Safe handling of

Ultra Large Container Ships in strong wind

Gothenburg Pilot 2016-12-01

by Henrik Sjöberg, Harald Roos, Andreas Edvall and Frederik Hallbjörner

Final report - version 2.0

Photo: Harald Roos

Photo: Sjöfartsverket

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CONTENT

Summary .................................................................................................................................... 4

Assignment ................................................................................................................................. 4

Problem definition ..................................................................................................................... 5

Initiate and stop a turn ........................................................................................................... 5

Drift due to impact from wind and current ............................................................................ 6

Reduction of speed when wind forces swing vessel in a not desirable direction .................. 6

Prediction of course over ground and sweep path in strong wind ........................................ 7

Maneuvering vessel to or from berth ..................................................................................... 8

Data collection ............................................................................................................................ 9

Wind restriction of today ........................................................................................................ 9

Accepted risk ........................................................................................................................... 9

Weather conditions ................................................................................................................ 9

Other ports ............................................................................................................................ 11

Shipowners criterias and instructions .................................................................................. 13

Simulator studies 2016 ............................................................................................................. 14

Aim ........................................................................................................................................ 14

Ship models ........................................................................................................................... 14

Conditions and crew ............................................................................................................. 15

Wind ................................................................................................................................... 15

Covered geographical area ................................................................................................ 15

Tugs .................................................................................................................................... 15

Extra pilots ......................................................................................................................... 15

Schedule ................................................................................................................................ 16

Evaluation form ..................................................................................................................... 17

Result of runs ........................................................................................................................ 18

Conclusions ........................................................................................................................... 19

Recommendations ................................................................................................................... 20

Windrestriction for large container vessels .......................................................................... 20

Quality assessment system ................................................................................................... 20

Checklist ............................................................................................................................. 20

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Calculation form ................................................................................................................ 21

Implementation of two tugs transom aft ............................................................................. 22

Implementation test onboard MSC Ditte 2016-08-09 .......................................................... 22

Simulator training for pilots .................................................................................................. 24

Appendix 1) Summary of simulator runs ................................................................................. 25

Appendix 2) Simulated drift angles due to wind and speed .................................................... 26

Appendix 3) Calculated wind and rudder moments ................................................................ 27

Appendix 4) Reflections from participating Pilot´s .................................................................. 28

Appendix 5) Reflections from participating Tug Captains ....................................................... 31

Appendix 6) Local routine for container vessels ...................................................................... 32

Appendix 7) Checklist for 15-17 m/s ........................................................................................ 34

Appendix 8) Live test with two tugs transom aft - Evelyn Maersk on May 10, 2016 ............. 36

Appendix 9) Vessels approved for two tugs transom aft ......................................................... 40

Appendix 10) Area overview .................................................................................................... 41

SUMMARY

One of the big issues for pilots is the last decade’s huge growth in the size of container ships, so called “Ultra Large Container Ships”, and how they act in severe wind conditions. This study’s intention is to find out, how to in advance take actions for safe navigation and maneuvering in the port of Gothenburg under extra ordinary weather circumstances. The authors serve as pilots in Gothenburg.

The report shows and describes major problems like the huge wind forces involved, initiating of turns, drift angles, speed reduction etc. Some other ports handling of this ship size and ship owner’s criteria have been scanned and also valid risk assessment in the port of Gothenburg. Further on the result of simulator studies are explained and also the use of tugs in a new method. It ends up in findings and conclusions and these are the base for future recommendations such as e.g. structured wind limit zones, a new routine in the QA system and additional training for pilots.

ASSIGNMENT

On behalf of the local Nautical Board for the Swedish Maritime Administration in Gothenburg, a group of four pilots, have been assigned to make a survey about how to safe handle the new generation of Ultra Large Container Ships (ULCS) in strong wind.

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PROBLEM DEFINITION

Over the past decade the Marine Industry has seen a considerable growth in the size of container vessels. The displacements of these vessels are now huge, normally above 150 000 tdw, and the area exposed to wind is normally between 13000 and 18000 square meters. These circumstances have a great impact on safe navigation in confined waters when wind and current exceeds certain levels. These kinds of tasks are not to be considered as normal pilot duties and there is a lack of adequate assessment facts and routines in order to support pilots in their decision making and on duty performance.

