IMCA M115 Collision of DP SV With Offshore Installations

AB The International Marine Contractors Association

Risk Analysis of Collision of Dynamically Positioned Support Vessels with Offshore Installations

www.imca-int.com

115 DPVOA October 1994

AB

The International Marine Contractors Association (IMCA) is the international trade association representing offshore, marine and underwater engineering companies. IMCA promotes improvements in quality, health, safety, environmental and technical standards through the publication of information notes, codes of practice and by other appropriate means. Members are self-regulating through the adoption of IMCA guidelines as appropriate. They commit to act as responsible members by following relevant guidelines and being willing to be audited against compliance with them by their clients. There are two core committees that relate to all members:

Safety, Environment & Legislation Training, Certification & Personnel Competence

The Association is organised through four distinct divisions, each covering a specific area of members’ interests: Diving, Marine, Offshore Survey, Remote Systems & ROV. There are also four regional sections which facilitate work on issues affecting members in their local geographic area – Americas Deepwater, Asia-Pacific, Europe & Africa and Middle East & India.

115 DPVOA

The Marine Division is concerned with all aspects of specialist vessel operations. Key aspects of its work include an annual seminar, in particular focusing on practical experience, annual reports on DP station keeping incidents, also incorporated in an electronic database available to members of the division, industry-leading guidelines for the design and operation of dynamically positioned vessels and a wealth of in-depth technical reports on a range of related issues.

DPVOA merged with AODC to form IMCA in 1995.

www.imca-int.com/marine

The information contained herein is given for guidance only and endeavours to reflect best industry practice. For the avoidance of doubt no legal liability shall

attach to any guidance and/or recommendation and/or statement herein contained.

DP Risk Analysis Contents

IMCA · 115 DPVOA Page 3

CONTENTS

1 INTRODUCTION ...............................................................................................41.1 Background ......................................................................................................... 41.2 Objectives............................................................................................................ 4

2 METHODOLOGY ..............................................................................................62.1 Vessel Failures likely to lead to Loss of Position ............................................... 62.2 Selecting Credible Failures ................................................................................. 62.3 Categories of Credible Failure ............................................................................ 62.4 Historical Frequency of Drift Off, Drive Off and Large Excursion.................... 72.5 Estimated Frequency of Contacting a Platform .................................................. 72.6 Comparison of Historical and Estimated Frequencies ........................................ 7

3 SELECTING CREDIBLE FAILURES.............................................................83.1 Reviewing the Incident Data Base ...................................................................... 8

4 CAUSES OF CREDIBLE FAILURES............................................................114.1 Categories of Causes ......................................................................................... 11

5 DRIFT OFF, DRIVE OFF AND LARGE EXCURSION..............................145.1 Incident Review ................................................................................................ 145.2 Analysis of Drift Off, Drive Off and Large Excursion ..................................... 14

6 ESTIMATED COLLISION FREQUENCY ...................................................166.1 Adjustment of Historical Frequency ................................................................. 166.2 Estimated Frequency of Platform Contact for all types of vessel ..................... 186.3 Distance from Platform..................................................................................... 21

7 DETERMINATION OF VESSEL IMPACT ENERGY................................227.1 Method .............................................................................................................. 227.2 Form for Calculation of vessel impact energy .................................................. 237.3 Simplified method for determination of vessel impact energy ......................... 24

8 CONCLUSIONS................................................................................................26

APPENDIX 1 Tables 1-15: DP Collision Incident Summary Sheets ......................27

APPENDIX 2 Complete List of Causes of DP Position Loss....................................43

APPENDIX 3 Tables 16-30: Frequency of Drift Off, Drive Off and Large Excursion...............................................................................................49

DP Risk Analysis Introduction


1 INTRODUCTION

1.1 Background

1.1.1 An agreement has been drafted between the HSE, DPVOA, AODC andUKOOA regarding the requirement for an offshore installation owner to includediving operations from diving support vessels in his safety case.

1.1.2 The agreement has been drafted specifically to deal with diving operations.However, it is pertinent to all DP vessels operating close to installations.

1.1.3 The Safety Case Regulations require that offshore installation operators shouldreduce the risks from major accidents to a level which is as low as reasonablypracticable (ALARP). The major accidents to be addressed are listed in theregulations. One of the major accidents to be addressed in the OffshoreInstallations (Safety Case) Regulations (1992, Regulation 2, Section 1, Sub-section b) is: "any event involving major damage to the structure of the installation or plantaffixed thereto or any loss of stability of the installation".

1.1.4 One of the causes of such a major accident may be loss of vessel positionleading to it colliding with an offshore installation.

1.1.5 Global Maritime has been requested by DPVOA to provide data for all theAssociation members on the reliability of DP vessel position keeping which willassist in assessing the risks involved in a vessel being dynamically positioned atan installation.

1.2 Objectives

1.2.1 Three essential parts of any risk assessment are:1 The identification of hazards with the potential to cause a major accident.2 The evaluation of the risk from such major accidents.3 The reduction of risks to persons affected by major accidents to the lowest

level that is reasonably practical.

To assess risk both the probability of an event occurring and the severity of theconsequences of that event must be estimated.

1.2.2 One of the major hazards associated with the operation of an installation isvessel collision. There are two basic types of collision defined as:Accidental a passing vessel running into an installationOperational an installation support vessel contacting the installation during

normal operations.

The objective of the analysis is to determine the risks involved in a dynamicallypositioned support vessel contacting an installation while the vessel isdynamically positioned, i.e. an operational collision.

DP Risk Analysis Introduction


1.2.3 The two basic causes of position loss towards a platform addressed in issue 1 ofthis report were as follows:Drive off The vessel is driven off position by its own thrusters because

the DP control system believes the vessel to be off position.Drift off The vessel drifts off position because of insufficient thruster

capacity or because DP control system believes vessel to bekeeping position.

Since the original issue the data has been re-examined and a third valid categorydetermined which we have called a "large excursion":Large excursion The vessel moves outside her footprint because of a

disturbance to the DP control system.

1.2.4 This report covers all three position loss causes above but collisions which mayoccur when the vessel is in transit to another installation are not considered.

DP Risk Analysis Methodology


2 METHODOLOGY

2.1 Vessel Failures likely to lead to Loss of Position

2.1.1 Three types of vessel with the following basic specifications have beenconsidered:

Type 1 Fully redundant DP systems (IMO equipment class 3)Separate engine rooms and systemsAlternative DP control stationSeparate cable routesThree bow thrusters if a monohullDual UPS

Type 2 Fully redundant DP systems (IMO equipment class 2)Separate engine rooms and systemsThree bow thrusters if a monohullDual UPS

Type 3 Fully redundant DP systems (IMO equipment class 2)Single engine roomTwo bow thrusters if a monohullSingle UPS

2.1.2 It has been assumed that each vessel has had a comprehensive FMEA and thatall critical failure modes have been identified. The types refer to existing vesselsrather than a theoretical ideal vessel.

2.2 Selecting Credible Failures

2.2.1 Global Maritime has a database of all DP incidents from 1980. The datacollection was founded by the UK Department of Energy until 1988. Since1990, Global Maritime, under the auspices of the DPVOA, has assumed the roleof collecting and assessing DP incidents and the data is available from 1980 to1992. The 1993 incidents are not published yet.

2.2.2 This database from 1980 to 1992 was reviewed for all incidents involvingpositioning failures critical enough to lead to the vessel contacting a platform.Failures that are no longer appropriate to any of the three types of vessel wereeliminated.

2.3 Categories of Credible Failure

2.3.1 The frequency of occurrence of different categories of the primary andsecondary causes of the incidents was also established to assist with thecalculation of risk for each type of vessel as well provide to guidance on riskreduction.

DP Risk Analysis Methodology


2.4 Historical Frequency of Drift Off, Drive Off and Large Excursion

2.4.1 The database was used to estimate the historical frequency of all position losseswhich were critical enough to lead to a vessel contacting a platform. Thefrequency estimate considered all position losses including those which have notled to contact with a platform. For drift off the weather direction is alsoimportant. Estimates were made for each of the three types of vessel for driftoff, drive off and large excursion.

2.4.2 The historical frequencies were adjusted to take into account unreportedincidents, insufficiently detailed reports and to reflect changes in operatingprocedures. While more serious incidents have been reported, many lesssignificant events were probably not regarded as incidents by some operators.These estimates are based on our appreciation of the differences between vesselsand owners and to ensure the study is conservative.

2.5 Estimated Frequency of Contacting a Platform

2.5.1 For all critical positioning failures, the probability of a position loss eventuallyleading to vessel contact with a platform was estimated. Estimating theprobability took into account the recovery times after a drift off or drive off ofthe three types of vessel.

Using these probabilities and the historical frequencies of position loss it hasbeen possible to estimate the frequency of a vessel contacting a platform.

2.5.2 These frequencies are stated in the number of incidents per hour the vessel is onDP as the database does contain some information on vessel DP hours,particularly for more recent years. Data on how many hours DP vessels spendworking adjacent to platforms is only available for a few vessels but theassumptions made closely match this data.

2.5.3 Providing estimates of incidents per DP hour will be sufficient for the offshoreoperator to calculate the risk to his installation based on past IRM records andproposed work loads.

2.6 Comparison of Historical and Estimated Frequencies

2.6.1 For drift off, drive off and large excursion on each of the three types of vessel, itis possible after the above analysis to compare the estimated frequency of avessel hitting an installation with the actual frequency of such incidents.

DP Risk Analysis Selecting Credible Failures


3 SELECTING CREDIBLE FAILURES

3.1 Reviewing the Incident Database

3.1.1 Appendix 1, Tables 1 to 15 show the results of a review of all the incidentsfound in the DPVOA Dynamic Positioning Systems' Incidents, updated toinclude document DPSI-3 issued in June 1993. For the analysis each incidentwas given an identification number which is shown in the first column of thetable.

