Bulk Carriers have been developed since 1950 to carry large quantities of non-packed commodities such as grains, coal and iron ore. Nowadays, there are some 5,000 bulk carriers around the world and this number points to some concerns that affect owners of these types of ship and ports. One of these problems is the big waiting time at the ports that reaches 12% of the global fleet around the world at any given moment. At Brazilian iron ore ports the time waiting average was of 6–8 days during 2006–2008. A concrete example is the VALE operation that responds from mineral resources exploration to mineral resources delivery, passing through mines, railroads, seaport terminals and shipping business, forming a logistic chain that can not be interrupted by the expected growth in trade and consequent port congestion. In view of this, PROJEMAR and VALE faced the challenge of designing ore carriers in such a way that it would not interfere with the logistics chain by delaying other ships at the loading or discharge terminal. As the cargo operation is taken as the initial point of the design conception, the expected final product is a ship able to safely take loading rates as high as 16,000 tons of ore per hour, with each hold loaded in one pour and the ship fully loaded in one pass, resulting in fewer pours into the holds of the ore carrier, faster loading operations and, consequently, a significant economy for the ship owner and for the port. The amount of extra steel needed over conventional designs: less than one percent. The fundamental idea of this new concept, which PROJEMAR calls “single-pour, single-pass” design, is a method of ballast control that is synchronized with the cargo loading, scientifically deballasting the ship during loading in a way that balances the forces induced by the incoming cargo. Potential hull loading stress problems can occur due to the manner in which ore cargoes are loaded and due to the amount of cargo which is loaded in an individual hold. To avoid the creation of any unacceptable stresses in the ship’s structure, loading studies considering the planning of cargo loading and discharging operations, maximum allowable and minimum required mass of cargo for each hold and for adjacent holds as a function of the draught at mid-hold position in form of hold mass curves, calculations of still water shear forces and still water bending moments for each port loading condition and structural analysis are required to be developed on the early design stages. This ship loading concept is creating a new generation of ore carriers in such a way that the main class societies are nowadays developing new specific class notation dedicated to these ships. The purpose of this paper is to present the “single-pour, single pass” concept development and how it has been applied to the design of the new 400,000 DWT ore carriers that are being built for VALE in Chinese and Korean shipyards, and to the 80,100 DWT Bauxite Carrier that are being built for LOG-IN in Brazil. The “single-pour, single pass” concept was also partially considered on the design of 12 VLCCs that are being converted to VLOCs for VALE in China with PROJEMAR’s design.

It is well known that ships vibrate due to waves. The wave induced vibrations of the hull girder are referred to as springing (resonance) and whipping (transient vibration from impacts). These vibrations contribute to the fatigue damage of fatigue sensitive details. An Ore Carrier of 400 000 dwt is currently being built by DSME, and at time of delivery, it will be the world’s largest bulk (ore) carrier. The scantlings of large ships must be carefully designed with respect to global loading, and when extending the design beyond experience, it is also wise to consider all aspects that may affect operation and the life time costs. The vessel will also enter a long term contract and is therefore to be evaluated for 30 year Brazil-China operation. In order to minimize the risk of fatigue damage, the vessel is designed according to DNV’s class notation CSA-2 requiring direct calculations of the loading and strength. Further it has been requested to include the effect of springing and whipping in the design. Reliable numerical tools for assessing the additional fatigue effect of vibrations are non-existing. DNV has, however, developed an empirical guidance on how the additional effect may be taken into account based on previous development projects related to the effect of vibrations on large ore carriers Due to the size and route of operation of the new design, it has, however, been required by the owner to carry out model tests in both ballast and cargo condition in order to quantify the contribution from vibration. The results from this project have been used for verification and further calibration of DNV’s existing empirical guidance. A test program has been designed for the purpose of evaluating the consequence in head seas for the Brazil to China trade. Full scale measurements from previous development projects of ore carriers and model tests have been utilized to convert the current model tests results into estimated full scale results for the 400 000 dwt vessels. It is further important to carefully consider how the vibrations are to be included in the design verification, and to develop a procedure for taking into account the vibrations which results in reasonable scantlings based on in-service experience with similar designs and trades. This procedure has been developed, and a structural verification has been carried out for the design. The final outcome of the model test was in line with previous experience and in overall agreement with DNV’s empirical guidance, showing a significant contribution from vibrations to the fatigue damage. The springing/whipping vibrations more than doubled the fatigue damage compared to fatigue evaluation of the isolated wave induced loading. The cargo condition vibrated relatively more than experienced on smaller vessels. Various sources to establish the wave conditions for the Brazil to China ore trade were used, and the different sources resulted in significant differences in the predicted fatigue life of the design.

