VINTERSJÖFARTSFORSKNING

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1 STYRELSEN FÖR VINTERSJÖFARTSFORSKNING WINTER NAVIGATION RESEARCH BOARD Research Report No 76 Hanna Leisti and Kaj Riska OBSERV - OBSERVATIONS OF SHIP ICE PERFORMANCE IN THE BALTIC Winter 2011 Finnish Transport Safety Agency Finnish Transport Agency Finland Swedish Maritime Administration Swedish Transport Agency Sweden

2 Talvimerenkulun tutkimusraportit Winter Navigation Research Reports ISSN ISBN

3 FOREWORD In its report no 76, the Winter Navigation Research Board presents the outcome of the project on observations of ship ice performance in the Baltic in winter The Finnish-Swedish Ice Class Rules include an ice performance requirement. The aim of this requirement is to ensure that merchant ships have such performance that they may follow icebreakers at an adequate speed and also move independently in lighter ice conditions. At present the ice performance requirement may be verified by ice model tests or more exact calculations. The aim of performance requirement is to make winter navigation fluent, efficient and economic; ships that have less ice performance, slow down the system. This report is giving the general view of the ice performance ability of the ships proceeding in the Gulf of Finland, the Bothnian Sea and the Bothnian Bay. The Winter Navigation Research Board warmly thanks Professor Kaj Riska and Ms. Hanna Leisti for this report. Helsinki and Norrköping June 2014 Jorma Kämäräinen Finnish Transport Safety Agency Peter Fyrby Swedish Maritime Administration Tiina Tuurnala Finnish Transport Agency Stefan Eriksson Swedish Transport Agency

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5 OBSERV- Observations of Ship Ice Performance in the Baltic Winter 2011 P

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7 CONTENTS 1. INTRODUCTION 1 2. DATA COLLECTION 2 3. THE ANALYSIS General Observations Ship Selection for Further Study Factors behind a Good Ice Performance Ice Class based on Ice Performance CONCLUSION 19 ACKNOWLEDGEMENTS 20 APPENDIX AIS based Ship Routes 21

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9 1. INTRODUCTION The Finnish-Swedish Ice Class Rules (FSICR) includes an ice performance requirement. The aim of this requirement is to ensure that merchant ships have such performance that they may follow icebreakers at an adequate speed and also move independently in lighter ice conditions. At present the ice performance requirement may be verified by ice model tests or more exact calculations. The aim of performance requirement is to make winter navigation fluent, efficient and economic; ships that have less ice performance, slow down the system. The original goal of this project was to find out whether the vessels, for which the ice performance required has been accepted based on model tests or more exact calculations, have an adequate ice performance in view of proceeding in ice. The data have been collected by direct observations from the icebreakers and from the IBNet, using Ship Notices, Waiting Time tables and the Harbour list. This project set out to collect data of ice performance of certain ships, but it was noted that there were several ships, other than which were already under observations, that showed less than good ice performance. Therefore the data collection was expanded to all ships that have shown less than good ice performance in the Gulf of Finland, the Bothnian Sea and the Bothnian Bay. After the winter, the characteristics of these ships were collected and the required engine output by the ice class was calculated. The data was analyzed keeping in mind the comments from the icebreakers and from the Ship Notices. This report is giving the general view of the ice performance ability of the ships proceeding in the Gulf of Finland, the Bothnian Sea and the Bothnian Bay. The common reasons for a poor ice performance are weak engine power which has also been reported in cases where 100% of the power is not used, inexperienced crew which includes language problems and disobedience when the crew does not obey the orders from the icebreakers. The cooling and towing problems are also common. In the towing problems the ship usually has unsuitable bow for towing. Other reasons are ballast problems, rudder failure, and propeller problems. Although the project gathers the reasons of poor ice performance, the project focuses in cases where weak engine power is mentioned. The aim of the data collection and analysis is to further develop the powering requirement in the FSICR to reflect even better the actual ice performance. The powering requirement given as an ice performance requirement is used in order to make the winter navigation system as efficient as possible. The requirement expresses the balance between having many icebreakers leading to high fairway taxes and having a high ice performance level in merchant ships leading to higher CAPEX and OPEX of the ships. The report should give some guidance in developing the powering requirements and/or the traffic restrictions as the ice performance requirements might as well be stated in the traffic restrictions. 1

