Walk to work offshore

Ampelmann Walk to Work Offshore

J. van der Tempel (TU Delft)D. Cerda Salzmann (TU Delft)

F. Gerner (TU Delft)J. Koch (TU Delft)A. Göbel (TU Delft)

(We@Sea project 2006-008)

http://www.ampelmann.nl/





Ampelmann Demonstrator Final Report 1-7-2008

Ampelmann Demonstrator

Final ReportV1.2

1 July 2008


Authors:

Dr.Ir. Jan van der Tempel Ir. David Cerda Salzmann Ir. Frederik GernerIr. Jillis Koch Ir. Arjan Göbel

Section Offshore Engineering Delft University of Technology

This project was carried out under the WE@Sea programme under number 2006-008-RL5


SummaryThe Delft University of Technology is developing a Demonstrator of the Ampelmann, a motion compensation platform for access to offshore wind turbines. The project is sponsored by the University, We@Sea, Shell, SMST and Smit. The goal is to design, build and operate this system in offshore conditions to further develop the safety system, operational procedures and prove the motion compensation capability of the system.For access to offshore wind turbines, the current limit for ship based transfer is Hs = 1.5 m (73% for Dutch North Sea conditions. The Ampelmann has been designed for a typical 50m long vessel and full compensation to Hs = 2.0 m (85%) with a possibility of allowing some motions when transferring in Hs = 2.5 m (93%). In this demonstrator phase, a smaller vessel (25 m) will be used to prove full motion compensation up to Hs = 1.0 m and test the reduced compensation mode for higher sea states.The platform design has a base diameter of 6 m and a cylinder stroke of 2 m. The gangway system is designed in such a way that after connecting to the turbine, the gangway can rotate and translate freely to compensate for small motions of the Ampelmann transfer deck in normal operation and larger motions for operation in the ride-through-failure mode. Maximum length of the gangway is 16m including a telescopic part of 6m. The vessel will keep a mean distance of 7 m.Regarding safety, the system is designed to have sufficient backup and redundancy to be able to continue an operation when a single component fails. This ride-trough-failure mode must last at least 10 s, depending on the part failing and the activity at the moment of failure and could even last more than 30s. During the ride-through-failure, the person transferring has enough time to finish or abort this accessing procedure and return to his seat on the Ampelmann or to escape to the offshore structure. When the access procedure is completed or aborted, the Ampelmann operator can retract the gangway and bring the system to its settled position. The procedure does have time limits after which the system automatically takes over to return the Ampelmann to a safe position. All component failure modes are studied in an FMEA (failure mode effect analysis) to come to sufficient redundancy, regular checks and maintenance philosophy. Furthermore, the operational execution is examined in a HEMP study to identify all critical steps and precautions to be taken by personnel on board the vessel and the Ampelmann.The project is executed by a team of 5 residing under the Offshore Engineering group, lead by Dr. Ir. Jan van der Tempel. The team is supported by a vast number of experts in all disciplinesfrom inside and outside the University and from the sponsoring companies in particular.The design of the Ampelmann Demonstrator started in September 2006. Final design was completed in December 2006. Components were ordered early January and delivered in May. System assembly was completed in 4 days in May. The unit was tested offshore on June 27th

and July 11th. Compensation of a sea state to Hs = 1.5m was excellent with only 4cm heave and less than 0.5o roll and pitch residual motions.Finalizing of the system was carried out over the summer. Onshore tests were completed on December 7th for an audience of Shell, SMIT, Vestas, Lloyd’s Register and Staatstoezicht op de Mijnen. The next day, the Ampelmann was installed on the SMIT Bronco and sailed to IJmuiden. On Friday, December 14th, a safe transfer was made to and from WTG 03 of the Offshore Wind farm Egmond aan Zee (OWEZ) owned by Shell and Nuon. The Ampelmann returned to Rotterdam where demobilization was completed on Friday, December 21st, just before lunch.The project met the set goals: design, build and test an Ampelmann unit with a compensation test inn Hs = 1.5m and a transfer in Hs < 0.5m. Durability testing and access in higher wave conditions will be done in future projects.The project was a success proving that motion compensation can be performed by an Ampelmann under offshore conditions and that offshore access can indeed be “as easy ascrossing the street”.

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II


Table of contentsSummary ...................................................................................

...................................................ITable of

contents.......................................................................................................................III

1. Introduction and background ...............................................................................

.......... 51.1 Demonstrator

project .......................................................................................................... 51.2 Project

goals ....................................................................................................................... 5

1.3Invention.....................................................................................

........................................ 51.4 History of the

Ampelmann ................................................................................................. 6

1.5 Document setup ...........................................................................................

....................... 62. Design

philosophy ............................................................................................................. 7

2.1 General design considerations .............................................................................

............... 72.2 Demonstrator design

goals ................................................................................................. 7

3. Ampelmann operational procedure ................................................................................

84. Platform

design ............................................................................................................... 10

4.1 Boundary conditions of platform......................................................................................

104.2 Design steps for

platform ................................................................................................. 11

4.3 Platform geometry .....................................................................................

....................... 165. Gangway

design .............................................................................................................. 18

6.Safety .........................................................................................

...................................... 226.1

Introduction ...................................................................................................................... 22

6.2 Failure Mode Effect Analysis (FMEA) ............................................................................ 22

6.3 Hazard Effect Management Process (HEMP) .................................................................. 24

7. Ampelmann Test Plan .............................................................................................

....... 258.

Testing ............................................................................................................................. 29

8.1Introduction ................................................................................

...................................... 298.2 Cylinder control and motion envelop

testing.................................................................... 298.3 Platform x-y-z

control ...................................................................................................... 30

8.4 Load-out: testing plug & play...........................................................................................

318.5 Offshore motion

compensation......................................................................................... 32

8.6 Offshore motion compensation test I................................................................................ 33

8.7 Intermediate: View on Delft ............................................................................................

. 358.8 Offshore motion compensation test

II .............................................................................. 368.9 Endurance test: World Port

Days ..................................................................................... 378.10 Onshore completion and

testing ....................................................................................... 37

8.11 Offshore Access..........................................................................................

...................... 389. Conclusions and

Outlook ............................................................................................... 43

10. Inventor’s contemplations...........................................................................

................... 44Appendix I Project Partners &

Sponsors............................................................................... 45Appendix II Test Report

OWEZ............................................................................................. 47

Appendix III Risk Analysis OWEZ access.............................................................................. 3

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1. Introduction and background

1. Demonstrator projectThis is the final report of the development of the Ampelmann Demonstrator. The project started on September 1st 2006 and ended on December 24th 2007 with the completion of this document. The goal of the project is to develop a full size Demonstrator unit of the Ampelmann, a system to compensate wave induced ship motions in a transfer deck to allow easy and safe access to offshore wind turbines. The project was carried out by the Delft University of Technology with co-operation of project partners Shell, SMIT and SMST and under the subsidy scheme of WE@Sea. Partners and sponsors are shown in Appendix I.

2. Project goalsThe project has the following goals:•Design and build an Ampelmann platform• Make it offshore proof• Make it safe• Test it offshore•If possible: transfer people to an offshore wind turbine. The details of design goals are described in chapters 2-6.

3. InventionIn the summer of 2002 Jan van der Tempel and David-Pieter Molenaar attended the World Wind Energy Conference in Berlin. One of the speakers discussed his solution for offshore access. The animation shown in that presentation was somewhat distorted with regard to scale. The comments from the audience were not really satisfactorily answered by the speaker.Later that afternoon, after having done a small tour of the city, Jan and David-Pieter sat down outside Café Adler, just around the corner from Checkpoint Charlie, discussing the access solution of the speaker. It was decided that an offshore engineer and a controls engineer should be able to tackle this problem once and for all.Beer in hand, the following requirements were drafted:

• Ship based system• No contact with structure• No requirements on structure

The basic problem is that the vessel moves in all six degrees of freedom. It was an easy step from that to the Stewart platform (also used for flight simulators) that is also capable of moving in these 6 DOFs. Should it be possible to measure the motions of the vessel accurately and feed these to the control of the Stewart platform fast enough, a stand-still transfer deck can be created. From this platform a simple gangway could be extended to the offshore wind turbine. The basic systems were therefore defined:

• Use a Stewart platform• Measure the ship motions on board (no reference to the structure or seabed)

To be able to discuss the invention in front of others, without giving away the clue, a code name was needed. Fun and effectiveness came together in picking the Ampelmann, the littleman in the pedestrian traffic light (Ampel) who wears a hat in the East-German part of Berlin; one of the few remaining artifacts of the DDR age. The choice proved even more effective as itprovides a fitting slogan to the system (created a few days later):

Offshore Access, as easy as crossing the street

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1.4 History of the Ampelmann

Invention and first explorations

Scale model testing

DemonstratorSept 06- Dec07 Demonstrator construction and testing (this project)

1.5 Document setupThe project was initiated with a simple goal: create and Ampelmann Demonstrator and show that it works offshore. Chapter 2 gives the background on design philosophies and chapter 3 the generic operational procedure of the Ampelmann giving access to offshore wind turbines. The next 3 chapters go into further detail on the different sub systems: the platform design (4), the gangway (5) and the safety approach (6). Chapter 7 gives the planning of the tests and chapter 8 the report of all tests and trials. Chapter 9 resumes briefly the conclusions and an outlook to further improvement. Chapter 10 is a personal review of the project manager and inventor.

