UKOOA Guidelines for Ship Installation Collision Avoidance

UKOOA Guidelines for
Ship/Installation Collision Avoidance
Issue 1 February 2003

UK Offshore Operators Association

Guidelines for

SHIP/INSTALLATION
COLLISION AVOIDANCE
ISSUE 1
FEBRUARY 2003

Whilst every effort has been made to ensure the accuracy of the information contained in this publication,
neither UKOOA, nor any of its members will assume liability for any use made thereof.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise,
without prior written permission of the publishers.
Crown copyright material is reproduced with the permission of the Controller of Her Majesty’s
Stationery Office.
Copyright  2003 UK Offshore Operators Association Limited

ISBN: 1 903003 20 2
PUBLISHED BY UK OFFSHORE OPERATORS ASSOCIATION
London Office:
2nd Floor, 232-242 Vauxhall Bridge Road, London, SW1V 1AU.
Tel: 020 7802 2400 Fax: 020 7802 2401
Aberdeen Office:
9, Albyn Terrace, Aberdeen, AB10 1YP
Tel: 01224 626652 Fax: 01224 626503
Email: [email protected]
Website: www.oilandgas.org.uk

Ship/Installation Collision Avoidance

CONTENTS
Page No
INTRODUCTION

iii

Purpose and Scope

iii

Contributing Organisations

iv

ABBREVIATIONS

vii

1

2

3

4

COLLISION RISK MANAGEMENT SYSTEM

1

1.1

Introduction

1

1.2

Responsibilities

1

1.3

Key Elements

2

BACKGROUND AND OVERVIEW

8

2.1

Introduction

8

2.2

Probability of Collision

8

2.3

Passing Vessels

9

2.4

Attendant Vessels

10

2.5

Offtake Tankers

10

2.6

Contingency Planning and Procedures

12

2.7

Incident and Near Miss Reporting

14

2.8

Reporting and Follow-up

15

2.9

Auditing

16

2.10 Performance Standards

16

PASSING VESSELS

17

3.1

Introduction

17

3.2

Assessing the Potential for Collision

18

3.3

Minimising the Probability of Collision

20

3.4

Collision Avoidance Measures

21

ATTENDANT VESSELS

26

4.1

Introduction

26

4.2

Assessing the Potential for Collision

27

4.3

Minimising the Probability of Collision

28

4.4

Collision Avoidance Measures

31

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5

4.5

Contingency Plans

34

4.6

Follow-up

34

OFFTAKE TANKERS

35

5.1

Introduction

35

5.2

Assessing the Potential for Collision

35

5.3

Minimising the Probability of Collision

36

5.4

Collision Avoidance Measures

39

Figures
Figure 1 Key Elements of Successful Health and Safety Management

2

Figure 2 Collision Risk Management – Summary Flowchart

5

Figure 3 Collision Avoidance Flowchart

6

Figure 4 Collision Avoidance Procedures – Passing Vessels

7

Addendum
1

Glossary of Terms

2

Promulgation and Detection – Passing Vessels

3

Systems Audits

4

Vessel Suitability and Inspection Formats

5

Field Checklist

6

Installation Data Cards

7

Incident and Near Miss Reporting Formats

8

References Including Relevant Codes and Regulations

9

Passing Vessel – Ship Collision Assessment

10

Vessel Impacts – Guidance on Loads and Consequences

11

Contacts

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INTRODUCTION
Purpose and Scope
This document gives guidance to Dutyholders on reducing the probability
of collisions between vessels and offshore Installations. It has been developed
by United Kingdom Offshore Operators Association (UKOOA), supported by
the Health and Safety Executive and with the assistance of other stakeholders.
Various accident types involving serious injury or loss of life, or which have the
potential to do so, are defined as ‘major accidents’ under the Safety Case
Regulations (SCRs). SCRs define ‘major accidents’ as:
a.

Fire, explosion or the release of a dangerous substance involving death or
serious personal injury to persons on the Installation or engaged in an
activity on or in connection with it.

b.

Any event involving major damage to the structure of the Installation or
plant affixed thereto or any loss of stability of the Installation.

c.

The collision of a helicopter with the Installation.

d.

The failure of life support systems for diving operations in connection with
the Installation, the detachment of a diving bell used for such operations or
the trapping of a diver in a diving bell or other subsea chamber used for
such operations.

e.

Any other event arising from work activity involving death or serious
personal injury to five or more persons on the Installation or engaged in an
activity in connection with it.

Regulations 8(1) (c) and (d) of SCR requires that a Dutyholder demonstrates in
their Safety Case that all hazards with the potential to cause a major accident
have been identified, that the risks have been evaluated and that measures have
been or will be taken to reduce the risk to people to As Low As Reasonably
Practicable (ALARP).
The ‘major accident’ definition (b) in the above Regulations includes impacts
from both infield (attendant) and passing vessels as events likely to involve
major damage to the structure of the Installation. Consequently, all types of
vessels with the potential to impact the Installation must be considered as a
Major Accident Hazard (MAH) under SCR.

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SCR are complemented by Prevention of Fire and Explosion, and Emergency
Response (PFEER) Regulations. PFEER requires the Dutyholder to assess
MAHs that may require Evacuation, Escape and Rescue (EER) and to identify
appropriate arrangements for dealing with them. Such arrangements will include
preparation for emergencies, an emergency response plan, detection of
incidents, communications, control of emergencies, muster areas, arrangements
for evacuation, means of escape and arrangements for rescue and recovery.
This guide focuses on the avoidance of ship/Installation collisions. Although the
concepts of risk and ALARP are referred to within the document, it is not
intended to provide detailed assessment of consequences of a collision.
Similarly only key considerations in the development of appropriate collision
response strategies are provided.
Hence, the guidance draws together and summarises current best practice on
avoiding collisions between vessels and Installations. For convenience it
addresses separately:
• Passing vessels – those en route to somewhere else
• Attendant vessels are vessels with legitimate business at the Installation
• Offtake tankers, a subset of attendant vessels, which interact with the
Installation in a specialised way and are therefore addressed in a
dedicated section
Recommendations made in this guide rely principally on checklists covering
management systems, vessel suitability, self-audit and pre-operational checks
(a form of risk assessment). They draw, wherever possible, on existing proven
industry standards.
The guide is aimed principally at operations in the United Kingdom
(UK) sector, and therefore refers to UK legislation, practices and organisations.
Other administrations and national associations may wish to adapt the principles
to their own sectors.

