CONTAINER SHIP FOCUS T E C H N I C A L N E W S A N D I N F O R M AT I O N O N C O N TA I N E R S H I P S
Welcome to the third issue of Container Ship Focus, a technical publication produced by Lloyd’s Register exclusively for the container ship industry.
IN THIS ISSUE 2
West’s trade imbalance with China makes and breaks fortunes
4
Preventing shaft bearing damage
7
Lloyd’s Register and Standard P&I Club publish container securing guidance
8
CRC notation – The way forward
10 Mandatory requirements for strength of towing and mooring equipment on new ships 11 New ShipRight procedure for container ships helps to assess hull stresses 12 News and upcoming conferences
NOVEMBER 2006 Issue 3
2 CONTAINER SHIP FOCUS
November 2006
West’s trade imbalance with China makes and breaks fortunes
The traditional trade imbalance between the West and Asia is good news for some and bad news for others. Either way, container ship operators reap the benefits. In Lloyd’s Register’s paper “Design Challenges of Large Container Ships”, presented in Singapore at ICHCA 2006, there is mention of the imbalance in the main east-west container trades.* Cargo leaving Asia is principally high value and voluminous, occupying every slot on container ships trading to Europe and the US West Coast. Conversely, the ‘back haul’, the return leg to Asia, tends to comprise mainly heavy cargoes. Unfortunately, there is often insufficient cargo on the back haul legs to fill the ships. The consequence is an accumulation of empty containers, in Europe and the US, which need to be returned to Asia.
One side of this story is told by a recent article in the Guardian entitled “The world’s largest container ship Emma Maersk – symbolic of trade imbalance with China”, which marvels over the ship’s cargo manifest and calls the ship “a floating world of British desires and necessities” on the eve of its first call into the port of Felixstowe. The article goes on to bemoan, however, the significant trade imbalance between the UK and China, pointing out that while China exported some £16bn of goods to the UK last year, only £2.8bn went the other way. The back haul trade has traditionally been bolstered by the carriage of heavy, low-value cargoes - any revenue for this leg is better then carrying lossmaking empty containers. Cargoes which have helped to fill some of the otherwise empty containers include scrap steel, plastic and waste paper. This was highlighted in a recent article in The Times bearing the headline "World's wealthiest self-made woman”, about a self-made businesswoman named Cheung Yan who has amassed a fortune of £1.8bn.
According to the article, Ms Cheung is chairwoman of China’s biggest paper-recycling company, Nine Dragons Paper. She began building her fortune in 1985 when, with less than $4,000, she set up a wastepaper trading business in Hong Kong. Within six years, on the back of a booming economy, she had accumulated a significant amount of capital, which she used to set up a scrap paper exporting company called America Chung Nam in Los Angeles with her husband. The company is now the leading exporter of scrap paper in the US. With China establishing itself as a huge manufacturing force, Ms Cheung spotted an opportunity for paper to package the countless products being exported around the world or marketed at home. The east-west imbalance in the container trades is, for many, a major problem – but clearly not for Ms Cheung, who had the foresight to turn it into a profitable advantage.
November 2006
Cold ironing Today’s vast order book for container ships, and especially post-panamax container ships, continues to cause nervousness in the market. Photo courtesy of AP Møller Mærsk A/S.
‘Cold ironing’ is the US Navy’s way of describing the practice of connecting a ship to a shore-side power supply in port with the ship's machinery shut-down, causing the hull to become ‘cold.’ This term is now commonly used to describe a new generation of different high voltage shore connections with fast plug connections and seamless load transfer without blackouts, which allow the full range of in-port activities to continue. The increasing use of such arrangements has been driven by concerns for the environment and the health of residents in port communities. There are existing installations for visiting container ships in the ports of Los Angeles and Long Beach, for instance. The facilities were installed following in-depth studies carried out by the state of California which showed that measures such as cold ironing could contribute to the improved health of local residents.