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July 2002 InventionJuly 02-Dec 03 Discussions with experts at DUTJan-Oct 2004 2 MSc projects on design of Ampelmann systemMar-May 2004 2 BSc students draft test planJune-Aug 2004 Testing of Seatex MRU and Octans measuring systemsAug 2004 System patented

Oct 2004 Acquiring funding from SenterNovem / ShellNov 2004 Start Proof-of-Concept phaseDec 2004 Arrival of platformJan 2005 Dry-testing on Simonita simulatorFeb 2005 Wet-testing in wave basin + demonstration for Industry and PressMar-May 2005 Writing a Business PlanJune-Dec 2005 Client contacts in offshore windOct-Nov 2005 Demonstration on TV, in Houses of Parliament and at European CommissionOct 05 – Aug 06 3 MSc students at Smit, Heerema and Shell for further developmentJan-Aug 2006 Demonstrator plan and financing


2. Design philosophy

2.1 General design considerationsThe Ampelmann concept has been based on a very limited set of design requirements. These requirements have remained fixed up to this point and serve to narrow the options for motion compensation to a digestible number.

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• Cancel all motions• Stand-alone system• Plug-and-play

-7 6-DoF system: Stewart platform-7 all systems on ship: power, measure, control, gangway-7 system can be installed on any vessel without interfacing

2. Demonstrator design goalsThe goal is to create an Ampelmann platform to design, test and show the following:

• System is offshore-proof• System operation is inherently safe, even when components fail• Test system offshore• Provide access to offshore wind turbines

The design requirements to reach this goal were defined as:• Platform must be large enough to test real offshore

applicability• Platform must fit all vessels longer than 25 m for

compensation up to Hs = 1 m• Platform must fit all vessels longer than 50 m for

compensation up to Hs = 2 m• Platform must be plug & play, installable within 1 day on vessels with standard

container fittingsThis lead to the following approximate geometry and characteristics:

• 2m stroke cylinders• Capable of full motion compensation up to Hs = 1 m

on a 25 m vessel and up toHs = 2 m on a 50 m vessel

• Hs < 1 m accounts for wave condition occurring 50% of the time off the Dutch coast

• Hs < 2 m accounts for wave condition occurring 85% of the time off the Dutch coast

• For more severe sea states, operation can also be tested easily

The design of the safety system is the key to the success of this Demonstrator phase. Experts from the offshore, offshore wind, automatic pilot, drive-by-wire and the medical life support systems fields of expertise are being consulted to translate the requirements from those disciplines regarding safety, reliability and redundancy to the Ampelmann operations. The main functionality of the Ampelmann system during component error or failure has currently been set to the following:

• The system always returns to its safe, settled position• The system never becomes a launching pad: introducing very large accelerations• When extending the gangway and when connected to the turbine, the system does not

shut down due to any failure but remains operational for at least 10 s and preferably 30 s (= 6 wave periods). This gives people on the gangway time to either retreat to the Ampelmann platform or step on to the turbine. The compensation characteristics must meet 95% of full compensation during this period. After the 10 s period, the platform returns to its safe, settled position.


3. Ampelmann operational procedureThe general operational procedure is depicted in the following 17 figures. Please note that these pictures are for illustration only and do not reflect any safety features.

1. Vessel sails to offshore wind farm, Ampelmann disengaged and turned off2. Vessel arrives at offshore wind turbine and engages Station Keeping Assistance

or Dynamic Positioning System3. Crew approaches Ampelmann

4. Crew arrives on transfer deck5. Gangway is retracted to prevent it from colliding with container during operation

6. HPU (Hydraulic Power Unit) is turned on, Ampelmann goes to neutral position (half of cylinder stroke)

7. Ampelmann is switched to compensation mode8. Gangway is turned toward turbine

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9. Gangway is extended toward turbine platform10. Gangway is engaged to platform11. Transfer of crew from Ampelmann to turbine

12. Gangway is disengaged from platform and retracted13. Gangway is rotated to neutral position14. Gangway is locked in position

15. Ampelmann compensation mode is switched off, Ampelmann returns to the neutral position

16. Ampelmann returns to the settled position17. Gangway is extended, HPU is switched off, vessel sails away.

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4. Platform design

1. Boundary conditions of platformIntroductionThe use of this Ampelmann as a demonstrator implies the following:

• Load cases are determined for demonstration purposes (higher than dedicated design)

• Maximum allowable dimensions are to be taken into account for transport and mounting on vessel.

Load CasesIn the design process, two load cases will be considered: one for cargo stabilization and one for personnel transfer. Both load cases are illustrated below in figures 4.1 and 4.2, corresponding values are listed in table 4.1.

Table 4.1 Load case values

Size limitsFor practical reasons, the Ampelmann platform is allowed to have limited dimensions, which are to be taken into consideration during the design process. The two main limiting factors are:

• Road transportation must be possible• Platform must fit on ship deck

For road transport, the limits shown in table 4.2 apply.

Figure 4.2 Load case 2Figure 4.1 Load case 1

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Load case 1 Load case 2

F1 10 ton 4 ton

F2 - 2 ton

F3 - 0.2 ton

Ftotal10 ton 6.2 ton

X1 - 14 m

X2 - 7 m


Table 4.2 Size limits for road transport

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xy

z

ob

xy

z

ot

top platform

actuator

gimbal

base platform

The deck space for the Ampelmann depends on the vessel. On a smaller vessel such as the Smit Bronco, the limited deck space will require the platform to be placed on top of two 20 ft containers, forcing the base plate to fit on a 6 m x 6 m square.

4.2 Design steps for platformIntroductionThe design process given in this chapter describes the procedures that are to be performed, in order to design the Stewart platform for an Ampelmann system, starting with the cylinderstroke length as the first design input. This basic Stewart platform configuration is shown infigure 4.3.

Figure 4.3 Basic Stewart platform configuration

Normal transport Exceptional Transport (exemption required)

max width 3.00 m < 4.00 m no convoy< 4.50 m 1 escort> 4.50 m 2 escorts

max length total vehicle

22.00 m < 40 m no convoy< 50 m 1 escort> 50 m 2 escorts

max height 4.00 m depends on route

max mass total vehicle

50 tonne < 100 tonne no convoy> 100 tonne 2 escorts


The entire design process is illustrated in figure 4.4 below; all blocks in this process are treated in this chapter.

Stroke length Load cases

Calculation Procedure

OtherGeometry

ParametersDesign Criteria

Size Limits

Preferred GeometryB

uckling

Figure 4.4 Design process flow chart

Stroke lengthThe main input parameter for this design procedure is the stroke length of the cylinders. The stroke length of a cylinder is defined as the difference between the minimum and maximumcylinder lengths as depicted in figure 4.5.

Minimum cylinder length

Maximum cylinder length

Stroke length

Figure 4.5 Stroke length

Other Geometry ParametersThe geometry of a Stewart Platform can be described by a set of 6 parameters. In this case, the following parameters will be used:

The first four of these parameters are illustrated in the figures 4.6 and 4.7 below.