Contributing Organisations
The following organisations have been consulted in developing this guide:
• Health and Safety Executive
• Maritime and Coastguard Agency (MCA)
• Trade Unions: National Union of Marine Aviation and Shipping Officers
(NUMAST) and Rail, Maritime and Transport Union (RMT)
• UKOOA Marine, Hazard Management, Structural and Floating Production,
Storage and Offtake (FPSO) unit Committees

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• International Marine Contractors Association (IMCA)
• Emergency Rescue and Recovery Vessel Owners Association (ERRVA)
• Chamber of Shipping
• Marine Safety Forum
• Intertanko
• Oil Companies International Marine Forum (OCIMF)
• International Association of Drilling Contractors (IADC)
• British Rig Owners Association (BROA)
• Scottish Fishermen’s Federation (SFF)
• Step Change in Safety

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ABBREVIATIONS
AHTS
AIS
ALARP
ARCS

Anchor Handling Tug Supply
Automatic Identification of Ships (IMO Resolution 22/9
Annex II)
As Low As Reasonably Practical
Admiralty Raster Charting Service

BPD
BROA

Barrels (oil production) Per Day
British Rig Owners Association

CMID
CPA
CRM

Common Marine Inspection Document
Closest Point of Approach
Collision Risk Management

DCR

Offshore Installations and Wells (Design and
Construction, etc) Regulations SI 913 1996
Det Norske Veritas
Dynamic Positioning (or Dynamically Positioned)
Digital Selective Calling
Department of Transport, Local Government and The
Regions (formerly DETR)

DNN
DP
DSC
DTLR
EER
ERRV

ESD

Evacuation, Escape and Recovery
Emergency Rescue and Recovery Vessel (formerly
Standby Vessel)
Emergency Rescue and Recovery Vessel
Owners Association
Emergency Shutdown

FMEA
FPSO
FSO
FSU

Failure Mode and Effect Analysis
Floating Production Storage and Offtake Unit
Floating Storage and Offtake Unit
Floating Storage Unit

GMDSS
GPS

Global Maritime Distress and Safety System
Global (Satellite) Positioning System

HSE
HS(G) 65
HSWA

Health and Safety Executive
Successful Health and Safety Management
Health and Safety at Work Act 1974

IADC
IMCA
IMO
ISM

International Association of Drilling Contractors
International Marine Contractors Association
International Maritime Organisation
International Safety Management Code

JOP

Joint Operating Procedure

ERRVA

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KIS

Kingfisher Information Services

LMIS
LSA

Lloyds Maritime Information Services
Low Specific Activity

MAR
MAH
MCA
MoD

Management and Administration Regulations
Major Accident Hazard
Maritime and Coastguard Agency
Ministry of Defence

NUI
NUMAST

Normally Unattended Installation
National Union of Marine Aviation and Shipping Transport
Officers

OCIMF
OIM
OSV
OSV Code

Oil Companies International Marine Forum
Offshore Installation Manager
Offshore Support Vessel
Guidelines for the Safe Management and Operation of
Offshore Support Vessels
Offshore Technology Report (O)

OTO
PFEER

Prevention of Fire and Explosion and Emergency Response
Regulations SI 743 1995

RIDDOR

Reporting of Injury Death and Dangerous Occurrences
Regulations SI 3136 1995
Rail, Maritime and Transport Union

RMT
SBV
SBV Guidelines

viii

SCR
SPM

Standby Vessel (See ERRV)
Guidelines for the Safe Management and Operation of
Vessels Standing By Offshore Installations
Safety Case Regulations SI 1992/2885
Single Point Mooring

TAV
TLP
TR

Towing Assist Vessel
Tension Leg Platform
Temporary Refuge

UK
UKCS
UKHO
UKOOA

United Kingdom
United Kingdom Contential Shelf
United Kingdom Hydrographic Office
United Kingdom Offshore Operators Association

VHF

Very High Frequency

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1

COLLISION RISK MANAGEMENT SYSTEM
1.1 Introduction
This section is included to give an overview of the systems required for
ship/Installation collision avoidance. It sets avoidance of collisions in overall
context of the Dutyholder’s Health, Safety and Environmental management
systems. For further guidance on Collision Risk Management (CRM) consult
‘Effective Collision Risk Management’ for Offshore Installations, Offshore
Technology Report (OTO) 1999 052, Health and Safety Executive January 2000.

1.2 Responsibilities
Overall responsibility for safe operations within the Safety Zone of any offshore
Installation lies with the Offshore Installation Manager (OIM). The Dutyholder
and the Installation management are responsible for implementing and
maintaining a CRM system appropriate to the Installation and its particular
location. This system should include:
• Management commitment to ongoing and effective CRM
• Clear policies
• Assessment of the probability of collision peculiar to the Installation
and location
• Provision of necessary risk reduction and control measures
• Appropriate procedures and communications for managing attendant vessels
• Ensuring the suitability of attendant vessels and the competence of their
crews, including their ability to implement CRM requirements
• Provision of appropriate equipment and procedures for detecting and
assessing the actions of passing vessels
• Provision of adequate competent Installation personnel with an appropriate
level of marine knowledge
• Provision of appropriate evacuation and rescue procedures and facilities
• An effective reporting and feedback system
• Regular audit and updating of the system
If applicable, the Dutyholder must ensure that any offtake tankers are suitable
for the particular operation and that crews are both adequate and competent for
the peculiarities of the operations at that particular field. Offtake operations
should be covered by field/vessel-specific Joint Operating Procedures (JOPs).
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Masters of passing vessels are responsible for the safe operation of their vessels
and for collision avoidance. They are excluded from Installation Safety Zones
but Dutyholders have limited ability to enforce this.
Masters of attendant vessels should comply with the reasonable instructions of
the OIM when within a Safety Zone. Although they remain responsible for the
safety of their crew, the safe operation of their vessel and for collision
avoidance. The master of an offtake tanker is similarly responsible for the safety
of personnel, for the safe operation of his vessel and for avoiding
contact/collision with the Installation or associated facilities.

1.3 Key Elements
The diagram below is taken from Successful Health and Safety Management
(HS(G)65) whose principles apply equally to CRM.
Policy

Organising

Auditing

Planning &
Implementation

Measuring
Performance

Reviewing
Performance

Figure 1 Key Elements of Successful Health and Safety Management

Therefore the Dutyholder should have in place a CRM system as outlined in the
following paragraphs.

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1.3.1

Management Systems

1.

Include clear corporate policies.

2.

Contain clearly stated and understood goals and objectives including a
hierarchy of measures to achieve those objectives.

3.

Demonstrate senior management commitment to effective CRM.

4.

Define responsibilities for CRM.

5.

Ensure the adequacy and competence of specialist personnel.

6.

Ensure the suitability of any support vessels required to implement CRM.

7.

Ensure that contractors operate to the same standards.

8.

Contain procedures for detecting, assessing and managing any potential
collision appropriate to the risks of the particular Installation and location.

9.

Audited at regular and appropriate intervals with independent feedback to
senior management on the effectiveness of the system.

1.3.2

Personnel Policies and Procedures

1.

Clearly understood responsibilities for implementing and maintaining
the system.

2.

Clearly stated policies.

3.

A safety organisation such that management have access to competent
persons with the necessary expertise.

4.

Means of ensuring the competency of personnel involved in CRM
(including Installation, attendant vessel and other contractor personnel).

5.

Means of ensuring that when personnel change, the same level of
competency and knowledge continues.