3.1.2 A total of 224 incidents were studied. There is no doubt about the probability ofsome of the hazards leading to contact with platforms as vessels have actuallyhit installations. These incidents are marked in column 2 of the tables with thenumber 1. No contact is indicated with a 0.

3.1.3 From the information in the database it is possible in most cases to determinewhether the vessel was near a platform when the loss of position occurred. Forthe analysis these incidents have been categorised as near misses. Theseincidents are marked in column 3 with the number 1. Those not categorised asnear misses are marked with a 0.

3.1.4 Many incidents did not occur near platforms but if a similar loss of position hadoccurred near a platform then a contact may have been possible. This does notinfer that the vessel would drift down on the platform from a range greater than,for example, 500 metres but rather that the excursion in open water was reportedto be large enough to have led to contact with a platform had the vessel beenoperating close to the platform at, for example, 25 metres. These incidents aremarked in column 4 with the number 1. No significant loss of position isindicated with a 0.

3.1.5 Some incidents were considered not to be applicable in this analysis for variousreasons such as:1 Advances in technology;2 Faults which have been remedied on all DP vessels;3 Operational methods which are no longer allowed.

These incidents are marked in column 5 with the number 1. One of the vesselcontacts is no longer considered feasible today this is shown in the contactcolumn and the not applicable column.

3.1.6 Columns 6 and 7 show the primary and secondary causes of the incident.The incidents were re-analysed for this study and in the vast majority of casesthe original conclusions have been confirmed. There is a column for additionalcomments which may show other causes or a particular feature of the incident.The last three columns show whether this incident could occur on the three typesof vessel defined for the analysis.

3.1.7 Tables 1 to 15 have been summarised in the following table, Summary Table 01.



TableNo Contact Near

MissSign.Loss

NotApp.

Type1

Type2

Type3

1 2 5 7 1 12 13 14

2 0 7 7 1 12 14 14

3 0 1 14 0 13 12 14

4 0 4 3 8 5 6 7

5 0 5 9 1 11 12 14

6 1 8 5 1 10 14 14

7 1 3 10 1 12 13 14

8 3 3 7 2 5 8 13

9 5 3 6 1 13 13 14

10 1 2 11 1 9 11 14

11 0 1 13 1 12 14 14

12 1 7 7 0 12 14 15

13 4 2 9 *1 9 13 14

14 1 8 5 1 14 14 14

15 4 2 3 5 9 9 9

Total 23 61 116 25 147 170 198

Summary Table 01* not applicable contact! also included in contact total

3.1.8 Of the incidents considered a further 25 (11%) were rejected as not beingapplicable to this study. Therefore 199 incidents have been considered ashaving the possibility of a loss of position with the potential to lead to contactwith an installation if the vessel was working adjacent to an installation.

3.1.9 These figures may also be expressed in terms of percentages of the total of 199.

Type of incident %Contact with installation 11Near miss with platform 31Significant position loss 58Total 100

3.1.10 It may be seen that 42% of incidents reported occurred when vessels wereoperating adjacent to platforms and 58% of incidents caused significant positionlosses when DP vessels were operating in open water.

3.1.11 Summary Table 01 shows the number of incidents likely to affect the three typesof vessel defined for the study. All but one of the incidents could have happenedon the lowest specification Type 3 vessel. One incident could only haveoccurred on a Type 1 vessel. Many of the incidents could occur on a Type 2vessel. There is a noticeable reduction in the number of incidents which mayaffect a Type 1 vessel but incidents like faults reloading off-line computers aretaken as equally likely on all types of vessels because it takes time to move DPcontrol to the back up and DP redundancy is only effective when the DP control



system and/or operator recognises the problem. It should be noted that nearlythree quarters of the incidents could still occur on the highest specificationType 1 vessels. Below is shown the percentage of the 199 incidents which couldhave occurred on the three types of vessel.

Vessel Type Incidents %1 147 712 170 913 198 100 All 199 100

3.1.12 However, some of these incidents would not be possible if the power generationand thruster systems were properly set up and the vessel was operating within itslimits to withstand a worst case failure. Such incidents are indicated in thetables with an asterisk. If such incidents are removed the figures would be:

Vessel Type Incidents Reduction % Reduction1 114 33 222 136 34 203 173 25 13

Approximately 20% of the drift off and drive off incidents may be reduced on allthree types of vessel by setting up the systems as designed and operating withinthe vessel's capability. The impact on large excursions is less, as would beexpected, because the excursions are not so dependent on the equipment on line.

DP Risk Analysis Causes of Credible Failures


4 CAUSES OF CREDIBLE FAILURES

4.1 Categories of Causes

4.1.1 The incidents were analysed to determine causes of failures. It was found thatthe causes fall into the five distinct categories associated with faults, operatorerrors, inadequate procedures or poor design, which are defined as:

1.0 DP control2.0 Thruster control3.0 Power generation and distribution4.0 Quality assurance5.0 Procedures

Quality assurance has not been used as a primary cause in incident evaluationbut many of the secondary causes are grouped under this heading.

4.1.2 These five categories show trends in incident causes which were furtherclassified as follows:

1.0 DP control1.1 Position, heading and environmental sensor faults1.2 Software faults1.3 Hardware faults1.4 Computer changeover errors1.5 UPS faults

2.0 Thruster control2.1 Hydraulic oil contamination2.2 Feedback signal faults2.3 Control system incorrectly set up2.4 Prime mover fault2.5 Propeller fouled

3.0 Power generation and distribution3.1 Generator load control fault3.2 Generator synchronisation fault3.3 Generator exciter or AVR fault3.4 Short circuit on generator or motor3.5 Earth fault3.6 Erroneous signals to power management system

4.0 Quality assurance4.1 Poor design4.2 Incorrectly installed4.3 Inadequate commissioning4.4 Lack of realistic testing on full DP4.5 Changes not documented on vessel4.6 No comprehensive FMEA4.7 Quality of third party equipment and personnel



5.0 Procedures5.1 Insufficient generators on line5.2 Insufficient thrusters on line5.3 Insufficient good references on line5.4 Incorrect thruster mode5.5 Computer reload errors5.6 Power system wrongly set up5.7 Incorrect DP control mode5.8 Maintenance during DP5.9 Poor maintenance5.10 Interference from other vessels5.11 Lack of care in shallow water5.12 Lack of care going on to and coming off installation5.13 Lack of care moving adjacent to installation5.14 Mishandling of wires, lifts, ROVs etc.5.15 Operating outside vessel capability5.16 Not observing changing conditions

4.1.3 A complete list of failure causes taken from the incident database may be foundin Appendix 2. There is a repetition of many of the incident types throughoutthe twelve year data collection period. Using Tables 1 to 15 the category ofincidents may be summarised using the two summary tables shown below.Summary Table 02 is for the primary causes of the incidents and SummaryTable 03 is for the secondary causes of incidents.

Category of Incident Primary Cause

1 2 3 4 5Table NoDP

ControlThrusterControl

PowerGen./Dist. QA Procedures

Op. Error

1 4 1 2 0 7

2 3 2 3 0 6

3 4 1 0 0 10

4 1 1 1 0 4

5 2 3 1 0 8

6 5 2 2 0 5

7 11 0 1 0 2

8 3 3 5 0 3

9 0 0 0 0 14

10 4 1 3 0 5

11 2 0 0 0 12

12 7 1 2 0 5

13 6 3 2 0 3

14 5 0 0 0 9

15 1 3 1 0 4

Total 58 21 23 0 97

Summary Table 02



Category of Incident Secondary Cause

1 2 3 4 5Table NoDP

ControlThrusterControl

PowerGen./Dist. QA Procedures

Op. Error

1 0 0 0 7 7

2 0 0 0 3 8

3 2 1 0 2 8

4 0 0 0 2 6

5 2 1 0 2 9

6 1 0 0 3 7

7 2 0 0 8 4

8 0 2 0 9 3

9 0 0 0 2 12

10 0 0 0 7 6

11 0 0 0 1 14

12 0 0 0 3 11

13 2 0 0 7 5

14 0 0 0 4 10

15 0 1 0 2 7

Total 9 5 0 62 117

Summary Table 03

4.1.4 The categories of incidents may be shown as percentages:

Category Primary SecondaryCause % Cause %

1.0 DP control system 29.1 4.62.0 Thruster control 10.6 2.53.0 Power generation/distribution 11.6 04.0 Quality assurance 0 31.35.0 Operator error procedures 48.7 59.1

4.1.5 Fourteen or approximately 2.5% of incidents had no secondary cause assigned tothem. This is because, generally, insufficient data was available for theseincidents. It should be remembered that the approach used to determine theprimary cause of an incident has been to ask the question “What triggered thisposition loss?”. The answer to this question is generally the final event leadingto the loss of position when there was in some cases a sequence of faults andmistakes. It is clear that the most effective method of risk reduction is improvedprocedures.

DP Risk Analysis Drift Off, Drive Off and Large Excursion


5 DRIFT OFF, DRIVE OFF AND LARGE EXCURSION

5.1 Incident Review

5.1.1 The database was reviewed to determine whether the reported incidents could bedivided into drift offs and drive offs. Appendix 3, tables 16 to 30 show theanalysis of the incidents using the same incident numbering system as that usedin Tables 1 to 15.