10 2. DATA COLLECTION The data used in this study were collected from several sources during the winter The main data were received from the Finnish and the Swedish icebreaker s direct observations, the other data were provided by the Finnish Transport Agency (Trafi), the Swedish Transport Agency and the Finnish Transport Agency. The Trafi and the Swedish Transport Agency provided the list of ships which obtained their ice class using direct assessment of the required ice performance (this is referred to in the subsequent report as direct calculation). The Finnish Transport Agency gave for the project the data in the IBNet which included the Ship Notices list, the Waiting Time list and the Harbour list. The icebreaker data collection started by briefing the icebreakers about the data needed. Icebreakers were asked to mark down on an Excel sheet the ships which had a lower ability to follow icebreakers or to proceed independently in easier ice conditions. Icebreaker were also asked to note the date, sea area, ice conditions and comments and reasons why a certain ship was marked down as having a poor ice performance. The data was collected from December 2010 to April 2011 and all Finnish and Swedish icebreakers were participating in these direct observations. A list of ships which were to be examined in more detail was received from the Finnish Transport Safety Agency (Trafi) and from the Swedish Transport Agency. These ships were built in years and their ice class was given based on direct determination of the ice performance i.e. from more exact calculations or based on the results from ice model tests, instead using the formulae given in the Finnish-Swedish Ice Class Rules (FSICR). The ice performance of these ships was observed and marked down during the observation period. In total 21 ships have been checked for the ice performance using direct assessment by Trafi (12 by the Swedish Transport Agency). Not all of these ships have visited Baltic Sea as only five of these ships were found on the IBNet data base (seven ships from the Swedish list). It was further checked whether any of these ships had visited Baltic in winter 2011 and sailed in ice. After this final check four ships remained from the five vessels in the Finnish list and only one ship from seven vessels in the Swedish list remained for further study. After the winter, a Waiting Time list was received from The Finnish Transport Agency. The Waiting Time list includes all ships which have been waiting for assistance of a Finnish or Swedish icebreaker during the winter This list gives the waiting time of the vessels and the location where the ship waited for an icebreaker. The Waiting Time list contained after some editing as some ships had been noted by several icebreakers even if the incident was only single 63 different ships. Most of these had an ice class IA but there were three IA Super ships and three IB ships. Most of the waiting incidents (205 cases in all) occurred in the Bothnian Sea or Bay and only 16 took place in the Gulf of Finland. During winter 2011 quite long waiting times occurred, the longest was 184 h, but these were due to closing down certain harbours and allowing ships in only in icebreaker escort. The average waiting time in the list is 31.3 h with a large standard deviation (150.3 h). Waiting times actually can be divided into two categories and the longer times are related to collecting ships into groups just north or south of the Quark. 2

11 The Finnish Transport Agency also provided a Ship Notices list which consisted cases that icebreakers had reported from winter 2000 to winter The Ship Notices list consists of cases where the icebreakers have noticed some exceptional features with certain vessels. The list presents the name of the vessel, the date, IMO number and icebreakers comments. The comments can be given using a code but the icebreaker crew can also write down comments. The Ship Notices list had 324 cases which were used as statistical data and as comparison basis with the winter 2011 data. The last data source was a Harbour list obtained from the IBNet. The Harbour list contains visits to Finnish ports during Only selected ports are included in the list (Inkoo, Kemi, Kokkola, Kotka, Mäntyluoto, Oulu, Pietarsaari, Raahe and Tornio). There were in total 2418 ship visits to these ports during the selected time. The list included information whether the ship was escorted to or from the port and thus this list was used to find ships not needing icebreaker escort. 3