1.3.3

Attendant Vessel (Including Offtake Tanker) Procedures

1.

Procedures for ensuring that the vessels and their critical systems are
fit-for-purpose.

2.

Means of ensuring that vessels which operate in close proximity to
Installations are manned by sufficient and competent persons.

3.

A culture which reinforces these procedures by maintaining
communications and follows up on incidents and near misses.

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1.3.4
1.

Means of detecting, anticipating and assessing a hazardous situation that are
appropriate to the level of risk.

2.

Adequate communications to deal with the situation and to mitigate
those risks.

3.

Well practiced procedures for dealing with the consequences and providing
a good prospect of rescue and recovery.

4.

Any required detection/assessment systems maintained as safety critical.

1.3.5

4

Passing Vessel Policy and Procedures

Risk Assessment and Performance Measurement

1.

Structured identification and assessment of hazards.

2.

Appropriate risk reduction and control measures.

3.

A mean of monitoring performance against those standards.

4.

A system for recording incidents and near misses, identifying trends and
feeding back to the CRM system.

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Management
Commitment
Clear Policies

Risk Assessment

Installation Design,
Impact Resistance
Promulgation of
Location
Collision Avoidance
Procedures
Support Vessel
Selection Management
Contingency Plans
Including Evacuation,
Escape and
Recovery (EER)
Consequences Planning

Reporting, Implementation,
Measuring and Reviewing
Performance

Audit

Figure 2 Collision Risk Management – Summary Flowchart
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Assess Collision
Probability

Attendant Vessels
Incuding Offtake
Tankers

Clear Policies

Passing Vessels

Installation
Vulnerability

Installation
Location

Vessel Suitability
and Manning

Promulgation
and Charting

Crew Competence

Detection and
Communications

Installation Marine
Knowledge

Procedures and
Checklists

Assessment of
Threat

Contingency
Plans

Near Miss
Reporting

Analysis and
Follow-up

Figure 3 Collision Avoidance Flowchart

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Reducing the
Probability

Passing traffic and collision frequency assessed
Location of Installation well promulgated
Responsibility for surveillance clearly understood
Detection and communications equipment suitable, crew
trained, proper maintenance
Regular exercises and drills

Detection and
Assessment

Detection range and Closest Point of Approach (CPA)
threshold agreed
Blind sectors covered during close standby
Time to CPA for first alert
24-hour communications with control room/OIM
Communications with approaching vessel
Times to CPA for subsequent alerts

Pre-planned
Actions

Support vessel communications/actions
Installation actions/musters
Identify point of impact and useable
Low Specific Activity (LSA)
Short notice response/evacuation
Collect and record evidence

Follow-up

EER procedures including vessel crews
Communications
Reporting

Warning off
Near Miss
Safety Zone infringement
Incident/collision
Prosecution
Closeout

Report to Installation/vessel personnel and industry

Figure 4 Collision Avoidance Procedures – Passing Vessels
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2

BACKGROUND AND OVERVIEW
2.1 Introduction
From the Health and Safety Executive Collision Risk Database (1997)
(OTO 1999 080), it is apparent that some 500 ships have collided with offshore
Installations in the UK sector between 1975 and 2000. Over 96% of the
collisions have involved attendant vessels (those with legitimate business at the
Installation). The number of near misses is likely to have been considerably
higher. About 20% of the reported incidents caused moderate or severe damage.
To date in the UK sector there have been no collisions which caused
catastrophic damage or loss of life. However, worldwide there have been a
number of collisions which caused total loss of the Installation.
The database prompted the Health and Safety Executive to commission a study
‘Effective Collision Risk Management’ (OTO 1999 052) which reviewed and
summarised collision data for the United Kingdom Continental Shelf (UKCS).
By its nature the offshore oil and gas industry requires marine support, hence it
is necessary for vessels to approach and work in close proximity to the
Installation. The increasing use of floating production/storage systems and
tanker offtake, introduces close proximity work with large vessels carrying
hazardous cargoes. Many of the UK’s oil and gas fields are in busy traffic areas
and virtually all experience some passing marine traffic, albeit rare in more
remote regions. Under the Safety Case Regulations (SCR), ship collision is
considered a Major Accident Hazard (MAH).

2.2 Probability of Collision
Risk can be defined as the product of the likelihood of experiencing a collision
and the potential consequences. The risk is then managed to acceptable levels,
under the As Low As Reasonably Practical (ALARP) principle, by mitigation
and control measures, including prevention, detection and emergency response.
This document does not deal in detail with the consequences. It concentrates on
best practice in reducing the probability of a vessel/Installation collisions.
In general, a vessel/Istallation collision is reasonably foreseeable. Historically,
the probability of an attendant vessel colliding with the Installation is nearly two
orders of magnitude greater than a passing vessel collision. The impact energy
from an attendant vessel collision is likely to be low, except in the case of a
shuttle tanker/Floating Production Storage and Offtake (FPSO) unit collision.
Although the probability of a passing vessel collision is low, the impact energy
could be high. In all cases, catastrophic consequences in terms of loss of life,
environmental impact and business risk are reasonably foreseeable.
For attendant vessels, probability of collision increases with the number of
Installation visits, by holding station in close proximity and for example
weather side working.

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Controls include:
• Minimising the number of visits
• Adjusting working and standby locations
• Vessel vetting
• Effective procedures
Human factors are undoubtedly relevant when working very close to
an Installation.
For passing vessels the Installation management has fewer options. The risks
can be assessed according to volume and type of marine traffic. When a
relatively high probability of collision exists, then risk reduction measures will
concentrate on promulgating the location widely in the shipping community,
on effective detection, intervention by the emergency rescue and response
provider or vessel and on good communications. Awareness, procedures and
effective escape and rescue provisions will mitigate the consequences.
Appropriate siting and protection of vulnerable areas such as risers and
accommodation and resilience of the overall structure can also mitigate
the effects.

2.3 Passing Vessels
Less than 4% of the collisions reported in the vessel/Installation Collision Risk
Database were caused by passing vessels (vessels bound somewhere else). The
vessels involved were generally small, principally fishing vessels, although
some collisions caused severe damage. A passing vessel is likely to be travelling
at sufficient speed for impact energy to be significant, even if the vessel is
relatively small. The incidence of passing vessel collisions shows no discernable
trends, occurring spasmodically throughout the period of the survey. The study
estimated that a passing vessel collision was likely to occur in the UK sector
about once every two years.
As shipping on passage is usually outside the influence of Installation
management, effective controls are very limited. However, collision is reasonably
foreseeable with the possibility of catastrophic loss. SCRs and PFEER (refer to
Addendum 8) require the Dutyholder to take reasonable steps to manage the risk.
The Dutyholder and the Installation management are responsible for providing an
effective system for detecting and responding to the threat from an errant vessel.
In all but a few cases, detection is carried out by the ERRV and its crew reporting
to the OIM. That vessel and its personnel must therefore be given clear guidance
on what is expected of them. They must have the capability, equipment,
knowledge and competence to meet those expectations.