Figure 1) Illustration of the possible lateral area of a large container vessel. Source: MSC

Figure 2) Calculated lateral areas depending on draft and deck cargo.

Figure 3) Calculated wind force acting in different wind speeds on 14000 sqm lateral area.

INITIATE AND STOP A TURN

On a steady course the increase of wind force generates essential turning forces on the ship and the navigator has to overcome these forces by using counter rudder and if necessary even increase of engine rpm. To initiate a turn in a certain direction and adequate rate requires forces in proposition with actual wind force, direction and exposed lateral area. That’s not a problem when turning into the wind but could be a really problem the other way. The same problem occurs when the navigator need to stop a swing. Especially when the ship has made a swing into the wind and the turn rate might get pretty high, and the fairway stretch requires another turn off the wind.

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Figure 4) Illustration of problem to initiate turn to starboard and predict sweep passing Danska Liljan.

Figure 5) Illustration of problem to initiate turn to port and predict sweep into the Tors harbour strait.

DRIFT DUE TO IMPACT FROM WIND AND CURRENT

When a ship is exposed to wind from especially the side a drift angle occurs. The magnitude is related to the strength of wind force, lateral area, draught etc. If a current push along the ship in the same direction another force adds the drift angle. The speed of the vessel has a great impact on the drift angle. In for example 13 knots the drift could be almost negligible and at a speed of 3 knots the drift could be severe under the same external conditions.

Figure 6) Illustration of a controllable drift angle at 12 knots speed on the Tors harbour strait.

Figure 7) Illustration of a dangerous situation with large drift angle at 3 knots speed passing the fortress

REDUCTION OF SPEED WHEN WIND FORCES SWING VESSEL IN A NOT DESIRABLE DIRECTION

When making forward speed the wind pressure along the ship side generates a substantial turning lever which affects the ship so that the bow will turn into the wind. In order to decrease the speed of the vessel the navigator first choice is to minimize rpm with remaining sufficient rudder force. This is no problem in nice weather conditions but the turning lever increase when the wind pressure on the ships side is getting higher. When the rudder is

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“hard over” and turning lever is not opposed the engine rpm must be increased to create larger rudder force.

Figure 8) Illustration of steering force generated by the rudder balancing the wind force.

PREDICTION OF COURSE OVER GROUND AND SWEEP PATH IN STRONG WIND

As the velocity of the vessel diminish the drift angle is getting higher. The navigator sets the course (heading) in a certain direction but the vessel travel in another direction (course over ground). This is not a problem where it´s space enough but in a narrow passage it could have a great impact on safe navigation. The large container ships have dimensions which easily double their beam even in quite small drift angles and navigator’s path and turning moments must be exact in the narrowest passages.

Figure 9) PPU sceeen shot from simulator run. Drift angle of 5 degrees at speed 9.2 knots.

Beacon No 24

Beacon No 25

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Figure 10) View from conning position at the same simulator run as above.

MANEUVERING VESSEL TO OR FROM BERTH

To bring a vessel of this size alongside the use of thrusters and tugs are needed. The wind force on the vessels actual loading conditions is essential and pilots make calculations based on information from the master. The forces should be enough to oppose forces created by wind and current and there must be margins included in calculations in order to overcome wind gusts or failures in thrusters or tugs etc.

Figure 11) Tugs and thrusters to overcome and balance the wind pressure. Normal margin is 25%.

Beacon No 24

Beacon No 25

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DATA COLLECTION

WIND RESTRICTION OF TODAY

Dry Cargo vessels with LOA exceeding 300 m Wind Restriction: max 20 m/s (mean wind at Måvholmsbådan)

ACCEPTED RISK

As the ship size increase and the infrastructure in the fairways remains, the margins for safe navigation becomes smaller. But keep in mind that the large container ships have no inbuilt improvement in better steering devices and more adjustable rpm-settings etc. The raise in maneuvering capacity is just more powerful thrusters in order to compensate the enormous growth of the exposed wind area. These effects are partially compensated by modern navigation instrument e.g. electronic chart system with predictors, radar overlays etc. Pilots are nowadays also equipped with a personal pilot computer which is a great support for safe navigation.