12 3. THE ANALYSIS 3.1 General Observations The most important part of the data analysis is to identify the reasons why certain ships have been marked down as having a poor ice performance. In total 324 cases from year 2000 to 2011 were found from the Ship Notices and 64 vessels were marked down on the Icebreaker s list. The Ship Notices list s 324 cases and the Icebreaker s list consist of ships which have had problems proceeding in ice or the icebreaker has had some other challenges with the vessel. This chapter summarises the reasons for the icebreaker s interest and gives an overview of the age and the size of the vessels in the Ship Notices list and in the Icebreaker s list. All the 324 cases were divided in the analysis into two periods, winter 2011 and winters in years In winter 2011, there were 79 cases of observations and in the period cases were found. Table 1 shows the main reasons and gives the number of the cases in these periods. Table 1. The reasons why certain vessels have had a poor ice performance. Table is divided in two periods. In winter 2011 there were 79 cases and in winters cases. Reason Weak engine power Does not use 100% of the power 33 / / 245 Inexperienced crew The crew does not obey the orders Language problems Engine cooling problems 22 / 79 3 / / / 245 Unsuitable for towing (sharp bow) 9 / / 245 Unsuitably positioned anchors 3 / 79 9 / 245 Ballast/draught problems 4 / 79 8 / 245 Rudder failure 1 / 79 4 / 245 Propeller problem/failure 1 / 79 2 / 245 Other 3 / / 245 Weak engine power or some other reasons in the engines are the main reasons for poor ice performance, 42% of all cases in winter 2011, 45% in winters and 44% in total. In winter % of the cases were related to the inexperience of the crew for winter conditions (22% in winters ). Problems with the crew were mentioned in many cases in the same notice as the weak engine. Cooling problems were usually linked to engine problems. Fewer problems seemed to be related to towing, ballast and propeller problems. The severity of winter 2011 and the request to pay more attention to reporting the performance of the assisted vessels can be inferred from the Table 1 as a 4

13 slightly larger number of notices in winter 2011 than the annual average during years (22 cases per year). Figure 1 presents the size and the age range of the vessels in the Ship Notices list. The deadweight of the ships in the list is mostly under 5000 DWT. From the figure it can be seen that the larger ships are usually fairly young, and there is a trend that older ships are also smaller ships DWT [t] Age [a] Figure 1. DWT plotted versus the ship age. All vessels mentioned in the Ship Notices list are plotted in the figure. The age range of the ships in the Ship Notices list is from 2 to 46 years. The ships experiencing most problems are a bit over 10 years old as Figure 2 shows. Only about 25% of all ships in the Ship Notices list were younger than 10 years. The ships that according to icebreaker s observations had some problems with engine power were separated from the other causes, and then it becomes even clearer that ships younger than 10 years old did experience in relative terms less problems related to engines (% of all engine related cases were ships younger than 10 years old). This fact can partly be attributed to the fact that the ice performance and ship powering requirements were changed in 2002 and the new rules required in relative terms more power from the smaller ships. The change in the powering requirements did have a positive effect. 5

14 0,12 0,10 n/n (N = 324) 0,08 0,06 0,04 0,02 0, Age [a] Figure 2. The age range of the ship in the Ship Notices list. Figures 3, 4 and 5 give an overview of the data from the Icebreaker s list. Some of the ships are the same as in the Ship Notices list, but the figures also include other ships, ships which are not included in the Ship Notices list. In total 63% of the ships were navigating in the Bothnian Bay when they received the attention of icebreakers (Figure 3), 19% of the ships were in the Gulf of Finland and 17 % were in the Bothnian Sea. Figure 4 presents the age range of the ships in the Icebreaker s list (this list includes only ships with questions with engines). Half of the vessels were years old, about 27% of the ships were built later than 2002 and the rest were older than 21 years old. Thus the conclusion of the effect of changing the powering requirement is valid also from this figure. 6

15 0,7 0,6 0,5 n/n (N = 64) 0,4 0,3 0,2 0,1 0,0 BB BS GF The Sea Area Figure 3. The sea area distribution among the ships from the Icebreaker s list. BB is the Bothnian Bay, BS is the Bothnian Sea and the GF is the Gulf of Finland. 0,12 0,10 Weak engine other 0,08 n/n 0,06 0,04 0,02 0, Age [a] Figure 4. The age range of the ships which were collected as direct observations from the icebreakers and marked down on the Icebreaker s list. 7

16 Figure 5 shows the size variability of the ships. The size of most of the vessels is less than 6000 DWT. The ships which had deadweight over 6000 tonnes had in relative terms less problems. This can partly be attributed to the power requirements but also to the fact that larger displacement is in general beneficial for ice performance. Figure 6 presents the average ice conditions where the vessels were navigating at the time of the icebreaker s observation. The level ice thickness in the observations varied from 30 cm to 80 cm, but most of the vessels were navigating in cm ice thickness DWT [t] Age [a] Figure 5. DWT plotted versus the age of the ships which were marked as having a poor ice performance in the Icebreaker s list. 8