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2.4 Attendant Vessels
The database shows that over 96% of vessel/Installation collisions in the UK
sector involve vessels with legitimate business there. Although the majority are
low energy collisions, attendant vessels caused about 10 times more
moderate/severe collisions than passing vessels. Over the period of the study,
frequency of such collisions has reduced. This may be due to improved marine
expertise, better control systems and better understanding of the causes.
The authors of the study suggested that improvements may be as a result of an
effective management system.
The report estimates that, based upon 1997 frequencies, 30 of the approximately
200 Installations in the UK sector were likely to experience a collision each
year. Although 83% of attendant vessel collisions caused only minor damage,
3% had severe consequences. With the steady progress to larger and more
powerful support vessels, the potential impact energy and resultant seriousness
of the collision increases.

2.5 Offtake Tankers
Improvements in offshore technology has accelerated the development of
marginal offshore oil fields in North West Europe and worldwide. Much of this
has been made possible by floating production systems. Although some are
connected to pipelines, economics tend to favour tanker offtake. Most involve
marginal fields, but some large assets with fixed Installations have used tanker
offtake since inception.
In the North Sea, offshore crude oil offtake has increased from 36% of total
production in 1995 to 47% in 2000. United Kingdom Offshore Operators
Association (UKOOA) estimate United Kingdom (UK) floating production and
offtake at around 1.5 million bpd in 2010 and 1.0 million bpd in 2020. Some
240 developments are likely to come forward in the UK sector for approval in
the next 25 years, the majority of which will use this method for exporting
produced crude oil.
Tanker offtake involves relatively large vessels, carrying hazardous cargo,
manoeuvring in a congested oil field. Loading buoys are used in some fields.
In others the offtake tanker moors to another floating vessel and is connected to
it by hose. Thereafter, it must maintain station and alignment relative to the
other vessel during the cargo transfer operation. Hence, the potential for
collision occurs during approach, cargo transfer and departure. A high standard
of vigilance is required throughout these operations. Some operations use a
towing vessel to assist with mooring and stationkeeping. Whilst this reduces the
probability of collision once in the towing mode, it does introduce a third vessel
into the manoeuvres. Overall, the worst case consequences of a collision can be
catastrophic in terms of loss of life, environmental damage and business risk.

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IMCA Report M150 on Shuttle Tanker Collisions published in February 1999
reviews the causes and estimates frequency of offtaker collisions with loading
buoys and with storage vessels. It differentiates between Dynamic Positioning
(DP) and non-DP offtakers. It notes a significant proportion of under-reporting,
but that reporting improves after an incident. The non-DP data set is much smaller
than the DP set.
The main points are:
• 156 incidents were analysed over the period from 1979 to 1998
• Of these 12 resulted in collision between the tanker and loading point
• The 12 collisions involved DP offtakers, but the non-DP set includes several
instances of very high hawser tension (effectively a near miss)
• Estimated frequency of major incidents
• DP offtakers once in 20,000 offtake hours
• Non-DP once in 5,400 offtake hours
• Frequency of other incidents, including non-critical loss of position:
– DP offtakers once in 2000 offtake hours
– Non-DP once in 735 offtake hours
The report estimates that a typical DP offtaker could be involved in a loading
point collision once in about ten years. Allowing for under-reporting, it also
estimates that the typical tanker could be involved in a stationkeeping incident
about 7 times per year.
Principle causes of the collisions are grouped as:
• Position references faults
• Main engine problems
• DP operator errors
Collisions in offtake operations are foreseeable, hence Dutyholders must use
their influence to manage the operation. Controls will include management
commitment, operating practices and procedures, weather thresholds, vessel
selection, Installation and vessel personnel competence, non-use of certain
vessels and cessation of part or all the operation.

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2.6 Contingency Planning and Procedures
2.6.1

General

Each Installation will have emergency procedures for actions in the case of a
major accident. This guide is concerned principally with avoiding
vessel/Installation collisions and with the immediate actions following of any
such collision. Emergency procedures will contain actions in case of a vessel
collision and should reflect the very short notice which may be available for
actions and evacuation.
Contingency procedures for vessel collisions are essential and should be
activated from the time that a threat of collision, from either an attendant or
passing vessel, is detected. Effective procedures must be in place to ensure that
the threat is detected as early as possible and that the resultant actions follow a
well thought through and exercised path.
It is essential that collision avoidance contingency plans and procedures are
exercised frequently and regularly. Regular and relief support vessels likely to
be on location must be involved in these exercises. In areas where the
probability of a collision is low, exercises are just as important as in high
probability areas. Both Installation and support vessel personnel will have to
respond rapidly to an unusual event.
2.6.2

Passing Vessels

Contingency plans should include:
• Responsibilities for detection, communication and assessment of the threat
• Time to possible impact for alerting the Installation to the threat
• Time to possible impact for initiating shutdown of plant and evacuation
• The decision points and actions for a controlled shutdown and evacuation in
the case of drifting vessel threat
• Actions of attendant vessel(s) in case of imminent threat
• Different actions and timescales depending on whether the vessel is under
power or drifting
Simple and concise procedures should include the distance/time at which a
vessel is identified as a threat, the time at which the Installation is alerted and
the process whereby the OIM and attendant vessel master monitor and assess
the threat. Responsibilities of key personnel should be clearly identified.

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2.6.3

Attendant Vessels

An attendant vessel collision may impart sufficient energy to cause severe
damage to the structure of the Installation and to itself. Hence contingency plans
should consider:
• Attendant vessel loss of propulsion or control
• Attendant vessel colliding with Installation at high speed
• Attendant vessel adrift in close proximity
• Rapid evacuation of the Installation personnel
• Rescue of the attendant vessel crew, if needed
• Fire and/or explosion
• Shutting down production and/or pipelines
2.6.4

Offtake Tankers

Each field/Installation OIM should have available a standard contingency plan
which can be adapted to particular offtakers in consultation with the master.
In amplification of the attendant vessels procedures above, it should address:
• Significant offtaker propulsion or control problem during approach
• Loss of position control at any time during the transfer operation
• Offtaker adrift, out of control, in the field
• Loss of or high mooring tension
• Collision or close quarters event between offtaker and FPSO
• Abort parameters
• Significant offtaker propulsion or control problem during departure
• Fire and/or explosion
• Support vessel casualty
Offtaker specific plans should be held by both units and confirmed by checklist
before each operation. Elements of the plan should be exercised periodically
with dedicated offtakers.