5.1.2 A summary of the analysis tables is shown below in Summary Table 04.

Summary Table of Frequency of Drift Off and Drive Off

Estimated DataHistorical Data

Drift Off Drive Off Large ExcursionTableNo

DriftOff

DriveOff

LargeExc’n

Type1

Type2

Type3

Type1

Type2

Type3

Type1

Type2

Type3

16 6 3 5 4 5 6 3 3 3 5 5 5

17 6 0 8 5 6 6 0 0 0 8 8 8

18 6 3 6 4 4 5 3 3 3 5 5 6

19 2 2 3 1 2 2 2 2 2 3 3 3

20 1 7 6 0 0 1 6 6 7 5 6 6

21 7 3 4 3 7 7 3 3 3 4 4 4

22 4 8 2 2 3 4 7 8 8 2 2 2

23 8 2 3 2 5 8 2 2 2 2 2 3

24 3 3 8 3 3 3 3 3 3 7 7 8

25 9 2 3 6 7 9 2 2 2 2 2 3

26 2 2 10 2 2 2 2 2 2 10 10 10

27 6 1 8 3 5 6 1 1 1 8 8 8

28 7 5 2 3 6 7 4 4 5 2 2 2

29 1 9 4 1 1 1 9 9 9 4 4 4

30 2 4 3 2 2 2 4 4 4 3 3 3

Total 70 54 75 41 57 69 51 52 54 70 71 75

Summary Table 04

5.2 Analysis of Drift Off, Drive Off and Large Excursion

5.2.1 Of the 199 applicable incidents 70 were drift offs, 54 were drive offs and 75were large excursions.

Incident Type No of incidents %Drift off 70 35Drive off 54 27Large excursion 75 38Total 199 100

DP Risk Analysis Drift Off, Drive Off and Large Excursion


5.2.2 This data may be further divided into the three types of vessel to compare howsusceptible the three types of vessel are to drift off, drive off and largeexcursion.

Drift OffVessel Type No of incidents %1 41 592 57 833 69 99Total drift offs 70 100

Drive OffVessel Type No of incidents %1 51 942 52 963 54 100Total drive offs 54 100

Large ExcursionVessel Type No of incidents %1 70 962 71 973 75 100Total Large excursions 75 100

DP Risk Analysis Estimated Collision Frequency


6 ESTIMATED COLLISION FREQUENCY

6.1 Adjustment of Historical Frequency

6.1.1 The database has three weak areas. Firstly, there is a relatively small number ofvessels, particularly for the early years, but the total number of vessel operatingyears for analysis is reasonable because the data has been collected for overtwelve years. Secondly, the database relies on vessel staff, vessel operators,charterers and field operators reporting incidents. It is very evident that incidentreporting has improved in frequency and quality in the last few years but it isstill not perfect. Thirdly, there is limited data for hours on DP and DP hoursalongside platforms. Such information is improving but not all vessel ownersautomatically gather such data for use by the DPVOA.

6.1.2 The majority of platform contacts should have been reported by the platformoperator or vessel owner to the statutory authorities but it has been assumed thatonly 88% of incidents have been reported due to the fact that others were veryminor and went mainly unnoticed by third parties.

6.1.3 It is reasonable that a larger percentage of incidents within the 500 metre zonewill not have been reported. We assume our figures represent 77% and thatincidents went unreported because no divers were in the water or the positionloss was interpreted as degrading the system to amber status rather than reddegraded status. There may still be a tendency for vessel staff to report only redstatus incidents or only go to amber status when the consequences of theincident really required a red status to be initiated.

6.1.4 From Global Maritime's past experience of reviewing DP vessel logbooks it maybe assumed that only two thirds of the DP position losses in open water havebeen reported for the reasons described in the previous paragraph.

6.1.5 Therefore realistic values for the number of incidents may be:

Type of incident No. No. AdjustedIncidents Increase No.

Contact with installation 22 3 25Near miss with platform 61 18 79Significant position loss 116 58 174Total 199 278

6.1.6 The database also shows that 19 of the incidents of platform contact occurredbetween 1980 and 1988, i.e. 2.11 per year. There were only 4 incidents ofplatform contact between 1989 and 1992, i.e. 1 per year. There have been twoplatform contacts in 1993, which brings the average between 1989 and 1993 to1.2 per year. There have been fewer contacts recently with more vesselsreporting but the exposure time is not well enough known to conclude thatcontacts are less likely.

6.1.7 The figures above in 6.1.5 may be shown in percentages as follows:



Type of incident No %Incidents

Contact with installation 25 9Near miss with platform 79 28Significant position loss 174 63Total 270 100

6.1.8 The database covers a 13 year period in which there have been an average ofabout 28 vessels reporting incidents. This may be taken as 364 vessel years ofaccumulated data. However during these 364 years, vessel on hire time and timeon DP were variable.

These variations may be simplified by assuming that DP vessels are on hire for70% of the year and 70% of the on hire time is actually on DP. The databaseincludes vessels that are continuously using DP as well as vessels which onlyhave a 100 hours per year on DP. Work is being done to determine hours peryear per vessel for the period 1980 to 1992. The above assumption checks wellwith a group of vessels that we do have data on.

6.1.9 Therefore the 360 vessel years may be converted to:364 x 365 x 24 = 3188640 vessel hours

Vessel on hire time may be:3188640 x 0.7 = 2232048 vessel hours

Vessel hours on DP may be:2232048 x 0.7 = 1562434 hours.

6.1.10 A conclusion may be drawn that there have been 278 significant position losseson DP vessels during 1562434 hours of operation. This is one position loss per5620 hours on DP or an adjusted historical frequency of 1.78 x 10-4 per DP hour.

6.1.11 Using the same vessel hours on DP, i.e. 1562434 hours, and the 199 incidents inthe data base, the unadjusted historical frequency of position loss is 1.27 x 10-4

per DP hour.

6.1.12 The adjusted number of contacts with platforms is 25. This gives an adjustedhistorical frequency of platform contact of 1.60 x 10-5 per DP hour.

6.1.13 Using the 23 platform contacts in the database, the unadjusted historicalfrequency of platform contact is 1.47 x 10-5 per DP hour. The contacts includethe crane or mast of a DP vessel making contact with a topside of a platform aswell as a hull platform contact.

6.1.14 These four frequencies may be summarised as:

Historical frequency Position loss 1.27 x 10-4 per DP hourPlatform contact 1.47 x 10-5 per DP hour



Adjusted historical frequencyPosition loss 1.78 x 10-4 per DP hourPlatform contact 1.60 x 10-5 per DP hour

6.2 Estimated Frequency of Platform Contact for All Types of Vessel

6.2.1 Figure 1 shows the chart for estimating the frequency of platform contact for alltypes of vessel and for each of the three vessel types.

6.2.2 The chart consist of five events which may cause a position loss to lead tocontact with a platform. The probability of position loss has been taken as1.0000. The final estimated probability of contact has been multiplied by theadjusted historical frequency of position loss to determine the estimatedfrequency of platform contact. Some of the probabilities for each step have beendetermined from the database and some are based purely on the judgement andexperience of the authors. The best result that may obtained from a simpleanalysis based on a relatively small sample is to estimate the frequency to thecorrect order of magnitude.

6.2.3 Step 1 – Type of position loss

The first step asks what type of position loss has taken place? From SummaryTable 04 in Section 5.0, it may be seen that of the 199 reported incidentsapplicable to this analysis, 70 were drift offs, 54 were drive offs and 75 werelarge excursions. It has been assumed that 35% of incidents are drift offs, 27%are drive offs and 38% are large excursions. It should be noted that the adjustednumber of incidents of 278 has not been used as it is not possible to assume thedivision between drive offs, drift offs and large excursion for unreportedincidents.

6.2.4 Step 2 – Vessel on DP near platform

From the adjusted figure of 278 incidents it may be seen that 63% of incidentsare assumed not to occur near a platform. Therefore it has been assumed that37% of the incidents have the potential for platform contact and 63% may nothave any potential to lead to platform contact. Many of the incidents do notoccur near platforms. Calculating the probability of a vessel drifting on to aninstallation from a range greater than 500 metres would require more detailedanalysis. Such an event would require a total loss of propulsion for at least 10minutes such that even last minute avoidance was impossible. Such an analysiswould have to involve all types of vessels, not just DP vessels, in order tocompare risks with other support vessels and passing vessel traffic.

6.2.5 Step 3 – Vessel moves towards platform

The probability of a drift off towards the platform is only less than that of a driveoff if there are limitations on the vessel types being considered for operatingupwind and upcurrent of platforms. This may not be the case for Type 1, 2 and3 vessels. A probability of 0.5 has been assumed for the vessel drifting towardsthe platform as this is conservative. A vessel not close to a platform and not onwindward side would be unlikely to drift onto the platform. On the other hand, adrive off may occur when the vessel is operating upwind or downwind of aplatform. The vessel is equally likely to drive towards the platform as away



from it. The probability of drive off towards the platform has also been assumedto be 0.5. The probability of a large excursion towards and away from aplatform is equally likely as a large excursion parallel to a platform and hencewe will also assume 0.5 for this position loss towards the platform.

6.2.6 Step 4 – Failure to recover DP control

Vessels are capable of recovering from a position loss. Recovery will depend onmany factors such as the experience of the DP operator, power systemautomation, machinery redundancy, etc. The time element and distance from theplatform will be critical. For close work to a platform, the probability ofavoiding contact from a drift off, drive off or large excursion may be very small.

As the distances increase the available time to recover from either type ofincident increases. For this analysis, a probability of failure to recover of 0.2 hasbeen assumed for drift off and 0.3 for drive off and 0.25 for large excursion.

6.2.7 Step 5 – Failure to avoid platform

Even though a vessel may fail to recover DP control and is moving towards theplatform there is a probability that due to a change in wind or current, or even alast minute avoidance measure using a thruster on manual control, it may bepossible to avoid contact. A very high probability of 0.8 has been assumed forfailure to avoid a platform in a drift off, 0.9 has been assumed for the failure toavoid a platform in a drive off and 0.8 has been assumed for failure to avoid aplatform from a large excursion. This is equal to the drift off case because theexcursion may take time to increase and hence have a time interval similar to adrift off.

6.2.8 The total probability of all types of vessel making contact with a platform is0.0379. Assuming that the probability of the initial position loss is 1.78 x 10-4

per DP hour then the estimated frequency of any type of DP vessel contacting aplatform is:

0.0379 x 1.78 x 10-4 = 6.75 x 10-6 per DP hour

6.2.9 This estimated frequency is less than historical frequency and adjusted historicalfrequency shown in Section 6.1.14 but if the adjusted historical frequency has infact decreased by a factor of two (see 6.1.6) then the results are surprisinglyclose, 1.60 x 10-5 (÷2) = 8.0 x 10-6 per hour.