Panamanians voted ‘yes’ to the expansion of the Panama Canal by an overwhelming majority. The expansion will see the construction of a third set of locks to accommodate increasing traffic from Asia, through the Canal, to the US and back.
The requirement to use cold ironing is soon to have a statutory footing, following the approval by the California Air Resources Board (ARB) of a new regulation to reduce emissions from auxiliary diesel engines operated on ocean-going vessels within state waters.
CONTAINER SHIP FOCUS 3
According to an advisory issued by the ARB, the regulation will require ship operators visiting California ports to reduce the air pollution from their auxiliary diesel engines through the use of cleaner marine distillate fuels or equivalent emission controls. One way that shipowners and operators can comply with the emission limit is through the use of shore-side electrical power. To do so, however, owners and operators must submit an application demonstrating that such alternative strategies will result in emissions that are no greater than would result from compliance through the use of the cleaner fuels stipulated in the regulation. The regulations are not yet in force, but are expected to become legally effective by the end of 2006. It is important, however, that ship safety and environmental benefits are given equal weight. The technical difficulties, hazards and potential for serious injury and damage are not to be understated. To address the potential hazards Lloyd’s Register has developed draft Rules for on-shore power supplies in consultation with a wide variety of stakeholders. We have also been invited to contribute to the ongoing industry discussions and working groups tasked with devising uniform standards for these arrangements. The aim is to harness best practice to mitigate the risks posed by the significant change to port operations that cold ironing represents.
Panama votes "Sí" to Panama Canal expansion On the October 22, 2006 Panamanians voted ‘Sí’ (‘Yes’ in Spanish) in a national referendum on Panama Canal expansion. The voting began on a quiet Sunday morning at 7:00 am. The enthusiasm and energy was apparent as each voter played his or her part in determining the direction and future of the canal. By law, expansion must be put to a vote in a popular referendum. The Panama Canal Authority (ACP) presented its formal proposal to the Panamanian government in April, and on the day of the vote 78% voted for expansion as of 9:30 pm EDT. According to the ACP’s report “Proposal for the Expansion of the Panama Canal - Third Set of Locks Project”, the containerised cargo trade between Northeast Asia and the US East Coast reflects the highest canal transit growth rate. This route currently represents more than 50% of the PCUMS – Panama Canal Universal Measurement System – volume of all containerised cargo transiting the canal and is anticipated to become a key growth driver for the canal. * A copy of the paper can be obtained from www.lr.org
For further information contact David Tozer, Business Manager – Container Ships, Lloyd’s Register E
[email protected] T +44 (0)20 7423 1562 F +44 (0)20 7423 2213
4 CONTAINER SHIP FOCUS
November 2006
Preventing shaft bearing damage
With the advent of ever larger and more powerful container vessels, it has become necessary to pay greater attention to shaft alignment design and propulsion shafting installation. A good shaft alignment is one in which all the supporting bearings are well loaded in the static condition and the system is flexible enough to withstand hull deflections and imposed forces so that the bearings remain well loaded in all operating conditions. For container ships, this requirement has historically been easier to fulfil than for other commercial vessel types such as oil tankers and bulk carriers. This has been due to the inherent flexibility of the shafting systems on container vessels as a result of the mid-position of the main engine and the subsequently long shaftlines.
Wiping damage at aft section of sterntube aft bearing on a 4,500 teu container ship.
It is somewhat counterintuitive that long shaftlines with many bearings are in fact easier to align than short shaftlines with few bearings. However, theory and practical experience demonstrate that the short, stiff systems found on vessels with high-powered machinery placed as far aft as practicable are the most problematic.
These design trends make the coupled propulsion shaft and engine system more sensitive to changes in bearing position. In order to prevent bearing failures, it has become necessary to pay greater attention to shaft alignment design and propulsion shafting installation on container ships.