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2.6.5

Evacuation Procedures

The evacuation plan will be part of the Installation’s emergency procedures.
This document does not attempt to cover the subject comprehensively, merely to
highlight special factors in dealing with the immediate actions required
following a collision:
• Rapid decisions on muster points away from the likely point of impact
• Using lifeboats/liferafts away from the point of collision
• Use of helicopters if available
• Making sure that lifejackets and/or immersion suits are readily available to
personnel at all times
• Evacuating enclosed spaces (including Temporary Refuge (TR) and control
rooms) rapidly, using alternative muster points on deck
• Rescuing a number of individuals from the water
Also refer to:
• Standby Vessel (SBV) Operating Guidelines Appendix 2 on evacuations and
escape planning
• Evacuation, Escape and Rescue (EER) guidance in the SCR (SI 1992/2885)
• Management of Emergency Response for Offshore Installations (UKOOA)

2.7 Incident and Near Miss Reporting
The studies referenced above accept a degree of under-reporting of incidents.
Neither contain systematic reporting of near misses although some are included.
Some models predict the number of near misses to be one to two orders of
magnitude greater than reported incidents. Hence, the potential for
vessel/Installation collisions in the UK sector is probably much greater than the
500 or so collisions reported for the North Sea oil and gas province in the 25-year
period reviewed.
Incidents in this context are easy to define eg a collision which actually
occurred. A near miss is more subjective, generally circumstances which could
escalate into an incident. Broad definitions are given in the Glossary of Terms in
Addendum 1.
Risk assessment techniques can predict the likely collision frequency but a
structured incident and near miss reporting system will identify trends and allow
further controls to be implemented. There is no sector-wide system in place but
Health and Safety Executive collate both collision reports and available near
miss data as part of the vessel/Installation Collision Risk Database.

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Near miss reporting systems currently in use include:
• Health and Safety Executive Safety Zone Infringement Report format
• Emergency Rescue and Recovery Vessel Owners Association (ERRVA)
‘Warning Off’ Reports
The reporting and analysis system should be simple to use, be accepted as useful
by personnel rather than a chore. It shall also provide feedback to organisations,
management and front-line personnel and have demonstrated management
support and be non-punitive. Hence on the latter point, published analyses
should be anonymous. The regulatory agency’s approach to such a system is
critical to its success but vessel and Installation operators must demonstrate
similar commitment.

2.8 Reporting and Follow-up
Most passing vessel collisions are reported comprehensively and should
continue to be. Reporting of attendant vessel collisions is probably less
complete, particularly when there is little or no damage. Similarly, there are
doubts over the completeness of offtaker incident reports.
In order to properly assess the probability of collision and to put effective
controls in place, it is essential that as many incidents, near misses and other
close quarters situation, are reported comprehensively and accurately. Various
reporting formats are in use, some examples are given in Addendum 7.
Responsibilities for reporting and following up any near misses which
threaten their Installation(s), should be set out in Dutyholders’ collision
avoidance procedures. When near misses involve attendant vessels and offtake
tankers, then the Dutyholder’s own vessel selection and operating procedures
should be reviewed. The Dutyholder should also review the incident with the
vessel operator.
In the case of passing vessel incidents, the Dutyholder should take the initiative,
but regulatory agency’s (Health and Safety Executive, Department of Industry
(DTI) and Maritime and Coastguard Agency (MCA)) assistance will be required
to follow up with offenders. At the least Dutyholder’s concerns should be
conveyed to the vessel and its operating management. In extreme cases and for
Safety Zone infringements, prosecution may be possible, but a high standard of
proof is required (refer to the Safety Zone Infringement Report (Addendum 7
for guidance).
Whenever lessons are learnt as a result of investigation and follow-up, these
should be shared with Installation and vessel personnel, owners, other operators
and the industry generally.
Periodically, Dutyholders should use available data to assess and update their
collision avoidance procedures.

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2.9 Auditing
All personnel from management through to workers on the Installation need to
have confidence that the CRM system and collision avoidance procedures are
effective. Hence, audits at appropriate intervals are essential to provide
assurance that they are working as intended.
Audits can be carried out by operator’s personnel familiar with but not involved
in the operation. Alternatively, outside Auditors can be chosen for their
specialist knowledge. In either case it is essential that the Auditor is sufficiently
independent to take an objective view and that he/she reports directly to a senior
level of management.
Templates for system audits are given later in Addendum 3. In broad terms
those audits should review the following:
• Demonstrated management commitment to CRM including ‘sign-off’ at
appropriate levels
• Identification of the level of risk of vessel collisions
• Mitigation and control measures, to reduce the probability to ALARP
• Operating practices designed to minimise the frequency of collisions
• Effective procedures to ensure the suitability of attendant vessels and the
competence of their crews
• Means of detecting and communicating with an approaching vessel and means
of alerting the Installation personnel to the threat (refer to Addendum 2)
• Appropriate facilities and procedures in place to evacuate and rescue
Installation personnel
• Contingency plans which address the risks to and rescue of vessel personnel

2.10 Performance Standards
Dutyholders must set standards for collision avoidance and regularly measure
performance against them. Data may include:
• Frequency at which all term chartered vessels are audited
• Percentage of spot vessels inspected
• Number of reported near misses
• Number of ‘warning off’ calls by ERRVs

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Negative measures of performance, which should also be assessed, include:
• Number of collision incidents
• Number of Safety Zone infringements
• Number of stationkeeping incidents involving offtake tankers
Examples of performance standard formats include:
• UKOOA Tandem Loading Guidelines, Background Report – Shuttle Tankers
• UKOOA Tandem Loading Guidelines, Towing Assist Vessel (TAVs)
Volume 2 Section 6
• UKOOA Health and Safety Management Systems Interfacing

3

PASSING VESSELS
3.1 Introduction
As mentioned above in Paragraph 2.3, incidence of passing vessel collisions in
the UK sector is very low. To date no passing vessel collision on UKCS has
resulted in the total loss of a vessel or an offshore Installation, although some
have come close and catastrophic collisions involving passing vessels have been
experienced worldwide. Passing vessel collisions are a MAH and must be
addressed accordingly. The operator should have a system in place for
managing these risks.
Design loads which offshore Installations can absorb, are such that an
Installation may not survive impact from anything of greater mass than a large
fishing vessel or small coasting vessel at operating speed. But apart from
choosing the location, the operator has little or no influence over the potential
for passing vessel collisions (refer to Addendum 10).
The primary causes of collision with offshore Installations include:
• Poor watchkeeping onboard the approaching vessel
• Ignorance of the Installation’s presence due to it being new, due to poor
visibility and/or poor radar watchkeeping
• Setting a course too close to the Installation due to ignorance or
irresponsibility

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Secondary causes or contributory factors may include:
• Vessel watchkeeper failing to detect the Installation due to inattention,
distraction or simply not expecting a structure in that area
• Vessel control failure at a critical point
• Vessel drifting out of control
• ERRV failing to detect an approaching vessel due to overload, distraction,
poor visibility, obstructed radar or visual view
• Unsuitability or inadequacy
(refer to Addendum 2)

of

ERRV

equipment

or

manning

• ERRV failure or inability to contact an approaching vessel because it is not
keeping a proper visual or radio watch
• Failure of approaching vessel to take avoiding action in sufficient time
Adverse weather can increase the probability of most of the above.
A common theme is poor watchkeeping, particularly on the approaching vessel.

