IMO BULK CARRIER SAFETY. Bulk Carrier Model Test Progress Report. Submitted by the United Kingdom

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1 INERNAIONA MARIIME ORGANIZAION E IMO MARIIME SAFEY COMMIEE 75th session Agenda item 5 MSC 75/5/3 12 March 22 Original: ENGISH BUK CARRIER SAFEY Bulk Carrier Model est Progress Report Submitted by the United Kingdom Executive summary: Action to be taken: Paragraph 2 SUMMARY his document reports on results to date of the model tests initiated following the Re-opened Formal Investigation into the loss of the m.v. Derbyshire. It is concluded that whilst attention has been focused on the vertical forces on hatch covers, the horizontal forces on hatch covers and coamings are of equal importance. Related documents: MSC 74/5/1, SF 44/4/1, MSC 75/5/1 Introduction 1 owards the end of the Re-opened Formal Investigation (RFI) into the loss of m.v. Derbyshire, the United Kingdom Government agreed to fund a programme of model tests at the Maritime Research Institute, Netherlands (MARIN). he research programme was agreed between the United Kingdom s Maritime and Coastguard Agency (MCA) and loyds Register of Shipping (R), and supervised by both parties. MSC 74/5/1 reported on the progress of the model test programme to March 21. his paper reports on the progress since that date and highlights some key results from the model tests and their subsequent analysis. A more detailed report including proposals for changes to IC66 Regulation 16 will be made available to SF All the model tests are now complete. he key results have been analysed by ancaster University, who confirmed their initial conclusion that the best fit to the impact loads data was given by the Generalised Pareto distribution. he results for each ship have been pooled to improve the reliability and consistency of the data, and the impacts for No.2 hold paired with those for No.1 hold. he preliminary results were discussed, in a conference organized by the Royal Institution of Naval Architects (RINA) 1 and sponsored by the United Kingdom s Department of ransport, ocal Government and the Regions (DR), in October 21. Electronic copies of the MARIN and ancaster University reports are available from the MCA website at 1 Design and Operation of Bulk Carriers Post mv Derbyshire he Royal Institution of Naval Architects, ondon 9 th -1 th October 21 For reasons of economy, this document is printed in a limited number. Delegates are kindly asked to bring their copies to meetings and not to request additional copies.

2 MSC 75/5/3-2 - Selected hull forms 3 A total of 235 tests have been carried out in head, bow quartering and beam seas on three models: two Capesize and one Panamax vessel. he principal particulars of the three vessels are given in the following table and the body plans are shown on figure 1. Phase 1- SSRC Capesize Phase 2 New Capesize Phase 3 - Panamax Scale 1:65 1:5 1:5 ength pp (m) Breadth (m) Depth (m) Draft Displacement (tonnes) 188,2 24,588 83,151 No of tests est conditions Phase1 Phase 2 Phase 3 Figure 1 Body Plans of MARIN models. 4 Figure 2 shows the range of conditions tested for each Phase of the programme, plotted against the Buckley survivability wave envelopes for the Northern and Southern hemispheres 2. he test condition for the Japanese model tests reported in SF 44/4/1 is also included for comparison. Figure 2 - est conditions Northern Hemisphere Survival Southern Hemisphere Survival Phase 1 ests Phase 2 test variant Phase 3 tests Japanese (SF 44/4/1) p (sec) 5 Figure 2 indicates that, in general, the MARIN test conditions are close to the Buckley survivability envelope, but that the Japanese tests are some way below the envelope. Other test conditions away from the survivability envelope were defined to test specific hypotheses, for example whether travelling at higher speeds in lower sea states would produce higher loads (which they did not). 2 he Design Wave Climates for World Wide Operation of Ships, Part 1: Establishment of Design Wave Climates. WH Buckley, SNAME 7R Report r-5, 21

3 - 3 - MSC 75/5/3 ertical loads 6 In their paper to the RINA conference, referenced above, Sole and Milne filtered the results for hatch No.1 to consider only the data derived from self propelled and zero speed tests, and made a logical case to apply different probabilities of non exceedance (p values) to the loads predicted by ancaster University for the intact and damaged conditions in the different sea states, as follows: North Atlantic PM spectrum Rotating ropical Storm Jonswap spectrum Intact Damaged A similar analysis has been carried out to that presented in the RINA paper, except that the data for hatch No.2 is added. he loads at the appropriate value of p were plotted on the basis of the factor H from IACS UR S 21, taking the parameter d f to the top of the hatch coaming, as proposed by Sole and Milne. Figure 3 shows the loads plotted against H. Also included for reference is the mean of 1/1 highest loads obtained at the two longitudinal positions reported in SF 44/4/1; however these loads extrapolated to p values corresponding to the above table will be considerably in excess of the other points in the figure. Figure 3 - ertical oads plotted against parameter H from IACS URS 21 2 URS21 Phase 2 Intact No1 Hatch Phase 2 Intact No 2 Hatch Phase 2 FP flooded No 1 Hatch Phase 2 FP flooded No2 Hatch Phase 2 No 1 Hold Flooded No 2 Hatch Phase 3 Intact No 2 Hatch Phase 2 No 1 Hold flooded No1 Hatch Phase 3 Intact No1 Hatch Phase 3 FP Flooded No 1 Hatch SF 44/4/1 14 Phase 3 FP Flooded No 2 Hatch Phase 3 No 1Hold flooded No 2 Hatch Phase 3 No 1 Hold flooded No 1 Hatch Phase 1 Intact No 1 Hatch 12 1 Phase 1 Intact No 2 Hatch Phase 1 No Hold flooded No 1 Hatch Phase 1 No1 Hold flooded No 2 Hatch Japanese 1/1 values (SF 44/4/1) Power (URS21) URS H 8 Figure 3 confirms that the vertical loads are well in excess of URS21, and the need for reconsideration of that standard. It is considered that the loads in damaged conditions, at a suitable reduced probability from the intact conditions, should be included in any revision of that standard. he original UR S21is based on intact conditions only, but inspection of the above figure shows that the loads from the intact conditions are in excess of UR S21.