Sensitivity of shaft systems With the advent of ever larger and more powerful container vessels, propeller and intermediate shaft diameters are increasing, with some single-screw ULCS designs now incorporating a propeller shaft diameter in excess of 1 metre. In conjunction with the larger drive shafts, main engine designs are also incorporating shorter cylinder spacings and larger crankshaft diameters.
The design stage is crucial in establishing a suitably flexible shafting system. It is important for the designer to minimise the value of the bearing influence numbers (the measure of shaft stiffness). It is also important to keep the static bearing loads high enough to prevent them from unloading during operation. In simple terms, this means that the sterntube forward bearing and
November 2006
plummer bearings need to be spaced sufficiently far apart. As a rule of thumb, the length/diameter ratios of the bearing spans should be kept above 10:1. To achieve this it may be necessary to omit the sterntube forward bearing in place of an aft plummer bearing located on the propeller shaft, immediately inboard of the engine room aft bulkhead seal. Table 1 compares the parameters of several selected container ship and oil tanker designs and shows the theoretical influence numbers. As a measure of sensitivity, the downward offset from the design position required to unload the sterntube forward bearing or, where no forward bearing is fitted, the aft-most plummer bearing is shown.
CONTAINER SHIP FOCUS 5
When combined with a design bearing load of 12 tonnes, it only takes 0.88 mm of downward displacement for the sterntube forward bearing to unload.
forward bearing to unload and the propeller shaft to run cross-axis in the aft bearing. This typically occurs during turns to starboard. The measurements additionally confirmed that successful sterntube aft bearing performance is dependent on achieving a static slope mismatch between the journal and bearing surfaces to within Lloyd’s Register’s limit of 0.0003 radians (0.30 mm/m).
A better design is the 6,000 teu vessel, which has a span of 11.0 metres between sterntube bearings, producing an L/D ratio of 11.3:1. Despite the larger shaft diameter, the sterntube forward bearing’s influence number is kept down to 6.7 tonne/mm.
These results are in line with the findings of numerous sterntube aft bearing failure investigations conducted by our Technical Investigations. The most common forms of propulsion shaft bearing damage are wiping or overheating at the aft end of the sterntube aft bearing. In a number of cases, such damage has occurred
The 6,000 teu design also has the advantage of a longer shaftline with more plummer bearings (six, compared to only three in the 4,500 teu design), which helps to reduce the influence number at the sterntube forward bearing.
Table 1: Sensitivity of selected shaft systems to bearing displacements
Vessel type
Sterntube forward bearing or aft plummer bearing (2nd bearing from aft) Prop. shaft Bearing Influence Downward offset to diameter static load number unload bearing (mm) (tonne) (tonne/mm) (mm)
2,000 teu container
640
11
3.9
2.82
4,500 teu container
792
12
13.6
0.88
6,000 teu container
975
31
6.7
4.63
8,000 teu container
971
30
12.5
2.40
150,000 dwt oil tanker
706
8
16.1
0.50
310,000 dwt oil tanker
801
18
27.4
0.66
Of the container ship designs studied, the 4,500 teu vessel has the most sensitive system, comparable to that of the oil tankers. An important aspect of the particular 4,500 teu design studied is that the shaft span between the forward and aft sterntube bearing supports is only 6.5 metres. This produces an L/D ratio of only 8.2:1 with a subsequently high influence number of 13.6 tonne/mm.