17 0,35 0,30 0,25 0,20 n/n 0,15 0,10 0,05 0, Average ice thickness [cm] Figure 6. The average ice conditions at the location where ships were navigating when they were observed as having a poor ice performance. Final, but actually quite crucial, observation is that no ships, the ice class of which was accepted based on showing an adequate ice performance based on ice model tests or more exact calculations, were found in the Icebreaker s list or in the Ship Notices list. This suggests that even if these ships have a lower power than given by the rule formulae, their ice performance is not deficient based on icebreaker observations. The amount of the ships in this special category is small, only five ships, and thus this conclusion must be seen as being tentative. 3.2 Ship Selection for Further Study In order to focus on the cause of poor ice performance, some ships were selected of further study. The more detailed examination of the ships required particular information of the ship hull. Because this kind of information is challenging to find, the number of analyzed ships was decreased by selecting only those ships that clearly had a weak engine power for a further, more detailed study. The project was initially only interested in ships with a weak engine power; the ships which had other reasons, than weak engine power, for the poor ice performance in view of the icebreakers were eliminated from the Icebreaker s list. The list had several 9

18 comments and reasons for the poor ice performance, but unfortunately also many of the cases were left without any comments. The cases without any comments were basically added to the analysis because the icebreakers were specifically requested to mark down ships with poor ice performance. Eventually, after the elimination, 64 vessels from original 94 cases in the Icebreaker s and Ship Notices lists were selected for further study. The following parameters were obtained for each ship from the IBNet database or some commonly available databases: Ice class DWT Build year Length overall Breadth Draft Power Speed Average ice condition Ice date Harbour. The average ice conditions, ice date and harbour were determined from the icebreakers comments or from IBNet comments. When the locations of the poor ice performance vessels were found, the ice conditions in the area were checked from the ice chart. The ice date is the ice chart date which is closest to the date of ship mentioned in the poor ice performance report. Only a few vessels seemed to have problems proceeding in light ice conditions, otherwise the ice conditions were severe for all ships, see Figure 6. In order to analyze the differences in the ice performance of the vessels selected for further analysis, some kind of index for the adequate ice performance should be developed. Ideally this index should describe the speed made in specified ice conditions using specified power but this kind of knowledge is not available. Thus it was decided to calculate the required propulsion power according to 2010 FSICR and define the ice performance index of each ship to be the ratio between the installed power and the required power (according to the ice class of the ship) P inst /P req. The parameters listed below are needed to calculate the required engine output: Length of the ship between the perpendiculars Length of the bow Length of the parallel midship body Maximum breadth of the ship Actual ice class draughts of the ship Area of the waterline of the bow Angle of the waterline at B/4 The rake of the stem at the centreline 10

19 The rake of the bow at B/4 Diameter of the propeller. The hull lines or at least general arrangement of the vessel is needed to calculate the required engine output, and these data is not easily available. An effort was made to get as much as possible of these data but in the end the data was obtained for 16 ships. These ships were then included in the further, more detailed analysis. The main goal of the analysis was to find some common factor for vessels with a poor ice performance, and therefore vessels with a good performance are also needed in order to compare the effect of several factors. The Harbour list was used to find the good ice performance ships. The ships which did not need icebreaker assistance, or which needed very little icebreaker assistance, were selected from the Harbour list and labelled to be good ice performance vessels. The required engine output was calculated for these vessels using the data from the general arrangement drawings or from the obtained data and thus the number of good ice performance ships was also limited due to a lack of data. In total 12 good ships were included in the study. One of the data sources was considered to be the Waiting Time list. It was assumed that this list would give an overview of ships which have a less good ice performance during the winter After analyzing the Waiting Time list, it was concluded that the Waiting Time list will not give any reliable information for this study. Winter 2011 was a very severe ice winter and the icebreakers were forced to regulate the traffic in the Bothnia Sea and in the Bothnian Bay. One of the ways regulating the traffic was to collect ships in certain areas where the ships could wait for icebreaker escort safely. All the ships were required to wait; better ice performance did not make an exception for this traffic control. This practice to concentrate the ships in certain areas had a pronounced effect on the waiting times in northernmost Baltic. Thus the Waiting Time list is not used to describe the quality of ice performance of ships. 3.3 Factors behind a Good Ice Performance The factors causing a good ice performance were investigated by comparing the poor ice performance ships with the good ice performance ships. The data for the comparison is obtained from the Icebreaker s, Ship Notices and Harbour lists the last list was used only to identify the good ships. The deadweight and the length between the perpendiculars of the ships were used to represents the ship size. As explained, 16 ships having a poor ice performance were selected for the final analysis. There were three IB ice class vessels and 13 IA ice class vessels. The length of the smallest vessels was slightly over 80 meters and the largest vessels were up to 160 meters long. These 16 vessels were compared with 13 ships of what was deemed as a good ice performance. The poor ice performance vessels were from the Icebreaker s and Ship Notices lists and the good ice performance ships were taken from the Harbour list. None 11