3.2 Assessing the Potential for Collision
The probability of a passing vessel collision is most readily assessed at the
design stage, when there is opportunity to influence the Installation’s location.
This can be done using appropriate shipping traffic databases and
vessel/Installation collision models. The traffic database contains analysis of
traffic levels at the location. The collision model uses this, in part, to determine
the likelihood of experiencing a collision (refer to Addendum 9). In critical
areas site-specific radar surveys may be needed to establish accurate traffic
patterns and levels. Local users such as ferry operators, regular shipping lines
and fishing organisations can usefully be consulted at this stage.
Assessment of traffic is a required part of the Application for Consent to Locate
submitted to Ports Division of the Department of Transport, Local Government
and the Regions (DTLR). This applies equally to fixed and mobile Installations.
Factors which affect the probability of collision and which need to be
assessed include:
• Traffic density close to the target location
• Proximity to ferry routes, traffic separation schemes, deep water routes
and/or constricted navigation channels
• Other types of shipping passing nearby
• Size, speed and peculiarities of passing traffic
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• Fishing activity, both en route to fishing grounds and fishing in the area
• Estimates of levels of competence among crews of regular traffic
Additionally, in busy areas, the authorities may require that potential
modification to traffic routes and any resultant increase in probability of
vessel/vessel collision be assessed.
It is essential to identify regular traffic passing through the area and to consult
with their representatives. These regular users should then be informed of
subsequent developments.
Although traffic density has a significant effect on the probability of collision,
other relevant factors are listed below:
• In the approaches to a busy port or in busy channels, navigators will
normally be on a high state of alert and once aware of the Installation will
take avoiding action, albeit at close quarters. This makes good
communications essential so as to identify those vessels which have or have
not detected the Installation
• Fixed Installations in low to medium traffic areas will become known and
even used as navigation reference points. Hence, navigators will be aware of
the Installation’s presence and take avoiding action. However, this can
increase the probability of collision if the Installation is used as a way point
and/or vessel navigation equipment is slightly inaccurate
• The existence and location of mobile units in open waters must be
promulgated widely, even if traffic density is low. There is a possibility of a
vessel setting a course close to the location, without knowledge of the
Installation’s presence. As a result navigators will not be expecting
obstructions and may approach at a lower alert state, with only occasional
radar and visual lookout
The primary concern is surface collisions with passing vessels. However,
a few collisions between submerged submarines and structures have occurred.
The Ports Division and Ministry of Defence (MoD) may require additional
promulgation and fitting of submarine beacons in areas where
submarine operate.
Fishing vessels can foul their gear on underwater facilities in oil and gas fields.
In extreme cases this hazards the lives of the fishing vessel crew and can
damage the facilities. Good communications with representative fishing
organisations and effective promulgation will improve awareness and may
lower the frequency of fishing vessel incidents.

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3.3 Minimising the Probability of Collision
3.3.1

Design

During design, it may be possible to adjust the location, it may also be possible
to take advantage of natural features such as shallow water for protection.
In some cases DTLR may require adjustment.
The requirements for detection of and communication with approaching vessel
should be addressed at the design stage. Effective marking of the Installation’s
presence is essential. Depending upon the level of risk, this may include
enhanced lighting, high visibility paint, radar reflectors, radar responders and
Automatic Identification of Ships (AIS) (refer to Addendum 2).
3.3.2

Promulgation (refer to Addendum 2)

The presence of an Installation must be promulgated to the marine industries,
in advance of emplacement and continually once on location.
Advance Promulgation
The following may be used as appropriate to local conditions:
• Consultation with and advice to identified generators of traffic such as ferry
operators, regular shipping lines and local fishing organisations
• Provisional notices to mariners via United Kingdom Hydrographic
Office (UKHO)
• Navigation warnings by radio and NAVTEX again via UKHO
• Rig move warnings for mobile Installations
• Kingfisher Information Services (KIS) fortnightly bulletins to the fishing
industry and inputs to fish plotters
After Emplacement
Some or all of the following should be used depending upon local conditions
and risk assessment:
• Regular repeats of navigation warnings
• Further notices to mariners
• Marking on navigation charts, paper and electronic
• Fish plotter databases, including FishSafe and similar systems designed to
alert fishermen to underwater structures
• Repeat advices to regular users
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• Dedicated guard vessels on location for short-term emplacements
• ‘All Ships Safety Call’ by Digital Selective Calling (DSC) from Installation
or support vessel followed by ‘Securite’ messages on Very High Frequency
(VHF) radio
• AIS or Racon
Note:

If a mobile Installation is drilling an exploratory well in a congested or
sensitive area, radar traffic surveys can be carried out from the unit or
support vessel. The data collected will be useful in planning for any
future developments.

3.4 Collision Avoidance Measures
3.4.1

Detection and Communications

Detection
Manned Installations should have a means of detecting approaching vessels
which is appropriate to the traffic density, the probability of collision and
potential consequences. The detection method will normally involve either
Installation personnel or support vessel personnel.
Addendum 2 offers guidance on possible levels of detection related to the type
of Installation, the relative openness of the location and traffic density.
Active detection of vessels approaching Normally Unattended Installations
(NUIs) is impractical unless within the radar coverage of a field support vessel
or radar system. The hazards which passing vessel collisions pose to such
Installations are environmental and commercial. Any such collision also
presents hazards to the vessel and to its crew. The Dutyholder must have a
considered policy in place for when the NUI is manned which is based upon the
probability of collision and the potential consequences and which ensures that
risks to personnel are consistent with ALARP.
Detection systems may include:
• ERRV radar and visual surveillance
• Installation/field radar surveillance
• Radar surveillance from shore or other facility
• Installation visual lookout – probably limited to marine vessels acting as
Installations
• AIS combined with radar in high-density traffic areas

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Radar detection has the advantage that the approaching vessel’s movements can
be plotted and accurately assessed. On the ERRV the radar and visual data is
interpreted by skilled marine personnel. Such personnel may not be present on
an Installation. Tracks of vessels relevant to the Installation can be determined
by integrating radar data with an accurate positioning system such as Global
Positioning System (GPS).
The disadvantages of ERRV detection are that certain sectors may be masked by
the Installation itself (refer to SBV Guidelines Section 3.6.3 on Radar Watch
During Close Standby). If the ERRV covers more than one Installation,
procedures and responsibility for radar surveillance of the approaches to all the
Installations must be clearly understood on vessel and Installations.
Installation mounted radar systems have the advantage of a wider horizon and a
steady platform. Modern systems can transmit the data in real time to the SBV
hence, removing the need for marine specialists on the Installation. Refer to
Addendum 2 for discussion on appropriate detection systems.
Note:

With the implementation of AIS, it will be possible to identify
approaching vessels within VHF range, whether they can be seen
visually or not; they could then be contacted by radio via Global
Maritime Distress and Safety System (GMDSS) procedures. Vessels of
300 GRT and upwards should be equipped with AIS by 2006. Full
implementation is due in 2008. Dutyholders for Installations in
high-density/high-risk areas may consider installing such detection
equipment as more and more vessels become equipped (refer to
Addendum 2).