+-----------------------------------------------------------------------+¦ ¦¦ YES ¦¦ +------- = 0.01036 ¦¦ YES ¦ 0.8 ¦¦ +-----¦ ¦¦ YES ¦ 0.2 ¦ NO ¦¦ +-----¦ +------ ¦¦ YES ¦0.5 ¦ NO 0.2 ¦¦ DRIFT +-----¦ +------ ¦¦ OFF ¦0.37 ¦ NO 0.8 ¦¦ +------¦ +------ ¦¦ ¦0.35 ¦ NO 0.5 YES ¦¦ ¦ +------ +------ = 0.01349 ¦¦ ¦ 0.63 YES ¦ 0.9 ¦¦ ¦ +-----¦ ¦¦ ¦ YES ¦ 0.3 ¦ NO ¦¦ ¦ +-----¦ +------ ¦¦ ¦ YES ¦0.5 ¦ NO 0.1 ¦¦ POSN ¦DRIVE +-----¦ +------ ¦¦ LOSS ¦OFF ¦ ¦ NO 0.7 ¦¦ ---------+------¦ +------ ¦¦ 1.0 ¦0.27 ¦ NO 0.5 YES ¦¦ ¦ +------ +------ = 0.01406 ¦¦ ¦ 0.63 YES ¦ 0.8 ¦¦ ¦ +-----¦ ¦¦ ¦ YES ¦ 0.25¦ ¦¦ ¦ +-----¦ +------ ¦¦ ¦ YES ¦ 0.5 ¦ 0.2 ¦¦ ¦ +-----¦ +------ ¦¦ ¦EXC'N¦ 0.37¦ YES 0.8 ¦¦ +-----¦ +------ ¦¦ 0.38 ¦ NO 0.5 ¦¦ +------ ¦¦ 0.63 ¦¦ ¦¦ ¦¦ DRIVE OFF + DRIFT OFF + LARGE EXCURSION ¦¦ 0.01036 + 0.01349 + 0.01406 = 0.0379 ¦¦ ¦+-----------------------------------------------------------------------+

Figure 1

6.2.10 There are fewer incidents for type 1 vessels and for type 2 vessels and therelationship from 5.2.2 is as follows:

Vessel Type No Incidents %All 199 1001 162 81.52 180 91.43 198 99.5

6.2.11 If Figure 1 is assumed to apply to all types of DP vessel considered here, whichis the most pessimistic assumption, then the frequency of contact for the threevessel types becomes as follows

Type 1 5.50 x 10-6

Type 2 6.18 x 10-6

Type 3 6.71 x 10-6

This shows about a 10% risk variation between each of the vessel types but insafety case terms they are essentially the same.



6.3 Distance from Platform

6.3.1 The above figures do not provide an indication of the relationship between thecollision risk and the distance the vessel is from the nearest point of contact.Several of the incidents where contact was made occurred when the DP vesselwas very close. We do not have exact figures but probably under 10m. Wewould recommend that the above figures are always used when the clearance tothe nearest point of contact is less than L/2 where L is the vessel's length overalland that the probability is reduced thereafter linearly so that at a clearance of 3Lthe probability is reduced by a factor of 10.

DP Risk Analysis Determination of Vessel Impact Energy


7 DETERMINATION OF VESSEL IMPACT ENERGY

7.1 Method

7.1.1 As part of the Health and Safety Executive's Safety Case requirements,DP vessels operating in close proximity to fixed platforms will be required togive an estimate of the energy with which the vessel would impact the platformin the event of loss of control. Loss of control can be taken as a completeblackout (drift off) in which case only environmental forces act or a DP controlmalfunction (drive off) in which case both thruster forces and environmentalforces act.

7.1.2 The attached form provides a simple method of estimating the impact energy fora given initial position from the platform. This is a conservative method becausefirstly it assumes that all forces act in a direction so as to force the vesseltowards the platform and secondly it assumes that the vessel would move with aconstant acceleration whereas in fact drag effects would act and a terminalvelocity would be reached at some point.

7.1.3 This method does require the knowledge of coefficients for forces, added massesand thruster details. If these data are not readily available then reference shouldbe made to DPVOA report GM-811-0992-1473a Issue 0 "Specification for DPCapability Plots", dated 2nd September 1992.

7.1.4 If the energies calculated by this simplified method are too high, then they canbe reduced by including the effects of drag. This can be done analytically butthe calculation is complicated by the fact that the solution depends upon the signof the relative velocity (i.e. current velocity minus vessel velocity) and it is infact easier to perform the calculation numerically on a spreadsheet. The inputrequirements are identical to those for the simplified method. The attachedfigure shows the relative effects of including and ignoring drag for the StenaSeawell.



7.2 Form For Calculation Of Vessel Impact Energy

VESSEL NAME

VESSEL TYPE

VESSEL LOCATION

CASE

INPUT DATA

DISTANCE FROM PLATFORM S m

DISPLACEMENT D t

ADDED MASS COEFFICIENT IN SURGE AM1

ADDED MASS COEFFICIENT IN SWAY AM2

ENVIRONMENTAL CONDITIONS

WIND SPEED Vw m/s

CURRENT SPEED Vc m/s

WAVE HEIGHT Hs m

WAVE PERIOD Tz s

FORCE COEFFICIENTS

WIND Cw kN(m/s)2

CURRENT Cc kN(m/s)2

WAVE (TYPE 1) Cwd1 kN(m/s)2

or

WAVE (TYPE 2) Cwd2 kN/m2

THRUSTER DETAILS

MAXIMUM THRUST FORWARD–AFT T1 t

MAXIMUM THRUST ATHWARTSHIPS T2 t

CALCULATIONS

WIND FORCE = Fw kN

CURRENT FORCE = Fc kN

WAVE DRIFT FORCE = Fwd kN

THRUSTER FORCE = T kN

TOTAL FORCE = Ftot kN

TOTAL MASS = m t

ACCELERATION = a m/s2

IMPACT VELOCITY = v m/s

IMPACT ENERGY = E MJ



7.3 Simplified method for determination of vessel impact energy

7.3.1 The method is summarised as follows:

1 Enter vessel distance(s) in metres from platform.

2 Enter vessel displacement (D) in tonnes and added mass coefficients (AM1and AM2).

3 Enter environmental conditions (Vw, Vc, Hs, Tz; these are all assumed to actin a direction to force the vessel towards the platform).

4 Enter wind and current force coefficients (Cw, Cc). Wave force coefficientsare generally given in terms of kN/m2 or kN/(m/s)2, so either Cwd1 or Cwd2should be entered.

5 Enter the maximum thrust (T1, T2) in tonnes in the forward-aft andathwartships directions. If the thrusters are fully rotatable, then the thrustshould be based on the maximum values with zero moment, e.g. if theavailable athwartship thrust is 54t at the bow and 111t at the stern, then thethrust at the stern should be taken as 54t and the total drive off athwartshipsthrust is 108t (T2).

6 Calculate the environmental forces as follows:Fw = Cw * Vw2

Fx = Cc * Vc2

Fwd = Cwd1 * (Hs/Tz)2 or Fwd = Cwd2 * Hs2

7 Select appropriate thruster force and multiply by 9.81 to convert to kN.

8 Determine the total force pushing the vessel towards the platform:Ftot = Fw + Fx + Fwd + T

9 Determine the total mass (m) using the appropriate added mass coefficient:m = (1 + AM1) * Dorm = (1 + AM2) * D

10 Determine the linear acceleration from:a = Ftot/m

11 Determine the impact velocity from:v = (2 * a * s)½

12 Determine the impact energy in MJ from:E = ½ * m * v2/1000



DP Risk Analysis Conclusions


8 CONCLUSIONS

8.1 The conservatively estimated frequency of DP vessel contact with a platform isbetween 1.60 x 10-5 and 6.75 x 10-6 per DP hour and that this figure should beused when the initial clearance is less than half the vessel’s length.

8.2 There is only a small difference in contact frequency between the various typesof DP vessel: most of the difference comes from drift off. Drive off and largeexcursions are almost independent of redundant DP vessel type.

8.3 Reduction in the frequencies of DP vessel contact to the level of 1 x 10-3 perplatform operating year would appear to be impractical as the above figures atbest equate to 6.1 x 10-2 per DP vessel year.

8.4 Not one of the reported incidents has led to a major accident involving structuraldamage to a platform. Therefore, the frequency of a major accident occurringwhich could cause structural damage to a platform may be less than 1 x 10-3 perplatform operating year. If the next collision caused significant damage thefrequency would be between 5.6 x 10-3 and 2.19 x 10-3 per year.

8.5 The most effective method of reducing risks of structural damage to aninstallation from a DP vessel collision to a level which is as low as reasonablypractical would be to address the hazards identified in the analysis. Betterprocedures would appear to be more effective risk reduction measures thanhardware improvements.

8.6 The database initially relied on reasonably good incident reports from 20 to 30vessels. There are now 44 vessels providing better reports. The recent data onvessel hours is more detailed and there has been a reduction in collisions withplatforms.

8.7 It is relatively simple to calculate DP vessel impact energies but they increasewith the distance from the platform until drag forces equal drift off or drive offforces.