Reduced margins really need to be considered due to the huge consequences of a failure or accident when handling these Ultra Large Container Ships (ULCS) in very confined waters. The risk of interaction or grounding at the crude oil terminal Torshamnen, obstruction of fairways and the risk of damaging cranes should be taken into account. The latter are in the port of Gothenburg situated very close to quayside, about two meters.

Other segment in the port has been considered with a low accepted risk and they are e.g. larger tankers (max 15 m/s), gas tankers and tankers under escort. For car carriers in dedicated parts of the port the use of wind pressure in tons already stipulate the no of tugs. A wind restriction has in this part been set to 16 m/s on arrival and 18 m/s upon departure.

WEATHER CONDITIONS

Autumn and winter are mostly humid and windy periods and it´s not seldom that visibility is poor and that the gales relieves each other on their way from UK to Scandinavia. From May to September weather conditions normally are pretty fair with just a few gales.

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Wind and visibility forecasts for Trubaduren and for the Port Approach are issued by Swedish Meteorological and Hydrological Institute (SMHI). Actual wind forces are obtained by gauges placed at Vinga, Måvholmsbådan, Torshamnen, Älvsborg and Karet. These values are distributed and visualized by internet or by inquiry to the VTS.

Along the coast there is a mainly a flow of north going current. When the wind is strong from south to south west the strength of the current increases considerable.

Figure 12) Example of SMHI Weather Forecast. Source: SMHI Bizmet

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OTHER PORTS

Hamburg Vice Chairman of Hamburg harbor pilots, Donatus Kulrisch: “Since one year ULCSs (>395m length) calling Hamburg and it was an extensive preparation for this kind of vessels. As we experienced already with the smaller ULCSs (>360m length) the wind is a major factor for safe manoeuvring.

These ships (<395m) are only allowed in the port of Hamburg, if certain fixed circumstances are fulfilled: Wind <= 6 Bft., for turning a window of two and a half hours around high tide (current less than 1,5kn) has to be met, the total minimal tugboat bollard pull required (between Minimum 140 to and 240 to (4 tugs)) depending on the actual wind force. These circumstances were agreed between the harbour pilots and the authorities after extensive simulator trials. All harbour pilots had to undergo special simulator training for this type of ship and have access to the approval for each ship type.

It makes sense to fix the limits and make them obligatory for in and outbound vessels, otherwise there will be an endless discussion with the authorities, agents and masters on board. And of course, the final decision to abort a manoeuvre is up to the master and pilot. Too many things (fog, gust, springtide, traffic, etc.) have to be considered and if one cannot be met, you should consider for example not to turn, or using another berth waiting for better weather. Of course we have got a table, where all the limits according to the size of the vessels are described.

Using tugboat is also done very much depending on the manoeuvre we are doing. Two tugs on the stern could be difficult, due to the short distance between the leads aft, but it is also practiced. Especially if the area for manoeuvring is limited. Using the spring lead aft to secure the third tug might be an option if the turning direction and the shore side is the same, then you can use the tug in push and pull. Using additional tugs for pushing only, is an option but limiting the use of the tug.

Nevertheless we face big problems (moored vessels) during the time in port, if the wind is increasing above 7 Bft. Therefore we have done test in the wind tunnel for verifying the formulas available.”

Rotterdam Joost Leenhouts, Manager Operations, Regio Rotterdam-Rijnmond: In the port of Rotterdam the wind limit is set to maximum 14 m/s for all container vessels with LOA > 375 meters regardless wind direction. In some part of the port the limit is set even lower. The limit refers to a forecast which is four hours ahead and can be updated with a possibility to abort the operation one hour before arrival to the berth area. The pilots board vessels of this size further out than normal in order to prepare computer installation and to gain a greater quantity of information needed. A minimum visibility limit is set to 500 meter.