In all cases the operator should ensure that detection methods are appropriate to
the probability of collision and potential consequences for the location and the
time required for effective response. They should also ensure that surveillance
data is interpreted by skilled marine personnel (also refer to SBV Guidelines
Section 3.2 on Errant Vessels.)
Communications
Whatever detection method is used, the operator of that system
(normally the ERRV master) must have access to communications equipment
and procedures which:
• Enable him to contact an approaching vessel by radio via GMDSS
procedures including use of VHF calling channels (see note above on AIS)
• Have back-up communications equipment with which to attract the attention
of an approaching vessel; these may include sirens, searchlights, signalling
lamps, maroons and rockets

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• Be able to communicate with the OIM and hence alert him of the
approaching threat
• Contact other vessels in the area to alert them to the threat and/or
seek assistance
3.4.2

Manning and Equipment

Manning
Both the Installation and the vessel(s) with responsibility for detecting
approaching vessels should be competently manned to carry out their duties.
If detection and communication is the responsibility of a support vessel,
then sufficient watchkeepers with appropriate, verified skills and competence
should be provided. The Dutyholder must be satisfied of this, whether or not he
is directly responsible for providing the vessel (refer to Offshore Support Vessel
(OSV) Code Appendices 2 and 3).
If detection, assessment and subsequent communication are the responsibility of
Installation personnel, then the Installation should be manned accordingly with
sufficient personnel, having the appropriate skills and knowledge, on duty
continuously.
Except in congested waters, the probability of collision is low. None the less
responsibilities in such an event must be clearly understood by both Installation
and support vessel personnel, regardless of the probability. Management must
ensure that responsible personnel are constantly alert. Procedures and
contingency plans should be exercised regularly to achieve this.
Equipment
Dutyholders should ensure that specialist equipment appropriate to the
probability of collision and potential consequences is provided and maintained
correctly. This may include:
• Radar surveillance systems of appropriate range and definition
• Radar beacons where indicated
• Identification systems such as AIS
• Communications systems, not only between Installations and attendant
vessels but also for communicating with approaching vessels by VHF radio
and in accordance with GMDSS procedures

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3.4.3

Assessing the Threat

In the case of a potential collision, the OIM will have to assess many things in a
short time, considerations will include:
• Speed of approach and time to CPA/collision?
• Time required by Installation to take action?
• Is vessel following a normal route?
• Is vessel apparently under power or drifting?
• If drifting, is it under control?
• Have communications been established with the vessel?
• What other options are available for contact?
• What is the size of the vessel and hence potential impact energy?
• Are other marine traffic or Installations in the area likely to affect vessel’s
course and actions?
• Weather conditions, their potential effects on the vessel’s actions and on
any evacuation?
• Are there other vessels that may assist?
• Where on the Installation is collision likely, is this a particularly
vulnerable point?
• At what point should the Installation consider shutting down vulnerable
operations?
• At what point should an evacuation commence?
Refer to SBV Guidelines in Addendum 4 and 5 of this document – Collision
Avoidance Strategy flowchart and notes on contingency planning below.
3.4.4

Contingency Plans

Each Installation should have in place succinct procedures for action when a
passing vessel poses a collision risk. Contingency planning should include:
• Responsibilities for detection, communication and assessment of the threat
• Time to possible impact for alerting the Installation to the threat
• Time to possible impact for initiating shutdown of plant and evacuation

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• The decision points and actions for a controlled shutdown and evacuation in
the case of drifting vessel threat
• Actions of attendant vessel(s) in case of imminent threat
• Estimating the point of impact for given wind and tide conditions and it’s
effects on the evacuation plan
Refer to Paragraph 2.6.
Note:

The plan needs to differentiate between actions required in case of a
powered vessel threat, when time is likely to be extremely short
and a drifting vessel when more time is available for considered action.

Actions of attendant vessels should not present hazards to the lives of crews,
increase the probability of collision by modifying the behaviour of the
approaching vessel or impair the attendant vessel’s ability to rescue personnel if
the collision should occur.
The Dutyholder should set parameters for implementing various levels of
response appropriate to the location, Installation and local traffic patterns.
The parameters for activating contingency plans may include:
• Vessel on a steady course with CPA <X.X NM expected to pass through
Installation Safety Zone in XX minutes
• Vessel due to pass through Safety Zone in XX minutes, has failed to
communicate or failed to respond to attendant vessel communications
• Vessel on apparent collision course due to impact Installation within
XX minutes
Dutyholder should determine the values (XX) as part of the Safety Case
risk assessment.
Refer also to the EER assessment guidance in the SCRs (SI 1992/2885)
and PFEER.

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3.4.5

Follow-up

Every incident or potential incident should be reported and followed up.
Only by so doing can the potential for collision can be properly assessed (refer
to Paragraph 2.8). In all cases, lessons and outcome should be fed back to the
Installation and vessel personnel and to respective managements.

4

ATTENDANT VESSELS
4.1 Introduction
Cargo operations account for the largest number of recorded infield vessel
collisions in the UK sector, followed by standby vessels, anchor handlers,
diving vessels, and a few survey vessel incidents. Collisions involving the last
two groups were almost exclusively caused by mechanical failure.
Collisions between construction/accommodation vessels and Installations are
almost unknown but are none the less foreseeable. They would probably result
from mooring/mechanical failure or stress of weather.
These results are consistent with exposure. Supply vessels are required to work
very close to Installations in marginal weather conditions as there is an increase
in recorded incidents in late autumn and winter. EERVs although constantly in
the vicinity of UK Installations, only make a close approach to cover overside
working. Collision incidents increases during the summer maintenance season
when more close standby is required. Although diving vessels set up very close
to an Installation, they are less frequent visitors, have more sophisticated control
systems and skilled Bridge Teams familiar with the risks.
Among the more obvious and frequently reported causes of attendant vessel
collisions are:
• Equipment failure
• Personnel misjudgement
• Weather (which includes environmental factors such as wind, tide, current
and wave drift and may also be considered to be ‘misjudgement’)
The Health and Safety Executive Report on Effective Collision Risk
Management (OTO 1999 052), breaks down reported causes by vessel and
operation at time of impact and Section 6.3 of the report should be consulted for
further details. In very broad terms it shows about 40% misjudgement, 30%
equipment failure, 10% weather and 20% unspecified causes. Misjudgement is
significant during close support work by supply vessels.