4 MSC 75/5/ he inclusion of design speed within the formula for factor H is also of concern, as the influence of speed is unclear from evidence from these tests. Figure 4 shows the impact of speed on the Phase 2 loads in the intact condition. Figure 4 - Effect of speed on vertical load 7 6 Phase 2 - Intact p= Zero Speed Speed = 13.5 knots Speed = 15.5 knots Head seas Bow quartering seas Significant wave height (m) 1 Figure 4 indicates that the effect of calm water speed on vertical load is not consistent across the range conditions tested, and further work is required to assess whether calm water speed is a primary or secondary parameter in relation to vertical loads. Horizontal loads 11 oads were also measured by MARIN in the longitudinal and transverse directions and some of this data has been analysed by ancaster University. Figures 5 and 6 show the maximum loads measured by MARIN for all three components for Phases 2 and 3 respectively for head and bow quartering seas. Figure 5 - Distribution of loads along the length of Phase 2 (Cape size) vessel Note: are ongitudinal oads are ransverse oads are ertical oads No 1 Hatch 25 2 No 5 Hatch No 2 Hatch x/ from FP Figure 6 - Distribution of the loads along length of Phase3 (Panamax) vessel Note: are ongitudinal oads are ransverse oads are ertical oads No 1 Hatch No 2 Hatch No 4 Hatch x/ from FP

5 - 5 - MSC 75/5/3 12 Figures 5 and 6 indicate that the longitudinal load on the forward coaming of No 1 hatch is between 2 and 3 times the vertical load. Also whilst the vertical load reduces towards midships, the longitudinal load reduces to a lesser extent, and on the Phase 2 Capesize the maximum longitudinal load recorded at No.5 hatch is greater than that at No.2 hatch. In both cases the transverse loads at No.1 hatch appear to be a similar order of magnitude to the vertical loads, and again reduce in magnitude more slowly towards midships. 13 Further analysis of the longitudinal loads against the corresponding vertical load for hold No.1 indicate a linear trend, for both vessels, but at a different ratio, as shown in figure 7 below. MARIN noted that the magnitude of the longitudinal forces appeared constant irrespective of freeboard. Further work is required to clarify the reasons for this difference, and to develop a simple way of estimating the longitudinal load from a calculated vertical load. Industrial sources indicate that the limiting load for hatch covers to avoid longitudinal displacement is about 45kPa, well below the longitudinal forces predicted from the model tests. Any revised standards therefore need to take into account the longitudinal forces. Figure 7 - ongitudinal oads for Hold 1 for Phase 2 and 3 models Phase 2 Bow seas Phase 3 Bow Seas inear (Phase 2 Bow seas) inear (Phase 3 Bow Seas) y = x y =.634x he longitudinal forces for hold No.2 can be estimated as a proportion of those for hold No.1 (about 83% for the Capesize and 68% for the Panamax). his could be influenced by the way in which the data was paired in the ancaster University analysis, but appears consistent with the MARIN values. Beam seas tests ertical oad (kpa) 15 A total of 11 tests were run for beam seas using the Phase 1-3 models, in the intact conditions, and 1 with No.1 hold flooded using the Phase 1 model. he sea conditions were chosen to give wave periods straddling the natural rolling period of each vessel, with the corresponding significant wave heights selected to be as close to the survivability envelopes as practicable. 16 Figure 8 shows the transverse loads plotted against a numeral, which takes into account both the local freeboard and the location along the length of the vessel, and appears to take into account in a logical manner the different loads associated with the Capesize and Panamax vessels. he MARIN data for No.1 hold has not been analysed by ancaster University, but the data as a whole shows a similar trend. It is anticipated that Figure 8 can be developed to provide a complete picture of the distribution of transverse loads in beam seas along the length of the vessel.

6 MSC 75/5/3-6 - Figure 8 - ransverse loads in beam sea conditions Cape Size No 2 Hold Cape Size No 5 Hold Panamax No 2 Hold Panamax No 4 Hold df*sqrt(2x/), where df is from URS21 to top of hatch cover and x/ from FP Hatch cover design standards 17 he United Kingdom considers that the results of this work should be used to develop up to date environmental loads, for hatch cover fastenings in the longitudinal and transverse directions, as well as for covers vertically. An update to UR S21 is considered an essential element in this process. 18 Whilst beam seas may be less important for Capesize and Panamax vessels with their side rolling hatch covers, they are significant for smaller vessels with longitudinally folding covers, and it is considered that further analysis is necessary to validate beam sea results on smaller vessels. 19 MSC 75/5/1 provides a progress report on the International Collaborative FSA Study on Bulk Carriers, and focuses on the initiating events and associated fatalities. It notes that a number of hatch cover failures have been initiated by side shell failure causing an internal pressure on the cover, and also notes that most fatalities occur after hatch cover failure. Consideration should then be given to means of relieving internal pressure, on covers not designed to withstand it, to avoid hatch cover failure. Action requested of the Committee 2 he Committee is invited to consider the above results and to instruct the Bulk Carrier Working Group to be established at this session to:.1 review the work undertaken to date;.2 endorse the proposal to update the hatch cover design environmental load criteria in the IC66; and.3 concur that the SF Sub-Committee should be instructed to take this into account when it is revising the IC 66.