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The port authorities have stated that the pilots decide the no of tugs to be used. The tugs used for this size of vessels should be at least 60 tons bollard pull (BP) but the tug providers offer up to 96 ton BP. The normal setup in windy conditions is three tugs, two aft and one forward. Sometimes four tugs are needed. In the portable pilot unit (PPU) there is access to an inbuilt program which assists the pilot with calculation tools to obtain the actual wind forces with included sufficient margins. All pilots certified for ULCS has undertaken special training in simulator to be prepared for handling these vessels in strong wind conditions.

Figure 13) Extract from Europort Wind Restrictions. Source: Loodswezen Rotterdam - Rljnmond

London Gateway

Figure 14) Extract from LONDON GATEWAY PORT TUG ALLOCATION TABLES. Source: Port of London Authority

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SHIPOWNERS CRITERIAS AND INSTRUCTIONS

OOCL OOCL declares limits of operation based on calculated wind forces, where they find forces less than 150 tons to be safe and forces exceeding 210 tons to abort berthing/unberthing. On calculated wind force 25% are added.

Figure 15) Extract from OOCL Singapore table for wind forces. Source: OOCL

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SIMULATOR STUDIES 2016

AIM

The motive is to find out if there is a reason, theoretical or findings from simulator studies, to review current wind restrictions?

SHIP MODELS

The simulator studies are based on the use of two different ship models with same equal lateral area, 14 000 square meters. Length over all (LOA) is almost 400 meters and the beam is 54 meters. The difference of these two models is the draught, 11 and 13 meters.

Figure 16) Pilot Card for one of the simulator models used in the studies.

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CONDITIONS AND CREW

WIND Wind forces: 16 m/s (32 knots), 18 m/s (35 knots), 20 m/s (40 knots), 22 m/s (45 knots) Wind directions: S, SW, W, NW

COVERED GEOGRAPHICAL AREA Inward bound;

• Vinga sand – Dynan (a considerable turn with subsequent speed reduction) • Dynan – Berth 610 (speed reduction and maneuvering area)

Outward bound;

• Berth 610 – Knippelholmen (leaving berth and speeding up)

TUGS Mainly vector tugs in the simulation system were used but on the final day also a live tug manned with experienced tug captains participated.

EXTRA PILOTS In order to verify our experiences, two pilots who were not familiar with the simulator were randomly called in to make two jobs each.

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SCHEDULE

Figure 17) Schedule of simulator runs day one and two.

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EVALUATION FORM

After every single simulator run the pilots have made a debriefing concerning the performance. How have available recourses been used? For example, what kind of engine orders and rudder angles have the pilot been forced to use to obtain a safe passage? How have the tugboats been situated or moved? The form contains a number of parameters which have to be judged on a scale 1-5 in order to estimate the risks e.g. to keep course, reduce speed to the planned speed at certain points etc.

Figure 18) Evaluation made of one of the simulator runs (Run 8).

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RESULT OF RUNS

Below is an example of how the runs are merged in a spreadsheet and divided into different colures. The green color is assessed as approved with margins, yellow in some way not safe and the red color shows runs where the performance of the runs showed unaccepted risk.

Figure 19) Extract from the evaluation summary of simulator runs.

Figure 20) Drift angle as a result of wind force, 250 tons abeam, draft 11 meters. See Appendix 2.

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CONCLUSIONS

After each day in the simulator, which were three days in total, all participants were asked to set down their reflections in a piece of paper. They were after the completed simulation merged together and analyzed by the group of involved pilots and the experiences learned are listed down below. The merged written reflections are found in appendix 4.