Bearing failure investigations The need to achieve a good static load on the sterntube forward or aft plummer bearing has been highlighted in recent investigations undertaken by Lloyd’s Register’s Technical Investigations. Measurements conducted on container vessels demonstrated how the bending moments imposed upon the propeller shaft change significantly during manoeuvring turns, causing the sterntube
during starboard turns when increased bearing load and slope mismatch between the journal and bearing surfaces has adversely affected the development and maintenance of a satisfactory oil film. Although the shaft alignment design calculations normally consider the hydrodynamic forces and moments generated by the propeller, we have found that overly simplistic assumptions
6 CONTAINER SHIP FOCUS
November 2006
Overheating damage at aft end of sterntube aft bearing on a 2,000 teu container ship. are often made which have led to poor alignment designs being submitted for class approval. It must be remembered that the propeller hydrodynamic forces and moments are predicted for the zero rudder condition only and often at one vessel draught condition. When the vessel turns or operates in different ballast conditions, the propeller hydrodynamic forces and moments can change significantly due to wake field variations. This causes the centre of propeller thrust to move from its predicted position, thereby invalidating the values assumed in the calculations. For further information contact Daniel Legg, Senior Surveyor, Engineering Systems, London Design Support Services, Lloyd’s Register EMEA E
[email protected] T +44 (0)20 7423 1757 F +44 (0)20 7423 1824
We have recently amended our shaft alignment Rules (Part 5, Chapter 8, Section 5) to require a sufficient static load on the sterntube forward bearing to prevent it from unloading in all operating conditions, including the transient conditions experienced during manoeuvring turns. The amended Rules also introduce formal requirements for bearing load measurements to be performed at the verification stage of the alignment process. When applied to container vessels, this will mean that shipyards will need to conduct jack-up load tests on the sterntube forward bearing, all the plummer bearings and the aft three main engine bearings at acceptance sea trials.
Final adjustments to the plummer bearing height will be made, where necessary, to optimise the alignment. The final bearing load measurements required by Lloyd’s Register are to be conducted in a sailing draught condition, with the engine warmed through in order to minimise the uncertainties of hull deflections, machinery thermal rise and propeller buoyancy effects.
November 2006
CONTAINER SHIP FOCUS 7
Lloyd’s Register and Standard P&I Club publish container securing guidance
Container ship design has advanced, but container lashing systems have not necessarily kept pace.
A Master’s Guide to Container Securing aims to provide masters and seafarers with best practice guidance on how to safely stow and lash containers into place to help prevent injury and loss. Lloyd’s Register and the Standard P&I Club have published A Master’s Guide to Container Securing. The book is the fifth in the Master's Guide series by Standard P&I and the second produced in association with Lloyd's Register. As the guide says, “In the early days of containerised transport, ships carried containers stowed on hatch covers, three or four high. A variety of lashing systems were in use. However, the most reliable system consisted of stacking cones, twistlocks, lashing bars, bridge fittings and turnbuckles (bottle screws). These systems were effective in lashing containers carried on deck to the third tier.
A Master’s Guide to Container Securing provides masters and seafarers with guidance and advice on container lashing.
“Today, ships are bigger and a post-panamax container ship will carry containers on deck stacked up to six, seven or eight tiers high. However, while the ships are able to carry containers stacked higher, the lashing systems are still only capable of lashing to the bottom of the third tier containers or the bottom of the fourth or fifth container tiers when a lashing bridge is fitted. Ship design has developed but container lashing systems have not.” The book is intended to help masters and seafarers to understand the principles of container securing, to describe the various securing methods and the fixtures and fittings which are used, to describe common causes of lashing failure and to offer advice on how losses can be minimised. The guide is designed to be as readable as possible.
The intention is that a copy will be available on-board every container ship which is classed with Lloyd's Register. Similarly, Standard P&I will be distributing the guide to their members. The previous four publications in the Master’s Guide series are: G
G G
G
A Master’s Guide to Ships' Piping A Master’s Guide to Berthing A Master’s Guide to Hatch Cover Maintenance (in collaboration with Lloyd's Register) A Master’s Guide to Accident Response.
A Master’s Guide to Container Securing may be viewed on the Lloyd’s Register website at www.lr.org. To obtain a copy, please contact your local Lloyd’s Register Group office.