DP Risk Analysis Appendix 1


APPENDIX 1

Tables 1-15: DP Collision Incident Summary Sheets



DP COLLISION INCIDENT SUMMARY SHEET

Table No: 1

Incident No Contact NearMiss

Sign.Loss

NotApp. Primary Cause Secondary Cause Comments Type

1Type

2Type

3

1 1 0 0 0 Op. error Procedures Careless 1 1 1

2 0 1 0 0 Op. error Procedures Sh water no radio ref 1 1 1

3 0 1 0 0 Op. error No QA/tests Insuff. refs 1 1 1

4 0 1 0 0 Op. error Procedures Thrust limits exceeded 1* 1* 1*

5 0 0 1 0 Swbd. fail Design No FMEA 0 1 1

6 1 0 0 0 UPS fault Design No FMEA 1 1 1

7 0 0 1 0 TW fault No QA/tests Inclinometer 1 1 1

8 0 0 0 1 Op. error Procedures Insuff. refs 0 0 0

9 0 0 1 0 Op. error Procedures Poor ref. 1 1 1

10 0 1 0 0 DP control Design PCB hardware 1 1 1

11 0 0 1 0 Mech fault/gens Design No FMEA 0 0 1

12 0 0 1 0 Ref fault No QA/tests DGPS 1 1 1

13 0 0 1 0 Op. error Procedures Sh water insuff ref 1 1 1

14 0 0 1 0 Op. error Procedures Computer reload 1 1 1

15 0 1 0 0 Thrust fault Poor PM Feedback transducer 1* 1* 1

Sub-Total 2 5 7 1 12 13 14

* not set up properly and/or exceeding safe working limits




Table No: 2


Sign.Loss


1Type

2Type

3

16 0 0 1 0 Op. error Procedures Unexplained 1 1 1

17 0 1 0 0 Weather Op. error Wrong azimuth mode 1 1 1

18 0 1 0 0 Op. error Procedures Insuff refs 1 1 1


20 0 1 0 0 Thrust. fault No QA/tests Wrong azimuth mode 1* 1* 1*

21 0 0 1 0 DP control No QA/tests Software for current 1 1 1


23 0 0 1 0 TW fault No QA/tests Poor design 1 1 1

24 0 0 1 0 DP control x2 Design Multiple failure 0 1 1

25 0 1 0 0 Op. error Procedures Insuff refs/unexplained 1 1 1

26 0 1 0 0 Thrust. fault Poor PM ECU settings 1* 1* 1

27 0 0 1 0 Swbd. fail 0 Fuse fault 1* 1* 1*

28 0 0 1 0 Swbd. fail 0 Circuit breaker fault 1* 1* 1*

29 0 0 1 0 Gov. fault 0 Low load 0 1 1

30 0 0 0 1 DP control 0 Hardware fault 0 0 0

Sub-Total 0 7 7 1 12 14 14




Table No: 3


Sign.Loss


1Type

2Type

3

31 0 0 1 0 DP control 0 Corrupted tape 1 1 1

32 0 0 1 0 Op. error 0 Maintenance during DP 1 1 1

33 0 0 1 0 Op. error Procedures Maintenance during DP 1 1 1

34 0 0 1 0 Op. error Gyro error Haste 1 1 1

35 0 1 0 0 Thrust. fail Op. error ECU settings 0 0 1

36 0 0 1 0 DP control No QA/tests A/B difference 1 1 1

37 0 0 1 0 Op. error Procedures Dredge hose in thrust 0 0 1

38 0 0 1 0 TW fault Design Bolt failure 1 1 1

39 0 0 1 0 Op. error Procedures Class 2-3 change over 1 0 0

40 0 0 1 0 Op. error Thr. fault x2 Thrust. control faults? 1 1 1

41 0 0 1 0 Op. error Thrust. fault Wrong azimuth mode 1 1 1

42 0 0 1 0 Op. error Thrust fault x2 Wrong azimuth mode 1 1 1

43 0 0 1 0 TW fault DP control Insuff. references 1 1 1

44 0 0 1 0 Op. error Procedures Insuff. references 1 1 1


Sub-Total 0 1 14 0 13 12 14




Table No: 4


Sign.Loss


1Type

2Type

3

46 0 0 1 0 Thrust. fault Poor PM Dirty oil filters 0 0 1

47 0 0 1 0 Procedures No QA/tests Insufficient power 1* 1* 1*

48 0 0 0 1 Gen. fault Procedures No position loss 0 0 0

49 0 0 0 1 DP control 0 Computer reload fault 0 0 0

50 0 0 0 1 Elec. fault 0 220V supply 0 0 0

51 0 0 0 1 Elec. fault 0 Radio interfer. with TW 0 0 0

52 0 0 0 1 DP control 0 Computer reload fault 0 0 0

53 0 0 0 1 DP control 0 Off-line computer fails 0 0 0

54 0 0 0 1 Gen. fault 0 Mech failure 0 0 0

55 0 0 0 1 DP control 0 Off-line computer fails 0 0 0

56 0 1 0 0 Operator error Procedures SBS fouls TW 1 1 1

57 0 1 0 0 Operator error Procedures Insufficient references 1 1 1

58 0 1 0 0 Operator error Procedures Insufficient references 1 1 1

59 0 1 0 0 Elect. fault Design Gen exexcit diodes 0 1 1

60 0 0 1 0 TW fault Op. error Insufficient references 1 1 1

Sub-Total 0 4 3 8 5 6 7




Table No: 5


Sign.Loss


1Type

2Type

3

61 0 0 1 0 TW fault Op. error Comp C/O position jump 1 1 1

62 0 1 0 0 Thrust. fault Op. error Faulty hydraulic v/v 1* 1* 1

63 0 0 1 0 Gen. fault Op. error Bustie tripped 0 1 1

64 0 1 0 0 Thrust fault Procedures Faulty feedbk transd 1* 1* 1

65 0 0 1 0 Op. error Design Calm weather DP soft. 1 1 1

66 0 0 1 0 Op. error TW fault Insufficient references 1 1 1

67 0 0 1 0 Op. error Procedures Sh water no radio ref 1 1 1


69 0 0 1 0 Op. error Procedures Insufficient references 1 1 1



72 0 1 0 0 Op. error Thrust fault Maintenance during DP 1* 1* 1

73 0 0 0 1 Op. error DP control No tests on new ref 0 0 0

74 0 0 1 0 Op. error DP control Push/pull mode too late 0 0 1

75 0 0 1 0 Thrust. fault No QA/tests Also poor PM 0 0 1

Sub-Total 0 5 9 1 11 12 14




Table No: 6


Sign.Loss


1Type

2Type

3

76 0 1 0 0 Other vessel Op. error Pull off Anchors 1 1 1

77 0 1 0 0 DP control No QA/tests Pull off Anchors 1 1 1

78 0 1 0 0 Elect. fault No QA/tests Gen load control 0 1 1

79 0 1 0 0 Thrust. fault Poor PM Faulty hydraulic v/v 1 1 1


81 0 1 0 0 Artemis fault Op. error Simplex vessel 1 1 1

82 0 0 1 0 Thrust. fault 0 Unexplained 1 1 1

83 0 0 1 0 Op. error Procedures Insufficient power 1* 1* 1*

84 0 1 0 0 Op. error Design Comp C/O error 0 1 1

85 0 0 1 0 DP control Procedures Syledis station change 1 1 1


87 1 0 0 0 Gen. fault Op. error Governor fault 0 1 1

88 0 1 0 0 DP control Design Buffer cap. exceeded 1 1 1

89 0 0 1 0 Op. error DP control C/O to faulty computer 0 1 1

90 0 1 0 0 TW fault Op. error Also Artemis fault 1 1 1

Sub-Total 1 8 5 1 10 14 14




Table No: 7


Sign.Loss


1Type

2Type

3

91 0 0 1 0 Elect. fault Op. error Earth fault ROV 1 1 1

92 0 0 1 0 DP control Op. error Software 1 1 1

93 0 0 1 0 DP control Procedures Multiple component failure 1 1 1

94 0 0 1 0 Op. error TW fault Artemis restricted 1 1 1

95 0 0 1 0 TW fault Procedures Perfect reference 1 1 1

96 0 0 1 0 TW fault DP control Insuf ref/perfect ref 1 1 1

97 0 0 1 0 TW fault Procedures Insuf ref/perfect ref 1 1 1

98 0 1 0 0 Elect fault/UPS Design UPS static switch 0 0 1

99 0 0 1 0 Elect fault/UPS Design UPS fault 0 1** 1

100 0 0 0 1 DP control Design One position ref 0 0 0

101 0 0 1 0 DP control No QA/tests Vessel moves wrong way 1 1 1

102 1 0 0 0 DP control No QA/tests New software 1 1 1

103 0 1 0 0 DP control Design Only 2 gyros 1+ 1+ 1+

104 0 0 1 0 DP control No QA/tests 2 gyros 1+ 1+ 1+

105 0 1 0 0 Weather Design Insuff anemom in use 1++ 1++ 1++

Sub-Total 1 3 10 1 12 13 14




Table No: 8


Sign.Loss


1Type

2Type

3

106 0 0 1 0 Weather Thrust. fault Insuff. power 1* 1* 1*

107 0 0 1 0 Gen. fault Design AVR/load sharing 0 1 1

108 0 1 0 0 Gen. fault Procedure C/O shaft gens on DP 0 0 1

109 0 0 1 0 DP control Design C/O to faulty computer 1 1 1

110 1 0 0 0 Thrust. fault Design Control voltage fails 0 0 1

111 0 0 1 0 Thrust. fail Procedures Hydraulic fault 0 0 1

112 0 0 0 1 Elect. fault Design No FMEA 0 0 0

113 1 0 0 0 Elect faults Design Gen exciter diodes 0 1 1

114 1 0 0 0 Elect. fault Design Gen SC/CB too slow 0 1 1

115 0 0 1 0 Elect. fault/UPS Design Single UPS 0 0 1**

116 0 0 1 0 DP control Design DP/manual switch fault 1 1 1

117 0 1 0 0 Thrust fault Op. error PCB in Az ECU 1* 1* 1

118 0 0 1 0 Op. error Thrust fault Thrust motor fault 0 0 1*

119 0 1 0 0 Op. error Design Radio interfer with Art 1 1 1

120 0 0 0 1 Op. error Design Using STW as VTW 0 0 0

Sub-Total 3 3 7 2 5 8 13




Table No: 9


Sign.Loss


1Type

2Type

3

121 0 0 1 0 Op. error Design Maintenance during DP 1* 1* 1

122 1 0 0 0 Op. error Design Insufficient references 1 1 1




126 0 0 1 0 Op. error Procedures Comp C/O error 1 1 1

127 0 1 0 0 Op. error Procedures SV affects TW and HPR 1 1 1

128 0 0 0 1 Op. error Procedures DP and moorings 0 0 0