• Always calculate actual wind force in tons. Do not only think wind in m/s or knots. • Be aware of that a large force is needed to initiate turns when wind direction is

unfavorable. • Be sure that you aim for the windward side in a turn to avoid the stern part to sweep

down on the leeside. • Take extra caution when wind is coming from SW-NW due to difficulties to reduce

speed. • A drift angle above five degrees is considered to be unsafe. • In order to minimize the drift angle, the speed should be kept higher than normal if

safe speed reduction can be carried out. • Watch out if the vessels minimum speed ahead is high. • Use large rudder angles and adjust the heading with engine rpm. • When entering turning area try to place the vessel right in turning circle. • Consider not to turn the ship “off the wind”. Turning port over in wind from NW-N

could be a better option. • Watch out for very large drift angles in low speed which will easy lead to

miscalculations in vessels movement. • Use all available sources of navigation aids. Only visual navigation is not good

enough. Sensors and electronic aids to be verified correct and precise. • Pay attention to that pilot duties under severe wind conditions with this size of

vessels is not “a normal day at work”.

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RECOMMENDATIONS

WINDRESTRICTION FOR LARGE CONTAINER VESSELS

Based on above studies we suggest that the wind restrictions for large dry cargo vessels are amended as follows:

Dry Cargo Vessel with LOA > 300 meter

Reference point referred to the forecast for mean wind at Trubaduren

Wind force ≥ 18 m/s Pilotage will not be carried out and neither pilots nor tugs will be ordered.

Wind force 15-17 m/s Agents, terminals and port authorities are advised to cooperate in order to avoid operations in this wind zone. It might require reallocation or reschedule of smaller tonnage in order to arrange so ULCS are not handled in these wind forces. Would it, due to prolonged gale or difficulties in planning, anyway be necessary to complete the operation, pilots and tugs are ordered and start their duties. Pilots plan the pilotage according to a special checklist but the final decision is made onboard by the pilot and the master.

Wind force ≤ 14 m/s Operation will be carried out. Please note that recommendations for tug use are calculated for wind force up to 10 m/s (20 knots). Pilot or master might require additional tugs.

QUALITY ASSESSMENT SYSTEM

The authors of this report suggest that a new routine should be implemented in SMA:s Quality Assessment System named e.g. “Handling of container vessels LOA > 300 m in wind above 15 m/s”. The routine should be based on findings and the established documentation, including a checklist and a calculation form.

CHECKLIST The following items should be taken into account by pilots and masters before they decide to bring in or out vessels from the port of Gothenburg. These checkpoints are set up in a separate checklist, which is a part of SMA:s quality system, to attach the Pilot Passage Plan and reviewed at the Master-Pilot Exchange.

• Actual draught. • Actual lateral area. Often retrieved from the cargo handling software onboard. • Speed at Dead Slow / Minimum Ahead.

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• Wind direction, mean wind and gusts. • Calculated wind force caused by gusts. • Number of tugs, type and bollard pull. • Ability to connect tugs, available leads and SWL for bollards and leads. • The sum of forces created by thrusters and tugs shall exceed the calculated wind

force during the intended maneuver. • Berthed crude oil tankers in Tors harbour. • The speed when connecting tug(s) aft to be maximum 10 knots. • The speed when connecting tug forward to be maximum 6 knots.

Proposed checklist is found in appendix 7.

CALCULATION FORM In order to support the pilot, a special template has been developed. This form facilitates the calculations and is a tool for decisions making due to e.g. exposed lateral area and different wind forces etc.

Figure 21) Calculation tool for decision support in wind range 15-17 m/s.

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IMPLEMENTATION OF TWO TUGS TRANSOM AFT

One of the main problems when the wind is picking up and entering a narrow passage with these large vessels is to be able to control the heading in a controlled way. On behalf of this study, it´s beyond doubt that two tugs transom aft would generate a higher level of safety, related to larger braking forces and a possibility to keep up the vessels speed a bit longer than under normal conditions.

Crew from Svitzer Scandinavia has attended under the simulator runs and some remarks have been noted. Both pilot´s and tug captains are agreeing on that test of set up should be carried out as soon as possible. Furthermore, the method should be discussed in a greater forum and an exercise program for both pilots and tug captains should be implemented.

There is also a need to investigate and plot the container vessels calling for Gothenburg in order to find out which of these ships are suitable for a set up with two tugs transom aft.