20 of the good ice performance ships were in ice class IB. There were nine IA ships and four IASuper ships. The length of the vessels varied from 80 to 170 meters. The Figure 7 presents the comparison of the good ice performance vessels (the red stars and the green stars) and the poor ice performance vessels (the black dots and the blue dots). In this comparison, the vessels are divided according to the ice class. The black/blue dot vessels have a IB and IA ice class and the red/green star vessels are IA and IASuper ships. For each ship, the ratio P inst /P req was calculated to represent the ice performance. The power of the ship is P inst and the P req is the engine output required according to the FSICR. The figures were made by plotting the ice performance index P inst /P req versus the ship size that is indicated by the deadweight (DWT) of the vessel in the top figure or the length of the ship between the perpendiculars (L pp ). In both figures there are two vessels for which two extra points are calculated. Icebreakers noted that the hull of these two ships was in a poor condition. Thus the required power is also calculated using a higher coefficient of friction for these ships. The blue squares are results of calculations where higher friction is used due to the poor condition of the ship hull (the coefficient of friction was increased from 0.15 to 0.3). The required engine outputs for these two vessels are also calculated using the rule value. 3,5 3,0 2,5 "Poor" IB "Poor" IA "Good" IA Super "Good" IA Friction added P inst /P req 2,0 1,5 1,0 0,5 0, DWT 12

21 3,5 3,0 2,5 "Poor" IB "Poor" IA Friction added "Good" IA Super "Good" IA P inst /P req 2,0 1,5 1,0 0,5 0, Lpp[m] Figure 7. Plot of the vessels ice performance index versus the deadweight (DWT) in the top figure, and the ice performance index versus the length of the ship (L pp ) in the bottom figure. The black and the blue dots represent the poor ice performance vessels from the Icebreaker list and the red and green stars are good ice performance vessels from the Harbour list. The blue squares are showing the ice performance ability when the friction from the hull is larger than in the rule formulation. The poor ice performance vessels which are less than 5000 DWT are all build before year 2002, this explains the low P inst /P req because the ships are build according to the old ice class requirements. The vessels with DWT from 5000 to have the P inst /P req about one and the over DWT vessel are all above the P inst /P req = 1. The building year for the vessels greater than 5000 DWT is between 1975 and There is only one good ice performance vessel which has lower DWT than 5000 t. This vessel is build earlier than The other two ships which have the ratio P inst /P req less than 1 are built later than The IA Super vessels are mostly above P inst /P req = 1. The building year of IA Super vessels are from 1995 to There is one ship that has the power ratio value about 3.3 but anyhow it has been noted to have a poor ice capability. This ship was included into the Icebreaker s list indicating thus a poor ice performance - without any comments. The Harbour list does not indicate that this ship has been assisted any more than other ships; thus it is an anomaly that it is included here at all. The comparison of the ice performance P inst /P req with the length of the ship between the perpendiculars (Figure 7, bottom) shows that overall the smaller vessels have lower ice 13

22 performance. When the ship size increases in length the ice performance P inst /P req increases. The Figure 7 shows four poor performance vessels which have ice performance index P inst /P req greater than 1.5. This number should yield a very good ice performance according to the Finnish-Swedish Ice Class Rules. This is in contradiction with the observations from the icebreakers. The condition of the hull, which is taken into account in the engine output calculations for two ships (blue squares) might be the reason why two of these four vessels are marked as poor ice performance vessels. The vessel with P inst /P req greater than 3 must have had some other reason to have difficulties proceeding in the ice field than the weak engine. Overall, the engine power ratio P inst /P req seems to describe the ice performance of the ships adequately as the better ships tend to have this ratio above one and less good ships tend to have the ratio below one. This ratio does not explain all the cases and thus the crew experience, too low ballast draught and other reasons are also influencing the ice performance. Because all the ships were operating in the same ice conditions, the comparison of their performance against a power that varies from ice class to ice class is not strictly correct. Each ice class is supposed to operate in different ice conditions. Thus a somewhat better ice performance index is obtained if the installed power is divided by the power required by the ice class IA. The ratio P inst /P req (IA) is calculated and plotted in Fig. 8 versus the deadweight. Figure 8 shows that the majority of the good ice performance ships have the P inst /P req (IA) larger than one and the majority of the poor ice performance ships have P inst /P req (IA) smaller than one. The small vessels in the study have generally a poor ice performance and the majority of the larger vessels seem to proceed adequately in ice. 14

