Feature 4 | CLASSIFICATION SOCIETIES


tanks on the fore deck using liquid nitrogen at –192°C,” explains Westerman. Bit Viking then successfully bunkered LNG, which has a temperature of –162°C, for a main engine test run at the pier. At the end of October, the vessel was finally ready for its official sea trial, with two GL surveyors onboard, during which she performed as expected and no major discrepancies were noted. Westerman says: “Key concerns in


this world premiere were the proper interpretation of class rules for safe construction, ensuring that the equipment manufacturers clearly understood the class rules, and anticipating how the flag administration would understand and accept the required risk analysis. Particular focus was on bunkering and how it should be performed, since this is a somewhat critical operation that requires special knowledge and equipment.” Te conversion of Bit Viking provided


a good opportunity to put the GL rules for gas as ship fuel to the test. Following the successful conversion, Westerman is optimistic: “The existing rules are sufficient for a conversion such as that of Bit Viking. However, some modifications will be made in the future as regulations such as MARPOL are updated to reflect the option of gas as a ship fuel.” While the environmental advantages


of LNG-fuelled ship engines are well-known, there are some drawbacks compared to fuel oil. The two 500m3 LNG tanks and the associated piping and valves add several hundred tonnes to the weight of the vessel, although the ship enjoys increased buoyancy and lifting capacity. An LNG-powered vessel at this developmental stage is slightly more expensive than a conventionally powered equivalent, which increases capital cost. Yet with the advent of cash incentives for lower emissions in some Scandinavian


countries, ship operators can also save money via rebates. Where Scandinavia has taken the lead,


others will surely follow. Under rules drawn up by the International Maritime Organization (IMO), vessels must cut SOx emissions from 1% today to 0.1% by January 2015. “Within the short period of operation since her conversion, Bit Viking has already achieved considerable benefits for the environment,” says Westerman. “Greenhouse gases have been reduced by 20 to 25%, a NOx gas by 90%, sulphur output has been cut entirely, and particle emissions have been brought down by 99%.” Bit Viking resumed commercial trading


in October 2011. Ever since, she has been performing as expected and the crew has successfully refuelled her from the shoreside facility at Risavika. Te vessel is now trading the length of the Norwegian coast between Oslo and Kirkenes on behalf of oil major Statoil. SRCT


ClassNK focusses on good conversion communications


Conversions of single hull tankers into FPSO and FSO vessels are increasing globally once again, and ClassNK aims to harness its know-how to the benefit of such schemes.


O


ne notable project that ClassNK is currently working on is the conversion of a single hull tanker


into an FSO at a yard in China. According to ClassNK: “For conversions, we believe that the most important thing is to ensure that converted FPSOs or FSOs, are just as safe as new vessels. Tis can be a difficult task, especially given that is much harder to ensure quality control for conversions than for newbuildings.” One issue that can slow down the conversion process


is communication


problems between the plan approval staff and the on-site surveyor in the event of unforeseen problems. At ClassNK however, the vast majority of surveyors undergo several years of training as plan approval staff before they are sent into the field. Te Japanese class


44


society adds: “As a result, our surveyors on-site can give clear instructions to the shipyard in accordance with our rules and guidelines and thus help ensure the project is completed successfully and on time. At the same time, we try and provide the best support to both the shipyards and the ship owners by only dispatching experienced surveyors with plan approval experience, as well as by rapidly reviewing submitted drawings and providing advanced analysis support.” One of the main challenges during the


conversion process which has been identified by ClassNK is developing a reliable and comprehensive reinforcement plan, which requires the results of complicated analysis such as fatigue life assessment. In order to complete this process as efficiently as possible, the society carries out fatigue assessment on


all the longitudinals, as well as representative primary support members in the cargo area, and develops a clear proposal based on the results. For older FSOs and FPSOs, ClassNK


can also provide lifetime extension support services, which can be used to extend the service life of existing vessels. By offering these services, the society says it hopes that it can help owners improve the cost efficiency of their FSO/FPSOs and ensure the safety of the vessels throughout their service life. Outside the FSO/FPSO conversion field,


another area of growing involvement for ClassNK is ballast water management. It is currently part of a Joint Research Project, together with various Japanese ship owners, educational establishments and equipment manufacturers, into the use of 3D laser


Shiprepair and Conversion Technology 1st Quarter 2012


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