32.2 so that it further specifies how to compute individual accelerations using wave load analysis. For worldwide trade, the individual accelerations using wave load analysis will use the same design basis as our Rules

for Hull Strength: a north atlantic scatter diagram with a 20-year return period. If required, we may also provide routedependent accelerations for trading routes more benign than the north atlantic. Such route-dependent accelerations will allow heavier containers on deck on routes such as europe–asia. The allowable container intake on deck is strongly dependent on the ship’s accelerations. In particular, the rolling

dirEct aNalysis Of accElEratiONs aNd stOwiNg arraNgEmENt classification rules determining the lashing arrangement are based on estimations of the most severe conditions likely to be encountered. Such values may be too conservative in trading areas with less severe conditions. iacS has published wave scatter diagrams for sea areas around the world with typical wave heights and periods based on observed data. a better representation of the true sea state for a given trading route is obtained when using such data, resulting in a more flexible stowing arrangement for that route.

example: accelerations for a 5,400 teu post-panamax container ship trading in the fe–eu route. the transverse acceleration (atransverse) is the most critical parameter. the stack weight may be increased from 158t to 187t when the values from direct analysis are used. the heavier containers are located in tier 5–8. the results depend on the gM value. the effect may be negligible for higher gM values.

acceleration 11

atransverse alongitudinal avertical

17 28

16 27

direct analysis [m/sec2] 2.05 1.35 3.60

dNV rule value [t] 3.5 3.5 13.0 16.0 30.5 30.5 30.5 30.5 158.0

direct analysis [t] 16.0 16.0 16.0 17.0 30.5 30.5 30.5 30.5 187.0

tier No

37 60

62 61

››

rule [m/sec2] 5.04 1.95 2.88

Schematic wave scatter diagram for fe–eu trade.

38 | container Ship update NO. 1 2013

8 7 6 5 4 3 2 1 stack weight

container capacity

acceleration is a decisive parameter as this will induce transverse racking forces and vertical corner post forces. We have Rules that provide such accelerations. However, the Rule-defined rolling acceleration has a certain built-in conservatism. This is in particular the case for wide beam ships with low GMs, where we should expect low rolling accelerations. In the case of a vessel with a 51m beam and 4m GM to which our container-securing software tool has been applied, we see that the allowable stack weight with accelerations according to our Rules is 137.5 t, while individual accelerations allow for 167.5 t. For a route-dependent Europe– Asia trade, the allowable stack weight is further increased to 180 t. For the same vessel, but with a lower GM of 1.2m, we see an even greater benefit from using individual accelerations: the allowable stack weight applying Ruledefined accelerations is 156 t, while applying individual accelerations allows 235 t. For a Europe–Asia trade, the allowable stack weight is further increased to 241 t. In recent years, DNV has developed a powerful modelling tool for wave load

analysis that significantly reduces the modelling time. The tool, WaqumExplorer, utilises the hull forms from a NAPA model in order to generate the panel model. Mass tuning is also based on information extracted from NAPA. The motions and accelerations are obtained by using the WADAM solver, which is a part of DNV Software’s SESAM package. WADAM applies 3-D radiationdiffraction theory and is recognised as being a state-of-the-art tool for frequency domain hydrodynamic analysis. The individual accelerations are delivered in a standard reporting format. Streamlined reporting is obtained by scripting the WADAM results so that an automatically generated report is ensured. In order to maintain the accuracy of the individual accelerations provided by wave load analysis, we will not provide functions representing the individual accelerations. However, in order to ensure a format that lashing makers can easily use in their lashing-system calculations, we will provide the individual accelerations in a table format that can be directly pasted into their tools.

Longitudinal acceleration mainly depends on the container’s vertical position and somewhat on the container’s transverse position. Therefore, longitudinal accelerations are given for each tier and each row of containers. Transverse acceleration is the most significant acceleration component when establishing the allowable container stowage. The transverse acceleration depends on the container’s vertical and longitudinal position, and is therefore shown for each tier and bay. Vertical acceleration mostly depends on the container’s longitudinal position and to some extent on the container’s transverse position. The vertical accelerations are therefore provided for each row and bay. In order to assist owners in obtaining an optimised container-lashing system, DNV will provide such individual accelerations for worldwide trade. This service will be covered by our newbuilding approval fee. For existing ships and newbuildings where owners are requesting route-dependent accelerations, we may provide individual accelerations at a low fee. 

container ship update NO. 1 2013 |

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