Time Series

Max Force

Max Velocity

Cylinder Size

Flow

HPUValves

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Rt = Radius top platform [m]

Rb = Radius base platform [m]st = Half separation distance between top gimbal pairs [m]sb = Half separation distance between base gimbal pairs [m]

lstroke= Cylinder stroke length [m]

ldead= Cylinder dead length [m]


Figure 4.6 Top platform parameters Figure 4.7 Base platform parameters The

dead length of a cylinder is defined as the minimum cylinder length (gimbal to gimbal)minus the stroke length; this is the length that is not used for length

augmentation.

Size LimitsWhen choosing values for the base and top radii, a special consideration must be given to the size limits mentioned earlier. A too large top or base platform might cause difficulties fortransport, assembly or mounting on the vessel.

Calculation ProcedureA set of calculation procedures can now be performed for different geometries in a MATLAB calculation sequence. Stewart platform geometries can be changed by varying top and baseradius, top and base gimbal distances and the dead length, while the stroke length remains fixed.By creating loops in the calculation program, all required calculations can be performed for a set of varying parameters, allowing a quick assessment within a large number of platform configurations.

In the calculation procedure, the following steps are performed. First, the workspace limits are determined for a given geometry. This is done by varying the displacements and rotations of the base plate in small steps while the top plate remains fixed. When one of the cylinders reaches its minimum or maximum length, the workspace limit is found. While doing this, a large amount of platform poses is defined. Next, the dexterity of the platform can be calculated for each pose. Finally, also for each pose the axial forces in each cylinder can be determined for both load cases.

The MATLAB sequence can eventually summarize the main results of the calculation procedure for each given geometry:

• Minimum dexterity• Maximum axial forces in cylinders• Workspace limits

By using design criteria, the different geometries can be assessed and the optimal geometry can be selected.

x

y

120°t1

t6

t5

t4

t3

t2

120°

sb

Rt

γt

x

y

120°

b1

b6

b5

b4

b3

b2

120°sb

Rb

γb

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Design CriteriaBased on the output of the calculation procedure, a preferred geometry can be selected using the following criteria.

First of all, the minimum dexterity of any Stewart may not be too low: platforms with low dexterities can become singular and cylinders will experience very high axial forces. In flight simulator design, a practical minimum value of 0.2 is used. However, the use of this value is questionable since dexterity is scale dependent. In this case, it is more efficient to compare the minimum dexterity of different platform architectures and discard the architectures that yield the lowest dexterities..

Second of all, a platform will preferably have low axial forces in its cylinders. High axial forces call for cylinders with a larger rod diameter and a larger casing diameter, which calls for a lot of other larger components making the platform more expensive.

Finally, the workspace limits are to be taken into account. Since the Ampelmann aims to compensate ship motions, the functionality of this system increases with a larger workspace. Generally, when comparing ship motions to the limits of the workspace of a Stewart platform, it becomes clear that the limiting degree of freedom of a Stewart platform is the heave. A platform that can perform large heave excursions is therefore preferred.

The assessment of different platforms is thus based on a combination between high dexterities, low axial forces and large heave excursions. It is advised to do a comparison between platforms with more heave but larger axial forces and platforms with less heave but smaller axial forces, for it is not yet known which criterion is the real design driver.

Preferred GeometryAfter the calculation procedure is performed, a preferred geometry can be selected for further research. It is however advised to select several geometries for a more exact assessmentbetween geometries once the corresponding cylinders, valves and HPU have been designed. A more precise comparison between different designs can then be based on financial arguments as well as workability percentages.

Maximum ForceOne of the results from the calculation procedure is the maximum axial force in the cylinders, both of tension and compression. It is obvious that a cylinder should be designed to withstand those loads. It should however be noted that these loads are merely the result of a static analysis; the forces caused by the accelerations of the top loads have not been considered. Since the mainpurpose of the Ampelmann is to keep the top load static, it can be assumed that the top loads will not experience large accelerations. There are however two situations to consider where theaccelerations can indeed have an influence on the cylinder loads: during start-up and in cases of emergency.

During start-up, the platform will first be in settled position and the top load has the same motions as the vessel. Next, the platform is lifted towards neutral position, while the top is in motion. Finally, motion compensation is engaged and the accelerations on the top platform become negligible. After transfer procedures, the platform compensation mode will be ended and the platform is lowered back towards settled position. During the lifting and lowering procedures, the accelerations caused by the vessel motions might cause extra loads on the cylinders. It is advised to have these forces calculated.

Consideration should be given to a worst-case-scenario, where an emergency might cause the platform to undergo unusual accelerations, which might lead to exceptionally high leg forces.

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BucklingThe first design step for the cylinders is to determine the rod size and the cylinder casing size by the buckling criterion. For this, DNV uses the following equation:

E ⋅π 2

1000 ⋅ L ⋅ Z ⋅ s

P =

Z = L1 + L2 + 1 + 1 L sin 2π L1

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I1 I2 I 2I1 2π L

DNV further states that a lower safety factor than 4.0 may be accepted for more accurately validated calculation methods. Relevant parameters to be included in such a method are:

- Yield strength of piston rod material- Bending moments caused by the rotation of the bearings- Guiding length- Clearance between gland and piston rod- Actual deflection curve.

It should be noted that the maximum axial force in a cylinder does not necessarily has to occur in combination with the maximum cylinder length. The buckling check could thus be performed for several length-force combinations, rather than just the combination of the maximum values of both parameters.

Cylinder SizeCylinder manufacturers can deliver cylinders in different standard sizes. It is advised to choose a cylinder with standard dimension for ease in production. Preferably, one chooses the cylinderwith the smallest dimensions that still satisfies the buckling criterion. Another check to perform concerns the bottom end and the annular end cross sections: the cross section area must be largeenough to allow the oil-pressure to withstand the maximum forces.

Time seriesUp tot this point, only static calculations have been performed on the Ampelmann. The next step in the design process is to take time series into account. For this, the preferred geometry,the future vessel and the exact location of the Ampelmann on the vessel is required. By combining the vessel's RAOs with different sea states (combinations of Hs and Tz), time series for the base plate of the Ampelmann system can be generated. By using these time series, the actual Ampelmann performance can be simulated: while keeping the top plate fixed, the baseplate motions are simulated. For each time step, the required cylinder lengths can be calculated. A statement can then be given on the Ampelmann performance: for each sea state, percentageof time can be calculated in which the cylinder lengths do not enable full motion compensation. By choosing an arbitrary boundary limit for this performance, the maximum sea state can be

With: P = Maximum axial load [kN]

s I1

I2

= Safety factor = 4.0= Moment of inertia of cylinder tube cross section [mm4]= Moment of inertia of piston rod cross section [mm4]

L = Maximum cylinder length gimbal-to-gimbal [mm]L1 = Cylinder tube length from gimbal [mm]L2 = Piston rod length from gimbal [mm]E = Modus of elasticity of the piston rod material

= 2.06 x 105 N/mm


determined in which the specified Ampelmann can operate. This sea state shall be used to generate a time series of the base plate motions for the subsequent calculations.

Maximum velocityThe time series for the Ampelmann base platform are not only used to determine the required cylinder lengths at any instant and thereby determining its performance. They also enablecalculating the velocities of all cylinders, which is required to determine the required flow inthe system. A set of time series, adding up to twenty hours of simulation is used for this.

FlowAfter determining the cylinder velocities, the flow in the cylinder can be determined from the following equation:

Q = v ⋅ A

with:Qv A

= Flow [m3/s]= Cylinder velocity [m/s]= Cylinder cross section area [m2]

Simulations using the time series yield the nominal and peak flows for each cylinder separately as well as for the entire system. To reduce the flow, a double acting cylinder is used with the annular end being charged with pump pressure. This significantly reduces the maximum required flow at the bottom end, because when the cylinder extends the flow from the annular end is available for the supply to the bottom end (Figure 4.8).

Figure 4.8 Used hydraulic concept

HPU & ValvesFrom the mean and peak values of the flow, the specifications for the valves, HPU and accumulators can be determined. The mean and peak power consumption can also be calculatedby simulations in the time domain, by considering the cylinder velocities and forces.

4.3 Platform geometryThe dexterity, workspace and maximum cylinder forces were determined for a set of different platform architectures by varying the different platform parameters with a step size. Based on the criteria mentioned earlier, a selection of the most promising geometries was made, shown in table 4.3. Finally, the platform geometry that enables the largest vertical motion was selected as the final geometry. This platform has a top radius of 2.75 m, a base radius of 3.00 m, gimbal half-spacings of 0.25 m on upper and lower platform and a cylinder dead length of 1.25 m.