For further information contact David Tozer, Business Manager – Container Ships, Lloyd’s Register E
[email protected] T +44 (0)20 7423 1562 F +44 (0)20 7423 2213
8 CONTAINER SHIP FOCUS
November 2006
CRC notation – The way forward
Lloyd’s Register has developed a new set of Rules for refrigerated containers which enables owners and operators to carry refrigerated containers below and on deck – and to give charterers confidence that this can be done without risk to their cargoes. Owners and operators are being pushed by charterers to carry ever increasing numbers of standard integral refrigerated containers onboard their ships. The inability to carry these refrigerated containers as hold cargo has been one of the main stumbling blocks to the ideal situation of total container flexibility. Historically, the hold carriage of refrigerated containers was limited to specialist thermally insulated ‘port-hole’ containers or those fitted with a non-standard water-cooled condenser in addition to the normal air-cooled condenser. As a result, devising a means of carrying refrigerated containers below deck, with their selfcontained refrigeration systems in operation, became a priority. Towards this end, Lloyd’s Register developed our Rules for the Carriage of Refrigerated Containers in Holds (CRCH Rules) in 2000. They were published as ‘Notice No. 2’ of the July 2000 edition of the Rules and Regulations for the Classification of Ships and were then included as Part 7, Chapter 10 of the July 2001 edition of the Rules for ships.
Previous to the development of our CRC Rules, refrigerated containers carried on deck could not be assigned a dedicated notation.
The feedback obtained from both shipyards and owners was that the Lloyd’s Register CRCH Rules did not adequately cover the following: 1. hold ventilation systems other than a ducted exhaust type 2. refrigerated container plug-in sockets and their associated electrical supply system 3. refrigerated containers with water-cooled condensers 4. deck-stowed refrigerated containers and the effects of waste heat dissipation. In response to these comments, we have developed Rules for the carriage of refrigerated containers (CRC Rules).
CRC notation It was proposed that the original CRCH Rules be completely revised to embrace the above issues and also be revised to take into consideration knowledge gained during subsequent discussions with owners, operators, charterers and shipyards. It was also proposed that the CRC Rules needed to allow an appropriate notation to be applied to any ship which has the facility to carry refrigerated containers.
The notation additionally differentiates between holdstowed refrigerated containers and those stowed on deck. Further descriptive notations cover items such as cargo storage regimes (such as chilled and frozen) and the amount of electrical power dedicated to container plug-in points. Assigning the CRC notation indicates that the design, installation and testing of the hold ventilation system achieves a satisfactory standard to allow the carriage of a specified number of integral refrigerated containers below deck. The Rules are based on the philosophy that it is advantageous to allow the shipyard’s ventilation system designer to submit a proposal without having to comply with prescriptive regulations, specific temperature limitations or airflow requirements. However, guidance air flow values are provided. Thus, the type of ventilation system proposed and its design, including aspects such as ductwork sizing, fan sizing, maximum air velocity, hold space temperature limitations and air sealing arrangements, are the prerogative of the system designer.
November 2006
Lloyd’s Register’s heat flow model During operation, a container’s integral refrigeration unit removes the total container heat load made up of the following: heat generated by the respiration of the cargo, heat transferred across the container’s boundary, heat carried in infiltration and airrefreshing air and heat generated by internal electrical equipment such as evaporator fan motors. This heat is transferred by the refrigerant and rejected through the container’s condenser to the atmosphere. When a number of containers are located in the same hold, the temperature inside the hold can increase significantly, adversely affecting the efficiency of the refrigeration units and their ability to maintain the containers’ internal temperatures. If sufficient fresh air is circulated through the hold, the temperature of the air in the hold can be maintained within acceptable limits.