On May 10, 2016 the first live test was performed on Evelyn Maersk. Svitzer Tyr and Svitzer Gaia were successfully connected transom aft and braked the vessel down to three knots while the main engine was running ahead. Details about the test is found in appendix 9.

Further tests will be held in order to ensure safe tug operation and to establish criteria´s for two tugs transom aft including a standard operational procedure.

IMPLEMENTATION TEST ONBOARD MSC DITTE 2016-08-09

In August an opportunity to test the new routine occurred. One of the pilots from the project was assigned, together with a colleague, to bring in ULCS vessel MSC Ditte. The wind conditions were just in the upper part of the yellow zone stipulated in the report. The circumstances were very good. Daylight and stable wind from WSW and according to the forecast, a very good tug setup and no interfering traffic made it a very good chance to verify suggested routine and limitations.

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Due to a very strong tug connected aft (90 ton BP) the setup of two transom tugs connected aft was never needed. The reflections that deviated from simulator experiences were that the drift angles weren’t as large as supposed but the strong pushing force from wind from aft perceived our expectations. The conclusions from the debriefing were that the pilotage was carried out in a safe and good manner and with good margins.

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SIMULATOR TRAINING FOR PILOTS

One of the conclusions was that a special training program should be developed in order to prepare Gothenburg pilots for the new routine. Therefore have all active pilots in Gothenburg during autumn 2016 completed such training.

The SMA Simulator Centre in Gothenburg has been used at four occasions where six pilots at each time spent one day in the simulator, supported by two pilots from the project.

The training program has been started with a short presentation of the report, new wind limits and how to work within the new routine. Three complete runs in different conditions and with both models have been carried out with structured debriefings. All participants’ opinions during these sessions have been brought together and finally, as far as appropriate, the routine and the checklist has been amended accordingly.

The really good outcome of the completed training is that Gothenburg pilots, with their participation, now are ready to work within the new routine. The proposed new wind limits for this category of vessels under these conditions have been verified by the group of pilots.

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APPENDIX 1) SUMMARY OF SIMULATOR RUNS

Vinga Sand - Dynan

Dynan – Berth 610

Berth 610 – Knippelholmen

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APPENDIX 2) SIMULATED DRIFT ANGLES DUE TO WIND AND SPEED

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APPENDIX 3) CALCULATED WIND AND RUDDER MOMENTS

Theoretical calculations of wind and rudder forces acting on respectively longitudinal center points (LCP) giving the approximate limit when the rudder force comes too small to keep the vessel on course (marked red in the tables below).

Calculated moments generated by wind and rudder on lateral area of 14000 m2 in 16 m/s.

Calculated moments generated by wind and rudder on lateral area of 14000 m2 in 20 m/s.

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APPENDIX 4) REFLECTIONS FROM PARTICIPATING PILOT´S

GENERAL

The two models used have different draughts, otherwise the same properties. We find definitely the model with less draught more difficult to handle, which also is in line with our practical experiences.

The actual wind force should always be calculated, based on the exposed wind area. To use only the wind speed when judging if an operation can be carried out is not good enough. Watch out if minimum speed is close to eight knots! The visibility during the entrance should be taken into account. E.g. a heavy rain shower with pro longed gusts or a snowfall in a bad timing will not add safety to the operation.

When vessels of this size are exposed to large drift angles undesirable effects appear. In the fairways the pilot need to set the heading towards obstructions close to the fairway in order to oppose the drift. Our opinion is that this becomes a considerable risk when the drift angle exceeds 5 degrees and increases. A longer gust or a rapid drop in wind speed could mess up the plan and be dangerous when larger drift angles occur. In order to reduce the vessel´s drift an approach with higher velocity than normal is therefore needed.

The use of available technique is necessary. Radar, Electronic Chart Display with predictor, turn rate indicators, actual speed of vessel including transverse speed of both stern part and the bow are essential for a good performance both for safe navigation in the fairways and for maneuvering along the berths.

OUTER PART

In the first part of the entrance to Gothenburg we started the runs in about 14 knots which is a normal speed at that point. In especially winds from SW to W, the pilot really need to be “on the toes” and strengthen the initial turn, in order to achieve a proper rate of turn when passing the “wheel over point” or even a bit earlier than normal.

