A part of BMT in Maritime Transport Effect of the Minimum Ballast Condition on Bulk Carrier Manoeuvrability for INTERCARGO. ISSUE DATE: 19th September 2008 REPORT NO: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability CONTENTS 1 TERMS OF REFERENCE............................................................................................. 2 2 BACKGROUND............................................................................................................ 2 3 OBJECTIVES OF THE STUDY..................................................................................... 2 4 METHODOLOGY.......................................................................................................... 2 4.1 General.................................................................................................................. 2 4.2 Capesize Bulk Carrier............................................................................................ 3 4.3 Met-ocean Conditions for Tubarao and Ponto de Madeira..................................... 3 4.4 Matrix of Scenarios................................................................................................ 4 5 SIMULATION RESULTS .............................................................................................. 6 6 DISCUSSION................................................................................................................ 8 7 CONCLUSIONS.......................................................................................................... 10 8 REFERENCES............................................................................................................ 11 APPENDIX A – SIMULATION RESULTS........................................................................... 12 Document Information Project Bulk Carrier Manoeuvrability Report Title Effect of the Minimum Ballast Condition on Bulk Carrier Manoeuvrability Client INTERCARGO Report ref: C12145.1R Prepared by: Mr Dimitrios Argyros Naval Architect, BMT SeaTech Ltd Approved by: Mr Simon Burnay Group Manager – Marine Safety & Compliance, BMT SeaTech Ltd Document History Version Changes By 1 Draft for Release DA, SB 2 Comments from client added SB Information contained in this document is commercial-in-confidence and should not be transmitted to a third party without prior written agreement of BMT SeaTech Ltd. © Copyright BMT SeaTech Ltd 2008 1 Report No: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability 1 TERMS OF REFERENCE BMT SeaTech Ltd (BMT) was instructed by INTERCARGO to conduct a simulation study to assess the effect on ship manoeuvrability of minimum ballast conditions for Capesize bulk carriers. The study was undertaken by BMT staff with the simulations being conducted using the PC Rembrandt ship handling and manoeuvring simulator, developed by BMT. This report describes the methodology adopted for this project and includes the relevant analysis, a summary of results, and appropriate conclusions. 2 BACKGROUND Due to the increased demand for raw materials such as iron ore, it is understood that a number of bulk terminals have been taking measures to optimise port throughput. This has resulted in terminals requesting fast ship turn-around times necessitating a very light ballast arrival condition in order to be able to load at high rates e.g. at up to 16000 tonnes per hour; in some cases also allowing 90% propeller immersion to facilitate this. It is therefore understood that a number of operators of large bulk carriers (Capesize) have reported problems with vessel manoeuvrability due to the requirement for arriving in a loading condition that results in a very large trim by the stern and significantly higher windage. Both of these effects are well known to have detrimental effects on vessel manoeuvrability ref [1], relative to normal loading conditions. 3 OBJECTIVES OF THE STUDY The aim of this study is to present and quantify the differences in vessel manoeuvrability due to the requirement for a minimum ballast condition versus the normal arrival loading condition. 4 METHODOLOGY 4.1 General The methodology employed for this study was to run a set of simulations for two ports where the loading rates are known to be 16,000 tonnes per hour ref [2] and [3]. Simulations were completed for arrival scenarios at the ports of Tubarao and Ponto de Madeira in Brazil, based on a matrix of scenarios derived from an analysis of met-ocean conditions for the area. Figures 4.1(a) – (b) present the nautical charts for Tubarao and Ponto De Madeira respectively, courtesy of UKHO. 2 Report No: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability Figure 4.1(a) – Tubarao Bulk Terminal Figure 4.1(b) – Ponto de Madeira Bulk Terminal 4.2 Capesize Bulk Carrier For the purpose of simulating the vessels which call at these ports, a Capesize vessel was selected that was felt to be typical for this class of ship. A ship model was provided with the principal characteristics given in Table 4.1 below. Normal Loaded Normal