NEWS ANALYSIS


Cause of giant ore carrier’s cracked hull remains elusive


T


he origins of the hull cracks in iron ore carrier Vale Beijing should become clearer this month, writes Julian McQueen.


Classification society Det Norkse Veritas, which, along


with the Korean Register, holds the ship’s classification, told Te Naval Architect that an investigation is “on-going and should be finalised during January”. Te ship, a 400,000dwt very large ore carrier, forms


part of the Brazilian mining company Vale’s move into shipowning and was built at STX Offshore & Shipbuilding in Korea. But the appearance of cracks in the vessel’s hull while it was docked at the Brazilian port of Sao Luis last month has raised questions over both the ship’s seaworthiness and its commercial potential. DNV is working with the ship’s owner “to ensure that


Vale Beijing can safely proceed to a discharge port”. But at the time of going to press, it said that conclusions have yet to be been drawn “on what caused the incident”. Te giant bulker forms part of Vale’s VLOC fleet of


which six, including Vale Beijing, of the ordered 35 ships are on the water. Te rationale behind that fleet is to lock in economies


of scale on the booming iron ore trade between Brazil and China. In contrast to Australia, China’s other major supplier of iron ore, the greater distance adds to the cost of transporting Brazilian cargoes. Te VLOC fleet is designed to meet China’s voracious appetite while, at the same time, keeping freight costs competitive. One economic argument for outsized bulk carriers (the


largest size being a capesize bulker) is that they can carry more cargo per trip. Te other centres on fast loading. Less time in port loading cargo strengthens the economic case behind the big ships. But the damage is thought to have been incurred


during loading. Indeed, one line of enquiry will focus on the impact of fast-loading on ship structure. In the case of Vale Beijing, the vessel’s hull will have


been designed and built to cope with all the expected forces that would arise from the loading process. It is understood that the ship also had DNV’s CSA 2 notation. Tis notation allows the vessel to calculate fatigue and ultimate strength in the cargo area. Vale officials have been quoted as saying that around 260,000 tonnes of cargo were onboard when the cracks appeared. Te depth of the vessel in the water also lends support to the view that it was not fully loaded at the time when the damage emerged. According to a report in shipping weekly Tradewinds,


expert opinion has suggested that in that condition, the shear forces on the hull would be greatest on the empty number five hold. However, cracks have appeared on


The Naval Architect January 2012


both sides of the ballast tanks surrounding the number seven hold. One possible explanation has considered the


position of that hold. The number seven hold is where the cargo hold connects to the engine room and longitudinal framing may change to transverse framing in the engine room. Tis could, it is argued, be a region of possible weakness. Certainly, the rate at which dry bulk carriers have been


loaded has been an issue in the industry for some time. As early as 1991, distinguished shipping commentator Michael Grey wrote of “the growing concern that concentrated loading of ore, in the absence of prudent operating practices, is exacting an untold cost in vessel damage”.


Is there a design flow in new vale VLOC series? The 361m, 383,000dwt bulker which was delivered in September last year cracked on its maiden voyage.


In part response to such concerns, the industry


has agreed to bring common structural rules on the construction of tankers and bulkers due to come into force from mid-2016. Getting to the bottom of problem of Vale Beijing is


vital to maintaining market confidence in the vessels which were already experiencing a frosty reception from some Chinese port authorities. However, it has been confirmed that the 388,000dwt Berge Everest, a VLOC operated for Vale by BW Group, has leſt the Chinese port of Dalian to refuel at Singapore prior to returning to Brazil. It is not thought that any of the other completed ships are scheduled to call at Chinese ports in the short term. Vale Beijing remains anchored off Brazil’s Ponta da Madeira Port. While the VLOC concept is very much a Vale project,


there have been signs that the company might be re-thinking its initial strategy of owning around 19 of the 35 possible vessels. In late December, the company hinted that it would be willing to sell the ships in a leaseback deal. NA


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