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Under the development of the Brazilian pre-salt onerous concession areas Petrobras contracted Enseada Industria Naval for the conversion of 4 (four) VLCC ships into the hulls of FPSOs P74, P75. P76 and P77, for which PROJEMAR have awarded a contract for the complete hull conversion engineering design. Even with the accumulated experience on the design of 12 (twelve) FPSOs conversions, nothing could be compared with 4 (four) ships being simultaneously converted in two shipyards, being one in Brazil and one in China, to receive 4 (four) Process Plants weighting about 35.000 t designed by 3 (three) different Topsides engineering designers. This paper intends to describe the main challenges and achievements of the engineering design work for the conversion design of the 4 (four) FPSOs, where the need to maximize standardization conflicted with the different hull configuration of the VLCCs that were being converted, with the different production characteristics of the two shipyards involved on the conversion work and with the different design philosophies of the Topsides engineering designers. These can be exemplified by: The need to face single hull and double side VLCCs that were built in different shipyards in Korea and Japan, what led to different main deck reinforcement and different strategies for steel renew;The different Topsides engineering led to different main deck reinforcements for the Topsides equipment and structures;The main equipment was standardized, but the different ship´s hull structure led to different structural solutions, and smaller equipment were acquired from local suppliers close to shipyards;Different arrangements and tanks configuration led to different piping designs;A new standard accommodation block needed to be fitted in different main deck structure configurations;Individual motions analyses were carried out for each FPSO, but needed to be validated by a unique model tests program;etc In summary, maximize the design standardization is a key path to improve construction productivity, but as an FPSO conversion design is essentially a tailor made activity, this duality was highly pronounced when dealing with the multiple simultaneous activities of the Cessão Onerosa FPSOs design.

Designed to operate in Campos Basin Offshore Brazil, the FPSOs P43 and P48 are a considerable mark on the offshore industry in terms of the number of innovative engineering procedures developed for their design. As the FPSOs are going to operate as permanent floating production units at the same location for 20 (twenty) years, a complete dedicated design was performed considering the specific site conditions. This was carried out not only to determine mooring system and structural design aspects but also to predict and govern operational behavior in motion and stability, the object of this paper. Motion analysis of permanent offshore floating units is normally performed taking into account the specific site environmental conditions. On the other side, stability analysis is normally performed with worldwide limits criteria. The result of this is a predicted motion behavior based on the typical loading conditions and site environmental data that are not necessarily aligned with the stability limits of the unit defined by a minimum GM curve, eventually causing unexpected operational conditions. The main idea on the Barracuda and Caratinga project was to combine the stability limits of the unit with the predicted motion analysis typical operation conditions, defining a normal operation region where the FPSO will operate to guarantee a global performance in accordance with the predicted analysis. Based on the minimum GM curve derived from intact and stability analysis, new maximum and minimum GM curves were determined based on mass properties combinations where the motion response will be permanently inside the design parameters. The intent of this paper is to present the work performed to define the maximum and a minimum operational GM curves for the FPSOs, including motion and stability analysis, hull girder and local structural limits and a considerable amount of real operational considerations, that results in a general overview of a very refined global response design developed for a special project. Introduction Reviewing the usual procedures adopted to perform the stability analysis and global motion analysis of FPSOs, one realizes that the stability analysis normally considers the Unit as a ship calculated for unrestricted service. On the other hand, the global motion analysis considers the Unit as a fixed structure under the action of the specific site environmental conditions. It is easy to understand that the stability of a ship-shaped offshore unit shall be similar to the stability limit of a ship with the same hull forms, but motion analysis are normally performed for the expected operational load condition, not for the stability limit of the unit. For offshore floating units that are not able to store oil on board, like a semi-submersible platform, the stability limits are quite close to the expected load conditions, as there are few possibilities to vary the load of the unit the mass properties do not change very much. On an FPSO, the oil storage capacity weight is much larger than the vessel lightweight and consumables combined. The different possible combinations of the cargo tank loading can result in considerable different mass properties values for the same draft.