130 0 1 0 0 Op. error Procedures Insufficient thrusters 1* 1* 1*

131 1 0 0 0 Op. error Procedures Crane snags platform 1 1 1

132 0 0 1 0 Op. error Procedures SV fouls TW 1 1 1

133 1 0 0 0 Op. error Procedures Sh water/insuf ref 1 1 1

134 0 0 1 0 Op. error Procedures Maintenance during DP 0 0 1

135 0 0 1 0 Op. error Procedures Wrong azimuth mode 1* 1* 1*

Sub-Total 5 3 6 1 13 13 14




Table No: 10


Sign.Loss


1Type

2Type

3

136 0 0 1 0 Op. error Procedures Cross haul fouls TW 1 1 1

137 0 1 0 0 Op. error Procedures Haste 1 1 1

138 0 0 0 1 Op. error Procedures Sh water/insuff ref 0 0 0

139 0 0 1 0 Op. error Procedures Insuff thrust and refs 1* 1* 1*

140 0 0 1 0 Op. error Procedures Insuff thrust and refs 1 1 1

141 0 1 0 0 Fire Design 0 0 1

142 0 0 1 0 Elect fault Design No FMEA 0 0 1

143 0 0 1 0 Elect fault/UPS Design UPS static switch 0 0 1

144 0 0 1 0 DP control Design Power management fault 0 1* 1*

145 0 0 1 0 Elect fault Design AVR fault/insuf power and thr 0 1 1

146 1 0 0 0 DP control No QA/tests Thrust in wrong direction 1 1 1


148 0 0 1 0 DP control Design Common computer fault 1 1 1

149 0 0 1 0 DP control No QA/tests Insufficient thrust and gens 1* 1* 1*

150 0 0 1 0 Thrust. fault Procedures Insufficient thrusters 1* 1* 1*

Sub-Total 1 2 11 1 9 11 14




Table No: 11


Sign.Loss


1Type

2Type

3

151 0 0 1 0 Op. error Procedures SV prop wash 1 1 1

152 0 0 1 0 DP control No QA/tests Software in calm weather 1 1 1

153 0 0 1 0 Op. error Procedures SV prop wash 1 1 1


155 0 0 1 0 Op. error Procedures Fouled thruster 1* 1* 1

156 0 1 0 0 DP control Procedures TW angles wrong in DW 1 1 1

157 0 0 1 0 Op. error Procedures Insuf power/mainten on DP 1* 1* 1*

158 0 0 1 0 Op. error Procedures Tides/insuff thrust 1* 1* 1*

159 0 0 1 0 Op. error Procedures Insufficient thrust 1* 1* 1*

160 0 0 1 0 Op. error Procedures Crane OL/insuf gens 1* 1* 1*

161 0 0 0 1 Op. error Procedures One position ref. 0 0 0


163 0 0 1 0 Op. error Procedures Wrong gen CB closed 0 1 1

164 0 0 1 0 Op. error Procedures Op C/O to faulty computer 0 1 1

165 0 0 1 0 Op. error Procedures Gyro diff/maint on DP 1+ 1+ 1+

Sub-Total 0 1 13 1 12 14 14




Table No: 12


Sign.Loss


1Type

2Type

3

166 0 0 1 0 Oop. error Procedures Large moves 1 1 1

167 0 0 1 0 Oop. error Procedures Insufficient thrusters 1* 1* 1*

168 0 1 0 0 Elect. fault Procedures Insuff gen/poor autosynch 0 1 1

169 0 1 0 0 Thrust. fault Design PCB fault on pitch control 1* 1* 1

170 0 0 1 0 Gen. fault Op. error Insuff generators 1* 1* 1*

171 0 1 0 0 Weather Op. error Insuff thrusters 1* 1* 1*

172 0 1 0 0 Weather Op. error Fault anem/insuf posn refs 1++ 1++ 1++

173 0 0 1 0 TW fault Procedures Insufficient references 1 1 1


175 1 0 0 0 DP control Procedures Software/insuff thrust 1 1 1

176 0 0 1 0 DP control Procedures Insufficient referneces 1 1 1

177 0 1 0 0 DP control Design Software in good weather 1 1 1

178 0 0 1 0 DP control Op. error C/O fault + C/O op error 0 1 1

179 0 1 0 0 DP control Procedures Fault in sensor data filter 1 1 1

180 0 1 0 0 Op. error Design Maintenance during DP 0 0 1

Sub-Total 1 7 7 0 12 14 15




Table No: 13


Sign.Loss


1Type

2Type

3

181 0 1 0 0 Op. error Procedures UPS fault/mainten on DP 0 1** 1**

182 0 1 0 0 DP control DP control Art fault/insuff refs 1 1 1

183 1 0 0 0 DP control Op.error Art fault/insuff refs 1 1 1

184 0 0 1 0 Power man softw No QA/tests No FMEA 1 1 1

185 0 0 1 0 DP control No QA/tests New Software 1 1 1

186 0 0 1 0 Elect. fault Design Thrust motor S/C 0 1 1

187 0 0 1 0 DP control Op. error Multiple comp hard faults 1 1 1

188 1 0 0 0 Thrust fault Design Wrong azimuth mode 1 * 1 * 1 *

189 0 0 1 0 Elect fault Design Burnt UPS cables 0 0 1

190 0 0 1 0 Elect fault Design Gen S/C 0 1 1

191 0 0 1 0 DP control Design DP deselects thrusters 1 1 1

192 0 0 1 0 Thrust. fault Design Fault prop feedback pot. 1 1 1

193 0 0 1 0 Op. error DP control Insufficient references 1 1 1


195 1 0 0 0 Op. error Procedures Comp C/O op error 0 1 1

Sub-Total 4 2 9 1 9 13 14




Table No: 14


Sign.Loss


1Type

2Type

3

196 1 0 0 0 Op. error Procedures Insuff thrust and refs 1 * 1 * 1 *



199 0 1 0 0 Op. error Procedures ROV in TW 1 1 1

200 0 0 1 0 Op. error Procedures Comp C/O position jump 1 1 1

201 0 1 0 0 Op. error Procedures Wrong gain/insuff thrust 1 * 1 * 1 *

202 0 0 1 0 Op. error Procedures Comp. reload Op. error 1 1 1


204 0 1 0 0 Op. error Procedures ROV in TW/insuff refs 1 1 1

205 0 1 0 0 Op. error Procedures ROV in TW/insuff refs 1 1 1

206 0 0 1 0 DP control Procedures Insufficient references 1 1 1

207 0 1 0 0 DP control Design Perfect reference 1 1 1

208 0 1 0 0 DP control Design Perfect reference 1 1 1

209 0 0 1 0 TW fault No QA/tests Also insuff references 1 1 1

210 0 0 1 0 TW fault No QA/tests Also insuff references 1 1 1

Sub-Total 1 8 5 1 14 14 14




Table No: 15


Sign.Loss


1Type

2Type

3

211 0 0 0 1 DP control Op. error Unexplained 0 0 0

212 0 1 0 0 Thrust. fault Op. error Faulty thrust control 1 * 1 * 1

213 0 1 0 0 DP control No QA/tests Wrong TW WD/insuff refs 1 1 1

214 0 0 1 0 Thrust fault Alarm faulty Poor PM 1 * 1 * 1

215 0 0 0 1 DP control Procedures DP to joystick fault 0 0 0

216 0 0 1 0 Elec fault Design Thruster motor S/C 1 1 1

217 0 0 0 1 Elect fault/comp Design Comp hardware fault 0 0 0

218 0 0 1 0 Elect fault Op. error Insufficient power 1 * 1 * 1 *

219 0 0 0 1 Op. error Procedures Setting up Op errors 0 0 0

220 1 0 0 0 Op. error Procedures DP/joystick confusion 1 1 1

221 1 0 0 0 Op. error Procedures Sh water/insuff refs 1 1 1


223 0 0 0 1 Op. error Design Joystick moved wrong way 0 0 0

224 1 0 0 0 Op. error Procedures Joystick moved wrong way 1 1 1

Sub-Total 4 3 2 5 9 9 9



APPENDIX 2

Complete List of Causes of DP Position Loss



DP CONTROL FAILURES

References

Insufficient referencesOnline refs are poorA poor reference is no referenceNot enough on lineNot enough on line and they are poorNot enough on line and one is near limitsNot enough on line and incoming reference is faultyNot enough variety of physical principlesNot enough for a moveRefs in use are used too quicklyNot enough time left to stabiliseShallow water, no radio referenceWorking near limits of two referencesMaking moves which put some or even all references out of limitsMaking moves in marginal weather where excursion put all position references out

of limitsInsufficient to approach platformInsufficient to leave platform

ArtemisPoorJumpsFixed station on semiWrong rangeOut of rangeCorrupt signal frozen fixed unit bearing Fixed unit bearing not correctly setRadio interference, see also TWFixed unit on semi is not correctly gyro stabilised

SyledisChange of co-ordinates when stations change

TWROV foulsBell foulsBell guide wires foulBell cross haul wires foulCrane foulsDiver foulsMooring wires foulSupply boat foulsStandby boat foulsHPR wire foulsIncorrect hydraulic pressureIncorrect tensionIncorrect wire lengthFaulty inclinometerFaulty measurement from inclinometer digital filter at large water depths



Radio interference, see also ArtemisHydraulic failureTidal current wire deflectionsHeave compensation too slowFaulty relaysSnags on wire resetting counterErroneous counter reading

hardware fault or designvibrationsoftware designspurious resets to zero

Using a surface TW as a vertical TW in shallow waterAlarms do not workWire pays out due to mechanical fault and gives wrong angular measurement

