Double hulls ? the way forward for bulkers?

Mention the word ?bulk carrier? and most of us conjure up images of rust-buckets which, all too often, are run by non-compliant owners and operators working on minimalist budgets with little or no regard for the safety of seafarers or the environment. Terminal operators who are motivated by economic greed are also guilty of causing serious structural damage to bulkers. All too often their main concern is to load at the fastest possible rate in total disregard of the ship?s ability to de-ballast and with no thought given to the resultant excessive sheer forces and bending moments.

Commercial pressure on shipbuilders by ship owners has also had its effect in the shape of light scantlings and poor workmanship in an effort to drive down the price of newbuildings. This is done with the apparent approval of some of the classification societies who are prepared to condone designs bordering on minimal acceptable standards. The final nail in the bulk carrier?s coffin is that routine maintenance is often neglected because of inadequate resources in the form of incompetent, inexperienced crews who are too few in number to make any difference.

This tarnished image is, however, undergoing a transformation following a spate of sinkings, which finally prompted the IMO and IACS to revise structural requirements for bulk carriers. In response, naval architects have come up with a number of new designs incorporating many of the proposed recommendations but the feature common to all is the double hull construction.

The double skin seems to be the way forward for those ship owners and operators of bulk carriers who aim to introduce vessels that are future proof in the sense that they meet not just current requirements but those it is anticipated regulatory bodies may introduce somewhere down the line. Two designs which have recently come onto the market stand out and appear to meet many of the proposed IMO requirements for improved safety and enhanced environmental protection. The ?Optimum 2000? and ?Diamond 53? designs benefit from a number of operational cost saving features and, it is claimed, are future proof.

Much of the success of the new designs will rest on the outcome of IMO?s deliberations over the double hull issue. There is still, within a number of flag states, considerable doubt as to whether there is enough evidence to prove that double skins are sufficient to stop bulker accidents. Other recommendations up for review include hatch-cover strengthening, improvements in the enhanced survey programme, further strengthening of forward holds and the introduction of a forecastle.

Optimum 2000 ? a design before its time or a timely one?

Designed by the Norwegian team, O-J Libaek & Partners, part of the Oslo-based ship broker of the same name, this design offers many advantages compared to the conventional bulk carrier which has altered very little since the 1960s apart from the increase in size and the virtual disappearance of the raised forecastle. Requiring only 600 extra tonnes of steel compared to a conventional caper, the Optimum 2000 design addresses many of the current weaknesses and safety concerns. It provides a significantly more robust hull giving a claimed risk reduction of 70% against a newbuilding of today in terms of loss of life and downtime associated with structural failure.

The design for this 171,000 dwt Capesize bulk carrier followed in the wake of the original development of the combination carrier, also called Optimum 2000, as a natural development. Apart from being double-hulled, the most notable features are an open hatch configuration with a centreline bulkhead, and longitudinal single piece hatch covers. Not only will this reduce the risk, there will be less damage to hatch coamings and cargo hold structures due to the ?open hatch? effect. It also provides a “cargo kindly” design with 11 obstruction-free holds that enable cargo to be grabbed or conveyed out of the holds without the use of bulldozers below decks. The state of the art vessel also includes provision for a protective raised forecastle while all pipes and cables below decks will be housed within a centreline space.

In terms of safety during loading, the vessel will be fitted with a highly effective anti-heeling system to keep the ship on an even keel when loading with a single spout, and there will be ballast-pumping capacity to meet an hourly loading rate up to 16,000t. This latter aspect is important since new ports have high capacity loading equipment and many bulkers are not capable of de-ballasting at matching rates resulting in a mismatch which can stress the vessel?s hull.

The danger of unseen flooding occurring has also been addressed and, while all cargo hold bulkheads are designed to take flooding of any hold in a loaded condition, there is a water ingress detection alarm for all holds and forward spaces and a remotely controlled bilge system for the forepeak spaces.

Aside from safety issues, any new design will have to satisfy commercial considerations in order to entice ship owners to part with their money. A number of claimed operational advantages include a more rapid turnaround in port as a result of quicker cargo handling capabilities The double-hull configuration overcomes the problem of cargo sticking between side frames and between corrugations leading to reduced corrosion of the hull structure and minimises bulldozer work and trimming in the cargo holds. It also offers a hull that is easier to access for inspection and maintenance of coatings thereby giving improved corrosion control.

Other operational design features are reinforced tank tops and hoppers to cope with grab discharges of up to 50t, an integral hold cleaning system where each hold is provided with two retractable hold cleaning machines and two top wing tanks for storage of dirty hold cleaning water. Sequential exchange of ballast water in open seas will also be facilitated thanks to the double skin hull. These advantages, the Norwegian designers claim, more than compensate for any increase in the building cost which is estimated at $1.5 million more than a conventional Caper.

The company, which has now patented the Optimum 2000 design, is currently in talks with a number of Asian shipbuilders to finalise the price of the design after which it will market the vessel and enter into negotiations with owners. Also involved are class societies, particularly DNV which has accorded the design its ?Nauticus newbuilding? notation featuring finite element analysis of cargo hold area, fatigue control of longitudinal material and torsional calculations.

Diamond 53 ? a shining example of a good idea

The second design is the Diamond 53, a new generation of geared ultra-handymax bulk carriers developed over the past year by Graig Carl Bro Ship Design in Shanghai, which is a joint venture company comprising UK-based Graig Group and Denmark?s Carl Bro. Offering owners and charterers significant operational cost savings, the 53,000 dwt bulker will, the designers claim, exceed any future standards arising from current deliberations by IMO and IACS into bulk carrier safety.

While the vessel has been designed with the future in mind, it is firmly based on operational experience both from owners and class. So although considered to be future-proof, the design reflects commercial requirements for maximised dwt, cubic capacity and fuel economy for economical operations. The vessel will have five wide hatched cargo holds each fitted with end-folding hydraulically operated hatch covers while the cargo handling gear will consist of four 36t electro-hydraulic luffing cranes. Classed with DNV as +1A1 Bulk Carrier, the design was developed with the aid of the full Nauticus package including a full 3D model.

Environmental concerns are addressed by fitting low emission machinery and easy ballast water exchange while the risk of heavy fuel oil spills is minimised because bunker fuel will be stored on coffered tanks in the engine room.

The design recently received industry endorsement when the Graig Group announced at this year?s SMM exhibition that it had signed a letter of intent with China Shipbuilding Industry Corp for the construction of four Diamond 53 bulkers. The deal includes options on a further four ships and the first in the series is scheduled for delivery in 2004 from Bohai Shipyard. CSIC will subsequently nominate which of its other northern yards will build the remaining three units of the opening series while Graig China?s experienced Shanghai-based supervision teams will oversee the building.

Although the value of the contract is not known, informed sources suggest that the unit price for one of these bulkers to be built in China is likely to be up to $3m less than a comparable vessel from the most efficient Japanese shipbuilders.