23 3,5 3,0 "Poor" IA "Good" IA 2,5 P inst /P req 2,0 1,5 1,0 0,5 0, DWT [t] Figure 8. Ice performance of the good and poor ice performance ships when the reference power is the power required for ice class IA Ice Class based on Ice Performance There were no comments on the Icebreaker s list about the vessels which obtained the Finnish-Swedish ice class based on the actual ice performance shown by more exact calculations about the thrust provided or based on ice model tests. The analysis of these vessels must thus be based on other methods than including them to the comparison carried out above. It was decided to investigate their actual progress in ice. This was done using the AIS data which was received from the Finnish Meteorological Institute. The vessel search from the AIS database revealed that some of the ships which were given an ice class based on the actual ice performance did not enter the Gulf of Finland, the Bothnian Sea or the Bothnian Bay during winter The original list of 33 ships decreased to 12 ships. Further elimination occurred when the ice chart data were compared with the ship routes drawn from the AIS data. The vessels which only proceeded in open water were deleted from the list of analysed ships. Eventually, only eight cases were examined further. Figure 9 presents an example of the ship route which was drawn for every vessel visiting the Gulf of Finland, the Bothnian Sea or the Bothnian Bay during winter In the figure, the ship route has been drawn in colour which indicates the speed of the vessel. 15

24 Purple and blue colours indicate slow speed, and green, yellow and red high speed. The FSICR limit for an adequate speed in ice is 5 kn. Figure 9. The route of a ship in February in the Gulf of Finland. The colour indicates the speed of the ship in knots, legend to the right. In order to examine the ability of the vessels to proceed in an ice field, the average speed of the vessel in the ice field was calculated using the AIS data. The route legs were chosen so that each leg contains similar ice conditions judged from the ice charts. Table 2 presents the results of the analysis. The table is divided into three months; January, February and April (none of the investigated ships were navigating in ice in March). In the table vessels are identified with letters. The date and the sea area where the speed calculation has been done are given in the table as well as the level ice thickness and also information if the ice field was ridged; these obtained from the ice charts. Finally, information about the possible compression in the ice field is given based on information obtained from the Finnish Meteorological Institute. 16

25 Table 2. The speed of the vessel when proceeding in the ice field. The table is divided in according to the months. The date gives the day when the ship has been moving in certain sea area. January Date Speed (kn) Ice thickness (cm) Ridges or hummocks (yes/no) Compression (yes/no) Sea area Ship A yes no Gulf of Finland yes no data Gulf of Finland Ship B yes no Gulf of Finland yes no Gulf of Finland no Ship C yes no Gulf of Finland February Date Speed (kn) Ice thickness (cm) Ridges or hummocks (yes/no) Compression (yes/no) Sea area Ship B no no Gulf of Finland no no Gulf of Finland Ship D no no Gulf of Finland no no Gulf of Finland yes yes Gulf of Finland no yes Gulf of Finland no yes Gulf of Finland no yes Gulf of Finland Ship E no no Bothnian Sea no no Bothnian Sea April Date Speed (kn) Ice thickness (cm) Ridges or hummocks (yes/no) Compression (yes/no) Sea area Ship A yes no Bothnian Sea yes yes Bothnian Sea yes yes Bothnian Sea yes no Bothnian Sea Ship D yes yes Bothnian Bay yes no Bothnian Bay In January vessels A, B and C were visiting the Gulf of Finland. The ships A and B made a good speed, but the vessel C had some difficulties. The ships B and D were in the Gulf of Finland in February and the ship E was visiting the Bothnian Sea. It can be noted that vessel D did slow down in ice noticeably during the February visit. Ice thickness was small at the time and location but there was compression in the ice field. In March none of the ships, which were under the observation, were navigating in ice in the Baltic Sea. In April ship A was visiting the Bothnian Sea and the ship D was visiting the Bothnian Bay. Ship D did not have any difficulties in the Bothnian Bay. The ship A was slowed somewhat in the Bothnian Sea on the 14 th of April. If the requirement for an adequate ice 17