CONTAINER SHIP FOCUS 9
To adequately assess all these heat loads and the interaction between the various refrigerated containers in a cargo hold for the purposes of writing the new CRC Rules, Lloyd's Register created a macro-volume model (MVM), which focuses on the bulk movement of heat. This bulk movement is referred to as the ‘reefer heat flow’. As the container refrigeration units are operational before loading, and their operation is quasi-steady over the duration of a voyage, the heat flow is assessed under steady-state conditions. The MVM was created in a spreadsheet to assess the heat balance for a container ship’s hold, to enable us to appraise proposed ventilation systems. The model can simulate any ISO arrangement of reefers, at a variety of cargo temperatures (see Table 1), and returns a value of ambient air flow required to maintain a target temperature in the hold. Modelling has been undertaken on existing ships to verify the program, and this has shown that the guidance air flow values given in the CRC Rules are conservative. The model considers each hold separately, and the hold input data includes number of rows, number of tiers, refrigerated container slots, non-refrigerated slots and void areas such as fuel tanks. For each slot, the model can show the effect of carrying, not only containers having different temperatures, but also different cargoes. Other aspects such as the effects of carrying empty containers can also be modelled.
Is this the ‘new’ reefer ship?
Table 1 – Cargo container set temperatures Name Temperature ºC ‘Banana’ 13.0 ‘Chill’ 2.0 ‘Frozen’ -18.0 ‘Deep Frozen’ -29.0
Giving confidence The development of the CRC Rules now allows owners whose ships have the ability to carry refrigerated containers to demonstrate that the facilities provided achieve certain design criteria. This will allow charterers to have confidence in the ship’s ability to carry their valuable refrigerated cargo in a satisfactory and safe manner. The historic view that it is not possible to transport refrigerated containers in enclosed holds has now been discredited. We now have the ability to verify the amount of ventilation required to ensure the effective carriage of refrigerated cargoes. We believe that our reefer heat flow model has the ability to not only determine air flow requirements but also the resulting hold space temperatures.
For further information contact Robbie Sillars, Senior Surveyor, Engineering Systems, London Design Support Services E
[email protected] T +44 (0)20 7423 1921 F +44 (0)20 7423 1824
10 CONTAINER SHIP FOCUS
November 2006
Mandatory requirements for strength of towing and mooring equipment on new ships “A new regulation on towing and mooring equipment has been added to SOLAS.”
Ships greater than 90 metres in length do not require towlines and mooring lines as a classification item; however, guidance is given in the Rules.
A new regulation, “Towing and mooring equipment”, has been added to SOLAS. The new regulation 3-8, “Towing and mooring equipment”, has been added to SOLAS Chapter II-1, Part A-1. The regulation reads: 1. This regulation applies to ships constructed on or after 1st January, 2007, but does not apply to emergency towing arrangements provided in accordance with regulation 3-4. 2. Ships shall be provided with arrangements, equipment and fittings of sufficient safe working load to enable the safe conduct of all towing and mooring operations associated with the normal operation of the ship. 3. Arrangements, equipment and fittings provided in accordance with paragraph 2 shall meet the appropriate requirements of the Administration or an organization recognized by the Administration under regulation I/6.*
For further information contact David Tozer, Business Manager – Container Ships, Lloyd’s Register E
[email protected] T +44 (0)20 7423 1562 F +44 (0)20 7423 2213
Container ships 4. Each fitting or item of equipment provided under this regulation shall be clearly marked with any restrictions associated with its safe operation, taking into account the strength of its attachment to the ship’s structure. In addition to this amendment to SOLAS, the International Association of Classification Societies (IACS) has developed and issued a second revision to Unified Requirement (UR) A2 and a new Unified Interpretation (UI) SC212. Copies of UR A2 and UI SC212 may be downloaded from the IACS website (www.iacs.org.uk). The requirements specify the strength of the towing and mooring equipment to be supplied and give criteria for the design and approval of associated support structure. These new requirements are applicable to new ships of all types and sizes which are constructed on or after January 1, 2007. They apply to continuations of existing series, even if the lead ship was built before this date. Currently, for ships under 90 metres Lloyd’s Register’s Rules specify the minimum number, length and strength of mooring lines. Towlines are not required for classification, but details are given in the Rules for guidance.
