Ship Type Expert Container
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In 1956 the modern container trade was born, when the Ideal X carried 58 containers from Houston to Newark in the United States. Since the delivery of the first purposebuilt containerized ships in the 1960s, DNV GL’s container fleet has grown into the largest in the world. To mark the anniversary of 60 years of “the box that changed the world”, we take a look at some of DNV GL’s most notable contributions to this sector.
For many years, German owners have contributed to the innovation of the container segment, placing some of the industry’s biggest players right on DNV GL’s Hamburg doorstep. “Our experiences in this field were closely connected to those shipowners and the first shipyards to build these vessels. We learned from each other and worked closely together on many technological and operational advances,” says Marcus Ihms, Ship Type Expert Container Vessels at DNV GL. Today, almost 40 per cent of the global container ship fleet sails under DNV GL class. “It’s staggering to see the rate at which boxships have grown in size and capacity. From 1972 to 1976 alone vessels more than doubled in capacity, from 1,600 TEU to 3,400 TEU. The 3,400 TEU vessels already had the principal dimensions of Panamax size. By the early 1990s, Panamax-size vessels were carrying 5,400 TEU,” he explains. This created a number of design challenges, such as deleting the longitudinal hatch girder to allow eleven-row container stowage in the cargo hold or increasing the number of tiers on the hatch cover. “DNV GL’s pioneering work in the field of structural design and our rules and regulations for container ships helped make these developments possible,” he adds. For example, DNV GL implemented improved methods of modelling and calculating hull structures for this design, such as the finite element method (FEM). “Today, FEM is the industry standard,” says Ihms.
Twin island concept enables ULCS
DNV GL has been closely involved in the evolution of container ship sizes – from Panamax, Post-Panamax, through to the new ultra-large container ships (ULCS) that hold close to 20,000 boxes. The feasibility study for the groundbreaking 6,200 TEU Post-Panamax project, which was the starting point for the rapid growth of Post-Panamax container ships, was guided by DNV GL experts, as were many other Post-Panamax container ship projects ranging from 8,500, 9,500 and 11,000 TEU supported and classed by DNV GL.
Most modern large container ships are based around the so-called twin island concept, where the accommodation block is located at the forward area and the engine room is located at the semi-aft. This idea emerged from the development of the 13,000 TEU design led by DNV GL and Hyundai Heavy Industries in 2005. Moving the deckhouse towards the midship section resulted in an increased nominal container intake, as well as improved hull girder strength and visibility for navigation. In addition, shifting the fuel tanks to below the accommodation block further improved the hull girder strength, trim capabilities and environmental protection.
These innovations culminated in the rise of the ULCS class. Launched in 2015, the DNV GL-classed MSC Oscar and her sister vessels, with capacities of over 19,000 TEU, are the world’s biggest container vessels. With a length of almost 400 m, a breadth of 59 m, a height of 30 m, a draught of 16 m and a deadweight of 199,000 t, they are not only the largest container ships but also among the world’s longest vessels.
Rapid growth of reefers
In the late 1990s, the amount of refrigerated cargo carried in containers significantly increased, boosting the demand for vessels with a higher reefer capacity. DNV GL worked with the industry to develop rules for the reliable transportation of reefer cargo, covering such vital factors as the required electrical power supply, ventilation and the space required to carry out repairs. In close cooperation with Hamburg Süd and Hapag-Lloyd, DNV GL also developed rules for the efficient and safe carriage of large numbers of reefer containers, summarized in the class notation RCP, which was first published in 2000 and recently revised.
As part of this trend DNV GL developed the first requirements for medium voltage (MV) equipment, such as MV switchboards and transformers, and the installation of MV cables on board container vessels. “Today every vessel above 8,000 TEU is automatically equipped with a medium voltage system,” says Ihms.
Route Specific Container Stowage
In 2013, DNV GL launched another innovation that would help its customers in what had become a very tight market. The new Route Specific Container Stowage (RSCS) notation, developed in cooperation with major German owners like Reederei Claus-Peter Offen and the Rickmers Group, was designed to help boxship owners and operators boost their vessel’s utilization rates by offering more flexible container stowage. Traditionally, vessel lashing system rules and layouts are based on the harsh conditions of the North Atlantic. DNV GL recognized that this represented a significant opportunity for vessels that operated in regions with more benign conditions.
Taking advantage of long-term statistical data on wave conditions, the RSCS notation for the first time allowed container stowage schemes that would take into account the variance in sea conditions on particular sea lanes. This meant that depending on the route and vessel, ship operators could stow heavier containers in higher positions on deck, increasing the centre of gravity of shielded stacks by up to 21 per cent. In addition, in-hold stack weight for 20-foot stowage could be increased by up to 25 per cent, as well as nominal capacity through the addition of an additional tier, where the line of sight is not affected. “The DNV GL class notation RSCS has become an industry standard. Since it became available in May 2013, DNV GL has approved lashing computers and stowage plans for more than 600 ships,” says Ihms.
The implementation of green propulsion concepts using alternative fuels such as LNG is also a field which DNV GL has been involved in for many years. The DNV GL-classed 15,000 TEU ship Sajir, owned by UASC, was the first ever LNG-ready ultra-large container vessel, setting a precedent for the use of alternative fuels in this segment. In the US, the first DNV GL-classed, LNG-powered container vessels are currently under construction, with Crowley Maritime’s two new LNG-powered con-ro ships at VT Halter Marine in Pascagoula as well as Matson’s two new Aloha-class 3,600 TEU container ships at Philly Shipyard.
Over the years DNV GL has teamed up with all the major container ship builders and designers to push the limits of design and construction. In a recent project, DNV GL carried out a technical and feasibility study for a new mega-boxship with GTT and CMA CGM (and its subsidiary CMA Ships). The Piston Engine Room Free Efficient Containership (PERFECt) concept vessel is LNG-fuelled, powered by a combined gas and steam turbine, and is electrically driven.
The development of the new DNV GL rule set, which entered into force at the beginning of this year, marks yet another milestone for DNV GL. “One of the key pillars of the new rules is the innovative concept to assess the structural strength of the hull. The introduction of so-called equivalent design waves marks a significant change in the way dynamic loads are calculated. The new advanced load approach is a major step towards a more realistic and accurate representation of the environmental loads,” says Ihms. “At DNV GL we are always looking for new ideas that will help build the next wave of innovations in the maritime world. The rules are easy to work with, industry-driven, efficient and ready for the future,” he concludes.
Ship Type Expert Container