HPRDiver picks up transponderMultiple reference failuresSupply vessel affects TWs and HPR

GyrosOnly 2 gyrosGyro manual switch over function not installed correctlyGyro difference, 2 degrees, large enough to affect positioning when making heading

changes far too close to platform

Computerscomputer reloadsUPSSoftware bug

current estimates wrongthruster allocation not tuned for calm conditionsoccasionally vessel moves wrong way making numerous small movessoftware improvements which unintentionally removed critical alarm

functionssome thrusters thrust in wrong direction in calm weatherpositioning instability in calm weatherstops both computers after software mods

hardware faultPCB faultspush buttonsPCB fault on C computerfaulty batch of co-processor chipsfault in sensor data filter leading to massive overshootmultiple spurious hardware faults on c computercomputer deselects thrustersoverheating

position jump at computer changeoverBuffer capacity exceeded in control programme

A/B differenceoverheatingwrong gain settingtransfer DP/joystick



transfer joystick/DPthruster allocation may be limited on DP joystickErroneous transfer from DP to manual and no alarmsArtemis card S/Csurge/sway control onlyyaw control onlyWrong azimuth mode

fixed in increasing environmental loadsfixed during movefixed during move and increasing environmental loads

Push/pull modewaiting too long in worsening weather to select

Operator shuts down on line computerReference sensor limit alarms do not work

Thruster faultsDebris in hydraulicsWater in hydraulicsFilter mesh too largeChanging filter during DP

Faulty azimuth feedback transducerFaulty pitch feedback transducerFaulty pitch feedback potentiometerFaulty hydraulic control valve

Fuse failure in control circuit caused full thrustFuse fell out in control circuit caused thruster to stop

ECU faultsmax pitch settings too highoverload trip settings too highoverload fast attack settings too highfault in PCB

Prime mover faultelectric motorengine

Maintenance during DPaffecting online thruster being maintained affecting online thrusters when maintaining offline thrusters

ProtectionPairs of thrusters also include main propellersThrusters erroneously tripped by fault in machinery monitoring systemFouled by wires used on construction projectFouled by ROVOverloaded switchboard preference trips thrusters rather than crane



Electrical faults

Short circuit thruster drive motorS/C thrust drive motor transferred from first to second swbdGen short circuit - circuit breaker too slow to clear fault Bustie opened on purpose due to faultClosing breaker on a shutdown generatorGen load controlGen load sharing faultGen synch controlExciter faultMultiple exciter diode faults affecting all generators leading to undervoltage on

sudden load demands - such multiple failures could affect type 1 and type 2vessels

AVR fault

Earth fault third party equipmentFailed auto start systemAuto start system left in manualChanging over shaft generators during high risk DP operations

Insufficient power not enough generators onlinePutting gens on too late in worsening weatherPutting generators on too late when setting up

Power management system receives false signals from generators on statusand/or power output leading to erroneous pitch reductionAVR fault causes overcurrent signal to power management system leading to

pitch reduction

UPSOscillator faultStatic switch faultLow battery voltage2 x UPS but only one set of batteriesS/C during TW wire counter maintenance fails UPSFuse fails on master unit and hidden fault on slave

FMEACommon power supplies to adjacent thruster control systemsTwo thrusters sharing same two hydraulic pumps

Switchboard fault discrimination trips thrusters before cranesAll engines trip on bearing fault on one engine



APPENDIX 3

Tables 16-30: Frequency of Drift Off, Drive Off and Large Excursion



FREQUENCY OF DRIFT OFF, DRIVE OFF AND LARGE EXCURSION

Table No: 16


Drift Off Drive Off Large ExcursionIncident No

Drift Off Drive Off Large Exc’n Type 1 Type 2 Type 3 Type 1 Type 2 Type 3 Type 1 Type 2 Type 3