Of particular note with regard to container ships is the Equipment Numeral used for establishing the strength of towing and mooring equipment. This numeral must take into account the profile area of any cargo carried on deck. This is a change from the current method, which excludes deck cargo from the calculation. It is anticipated that this will have the effect of increasing the equipment numeral by one step, irrespective of ship size. There will be exceptions where a greater or zero increase in the numeral will result, but for most new container ships, there will be an increase in the required strength, length and number of mooring lines over and above the minimum basic standard currently recommended by class. The new regulations also define requirements for the design and strength of shipboard fittings (including bollards and bitts, fairleads, stand rollers and chocks) and supporting hull structure. Our Rules and Regulations for the Classification of Ships are currently being amended to incorporate the above amendments. *Refers to MSC/Circ 1175, Guidance on shipboard towing and mooring equipment (available as a download from www.imo.org).
November 2006
CONTAINER SHIP FOCUS 11
New ShipRight procedure for container ships helps to assess hull stresses When a ship twists, warping (fore and aft) stresses are generated and these are resisted partly by shear forces in the transverse bulkhead topside structure – principally at upper deck level. This effect is quite small because the bulkheads are slender.
Lloyd’s Register’s has published a new ShipRight procedure for the Structural Design Assessment of container ships. Lloyd’s Register’s Structural Design Assessment (SDA) and Construction Monitoring (CM) procedures are mandatory for container ships with a beam of panamax size or greater and for other container ships of abnormal hull form, or of unusual structural configuration or complexity.
A new SDA procedure for container ships is supported by software.
In May 2006 a new version of the SDA procedure was released to provide guidance on the direct calculation methods to be applied to a number of new features which are being used in the design and build of the latest container ships, principally the positioning of fuel oil tanks within the cargo holds, driven by the introduction of MARPOL Annex 1, Regulation 12A.
ShipRight SDA software provides support Lloyd’s Register ShipRight SDA software has been developed to support the application of the SDA procedure. The software is designed to interface with shipbuilders’ own systems and provides load generation and post-processing of stress and buckling results which are automatically assessed against the SDA criteria. Key features include: G ship modelling – users can create a ship model using the software or work with models imported from CAD systems or in NASTRAN format G automatic generation of many of the SDA load components – for example, to identify a tank within the finite-element model, all that is required is a single reference point anywhere within the tank. The software identifies the tank boundaries and automatically applies pressure loading as appropriate G automatic wave balancing – when assessing the structural strength of a large container ship it is necessary to model the entire ship and balance it on a wave profile. Our ShipRight SDA software can automatically adjust draught and trim to achieve equilibrium. Additionally, the wave height can be adjusted to achieve the required bending moment value at midships. G automatic loading of fine mesh models and transfer of boundary deflections obtained from the full ship model G automatic stress assessment against the SDA or user-defined criteria G automatic panel buckling calculations and assessment G automatic report generation in Word format.
Positioning the fuel oil tanks within the cargo holds can have a significant effect on the distribution of stress within the hull of a container ship, particularly when the ship is subjected to torsional loads such as those produced by uneven distributions of cargo, ballast water and fuel and by the twisting of the hull in oblique seas. For a ‘conventional’ container ship, the cargo hold region is generally U-shaped in section and the centre of twist – which is close to the shear centre – is about D/2 below the baseline. For a closed section, such as the engine room and at the forward end, the centre of twist is within the ship, at about D/2 above the baseline.