Ballast Minimum Ballast Parameter Condition Condition Condition Length Overall [m] 289.0 289.0 289.0 Length Between Perp. [m] 279.0 279.0 279.0 Breadth [m] 45.0 45.0 45.0 Mean Draught [m] 18.0 8.2 5.3 Stern Trim [m] 0.0 1.2 5.15 Propeller Immersion [%] 100% 100% 95% Rudder Immersion [% of area] 100% 73% 65% Table 4.1 – 180,000 DWT Capesize Vessel Model Principal Particulars 4.3 Met-ocean Conditions for Tubarao and Ponto de Madeira A brief analysis of wind, wave and current conditions was undertaken for the ports to be assessed. The results of this analysis are as follows: Figures 4.2(a) – (c) present the data used for the Port of Tubarao to establish the tide heights, wind and wave data to be used in the simulations. Figures 4.3(a) – (c) present the equivalent data for Ponto de Madeira. 3 Report No: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability Tubarao Ponto de Madeira Figure 4.2(a) – Tubarao Tidal Data Figure 4.3(a) – Ponto de Madeira Tidal Data Figure 4.2(b) – Tubarao Wind Data Figure 4.3(b) – Ponto de Madeira Wind Data Figure 4.2(c) – Tubarao Wave Data Figure 4.3(c) – Ponto de Madeira Wave Data 4.4 Matrix of Scenarios Based on the analysis of the data presented in Section 4.3, the scenario matrix was derived and is presented in Table 4.2 below. The scenario matrix was derived by analysing the data presented in Figures 4.2 and 4.3 to obtain the following information: - Typical tidal ranges in neap and spring cycles. - Wind and wave data relating to the probability of occurrence e.g. conditions that occur 50% 25%, 10% and 1% of the time. - Current conditions based on available public data e.g. Admiralty South American Pilot. 4 Report No: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability Tidal heights were selected for each port that gave a typical height of tide combined with the relevant current flow. For Tubarao, it was determined that there is a general South-west current flow parallel to the shoreline of circa 1 knot. This was therefore applied with a tidal height of 0.8m representing a typical mid-tide condition (i.e. maximum current flow). The current was defined to be realistic inside the port breakwaters such that the effect is reduced when close to the berths. For Ponto de Madeira, the tidal height is much larger (reaching a range of up to 6 metres), in which case stronger currents can be expected. Based on the data available, a 2 knot current was selected as being significant, but not extreme. Again a mid-range tidal height of 4 metres was selected. For wind and wave conditions, analysis was made of the percentage occurrence data in Figures 4.2 and 4.3 to derive the typical wind speeds and directions for prevailing conditions (i.e. the majority of the time, or circa 30-50% probability), stronger conditions ( e.g. 25% or 10% probability) and storm conditions (less than 5% probability). The vales used as presented in Table 4.2 were only included if they represented feasible conditions, i.e. they are practically as well as theoretically possible to occur and hence conditions with a very low probabilities of occurrence were not included. Wind Current Tide Waves Height Port ID Condition Speed Dir Speed Dir Ht Period Dir +CD [kts] [deg] [kts] [deg] [m] [sec] [deg] [m] T1 Ballast 10 30 1 225 0.8 1.5 7.5 90 T2 Ballast 14 30 1 225 0.8 1.5 7.5 90 T3 Ballast 20 30 1 225 0.8 2.5 10.5 90 Tubarao T4 Light Ballast 10 30 1 225 0.8 1.5 7.5 90 T5 Light Ballast 14 30 1 225 0.8 1.5 7.5 90 T6 Light Ballast 20 30 1 225 0.8 2.5 10.5 90 M1 Ballast 15 90 2 0 4 1.5 5.5 30 M2 Ballast 20 90 2 0 4 2.5 6.5 30 M3 Ballast 20 30 2 0 4 2.5 7.5 30 M4 Light Ballast 15 90 2 0 4 1.5 5.5 30 Ponto M5 Light Ballast 20 90 2 0 4 2.5 6.5 30 de M6 Light Ballast 20 30 2 0 4 2.5 7.5 30 Madeira M7 Ballast 15 90 2 180 4 1.5 5.5 30 M8 Ballast 20 90 2 180 4 2.5 6.5 30 M9 Ballast 20 30 2 180 4 2.5 7.5 30 M10 Light Ballast 15 90 2 180 4 1.5 5.5 30 M11 Light Ballast 20 90 2 180 4 2.5 6.5 30 M12 Light Ballast 20 30 2 180 4 2.5 7.5 30 Table 4.2 – Scenario Matrix The manoeuvres required for arrivals at each port can be summarised as: 5 Report No: C12145.1R INTERCARGO Bulk Carrier Manoeuvrability Tubarao Ponto de Madeira - Course keeping during deceleration - Course keeping during deceleration - Swinging - Steady turn / swinging - Backing into berth - Coming alongside - Coming alongside The simulations were conducted by BMT’s experienced marine staff in a manner to enable suitable comparison between specific manoeuvres for the two loading conditions. Tugs were applied in the simulations to aid berthing and control of the ship. The available tugs were determined from publically available information (e.g. http://www.magioli.com/pmadeira.htm#P) and they were controlled using the PC Rembrandt on-screens controls, applying normal nautical practice for the tug use. In the absence of specific information, the tug sizes available for Tubarao were assumed to be the same as Ponto de Madiera. 5 SIMULATION RESULTS The full set of simulation results are presented in Appendix A.