Versatile newbuilding for Dag Engström

Flexibility is the name of the game in the short-sea trade. While most owners claim their roro newbuildings are state-of-the-art multi-purpose vessels, it is unusual to come across a design which is truly an ?all in one? design concept. A new 13,000 dwt freight roro vessel, ordered by Swedish shipping company Dag Engström Rederi, is likely to be about as close to an ?all in one? vessel as there can be. This ship, to be named Romira, is being built at the Chinese yard of Zhonghua and is scheduled for completion within the next couple of months. Unlike a number of recent roro newbuildings, Engström has resisted the temptation of taking shortcuts that would result in operational compromise. Loading, unloading, berthing, and operation at sea are designed for the highest efficiency and safety with a minimum of manpower involved. The design, developed in conjunction with Skipskonsulent of Bergen, which is part of the Vik & Sandvik group, is focused on cargo flexibility, economy and a high environmental profile. Although the vessel?s delivery from the Chinese shipyard has been much delayed from the original date of April 2001, Romira promises to be a milestone in the roro freight carrying sector, says a spokesman for the Bergen-based consultants, marrying Engström?s 20-year experience in the trade with a pragmatic approach to ship design. Chinese yards customer orientated The Zhonghua yard has produced a vessel tailored to the client?s own concept. The contract price it offered to the owner was extremely competitive and it has been able to comply with the owner?s requirements in terms of design and equipment. Chinese shipbuilders argue that what they save on labour and steel costs they can invest in top quality European equipment. Compromises on equipment specifications are commonplace in Europe, say Chinese shipbuilders, because European yards have such high costs elsewhere. This means, say the Chinese, they can be more customer oriented in their approach to shipbuilding. The equipment selected for Romira is from suppliers and sub-contractors well know to Engström as Table 1 shows. London rules give greater scope By designing the ship with the full freedom of the current tonnage measurement rules, the so-called London rules, it has been possible to create the lines and underwater hull shape in such a way as to optimise the speed-consumption relationship. “It is absolutely necessary to start the design phase with the new rules wholly in mind from the beginning,” argues Engström boss Dag Engström. Another positive effect has been the freedom to design for a centre of gravity that would give the ship a moderate stability and transverse acceleration forces to the benefit of freight security. In contrast, the former Oslo tonnage measurement rules ? applied up to the mid 1990s ? made true flexibility difficult because of parameters relating to freeboard, unregistered space in open shelter decks, double bottom depth and frame depth. Engström considers that many of the larger roro?s were accordingly too stiff and the ensuing transverse acceleration forces led to cargo damage and loss. Although the two-in-one concept of roro cargoes plus containers has been reasonably successful, the reality is that the most economically viable vessels have been designed and optimised for specific trades and, when a change is called for, have been converted or modified subsequently. Although the London 1969 rules came into effect for newbuildings from 1982 and for existing ships from 1994, it is contended by industry pundits that there has been a long period in which former design concepts have been adapted to the new regulatory environment. The reality of the regulations is that they give owners and designers greater freedom to form lines and underwater shapes to optimise seakeeping, speed and fuel consumption in addition to free heights and breadths allowing for all possible multiples of trailers, cassettes, cars and containers. It is possible to place the centre of gravity to give a ship a moderate GM (transverse metacentric height), irrespective of whether the average weight of the cargo unit is 20t or 80t. And the registered tonnage of individual hulls can be increased dramatically for roro ships and other open shelter deck types. Capacious workhorse What sets Romira apart is its cargo carrying capabilities. No longer tied to the old grt rules, the internal layout of the vessel has been determined by the characteristics of the cargo. Designed with a free height of 7m on all decks, and transverse multiples based on trailers, cassettes and containers, the ship is able to accommodate all possible cargo combinations. As an example, 9 lanes of cassettes can be stowed on upper and main deck based on a lane width of 2.67m. If trailers or mafis are transported, eight lanes will be utilised with a lane width of 2.97m. On the tanktop deck it is possible to accommodate eight lanes of cassettes or seven lanes of trailers. This makes it possible to load cassettes in some areas and mafis or trailers in other areas reflecting the vessel?s flexibility. With a beam of more than 25m, under the London rules, owners