26 performance is that the ship is able to proceed with an average speed of 5 knots in ice, then it can be concluded that the ships with the actual ice performance as the basis for ice class are behaving well in ice. Only the ship D heading to Hamina February 24 was slowed down noticeably. The ship was south of Kotka in the middle of the Gulf of Finland proceeding independently. 18

27 4. CONCLUSION This project was initiated to study the principles of granting an ice class based on actual ice performance shown by more exact calculations of the thrust provided or by ice model tests of ice resistance, instead of using the rule formulations. A list of this kind of special ships was made and the operation of these ships was observed mainly based on the AIS data. At the same time the icebreaker crews were briefed to observe the ice performance of the assisted ships and mark down any ship that deviated from the average ships. This way incidents were collected from winter 2011 to form a list called the Icebreaker s list in this study. Notes from similar incidents from the earlier notes included in the IBNet database was also collected to form the Ship Notices list. Finally, in order to investigate the demarcation line between good and poor ice performance, ships in the Harbour list were examined and the ships needing none or very little icebreaker assistance were labelled as good ice performance ships. This formed the data base of this project. These lists are not published here in order to guarantee the ship anonymity. Even if there is quite large scatter in the data and also the icebreaker observations include a degree of subjectivity, several conclusions can be drawn from the project based on the data analysis. 1. None of the ships for which the ice class is based on the actual ice performance were noticed by the icebreakers as having any worse ice performance than other similar ships. This indicates that the ice performance of these ships seems to be adequate. The errors created by the small sample size must, however, be recognized. 2. The ships in special ships list did proceed in ice at an adequate speed, in general. This suggests that the evaluation of the ice performance is correct. It should be noticed, however, that the ice class is mostly given based on exact calculations for the thrust. 3. When an index for ice performance, the ratio of installed to required power P inst /P req was calculated for a sample of poor ice performance ships and good ice performance ships, it is noticed that this ratio explains quite well the quality of the ships ice performance. This indicates that the rule formulation in the Finnish-Swedish Ice Class Rules is not deficient. 4. There was large number of ships the crew competence of which the icebreakers found lacking. This emphasises the fact that some formal training and/or ice navigation experience should be required from ships receiving icebreaker escort. 5. The ships built according to earlier versions of the FSICR earlier than 2002 when the powering requirements were updated seem to have more trouble in ice. This conclusion is especially valid for smaller ships. This suggests two things; firstly that the new powering formulation is adequate and secondly, if some means in the traffic restrictions to restrict the less ice capable ships are used, that ships built according to older versions of the FSICR are required to have higher power. 6. The investigation was somewhat handicapped by the lack of all the data needed for ship ice capability assessment. These data accumulates and the data collection methods get more sophisticated by time; thus it would be an advantage to continue this project as a regular basis. 19

28 ACKNOWLEDGEMENTS This project is based on an efficient data collection from incidents reported by icebreakers and on obtaining ship data for analysis. Thus the assistance of the Finnish and Swedish icebreaker crews was essential for the project. The crews filled in the forms and gave comments also in other formats. Hopefully the project results can be used to make the winter navigation system more efficient and this way reward the data collection by icebreakers. Ms. Mirva Hannukainen at the Icebreaking Office at the Finnish Transport Agency collected herself a lot of data and also assisted in the communication with the icebreakers. Without her efforts the project would not have been possible. Dr. Jorma Kämäräinen from Trafi and Mr. Albert Wiström from the Swedish Transport Agency gave much of the ship data without which the project would have been impossible. Mr. Jukka-Pekka Jalkanen from the Finnish Meteorological Institute assisted in obtaining and analyzing the AIS data; without his efforts this part of the work would have been impossible. Finally the funding from the Winter Navigation Research Board is gratefully acknowledged. 20

29 Appendix AIS based Ship Routes Ship A January Ship B January 21

30 Ship C January Ship B February 22

31 Ship D February 23

32 Ship E February 24

33 Ship A April Ship D April 25