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Table 4.3 Comparison of platform geometries

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Geometry parameters [m] Platform height [m]

Axial Cylinder Forces [kN]

Dexterity [-] Excursions from neutral position [m]

Excursions from neutral position

[°]

Rt Rb st sb ldeadSettled Neutral

Fmax Fminmax min x y z rl pt yw

2.75 3.00 0.25 0.25 1.25 2.15 3.40 66.8 -33.7 0.233 0.149 3.63 3.31 2.50 55 53 76

3.00 3.00 0.25 0.25 1.50 2.39 3.63 66.3 -35.2 0.234 0.154 3.79 3.43 2.48 50 48 73

2.75 3.00 0.25 0.50 1.00 2.02 3.25 67.8 -35.7 0.233 0.138 3.59 3.30 2.46 55 53 75

2.50 3.00 0.25 0.25 1.25 2.25 3.47 65.4 -34.2 0.231 0.133 3.59 3.29 2.45 61 58 83

3.00 3.00 0.25 0.50 1.25 2.27 3.49 67.6 -38.1 0.234 0.145 3.75 3.42 2.44 50 47 72

3.00 3.00 0.50 0.25 1.25 2.27 3.49 67.2 -37.7 0.234 0.150 3.75 3.42 2.44 51 48 72

2.75 3.00 0.25 0.25 1.50 2.51 3.72 65.9 -36.3 0.233 0.139 3.74 3.41 2.42 55 52 79

2.50 3.00 0.25 0.50 1.00 2.10 3.31 66.5 -34.5 0.232 0.124 3.56 3.28 2.42 61 57 81

3.00 3.00 0.25 0.25 1.75 2.74 3.95 68.3 -37.5 0.234 0.146 3.89 3.53 2.41 50 47 76


5. Gangway design

Telescopic requirementsThe main dimensions of the gangway are displayed in table 5.1.

Table 5.1 Dimensions of the gangway

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The required minimum and maximum length of the gangway (telescopic behaviour) is determined using figure 5.1 and is listed in table 5.2.

Table 5.2 Determination of the length of the gangway

Figure 5.1 The neutral length of the gangway

The required survival modes of the telescopic behaviour of the gangway are determined by table 5.2 and illustrated in figure 5.2.

Length Max 15.000 mmMinimum telescopic behavior: 6.000 mm (3m each way).This result in a overall length of the gangway in stored position and survival mode of at most 9m

Width Min As small as reasonably practicable (check with regulations!)

Length determination: Length [mm]X1 Mid-point Smit Bronco 5.000X2 Clearance vessel – offshore structure 7.000X3 Connection device 1.000X4 Neutral length gangway (= x1 + x2 ) 12.000

Y1 Maximum offset vessel in survival mode +/_ 1500Y2 Extra safety margin +/_ 1500

Z1 Maximum length in stored position and survival mode (neutral length - offset - safety margin)

9.000

Z2 Maximum length in survival mode (neutral length + offset + safety margin)

15.000


Figure 5.2 Survival modes telescopic behaviour gangway

Flexibility gangwayThe required rotational flexibility of the gangway is listed in table 5.3. These are split in:

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- Directional mode:- Operational mode:

Active steering of the gangway to the offshore structure Passive mode while the gangway is connected to the offshore structure with the Ampelmann in full compensation. Passive mode while the gangway is connected to the offshore structure with total failure of the Ampelmann.

- Survival mode:

Table 5.3 Required rotational flexibilities of the gangwayYaw turntable Active (directional): min. 2 x 180°

Passive (operational mode): -3°/+3° (min. requirements) Passive (survival mode): -45°/+45° (negotiable)

Pitch gangway Active (directional): min. -10° max. 10° (-7 Connection at 0°) Passive (operational mode): -3°/+3° (min. requirements) Passive (survival mode): -20°/+20° (negotiable)

Roll gangway Active (directional): 0°Passive (operational mode): -3°/+3° (allowable at tip gangway)Passive (survival mode): -20°/+20° (allowable at tip gangway &negotiable)

Telescopic Active (directional): 6000mm lengthPassive (following max rest motions): 6000mm length -7 preferable more if reasonably practicable


Yaw.A controlled rotation of 2 times 180° (Directional) is minimal required. The resulting yaw motions during operation will be maximally 2°. If the Ampelmann fails a passive survivalrotation of plus and minus 45° is required (negotiable). The directional, operational and survival angles of yaw are displayed in figure 5.3.

Figure 5.3 Yaw motions in directional, operational and survival mode

Pitch.During operation the gangway must be positioned between an angle of 0° and 22°. When in survival mode a maximum angle of 30% is required as shown in figure 5.4.

Figure 5.4 Pitch motions of the gangway

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Loads:- Operational loads on tip:The maximum operational loads on the tip of the gangway are displayed in table 5.5. The total maximum combined load is 440 kg.

Table 5.5 Maximum operational loads on tip

NB: No safety factor has been used yet for the maximum load.

- Survival loads on tip:The maximum survival loads on the tip of the gangway are displayed in table 5,6. The total maximum combined load is 640 kg.

Table 5.6 Maximum survival loads on tip

NB: No safety factor has been used yet for the maximum load.

The result of the design process is shown in figure 5.5 as a composition photo of all extreme positions of the telescopic access bridge.

Figure 5.5 Extreme positions of telescopic access bridge

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Mass on tip determination: Min1 person (x 100kg) 100 kg1 x load 40 kgConnection (specified by SMST) 300 kgTotal 440 kg

Mass on tip determination: Min3 persons (x 100kg) 300 kg1 x load 40 kgConnection (specified by SMST) 300 kgTotal 640 kg


6. Safety

6.1 IntroductionThe Safety Strategy of the Ampelmann strives after a fail-safe Ampelmann system. The Ampelmann Demonstrator will be designed following two types of safety management systems:• Failure Mode Effect Analysis (FMEA): Safety management system that prevents,

detects and corrects failures with respect to potential breakdown of its system components.• Hazard Effect Management Process (HEMP): Safety management system that reduces the

risk of potential hazards in the different operational modes.

6.2 Failure Mode Effect Analysis (FMEA)This section describes the approach of a fail-safe Ampelmann design. In this approach, the design process of the Ampelmann is characterized by the identification (1) of all conceivable failure modes with respect to its system elements. This allows best preventive measures (2) followed by a continuous failure-mode detection system (3) completed with a full set of corrective (back-up) measures (4).The intended effect of a full set of preventive measures is to achieve that the disclosure of any failure of a system element is actively prevented at all time. The intended effect of the set of detective and corrective measures is to automatically detect and instantly correct any failure (initiate back-up systems) once failure of a system element still reveals. This latter set of safety measures (detection & correction) must ensure a safe Ride-Through-Failure (RTF) of any single failure for at least 30 seconds. The first 15 seconds (phase 1) will allow all personnel to safely exit the gangway. In second 15 seconds (phase 2: 15s-30s) the gangway will be disconnected from the structure and the Ampelmann will disengage the compensation mode into neutral and settled position. This second phase is called: Controlled Down (CD). Depending on the type of disclosed failure (and available back-up options), a Controlled Down shall be operated manually or initiated full automatically by the safety system.When for a system element all potential failure modes have been identified and sufficient detection and corrective (back-up) measures have been incorporated, the system element will be identified to be fail-safe. When a system element engenders potential failures that are either hard to detect or hard to be corrected, this element will be pointed out to be critical. In the safety strategy of the Ampelmann, ‘striving for a fail-safe Ampelmann design’, the number of components that listed to be critical needs to be stringently reduced.As point of departure for this Failure Mode Effect Analysis, the Ampelmann system is subdivided into 3 main modules, 18 sub-components and ‘x’ system elements. For each sub- component the failure modes of its system elements are listed in a FMEA-matrix.