have full freedom to locate the main deck at the optimum level. This optimal location of the main deck on Romira offers the possibility to double stack containers on Mafi trailers on all three decks giving a total payload of 220 Mafis corresponding to 870 teu or 430 feu boxes. Alternatively, cassettes can be used for double stacking of containers and for paper and other forest products throughout the three decks to the tune of 200 cassettes and 20 Mafi trailers, equivalent to around 850 teu. If needed, it is possible to fit a car deck in the upper part and still have trailer height underneath. Where car carrying capacity is the prime consideration, it is possible to fit two fixed or hoistable decks and thereby load in three different levels in all cargo areas giving a car capacity of about 2,000. Other stowage intake possibilities are 212 trailers plus 600 cars, or a paper load taken in ?storo? fashion on any or all decks without the need for additional dunnage or protection. There is currently no other roro with these capabilities, believes Engström. Romira has three cargo decks linked by two internal fixed ramps with an incline of about 7 deg. and a free width of 4.1m. Cargo is loaded and discharged via the main deck stern threshold by means of a Hamworthy KSE combined door ramp. There are 30 reefer points on the upper deck and 20 on the main deck which are continuously monitored through a computerised system from both the bridge and the cargo control room. The vessel is certified to transport a wide range of dangerous cargoes while the lower deck is certified to transport vehicles with petrol in their tanks. The total lane metres for trailers and mafis is 2,700 while for cassettes it is 2,930. All decks are completely flat with no knuckles and are designed for an 80t payload on cassettes or mafis. Safe loading and unloading is aided by a high capacity ventilation system with 30 air changes per hour and a pump based automatic anti-heeling system with a 2 x 1,700 m3/hour capacity. Large ballast tanks fore and aft are linked via a pair of 600m3/hour pumps to ensure the vessel is able to maintain a constant trim for the 15m long stern ramp throughout the vessel?s loading cycle. Closed-circuit TV cameras are installed on all cargo decks and ramps including the stern ramp and its shore approach. Power of one For reasons of fuel economy, capital costs and operational expenses, Engström endorses the concept of one large main propulsion engine ? particularly in view of the company?s previous newbuilding, which has been in service for nearly 10 years without suffering any engine breakdowns. The single Wärtsilä 12V46C medium-speed main engine has an output of 12,600 kW which is sufficient to enable Romira to achieve a service speed of 20 knots at trailer draught. At a deeper design draught of 7.4m, the service speed will be 18 knots with considerable margins. Despite this, Engström believes that it is essential to have some get you home propulsion redundancy to avoid cargo damage that could be induced by rolling and pitching in heavy weather in the event of main engine breakdown or stoppage. For the first time on a roro vessel, the gearbox will incorporate a PTO/PTI (power take off/power take in). This will allow the ship to be propelled at a reduced speed of about 10 knots using the two 1,000kW gensets and a large shaft alternator which doubles up as a 2,000kW motor. The motor can additionally be used to boost the main diesel engine output if required. The slender hull form makes it possible to reduce fuel consumption at 16 knots by as much as 37% compared with more traditional types of roro built in the 1990s, says a spokesman from Skipskonsulent. It is claimed by the designers that the vessel will have a better fuel consumption than most roro ships having half the capacity. To facilitate harbour manoeuvres, Romira is fitted with a Schilling high lift rudder. This rudder provides a unique combination of high turning angle and braking effect which is very useful for crabbing manoeuvres providing a 90 deg. thrust at the stern of the ship with a 67.5 deg. rudder angle. The newbuilding will also be equipped with a pair of 700kW bow thrusters in addition to a 700kW stern thruster. By positioning the superstructure aft, the ship?s seakeeping capabilities are improved, say the designers, especially in the ?hove to? position since the windeye can be achieved with a minimum of propulsion and strain to the vessel and its cargo. To ensure an acceptable GM in all loading conditions, a pair of large flume anti-roll tanks have been installed above the mooring deck forward and integrated as part of the streamlined cargo protection bulwark. In addition, the unused spaces in the flare of the bow contain ballast tanks which help to raise the centre of gravity of the vessel in lightly loaded conditions thereby making the vessel cargo friendly. Environmental issues are well catered for with low bunker consumption in combination with low NOx installations. All fuel and oil tanks have double hull protection while special facilities on board means that very little chemicals are used and those that are are environmentally friendly. n