However, the introduction of tanks within the cargo holds has a big effect – they increase the enclosed area of the hull crosssection and therefore increase the St Venant torsional stiffness. The centre of twist of the hull moves up sharply into the hull in the region of the tanks, and the entire stress distribution within the hull is changed. In addition, the ‘hard spots’ created at the ends of the fuel tanks, at the top of the tanks, must be examined carefully to ensure that the design will perform effectively – leakage due to cracks at this point could lead to fuel oil ingress into the cargo holds. All of these aspects, and the local strength issues associated with such arrangements, are addressed in the new procedure. The new procedure also includes a revised, simplified method of fatigue assessment for hatch corners, which recognises the benefit of high-tensile steel on the fatigue performance of unwelded material. This has been introduced as a result of Lloyd's Register's on-going programmes of fatigue assessment and testing. The new ShipRight SDA procedure can be accessed from ClassDirect Live (www.cdlive.lr.org).
For further information contact Sue Rutherford, Technology Manager, Research and Development, Lloyd's Register E
[email protected] T +44 (0)20 7423 2538 F +44 (0)20 7423 2061
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November 2006
Classification news
Horizons
Upcoming conferences
Lloyd’s Register’s Classification News delivers up-to-date information on issues requiring urgent and immediate dissemination to the marine industry. Recent inspection and statutory alerts we have issued include:
Horizons is our quarterly technical publication for the marine industry. Topics recently covered include:
Lloyd’s Register will be presenting at the following container ship conferences in the upcoming months:
• Changes to the Rules and Regulations for the Classification of Ships, 2006 – Part 1: The Regulations (Applicable to all Lloyd’s Register-classed ships)
• revisions to MARPOL Annex I • improving Port State Control performance • a profile of leading ship operator Teekay Shipping.
• Changes to the Rules and Regulations for the Classification of Ships, 2006 - Part 1: The Regulations (Applicable to ESP ships) • Removal of redundant, expired or replaced certificates from ships' files
• EU Sulphur Regulations applicable to passenger ships on regular services in EU waters • Daniamant Rescue Dan M and Rescue Dan W lifejacket lights replacement • Canada introduces new mandatory ballast water regulations. Classification News is available free of charge. These issues, together with the archive of alerts, may be viewed electronically at www.cdlive.lr.org
C O N TA I N E R S H I P F O C U S For further information on our marine services relating to the container ship sector, please contact David Tozer, Business Manager – Container Ships: T +44 (0)20 7423 1562 F +44 (0)20 7423 2213 E
[email protected]
Managing Editor: Dolly Robinson Marine Media Manager T +44 (0)20 7423 1682 E
[email protected]
RINA Design & Operation of Container Ships, November 22-23, 2006, London, UK
Horizons includes regular features on:
“Development of requirements to safeguard large container ships from the effects of bow flare slamming”, Ling Zhu, Lloyd’s Register
• legislative developments • the latest in ship technology • recent deliveries to Lloyd's Register class • forthcoming exhibitions and technical papers.
“Energy prices and container shipping”, Andrew Penfold, Director, Ocean Shipping Consultants Ltd and David Tozer, Business Manager – Container Ships, Lloyd’s Register
Horizons can be downloaded from our web sites (www.lr.org and www.cdlive.lr.org). If you would like to receive a hard copy, please contact:
“Design of container ships for safer securing and access”, Brian Sherwood Jones and Roland Ives, Lloyd’s Reigster and Roy Smith, Hutchinson Ports
Adele Williams Lloyd’s Register 71 Fenchurch Street London EC3M 4BS, UK T +44 (0)20 7423 2309 F +44 (0)20 7423 2213 E
[email protected]
Boxship 2006, December 56, 2006, Shanghai, PRC “Impact of bunker prices on container ship design”, David Tozer, Business Manager – Container Ships, Lloyd’s Register and Andrew Penfold, Director, Ocean Shipping Consultants Ltd “Container ship propulsion efficiency enhancement”, John Carlton, Head of Technology and Investigations, Lloyd’s Register
Container Ship Focus is produced by Marine Business Development. Lay-out by theclubb design consultants. Care is taken to ensure that the information in Container Ship Focus is accurate and up to date. However, Lloyd’s Register accepts no responsibility for inaccuracies in, or changes to such information.
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