1 0 0 1 0 0 0 0 0 0 1 1 1

2 0 1 0 0 0 0 1 1 1 0 0 0

3 0 0 1 0 0 0 0 0 0 1 1 1

4 1 0 0 1* 1* 1* 0 0 0 0 0 0

5 1 0 0 0 1 1 0 0 0 0 0 0

6 1 0 0 1 1 1 0 0 0 0 0 0

7 0 0 1 0 0 0 0 0 0 1 0 0

8 N/A N/A N/A 0 0 0 0 0 0 0 1 1

9 1 0 0 1 1 1 0 0 0 0 0 0

10 0 1 0 0 0 0 1 1 1 0 0 0

11 1 0 0 0 0 1 0 0 0 0 0 0

12 0 1 0 0 0 0 1 1 1 0 0 0

13 0 0 1 0 0 0 0 0 0 1 1 1

14 1 1 0 1 1 1 0 0 0 0 0 0

15 0 0 1 0 0 0 0 0 0 1 1 1

Total 6 3 5 4 5 6 3 3 3 5 5 5




Table No: 17




16 0 0 1 0 0 0 0 0 0 1 1 1

17 1 0 0 1 1 1 0 0 0 0 0 0

18 0 0 1 0 0 0 0 0 0 1 1 1

19 0 0 1 0 0 0 0 0 0 1 1 1

20 0 0 1 0 0 0 0 0 0 1* 1* 1*

21 1 0 0 1 1 1 0 0 0 0 0 0

22 0 0 1 0 0 0 0 0 0 1 1 1

23 0 0 1 0 0 0 0 0 0 1 1 1

24 0 0 1 0 0 0 0 0 0 1 1 1

25 0 0 1 0 0 0 0 0 0 1 1 1

26 1 0 0 1* 1* 1 0 0 0 0 0 0

27 1 0 0 1 1 1 0 0 0 0 0 0

28 1 0 0 1 1 1 0 0 0 0 0 0

29 1 0 0 0 1 1 0 0 0 0 0 0

30 N/A N/A N/A 0 0 0 0 0 0 0 0 0

Total 6 0 8 5 6 6 0 0 0 8 8 8




Table No: 18




31 1 0 0 0 1 1 0 0 0 0 0 0

32 1 0 0 1 1 1 0 0 0 0 0 0

33 1 0 0 1 1 1 0 0 0 0 0 0

34 0 1 0 0 0 0 1 1 1 0 0 0

35 0 0 1 0 0 0 0 0 0 0 0 1

36 0 1 0 0 0 0 1 1 1 0 0 0

37 1 0 0 0 0 1 0 0 0 0 0 0

38 0 0 1 0 0 0 0 0 0 1 1 1

39 1 0 0 1 0 0 0 0 0 0 0 0

40 0 0 1 0 0 0 0 0 0 1 1 1

41 0 0 1 0 0 0 0 0 0 1 1 1

42 0 0 1 0 0 0 0 0 0 1 1 1

43 0 1 0 0 0 0 1 1 1 0 0 0

44 0 0 1 0 0 0 0 0 0 1 1 1

45 1 0 0 1 1 1 0 0 0 0 0 0

Total 6 3 6 4 4 5 3 3 3 5 5 6




Table No: 19




46 0 0 1 0 0 0 0 0 0 1 1 1

47 1 0 0 1* 1* 1* 0 0 0 0 0 0

48 N/A N/A N/A 0 0 0 0 0 0 0 0 0

49 N/A N/A N/A 0 0 0 0 0 0 0 0 0

50 N/A N/A N/A 0 0 0 0 0 0 0 0 0

51 N/A N/A N/A 0 0 0 0 0 0 0 0 0

52 N/A N/A N/A 0 0 0 0 0 0 0 0 0

53 N/A N/A N/A 0 0 0 0 0 0 0 0 0

54 N/A N/A N/A 0 0 0 0 0 0 0 0 0

55 N/A N/A N/A 0 0 0 0 0 0 0 0 0

56 0 0 1 0 0 0 1 1 1 0 0 0

57 0 1 0 0 0 0 0 0 0 1 1 1

58 0 1 0 0 0 0 1 1 1 0 0 0

59 1 0 0 0 1 1 0 0 0 0 0 0

60 0 0 1 0 0 0 0 0 0 1 1 1

Total 2 2 3 1 2 2 2 2 2 3 3




Table No: 20




61 0 0 1 0 0 0 0 0 0 1 1 1

62 0 0 1 0 0 0 0 0 0 1 1* 1

63 0 0 1 0 0 0 0 0 0 0 1 1

64 0 0 1 0 0 0 0 0 0 1* 1* 1

65 0 0 1 0 0 0 0 0 0 1 1 1

66 0 1 0 0 0 0 1 1 1 0 0 0

67 0 1 0 0 0 0 1 1 1 0 0 0

68 0 1 0 0 0 0 1 1 1 0 0 0

69 0 1 0 0 0 0 1 1 1 0 0 0

70 0 1 0 0 0 0 1 1 1 0 0 0

71 0 1 0 0 0 0 1 1 1 0 0 0

72 0 0 1 0 0 0 0 0 0 1 1 1

73 N/A N/A N/A N/A 0 0 0 0 0 0 0 0

74 1 0 0 0 0 1 0 0 0 0 0 0

75 0 1 0 0 0 0 0 0 1 0 0 0

Total 1 7 6 0 0 1 6 6 7 5 6 6




Table No: 21




76 0 0 1 0 0 0 0 0 0 1 1 1

77 0 0 1 0 0 0 0 0 0 1 1 1

78 1 0 0 0 1 1 0 0 0 0 0 0

79 0 0 1 0 0 0 0 0 0 1 1 1

80 1 0 0 0 1 1 0 0 0 0 0 0

81 0 1 0 0 0 0 1 1 1 0 0 0

82 0 1 0 0 0 0 1 1 1 0 0 0

83 1 0 0 0 1* 1* 0 0 0 0 0 0

84 1 0 0 1 1 1 0 0 0 0 0 0

85 0 0 1 0 0 0 0 0 0 1 1 1

86 N/A N/A N/A 0 0 0 0 0 0 0 0 0

87 1 0 0 0 1 1 0 0 0 0 0 0

88 1 0 0 1 1 1 0 0 0 0 0 0

89 1 0 0 1 1 1 0 0 0 0 0 0

90 0 1 0 0 0 0 1 1 1 0 0 0

Total 7 3 4 3 7 7 3 3 3 4 4 4




Table No: 22




91 1 0 0 1 1 1 0 0 0 0 0 0

92 1 0 0 1 1 1 0 0 0 0 0 0

93 0 1 0 0 0 0 1 1 1 0 0 0

94 0 0 1 0 0 0 0 0 0 1 1 1

95 0 1 0 0 0 0 1 1 1 0 0 0

96 0 1 0 0 0 0 1 1 1 0 0 0

97 0 1 0 0 0 0 1 1 1 0 0 0

98 1 0 0 0 0 1 0 0 0 0 0 0

99 1 0 0 0 1 1 0 0 0 0 0 0

100 N/A N/A N/A 0 0 0 0 0 0 0 0 0

101 0 1 0 0 0 0 1 1 1 0 0 0

102 0 1 0 0 0 0 1 1 1 0 0 0

103 0 1 0 0 0 0 1 1 1 0 0 0

104 0 1 0 0 0 0 0 1 1 0 0 0

105 0 0 1 0 0 0 0 0 0 1 1 1

Total 4 8 2 2 3 4 7 8 8 2 2 2




Table No: 23




106 1 0 0 1* 1* 1* 0 0 0 0 0 0

107 1 0 0 0 1 1 0 0 0 0 0 0

108 1 0 0 0 0 1 0 0 0 0 0 0

109 1 0 0 1 1 1 0 0 0 0 0 0

110 0 0 1 0 0 0 0 0 0 0 0 1

111 0 0 1 0 0 0 0 0 0 1 1 1

112 N/A N/A N/A 0 0 0 0 0 0 0 0 0

113 1 0 0 0 1 1 0 0 0 0 0 0

114 1 0 0 0 1 1 0 0 0 0 0 0

115 1 0 0 0 0 1 0 0 0 0 0 0

116 0 1 1 0 0 0 1 1 1 0 0 0

117 0 0 1 0 0 0 0 0 0 1* 1* 1*

118 1 0 0 0 0 1* 0 0 0 0 0 0

119 0 1 1 0 0 0 1 1 1 0 0 0

120 N/A N/A N/A 0 0 0 0 0 0 0 0 0

Total 8 2 3 2 5 8 2 2 2 2 2 3




Table No: 24




121 1 0 0 1* 1* 1 0 0 0 0 0 0

122 0 0 1 0 0 0 0 0 0 1 1 1

123 0 1 0 0 0 0 1 1 1 0 0 0

124 0 0 1 0 0 0 0 0 0 1 1 1

125 0 0 1 0 0 0 0 0 0 1 1 1

126 1 0 0 1 1 1 0 0 0 0 0 0

127 0 0 1 0 0 0 0 0 0 1 1 1

128 N/A N/A N/A 0 0 0 0 0 0 0 0 0

129 0 1 0 0 0 0 1 1 1 0 0 0

130 1 0 0 1* 1* 1* 0 0 0 0 0 0

131 0 0 1 0 0 0 0 0 0 1 1 1

132 0 0 1 0 0 0 0 0 0 1 1 1

133 0 1 0 0 0 0 1 1 1 0 0 0

134 0 0 1 0 0 0 0 0 0 0 0 1

135 0 0 1 0 0 0 0 0 0 1* 1* 1*

Total 3 3 8 3 3 3 3 3 3 7 7 8




Table No: 25




136 0 1 0 0 0 0 1 1 1 0 0 0

137 0 0 1 0 0 0 0 0 0 1 1 1

138 N/A N/A N/A 0 0 0 0 0 0 0 0 0

139 1 0 0 1* 1* 1* 0 0 0 0 0 0

140 1 0 0 1 1 1 0 0 0 0 0 0

141 1 0 0 0 0 1 0 0 0 0 0 0

142 0 0 1 0 0 0 0 0 0 0 0 1

143 1 0 0 0 0 1 0 0 0 0 0 0

144 1 0 0 1 1 1 0 0 0 0 0 0

145 1 0 0 0 1 1 0 0 0 0 0 0

146 0 1 0 0 0 0 1 1 1 0 0 0

147 1 0 0 1 1 1 0 0 0 0 0 0

148 1 0 0 1 1 1 0 0 0 0 0 0

149 1 0 0 1* 1* 1* 0 0 0 0 0 0

150 0 0 1 0 0 0 0 0 0 1* 1* 1*

Total 9 2 3 6 7 9 2 2 2 2 2 3




Table No: 26




151 0 0 1 0 0 0 0 0 0 1 1 1

152 0 0 1 0 0 0 0 0 0 1 1 1

153 0 0 1 0 0 0 0 0 0 1 1 1

154 1 0 0 1 1 1 0 0 0 0 0 0

155 0 0 1 0 0 0 0 0 0 1 1 1

156 0 0 1 0 0 0 0 0 0 1* 1* 1

157 0 0 1 0 0 0 0 0 0 1 1 1

158 0 0 1 0 0 0 0 0 0 1* 1* 1*

159 0 0 1 0 0 0 0 0 0 1 1 1

160 1 0 0 1* 1* 1* 0 0 0 0 0 0

161 N/A N/A N/A 0 0 0 0 0 0 0 0 0

162 0 0 1 0 0 0 0 0 0 1 1 1

163 0 0 1 0 0 0 0 0 0 1 1 1

164 0 1 0 0 0 0 1 1 1 0 0 0

165 0 1 0 0 0 0 1 1 1 0 0 0

Total 2 2 10 2 2 2 2 2 2 10 10 10




Table No: 27




166 0 0 1 0 0 0 0 0 0 1 1 1

167 1 0 0 1* 1* 1* 0 0 0 0 0 0

168 1 0 0 0 1 1 0 0 0 0 0 0

169 0 0 1 0 0 0 0 0 0 1* 1* 1*

170 1 0 0 1* 1* 1* 0 0 0 0 0 0

171 0 0 1 0 0 0 0 0 0 1* 1* 1*

172 0 0 1 0 0 0 0 0 0 1 1 1

173 0 0 1 0 0 0 0 0 0 1 1 1

174 0 0 1 0 0 0 0 0 0 1 1 1

175 1 0 0 1 1 1 0 0 0 0 0 0

176 0 0 1 0 0 0 0 0 0 1 1 1

177 0 0 1 0 0 0 0 0 0 1 1 1

178 1 0 0 0 1 1 0 0 0 0 0 0

179 0 1 0 0 0 0 1 1 1 0 0 0

180 1 0 0 0 0 1 0 0 0 0 0 0

Total 6 1 8 3 5 6 1 1 1 8 8 8




Table No: 28




181 1 0 0 0 1 1 0 0 0 0 0 0

182 0 1 0 0 0 0 1 1 1 0 0 0

183 0 1 0 0 0 0 1 1 1 0 0 0

184 1 0 0 1 1 1 0 0 0 0 0 0

185 1 0 0 1 1 1 0 0 0 0 0 0

186 1 0 0 0 1 1 0 0 0 0 0 0

187 0 1 0 0 0 0 1 1 1 0 0 0

188 0 1 0 0 0 0 1* 1* 1* 0 0 0

189 1 0 0 0 0 1 0 0 0 0 0 0

190 1 0 0 0 1 1 0 0 0 0 0 0

191 1 0 0 1 1 1 0 0 0 0 0 0

192 0 0 1 0 0 0 0 0 0 1 1 1

193 0 0 1 0 0 0 0 0 0 1 1 1

194 N/A N/A N/A 0 0 0 0 0 0 0 0 0

195 0 1 0 0 0 0 0 0 1 0 0 0

Total 7 5 2 3 6 7 4 4 5 2 2 2




Table No: 29




196 1 0 0 1* 1* 1* 0 0 0 0 0 0

197 0 1 0 0 0 0 1 1 1 0 0 0

198 0 1 0 0 0 0 1 1 1 0 0 0

199 0 0 1 0 0 0 0 0 0 1 1 1

200 0 1 0 0 0 0 1 1 1 0 0 0

201 0 0 1 0 0 0 0 0 0 1* 1* 1*

202 0 1 0 0 0 0 1 1 1 0 0 0

203 N/A N/A N/A 0 0 0 0 0 0 0 0 0

204 0 1 0 0 0 0 1 1 1 0 0 0

205 0 1 0 0 0 0 1 1 1 0 0 0

206 0 1 0 0 0 0 1 1 1 0 0 0

207 0 1 0 0 0 0 1 1 1 0 0 0

208 0 1 0 0 0 0 1 1 1 0 0 0

209 0 0 1 0 0 0 0 0 0 1 1 1

210 0 0 1 0 0 0 0 0 0 1 1 1

Total 1 9 4 1 1 1 9 9 9 4 4 4




Table No: 30




211 N/A N/A N/A 0 0 0 0 0 0 0 0 0

212 0 0 1 0 0 0 0 0 0 1* 1* 1*

213 0 0 1 0 0 0 0 0 0 1 1 1

124 0 0 1 0 0 0 0 0 0 1 1 1

215 N/A N/A N/A 0 0 0 0 0 0 0 0 0

216 1 0 0 1 1 1 0 0 0 0 0 0

217 N/A N/A N/A 0 0 0 0 0 0 0 0 0

218 1 0 0 1* 1* 1* 0 0 0 0 0 0

219 N/A N/A N/A 0 0 0 0 0 0 0 0 0

220 0 1 0 0 0 0 1 1 1 0 0 0

221 0 1 0 0 0 0 1 1 1 0 0 0

222 N/A N/A N/A 0 0 0 0 0 0 0 0 0

223 0 1 0 0 0 0 1 1 1 0 0 0

224 0 1 0 0 0 0 1 1 1 0 0 0

Total 2 4 3 2 2 2 4 4 4 3 3 3

IMCA M115 Collision of DP SV With Offshore Installations

Documents