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Differentiation Ampelmann system:

Main components: Container Hexapod Gangway

Sub-components: Hydraulic Power Unit AccumulatorsMotion SensorsMotion Control Cabinet Programmable Logic Controller

Sub-components: Cylinders Manifolds + valves Sub-manifold Electrical Umbilical Hydraulic hoses Bottom FrameTop Frame User Interface 1User Interface 2

Sub-components: Telescopic gangway Turn TableQCDC: Quick

Connector DisConnector Leverrope

Flowchart:

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6.3 Hazard Effect Management Process (HEMP)This section describes the effect of any failure or hazard (operational, accidental or environmental) in the different operational modes of the Ampelmann. This is called the Hazard Effect Management Process (HEMP). The HEMP first lists all hazards (HAZID: Hazard Identification) in order to point out the Hazardous Operations (HAZOP).With respect to the transfer of personnel using the Ampelmann system, the basic Ampelmann operation listens to 12 different phases in which 5 different safety scores are applicable:Safety score 1: Failure is not noticed and has no effect on the process. Safety score 2: Failure is not noticed and has a small effect on the process.Safety score 3: Failure leads to annoyance but can be easily solved Safety score 4: Failure can be corrected but leads to a short delaySafety score 5: Failure cannot be corrected and leads to failure Ampelmann.With respect to the most critical operational mode, the transfer of personnel to and from offshore structure, the safety score may not be beyond score number 2. For all other operationalmodes, the safety score must be below 4. Only in the testing pre-check phase of the Ampelmann and the test-phase of the station keeping of the vessel the required safety score may be equal to 4.

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7. Ampelmann Test Plan

IntroductionThis document describes the tests that will be carried out to prove the suitability of the Ampelmann Demonstrator for access to offshore wind turbines. The test plan is set up in such away that all tests are performed to meet Performance Based Standards: pre-set goals that mustbe met during the test before the next test can commence.

Preceding testsThe Ampelmann Demonstrator project has been running since September 2006. The Demonstrator was operational at the end of May 2007 and several tests have already been done.A short summary of these tests is given here as background. Some of the test me reoccur in theoffshore tests, others are conclusive on their own.

Single cylinder controlThe first test was to control every cylinder individually and tune the control of the hydraulic valves, the position transducers and the hydraulic pressure transducers. Small deviations percomponent have been identified and are incorporated in the control system to assure accuracy.

Motion envelope testingAll extreme motion envelopes were visited to check whether there would be no collision op components in any possible extreme platform orientation.

Simultaneous cylinder controlIn this test the control of the all cylinders simultaneously was tested, resulting in control of the platform through set points of the transfer deck being continuously translated to requiredcylinder length. The test resulted in a demonstration sequence in which all six degrees offreedom can be simulated by the transfer deck.

Coupling of OctansThe final loop in the control system is that the set points of the transfer deck are delivered by continuous measurements from the Octans. The system proved be capable of following theOctans motions or counteracting them.

Offshore motion compensation test IThe system was mounted on a barge and towed to the entrance of the Port of Rotterdam. The significant wave height was around Hs = 1.0 m and the compensation of the vessel motions wasregistered visually from the deck of the barge. The system performed very well. The test proved the basic working of motion compensation and that the system is waterproof.

Offshore motion compensation test IIThe same configuration was tested two weeks later with a further update of the control system and with a second Octans that was mounted on the transfer deck. The wave conditions wereslightly higher: Hs = 1.25 – 1.5 m. The processing of the Octans data showed a residual motionof the transfer deck to be less than 4 cm heave and less than 0.5o roll and pitch. As a fixed structure was not available at the site, surge and sway would not be determined accurately. Furthermore, the experience of being on the operating Ampelmann was tested by placing a team member on the transfer deck with sufficient safety precautions for accidental control errors. The motion compensation was engaged 4 times and 2 emergency stops were also executed. The sensation of being on the platform was like being onshore, although slight trembling of the transfer deck was noticeable due to the fact that the deck was not fully completed yet. This meant that the deck did not yet have its eventual stiffness. The need for a non-transparent deck was proven again: looking down through the grating and seeing barge and

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cylinders move makes the person on the transfer deck feel unstable. When looking to the horizon or passing ships, the sensation of being on a vessel is lost instantly.

Component redundancy checkingThe Ampelmann Demonstrator has been designed to have nearly all critical components to have a backup. In case of a single failure, the platform can continue its operation on a backupcomponent until the transfer of the person is completed. The component failure modes havebeen identified and control algorithms have been programmed to detect errors and switch to the backup component. All failure modes have been tested manually and the system operation was not interrupted. The redundant components are:

- cylinder valves- position transducers- wiring- control computers- PLC’s- power packs- electricity supply- motion measurement system

Onshore testingThe following tests will be carried out before fitting the Ampelmann on the vessel. The tests incorporate the full system functionality including transfer deck and telescopic access bridgeand the training of the operator.

Transfer deck and telescopic access bridge functionalityThe topside of the Ampelmann has an additional three degrees of freedom: luffing (TAB up and down), telescoping (TAB in and out) and sluwing (rotation of transfer deck. These degreesof freedom are tested first separately and then simultaneously. Furthermore, these degrees offreedom are controlled actively but have a safety overflow mode to prevent make them follow residual motions passively. This overflow mode is tested by pushing the TAB against a dummy boat landing and creating motions with the Ampelmann platform to simulate motion compensation failure. The setting of the overflow mode is variable and will be adjusted during this test to get acquainted with the sensitivity of the system.

Failure mode alarm testAll failure modes have a pre-determined alarm sequence. All modes will be simulated to check whether all alarm systems function correctly. These systems are for example: the operator control console, warning light, traffic light and sirens.

Load testing gangway and transfer deckThe design loads are tested on the transfer deck and gangway to make sure the system is secure in case of overloading. The gangway will be loaded with 400 kg, transfer deck with 500 kg. Furthermore testing of contact force against the dummy boat landing is performed.Boat landing docking procedureThe Ampelmann operators will go through a training sequence in which they dock the Ampelmann TAB against the dummy boat landing. The first series of tests will be carried outfrom a stationary Ampelmann deck at several heights. In the second series, the transfer deck will be actuated with the residual motions measured during the second offshore compensation test. Then the residual motions are increased to a sea state beyond the design limits of theAmpelmann platform: Hs = 2.5 m. These residual motions are generated by a vessel motion simulator and will result in occasional heave of the transfer deck. The final series of landingswill incorporate failure mode testing in which the Ampelmann is turned on at random to simulate ship motions in a Hs = 1.0 m sea state. The operator will then have to retrieve thegangway safely following the emergency procedures.

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Redundancy checkingAgain, the redundancy of the components is tested actively, with the operators present to have them witness the failure modes and the associated control panel messages.

Access testWhen the training program of the operators is completed, the people who have been selected to make the transfer to the offshore structure, will perform a complete dry run of the docking procedure: check of the Ampelmann system, including performance test. Access to transfer deck, strapping into seat, Ampelmann engaged to neutral height, including residual motions. Docking of the TAB against dummy boat landing and transfer of 2 persons following standard procedures. Furthermore, several failure modes are tested to make the operator and personnel familiar with the procedures, signals and codes.

Offshore testing of the Ampelmann DemonstratorThe following tests will be carried out offshore during the final test phase. Each test will be described in detail on a separate test form with measurable results that need to be met at the endof the test. Only when a test has been completed satisfactory will the next test commence. Upon failure of completing a test satisfactory, a meeting is held where all available data is analyzed and a plan of action is drafted. This can either be to perform the test in a different manner or toalter the consecutive test steps.

Ship safety testing• Man overboard training in port with Ampelmann engaged to dummy wind turbine. Test

is carried out with buoy as man-overboard. 3 x testing• Engine failure test in port: all 3 engines one failure (main port, main starboard,

bow thruster. Again Ampelmann engaged to dummy wind turbine.• Power failure in port, 1 test to check whether secondary power restores control within 5

seconds• Man overboard training offshore, just outside the port. Training with buoy, only once.