If the above actions were fulfilled in a proper way, we noted that going through the large turn in the “Måvholm Bend” could be carried out in a safe way in wind up to 35-40 knots and with a considerable north going current. The pilot needs to keep the vessel closer to the windward side and keep the rotation in the ship through the whole bend. Avoid the leeside due to a large sweep path in the bends.

When entering the straight passage W of the crude oil terminal it´s time to reduce the speed. Again we will rise a slightly caution concerning wind from SW to W and also up to NW. The wind from somewhere on the stern part of the ship creates beyond the difficulties in turning also a “pushing force”. The value of this force could be similar to the use of one tug in braking position just to equalize the effect of the wind.

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When the engine rpm was reduced, increased rudder angles were necessary to maintain the same steering force. In southerly wind the increased drift angle together with large rudder angles reduced the speed in a more efficient way compared to winds between SW and NW.

INNER PART

We started the runs just east of the crude oil terminal at a speed of 9 knots which should be suitable under these conditions when the vessel is affected of strong wind and some current. We had been able to reduce the speed to this level, without major problems, in almost all runs except the heavy ones from SW-W, where there were difficulties in reducing speed all the way down to the desired level. At this point the tugs need to be secured on the aft part and they should be ready to start brake the speed at around 8-9 knots. In the retardation phase from this level it should be a great advantage with two tugs in a position to break down the velocity. It will give the pilot an opportunity to keep engine ahead and also increase the rpm if necessary in order to keep the heading in the desired direction. There is also a possibility to use the windward side tug immediately after connection in “indirect towage” to oppose the vessels effect of turning into the wind.

When the wind force reach levels of 150 – 200 tons, especially when the wind is coming from SW-NW, the method with two tugs connected transom aft have a notable impact for safe handling of ULCS in order to more rapidly brake down the speed. The simulator runs showed that we safely could bring in the ships with this method under such circumstances. For these models, with 14 000 square meters lateral area, it meant safe operation equal to around 16 m/s (> 30 knots) regardless of wind direction in the port area and includes the desired 25% safety margin.

We found out in these cases a speed of around five knots when passing the fortress was the best possible in order to minimize the drift. With two tugs aft there is no problem to reach 2-3 knots before starting the swing. If the vessel is slowed down to early enormous drift occur which creates scenarios we haven’t dealt with before. Such drift with these masses and wind forces should be avoided.

When turning the vessel, the pilot needs to pay a great attention upon the ships movements. It´s very easy to do as “we always have done” according approach etc. and we found out that this is a major risk. The use of predictor, turning rate, velocity forward/aft and for stern and bow should be assessed at all the time. A preplanned turning circle achieves a better outcome and help the pilot to conduct his duties in a proper way.

The pilot should consider not turning the ship off the wind. We found that it was a much better solution to turn port over when the wind came from NW. The tug resources could advantageously be used mainly at the aft part of the vessel. When the vessels head is around the wind direction there are great opportunities to shift the tugs in order to have most effective set up for approaching the berth.

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The conditions we have simulated are not normal for pilots in Gothenburg. With the increased number of Ultra Large Container Ships calling Gothenburg the scenarios simulated will be more frequent in the future and must be handled in a more structured way. It is also important to continue and even extend the simulator training program for the pilots.

DEPARTURE

We have simulated a number of departures from the berth and found maneuvering safe up to 200 tons wind force, using three tugs and a strong bow thruster. We found that if we are able to break away from the berth, we also will be able to handle the drift angle out to the fortress. The vessel needs to be able to increase the speed so we can pass the fortress with at least 5 knots and the crude oil terminal with at least 8 knots.

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APPENDIX 5) REFLECTIONS FROM PARTICIPATING TUG CAPTAINS

When connecting two tugs transom aft it´s desirable with a minimum distance of 30 meters between the fairleads. The tugs should preferable use different length of their lines to minimize the risk of collision. The tug which is aimed to be reallocated for the mooring sequence should be on the shortest line.