Station keeping• Upon arrival 500m zone structure: 1 test for station keeping -7 check maneuverability

and tidal current• @ 50m from structure: 1 test of 5 minute station keeping, again check tide• @ 20m from structure 2 test of minimum 5 minutes• @ 10m from structure 3 tests of 10 minutes, different headings

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Engaging Ampelmann• Test in port, all systems functioning, once• Test in port, extend gangway against dummy boat

landing, 3 times• Test in port, gangway against boat landing residual

motions of 25 cm, 3 times• Test in port, gangway against boat landing failure

mode in 1.5m Hs, 3 times• Test offshore, just outside port: engage Ampelmann, 3

times, min 5 minutes• Test offshore, just outside port: engage Ampelmann, operate gangway max

extension and luffing, 3 times, min 5 minutes• @ 20m from structure: engage system and measure compensation visually, 3

times, min 5 minutes• @ 20m from structure: engage system operate gangway, no connection, 3 times, min 5

minutes• @ 7m from structure, engage system, operate gangway and connect, at least 3 minutes,

3 times

Offshore Access• Engage system, operate gangway and connect, when safe: transfer one

person, disconnect• Engage system, operate gangway and connect, when safe: retrieve person, disconnect• Engage system, operate gangway and connect, when safe: transfer two persons,

disconnect• Engage system, operate gangway and connect, when safe: retrieve persons, disconnect

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8. Testing

1. IntroductionThe testing of the Ampelmann Demonstrator comprises all tests performed from the moment the unit was assembled to the final test of transferring a person to an offshore wind turbine. In building the software of the unit, several tests were performed as part of the building process. Of all major tests a plan was drafted and records were made. This chapter gives a broad overview of the different test phases.

2. Cylinder control and motion envelop testingUpon completion of the assembly of the Ampelmann main system, the hydraulic hoses were connected to the first cylinder to start fine tuning of the motion control software. To prevent other cylinders from interacting with the tuning activities, the cylinder was connected directly to the power pack as shown in figures 8.1.

Figure 8.1 First cylinder connected directly to power pack and control system testing

When the cylinder control was tested sufficiently, the hydraulic piping was fitted to theplatform and the hydraulic hoses connected to all 6 cylinders as shown in figure 8.2 which

gavethe opportunity to test motions of all 6 cylinders simultaneously. In this phase all cylinders were controlled on extension only: no platform control was fitted yet.

Figure 8.2 Fitting of hydraulic piping and connection of hoses to all 6 cylinders.

Having control over all 6 cylinders enabled the motion envelop testing. As the platform

canreach an umbrella of positions, it is critical in the testing to check whether all

components canfollow the cylinder positions without components touching or even damaging each other. Figure 8.3 shows the system in different extreme positions. All components passed the test and no adaptations were required for the platform to reach all cylinder length combinations that are possible.

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Figure 8.3 Motion envelop testing

8.3 Platform x-y-z controlAfter the control of 6 individual cylinders was tested and the platform envelop checked, the transformation of single cylinder control to platform orientation control was introduced. By controlling the top platform centre point orientation and re-calculating the required cylinder lengths, the platform can be controlled by feeding it harmonic signals, ship motions, or the measurements from the Octans. To test and demonstrate the workings of the platform and to prepare software and control panel integration, a panel was made to turn the system on and let it perform the six degrees of freedom motions: surge, sway, heave, roll, pitch and yaw as shown in figure 8.4.

Figure 8.4 Six degrees of freedom control via control panel

Yaw

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Surge

Sway

Heave

Roll

Pitch


At this stage, the Octans was also connected to the system, but manual control by moving the Octans proved very uncomfortable due to the scale effects between human reach and the platform reach. Furthermore, very fast motions can be performed easily by moving the Octans and with the Ampelmann running at maximum velocity, it can follow, but again at a very uncomfortable high velocity for spectators. Further manual testing was therefore discontinued.

8.4 Load-out: testing plug & playThe Ampelmann Demonstrator was designed to be “plug & play”: easy to install on any vessel within an acceptable time frame. The first test of this was the load-out at Heerema Zwijndrecht. The advantage on site was the abundant presence of cranes, multi-wheel trailers and other lifting equipment. Preparation for load-out took 3 hours: unbolting the platform from the mud- plates and preparing the control computers to be moved. Figure 8.5 shows the lifting of the system onto the multi-wheel trailer.

Figure 8.5 Preparation for load-out: lifting Ampelmann and power packs onto the multi-wheel trailer

The load-out itself took less than 2 hours: rolling the system out of the construction hall and lifting it onto the barge. For this lift, the power packs and Ampelmann were still connected via the hydraulic hoses. This meant only one lift was required, but it also made it necessary to use a spreader bar and two cranes as shown in figure 8.6.

Figure 8.6 Transport to quay side and lifting with spreader bar and two cranes

The system was installed on a SMIT barge and fixed to it by welding the footplates and fixing the power packs and containers using steel profiles. Installation and welding is shown in figure 8.7.

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Figure 8.7 Installation on barge, fixing of containers and general layout

As only the electrical control umbilical needed to be connected, the time to be operational after lifting was less than 1 hour. The entire load-out took approximately 8 hours, spread over 2 days. Biggest improvement to be introduced was the disconnection of the hydraulic hoses from the power packs. Although an extra lift is then needed, the expensive and complicated duo lift can be abandoned.

8.5 Offshore motion compensationAfter the unit was installed on the barge, the system was maneuvered to Rotterdam. During transit, the first motion compensation test was done. Although the waves on the river were in the order of centimeters, the system proved stable for small wave motion compensation. Figure8.8 shows pictures of the departure on the Maiden Voyage, figure 8.9 the transit to Rotterdam.

Figure 8.8 Departure on Maiden Voyage from Zwijdrecht to Rotterdam

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Figure 8.9 Transit to Rotterdam

8.6 Offshore motion compensation test IAfter arriving in Rotterdam at the SMIT head office, the final checks were made for the sea- worthiness of the Ampelmann. An oil response kit was installed on board as was fire extinguishing equipment and man overboard kit. Final preparations being made to the platform is shown in figure 8.10.

Figure 8.10 Final preparations before first offshore trial

On the 29th of June, the Ampelmann was taken offshore by the SMIT tug Eerland 28. The tests were carried out at the mouth of the Port of Rotterdam, off Hook of Holland, as shown on the map in figure 8.11. Weather conditions resembled fall more than summer with only 12oC, clouds, rain and a sea state just above Hs = 1.0m at the test site. The system was tested first for heave, pitch and roll compensation. Later surge and sway were added. For yaw a reset button was created. The surge and sway motions are doubly integrated accelerations, slowly drifting with the vessel co-ordinates, the heading is a true compass measurement without drift. When following it throughout longer period tests, the increasingly yawed platform disallows other motion compensation.Station keeping performances of the barge and tug were moderate, but sufficient for the first tests. Visual check against the horizon gave very good confidence on motion compensation, but video footage shot from the barge or tug was influence by the ship motions (the human eye cancorrect for vessel motions, cameras cannot). It was therefore decided to have a camera onshore and a measurement device on the platform for the next test.Pictures of the tests are shown in figure 8.12.

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Figure 8.11 Sailing route from SMIT HQ to test site at mouth of the Port of Rotterdam

Figure 8.12 Images of offshore testing on the 29th of June 200

Test site

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8.7 Intermediate: View on DelftAfter the first offshore test, the Ampelmann was transferred to Delft to give the sponsors, industry, University staff and students and the press the opportunity to see the Ampelmann. At the same spot where famous Dutch painter Vermeer painted his “View on Delft” the Ampelmann was demonstrated as shown in figure 8.13.

Figure 8.13 View on Delft by Vermeer and by the Ampelmann Team

As waves are non-existent on the Rijn-Schie kanaal in Delft, attempts were made to create dynamic response of the barge by rolling and/or swaying the Ampelmann transfer deck in the roll frequency of the barge. Conclusions of these tests were that the barge only responds slightly to sway, roll does not give noticeable response. The natural frequency of roll is 0.29 Hz. But any induced roll of the barge was damped in one stroke. It was therefore decided only to show the six degrees of freedom and a series of measurements from the first offshore tests, simulating the wave motions in the transfer deck, rather than compensating them. The pictures in figure 8.14 give an overview of the preparations in Rotterdam, the trip to Delft and the demonstration.

Mayor of Delft: B. Verkerk; Chairman DUT: H. van Luijk; Director NZW: H. den Rooijen; Ampelmann: Jan van der Tempel

Figure 8.14 Preparations in Rotterdam, sailing to Delft, speakers and the Demonstration on 3rd of July 2007

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8.8 Offshore motion compensation test IIOn July 11th, the Ampelmann was again sailed to the test site for a second motion compensation test. Weather conditions were less cold, but with more wind from westerly directions, wave heights were reaching Hs = 1.5m. The tests started around noon at the outer reaches of the break waters, but later in the afternoon, the vessel moved into more sheltered areas as above Hs = 1.5m waves were building up, which was beyond test procedures.The following additional test features were added:•Second Octans on transfer deck to measure residual motions• Test with person on transfer deck•Filming form onshore location to record compensation capabilities from stationary location Figure 8.15 shows an overview of the tests.

Figure 8.15 Second offshore motion compensation test on July 11th 2007

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The main conclusions or the test were the following:• Motion compensation on a 30m barge in Hs = 1.5m works properly• Residual motion: heave: less than 4cm, roll and pitch: < 0.5o

• Experience on transfer deck: as if onshore; connection with vessel completely gone• Addition of visual separation needed: seeing the cylinders move underneath gives strange

feeling -7 fitting of cloth underneath transfer deck

8.9 Endurance test: World Port DaysUpon completion of the offshore motion compensation tests, the Ampelmann Demonstrator returned to Heerema Zwijdrecht for completion of the hydraulic system, extension of the internal measurement system and testing of the redundancy. Furthermore, the transfer deck was developed further to include the telescopic access bridge.At the beginning of September, the Ampelmann Demonstrator was invited by SMIT and the organization to give a demonstration at the World Port Days in the Port of Rotterdam. This three day event would be opened by local folk singer Gerard Cox, performing from theAmpelmann. Furthermore, the Ampelmann technology was demonstrated to an audience of 50,000. Figure 8.16 shows Gerard Cox performing.

Figure 8.16 Opening of World Port Days by Gerard Cox on the Ampelmann Demonstrator

The remainder of the weekend, the public could control the six degrees of freedom of

theAmpelmann. For a full two and a half day children and their parents were invited to

use thecontrol panel and let the Ampelmann make motions. The weekend was primarily an endurance test for the system operating 10 hours on end and being operated by untrained personnel. Allsystems functioned without problems.

8.10 Onshore completion and testingThe week after the World Port Days, the Ampelmann was demobilized and shipped from SMIT in Rotterdam to SMST in Franker, in the North of the Netherlands. At SMST the transfer deck and telescopic access bridge had been constructed and for final finishing of hydraulics and control it was beneficial to be close to the workshop. Figure 8.17 shows the transport route from SMIT to SMST.Upon arrival, the Ampelmann was re-assembled and final control testing could commence. The main goal was to have all redundant systems ready and tested before the final offshore test. Furthermore, the tuning of the gangway controls could be tested and optimized. With structural, hydraulics and control experts of SMST nearby, the system completion could be finished. The final onshore tests were to land the gangway on a copy of the OWEZ boat landing, as shown in figure 8.18.

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Figure 8.17 Transit from SMIT in Rotterdam to SMST in Franker

Figure 8.18 Training of operator and transfer crew on onshore copy of OWEZ boat landing

The tests ended with an demonstration on Friday, December 7th for representatives of Shell, NZW, Vestas, Staatstoezicht op de Mijnen and Lloyd’s Register. The demonstration included an introduction to the platform, visual inspection and a transfer. Several comments were recorded and used for further improvement to prepare for the offshore access tests.

8.11 Offshore AccessThe next day, the Ampelmann was shipped from Franker to Harlingen on a barge. De- mobilization took from 6:00 to 13:00. In the afternoon, the Ampelmann and one power pack were installed between 14:30 and 17:00, when darkness made installation work on the tight

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deck less safe. The next day, the installation continued with installation of the power pack, transfer deck and control computer between 10:00 and 12:00. The remainder of the day was spent on welding the Ampelmann to the deck and re-connecting hydraulics and electronics. The system was operational at noon on Monday. De-mob and Mob are shown in figure 8.19.

Figure 8.19 De-mobilizing from Franeker and installation on SMIT Bronco in Harlingen

On Tuesday, December 11th, the SMIT Bronco set sail for IJmuiden. Offshore conditions werebeyond the Ampelmann testing conditions: Hs > 2.0m. Nevertheless, the system can

run insimulation mode and was able to compensate all measured motions with less than 15 cm residual movement due to cylinder length limitations. These results exceeded ship motionsimulations: they were more conservative than the real situation. Figure 8.20 shows the tourfrom Harlingen via the Shell co-owned offshore wind farm OWEZ to IJmuiden.

Figure 8.20 Sailing from Harlingen to Ijmuiden, Tuesday, December 11th 2007

Unfortunately, the sailing trip had some negative effects on the functioning of one of the powerpacks. Due to moist in the connectors, the power pack did run, but would not start its

hydraulic pump. Offshore correction by feeding it by-passed information from the Ampelmann PLC did help and made the power pack functioning within 2 hours, but an intermediate shutdown during the first test resulted in aborting further efforts. The power pack controls were repaired the next morning in the Port of IJmuiden. Figure 8.21 shows images of the transit to Ijmuiden.

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Figure 8.21 Transfer from Harlingen to IJmuiden: setting sail on the Waddenzee, passing ECN in Petten (shot from behind HAWT and zoom (pictures: Jos Beurskens))maximum roll: 11

degrees, maximum heave: 2.8m (Ampelmann: 2.5m) And OWEZ at touching distance………

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The Ampelmann was further prepared for the offshore trials and all licences were gather to be able to enter the Offshore Wind farm Egmond aan Zee (OWEZ). Both operator, Noordzee Wind (NZW), a joint venture of Shell & Nuon, and the maintenance contractor BCE (Vestas and Ballast Nedam) were co-operative and critical to make the effort safe. The Risk Analysis to acquire a Permit to Work is shown in Appendix III. The most significant outcome of the safety meetings was to land the Ampelmann gangway not on the ladder, but beside it. By pressing the tip against the structure and the side of the ladder, it could be fixed in all directions. Should contact be lost and the gangway move up, it would not hit the person who just transferred while he was climbing the ladder. The OWEZ wind turbines have an additional benefit for this working method: the tip could be landed at the level of the spider deck. The person transfer therefore only needs to step on the ladder and step sideways directly out of reach of the gangway. The ladder and spider deck are shown in figure 8.21.

Figure 8.21 Landing at spider deck level

The transfer was executed on Friday, December 14th 2007. The mv Fortuna accompanied the SMIT Bronco and had an MOB boat in the water on standby. The conditions were ideal for testing a transfer, but not for demonstration of motion compensation behaviour: < 0.5m wave height. The transfer was executed by Jan van der Tempel to WTG 03. Figure 8.22 shows the images of the transfer.

Figure 8.22 Transfer to WTG 03 on December 14th 2007

The following days more landings were performed under different approach angles and tidal conditions. The co-ordination between operator and Master improved significantly. Improvements to the station keeping on manual control were implemented over the weekend. Detailed description by the Shell representative on board are shown in appendix II.

On Wednesday, December 19th, the SMIT Bronco left IJmuiden and set sail to Rotterdam where the Ampelmann was de-mobilised and stored for future projects.

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9. Conclusions and OutlookThe project goals were very simple and straightforward:• Design and build an Ampelmann platform• Make it offshore proof• Make it safe• Test it offshore• If possible: transfer people to an offshore wind turbine.

The Ampelmann Demonstrator project reached these goals. The platform has performed well to a sea state of Hs = 1.5m with only 4cm heave residual motions in the transfer deck. Furthermore, a series of landings on offshore wind turbines have been executed in the OWEZ wind farm. On Friday, December 14th 2007, a safe transfer was made to and from turbine WTG 03. Wave conditions were minimal. During that week a maximum wave height of Hs = 0.5m was encountered while landing the gangway against the monopile.

Improvements on the design and control system of the Ampelmann Demonstrator have been ongoing throughout the project, up to the last tests. The system proved to be robust and offshore proof. The main improvements will be made in the Station Keeping Assistant: a device to tell both the Vessel Master and the Operator what the relative positions are. Furthermore, the operational experience has changed the team’s view on redundancy. In this Demonstrator, all redundancy was externally monitored and enforced by PLC and control computers. Though functional, inherent system redundancy will be an easier way forward, tackling failures at the core and not at the end of the flow lines.

The Ampelmann Demonstrator proved that offshore access can be made as easy as crossing the street.