When the pilot start to use the tugs transom aft for reducing the speed the best option is to use both tugs equal and to start with 25% in order to stabilize the maneuver. Then gradually increase the brake power of the tugs.

If possible the rudder should not change from side to due to disturbing water flow. If such an incident occurs, one of the tugs should be stopped and the other one to be used with increased power.

Reallocation of tugs: If for example a tug should be moved from stern position to quarter position, the one closest to new position should be reallocated. Best option for this shift is when the assisted vessel is coming close to the wind direction and when the speed is almost zero. It will not be a problem to transact this action even if the vessel is in a turn. These tugs shall be connected on long lines.

When one tug is connected aft and one on the quarter so use preferable the latter for lifting and the stern one to amplify the power needed. It might be problem for the tug connected on the quarter If they are used in the opposite way.

If the pilot would like to use one of the tugs in indirect mode, the established communication method used when escorting should be used.

Finally, the tug which is connecting forward, even in case of type Voith Schneider, is subject to safety issues in the tug company’s Safety Management System. One of the boxes to be checked when connecting forward is that the speed not exceeds 6 knots.

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APPENDIX 6) LOCAL ROUTINE FOR CONTAINER VESSELS

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APPENDIX 7) CHECKLIST FOR 15-17 M/S

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APPENDIX 8) LIVE TEST WITH TWO TUGS TRANSOM AFT - EVELYN MAERSK ON MAY 10, 2016

In order to confirm the results from the simulator studies, a live test with two tugs transom aft was performed on Evelyn Maersk on May 10, 2016.

Svitzer Tyr (70T ASD) was connected via starboard fairlead transom aft, in the western part of the Tors harbor strait. The speed was 9.1 knots. Subsequently, Svitzer Gaia (70T ASD) was connected via port fairlead transom aft. The aft station onboard Evelyn Maersk was manned with two teams and the connecting procedure went very smooth with only three minutes between the two tugs being connected.

After passing “Dynan” the two tugs started to brake with 25% each. The main engine was running dead slow ahead and the speed was 8.8 knots. After tug captains confirmed that the situation was under control and the tugs were acting stable, the brake force was increased to 50% and shortly also up to 75%. Six minutes later the speed reached 5.0 knots. At this point the main engine was increased to slow ahead. The speed remained unchanged (five knots) with 75% brake on both tugs.

The approach was now to be adjusted according to the departing vessel, occupying the berth. Therefore, the main engine was again put on dead slow ahead and three minutes later the speed was down to 3.2 knots. The main engine and the tugs were stopped and the vessel was drifting, awaiting berth.

During the swing to starboard, Svitzer Gaia was used and pulled nine o´clock. After half the swing she was stopped and disconnected. The disconnecting did take some time and the second tug, Svitzer Tyr, could not assist as long Svitzer Gaia still was disconnecting. During this time the swing was a bit delayed. The proper disconnecting procedure to be discussed further in meetings between pilots and tug captains.

The above test was documented by pilots and tug captains in separate reports and the operation was found safe and successful.

This test is to be considered as the first test in a series of several tests in good weather in order to ensure safe tug operation and to establish criteria´s for two tugs transom aft including a standard operational procedure.

Pilot card and test protocol below:

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Pilot Card of Evelyn Maersk. Source: Maersk

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Test protocol with two tugs connected transom aft for reducing the speed.

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03:55 Speed 9.1 knots, Dead Slow Ahead. Svitzer Tyr connected.

03:58 Speed 9.2 knots, Deas Slow Ahead. Svitzer Gaia connected.

04:03 Speed 8.8 knots, Dead Slow Ahead. Start to brake 25-75%.

04:09 Speed 5.0 knots, brake 75%. Main Engine increased to Slow Ahead.

04:12 Speed 4.9 knots, brake 75%. Main Engine reduced to Dead Slow Ahead.

04:15 Speed 3.2 knots, brake 75%. Brake test completed.

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APPENDIX 9) VESSELS APPROVED FOR TWO TUGS TRANSOM AFT

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APPENDIX 10) AREA OVERVIEW