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10. Inventor’s contemplationsWe have done what everyone outside our team deemed impossible. We have built a fully operational unit with 1.5 years. We gathered all knowledge and experience and got it done. We started with a 1m stoke cylinder platform and redesigned in December to 2m stroke which made the project base completion less than a year. Assembly of the core system took only 4 days, for a team that had never done this before. Many called us “deadline junkies” for completing all demonstration goals over summer: with the system assembled end of May, we were able to do offshore tests end of June. And present it to the press early July. Being able to have kids operate it early September was an engineering feat in itself. The relaxedness came only when everything moved to Friesland, where distance to Delft provided the much need relaxation to test all that was needed. When we were at the Offshore Wind Energy Conference in Berlin, the very place Ampelmann was invented, speed pick up again, probably beyond common belief. Presentation on the 6th of December of what was to happen became reality within 2 weeks. The full 5 days of offshore testing provided enough data to improve the system to promote the system from prototype to fully operational unit.We were able to find the minor weaknesses in the design and address many during testing. And we had all knowledge and tools onboard to fix them. Ampelmann commissioning takes a day, fixing minor problems only hours. Much will need to be improved but all is there for any challenge.

I am proud to have worked with all of the Dutch industry: from builders of components to system integrators to critical end-users. WE did it, all of us!

If there will ever be a time and place to thank all, it is now in this beautiful picture show and for me on Christmas Eve: we did it! You did it! Thank you! And be proud!

Ampelmann has always been more than just a cool image, it has become an icon of accomplishment, and we made it happen. I am grateful and forever in dept to all those beautiful people who owned this idea as I did.

Most indebted I am to my team: Frederik, David, Jillis and Arjan. You gave more than I could ask. When weekends became working days and sleep a luxury, you were there, always. You were there even when I was not. The perfect proof of a perfect team!

Beauty is in the eye of the beholder, and the Ampelmann is beyond beholding…

THANK YOU!

Jan van der Tempel

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Appendix I Project Partners & Sponsors

Partners:

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Sponsors:

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Appendix II Test Report OWEZ

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AMPELMANN DEMONSTRATOR

OFFSHORE WINDPARK EGMOND AAN ZEE (OWEZ)Offshore Access & Egress O&M Procedure

Ampelmann-RA-OWEZ-V2.0 OFFSHORE WINDPARK EGMOND AAN ZEE (OWEZ)Offshore Access & Egress O&M Procedure

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Appendix IIIRisk Analysis OWEZ access




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Offshore Tower Access

Routine access to

ladder

Trapping of feet between ladder rungs and tip of the gangway

• Sea - Swell / State Injury 3 4 12 • Trained personnel• PPE to include – floatation suit –

Life Jacket – Head protection Gloves– Safety Footwear.

• SOP to be followed• Transfer to WTG not to take place

over the set parameters for sea state (vessel master has overall authority).

• Tip of gangway pushes against side of inclined ladder above boat landing to prevent being trapped

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Routine access to

ladder

Impactinginto fenders & ladders.

• Sea - Swell / State Damage to: LaddersJ Tubes Vessel

3 3 9 • Competent Vessel Master• Competent Ampelmann operator• Rubber fender on tip gangway• Gangway in freefloating mode

to follow any residual motions• Transfer to WTG not to take place

over the set parameters for sea state (vessel master has overall authority).

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Routine access to

ladder

Impactinginto fenders & ladders.

• Sea - Swell / State Injury 3 3 9 • Vessel Master to check sea state with Marine Coordinator before departure

• Local Sea conditions to be assessed by vessel master.

• Each engineer to personally assess the sea state for accessing tower - is it within their own capabilities. One man says no, no one to accesses the tower.

• Ampelmann operations limit exceed maximum prescribed sea state limit for testing

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Climbing ladder

Slip on ladder Fall into water Fall onto boat Carrying tools/equipment

• Marine growth and moisture

• Falling tools or Equipment

Injury Drowning Hypothermia

5 3 15 • Good grip footwear• Maintain 3 points of contact with

the ladder while climbing.• Work Boat on stand by

throughout climb.• Correct survival equipment for

water temperatures.• Rescue equipment on Work Boat.• Personnel will not climb access

to turbine with tools or equipment.

• Standby boat ready to pick up MOB

• Gangway turned away from ladder

• No tools carried by transferring crew

• Access to higher ladder: no marine growth

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Climbing ladder

Hit by falling objects • Dropped tools or equipment

Injury to: Person climbing ladder. Personnelin boat.

3 3 13 • All persons to wear hard hats when in the vicinity of WTG.

• No tools carried by transferring crew

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Offshore Tower Egress

Routine Access to

Boat

Fall into water Fall into boat

• Sea – Swell / State Injury Drowning Hyperthermia

5 3 15 • Trained personnel• PPE to include – floatation suit –

Life Jacket – Head protection Gloves– Safety Footwear.

• SOP to be followed• Transfer to & from WTG not to

take place if over the set parameters for sea state (vessel master has overall authority)

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Offshore Tower Egress Personnelstranded on WTG

• Change in sea state (to severe).

Inability tosafely access/

5 3 15 • Work boat to be on standby within the Wind Farm at all times.

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Adverse weather • Snow, sleet, hail• Visibility less than 700m

egress WTG. • Personnel not to be placed on WTG if there is any doubt of being able to get them off.

• Work Boat to have adequate capacity to evacuate all operatives working within the wind farm.

• Weather to be monitored regularly – Personnel to be evacuated from WTG’s before the conditions deteriorates.

• Work Boats to carry WTG Survival Packs containing welfare equipment for enforced stay on a WTG.

• Do not access ladder when visibility drops below 700m

Ampelmann operation

Access/egress

Falling into water Fallingonto gangwayBeing hitby gangway

Component failure:• Loss of hydraulic

power• Loss of electrical

power• Loss of valve

control• Failure of position

transducers• Failure of measurement

system• Failure of control

computer


5 3 15 • Redundant power pack and Piston type accumulator

• UPS electrical power back up with relay switches

• Double valves on cylinders• Double position transducers• Double measurement device• Failsafe redundant control

computers

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Ampelmann operation

Access/egress

Falling into water Fallingonto gangwayBeing hitby gangway

Loss of contact tip– structure due to:• Ampelmann exceeds

motion envelope• Gangway too short


5 4 20 • Limit to maximum workable sea state < than maximum Ampelmann sea state

• Warning to captain and operator about extension gangway: only in

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• Gangway not fast enough

• Station keeping vessel

green area: transfer• Accumulators to supply

additional hydraulic capability for high velocity telescoping (0.5m/s)

• Station keeping assistant display on bridge for captain

Ampelmann operation

All operations

Oil spill • Leaking seal• Broken hose

Pollution 4 3 12 • Visual inspection before operation to detect seal leaks/damaged hoses

• Biologically degradable hydraulic oil

• Oil spill kit on board• Swivels on rotating hoses• Oil spill provisions installed

around platform• Drums to accommodate

polluted oil spill gear

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Ampelmann operation

All operations

Hit bymoving cylinders

• Ampelmann operating Injury 5 5 25 • No people in reach of Ampelmann on deck

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Ampelmann operation

All operations

Fall into water Fall on platform

• Ampelmann and support structural failure


4 2 8 • System design according to Lloyd’s Register

• NDT of critical joints platform• Load test of SWL x 1.5 = 450 kg

at tip with certificate of test by Lloyd’s

• All crew not transferring strapped in on Ampelmann

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Station keeping Collision • Engine failure• Vessel drifting• Captain judgment

Damage structure/vesse lInjury

4 4 16 • Double engines and abort at 1 failing

• Station keeping on most favorable side for environmental conditions: vessel drifts away from structure

• Station Keeping Assistant display

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Severity1 No or insignificant damage.2 Minor damage or illness. First aid treatment.3 Serious damage or illness. Loss of working

hours.4 Serious damage or illness. Disablement.5 Fatality or Major Injury of one or more persons.

Probability:1 Unlikely. No knowledge of any such

cases.2 Not likely to occur but may occur.3 Now and then, occurs occasionally.4 Likely, could occur more than once.5 Frequently, could occur regularly.

Risk Code:1–8: Low risk. No or acceptable risk. Activity can be carried out.9–15: Medium risk. Operations to be carried out only after the

appropriate management have given its approval after consultation with specialists.16-25: High risk. Must be reduced. Operation shall not be carried out.

on bridge for captain• Constant communication

between captain and operator• Operator measures distance to pile

with laser, operation between 5m and 9m distance between structure and vessel




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Walk to work offshore

Technology

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