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4.2 Assessing the Potential for Collision
The potential for attendant vessel collision is related to the working area,
weather and tidal conditions, frequency of vessel visits and the operating culture
in relation to marine activities. These should be examined in greater or lesser
detail by means of risk assessment which includes marine expertise (ideally the
vessel operators).
The potential consequences to the Installation of a collision vary with the speed,
size and type of vessel. The point of contact on the vessel is also a factor.
Although this document does not address consequences of collision in detail
following are some considerations:
• A small supply or standby vessel which experiences a slow sideways
collision imparts low impact energy at the point of contact
• A large supply vessel at near full speed colliding bow on would cause
severe damage
• Anchor handlers are very stiff in the region of the stern roller and can cause
severe local damage even at relatively low speed
Among the underlying causes of attendant vessel collisions are:
• Failure to ensure adequate, competent and knowledgeable crew on both
vessel and Installation
• Lack of marine understanding by Installation personnel eg calling in a supply
vessel in marginal conditions
• Excessive numbers of Installation visits due to poor planning
• Excessive time ‘standing by’ for the next lift or remaining connected to a
bulk hose
• Standby vessels ‘dodging’ too close to or upwind of the Installation
• Steering directly for the Installation on approach
• Poor relationships/communications between vessel and Installation which
fails to promote good planning and early warning of developing problems
• Not consulting the master or not trusting his judgement
• Inadequate bridge manning and hence failure to anticipate a developing
problem when the senior watchkeeper is distracted by other tasks
• Bridge personnel distracted by other tasks eg communications, paperwork
• Not adhering to procedures/guidelines

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• Poorly sited or inadequate reach cranes
• Weather side working in marginal conditions
• Bulk hoses of the wrong length
• Lack of appreciation, by vessel personnel, of the dynamics of working with
floating Installations, particularly those free to rotate
• Lack of understanding of thrusters/wash interaction when working with
powered floating Installations
• Selection of vessels unsuitable for the task
• Multi role vessels with inadequate power or manoeuvrability
• Vessel crew fatigue, often a consequence of inadequate work planning
Any of the above can be exacerbated by an unexpected equipment failure or
worsening weather. As these causes are foreseeable, they should be
planned against.
At no time should the vessel master or officers be under any pressure or
obligation, either direct or indirect, to commence or continue with operations
where the safety of personnel, the vessel or the Installation is prejudiced.
No operation should be undertaken without prior assessment of the risks.
This may be a toolbox talk using checklists for routine operations or a more
formal risk assessment for unusual or exceptional operations. In all cases key
personnel who will be carrying out the task must be involved in the risk
assessment (refer to OSV Code Section 9.6 Weather Side Working Risk
Assessments).

4.3 Minimising the Probability of Collision
4.3.1

Vessel Suitability and Vetting

The Dutyholder must be satisfied that vessels visiting and/or working at their
Installations are suitable for the task. It is the owner’s responsibility to provide a
vessel which is fit-for-purpose, given an accurate scope of work.
Support vessels must be capable of operating at the location, in the worst
expected weather and tidal conditions, be suitable for the planned work and
the peculiarities of the Installation. For example, a large modern supply vessel
may be more suitable due to higher operating standards and power,
despite greater potential impact energy. A small, underpowered and poorly
manned vessel may be less suitable due to the greater potential for loss of
control. Other considerations include:

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• Strong tides
• Heavy passing traffic
• Excessive overhang
• Freedom of the Installation to weathervane
• Dynamic positioning and thruster interaction between vessel and Installation
• Working alongside ship-shape Installations
• Short crane reach
• Cranes limited to one side
When Dutyholders do not directly charter support vessels, they must still satisfy
themselves as to vessel suitability and capability. They should agree vetting
procedures with the operator or service company responsible for providing the
vessels. Refer to the Guidance for Health and Safety Management Systems
Interfacing issued by Step Change in Safety.
Term chartered vessels should be inspected on behalf of the management by a
Marine Specialist, familiar with the workscope. Pool vessels should have at
least an in-date UKOOA Common Marine Inspection Document (CMID),
backed up by spot inspections. For spot chartered vessels, the Dutyholder must
make a judgement on the necessity of a specific fitness-for-purpose inspection
based on the vessel’s specification, plus the vessel and its owners reputation in
the area. If in doubt the vessel should be inspected, its capability and the crew’s
competence verified.
In general vessels should operate in line with the UKOOA OSV Code and/or the
Standby Vessel Operations and Survey Guidelines. Examples of industry
standard codes and inspection/audit formats are given in the Addendum 4.
The Dutyholder should also ensure that the vessel and its crew:
• Understand what is expected of it
• Hold the field/Installation data card (OSV Code Appendix 8 and Appendix E)
• Holds vessel operator procedures relevant to the particular operation
• Hold and familiar with appropriate UKOOA guidelines mentioned above
• Hold any field or operator-specific information
• Aware of and in possession of any specific CRM procedures for the location

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4.3.2

Manning

All field vessels must be manned by marine crews adequate and competent for:
• The type of vessel
• The type of operation
• The locality and peculiarities of the Installation
• The required working hours and rotation
Supply vessels are not normally manned for round the clock cargo operations,
hence if such operations are likely, sufficient bridge and deck personnel must be
carried to ensure adequate rest, including a night master or driving mate.
Anchor handling vessels chartered for extended operations should be manned
for round the clock working. Otherwise, vessel rest periods must be built into
the programme.
Similarly, standby vessels are not normally manned for extended round the
clock close standby. If such support is anticipated, then manning should
be adjusted.
As part of the vessel vetting process, manning standards and procedures should
be verified. These should include:
• Two-man bridge manning within an Installation Safety Zone (supply and
standby vessels)
• Engine room manning at critical periods, including safety zones
• Adequate deck crew for cargo operations
• Adequate crew for anchor handling, including round the clock working if
required
• In heavy traffic areas, consider need for additional bridge watchkeepers
specifically for detection and communications duties
• In general, sufficient manning for adequate crew rest and avoidance
of fatigue
Refer to OSV Code Appendices 1 and 2 on Manning and Training and the
International Marine Contractors Association (IMCA) CMID.

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4.4 Collision Avoidance Measures
4.4.1

Support Vessel Operations

Masters and Installation personnel must be prepared for potential problems
whilst vessel is in close proximity and must make adequate contingency plans.
These plans should be exercised at regular intervals, when safe to do so,
particularly in relation to potential control/mechanical/propulsion failures.
During field operations the master and Installation personnel should continually
review prevailing conditions and actual operation as an ongoing risk
assessment, factors to be reviewed include:
• Environmental conditions, for example tidal conditions, changes in wind
direction and strength and seastate
• Changes in workscope, for example extended duration and commencement
of hose work
• Human factors, for example likely duration of task, fatigue and rest periods
In general refer to the guidelines Task-based Risk Assessment produced by Step
Change in Safety.
It is the master’s prerogative to modify or suspend any operation which involves
unacceptable hazards to personnel, the vessel or the Installation. He should
discuss this with Installation personnel unless the urgency of the situation
demands immediate action. The master should question any instructions
received, which potentially hazard personnel, the vessel or the Installation.
The work programme and/or field rotation should be planned so as to minimise
Installation visits. Vessel movements within the field should be based on the
precautions below plus any others appropriate to the particular trade, operation
or location:
• Steer offset courses to or from Installations during passage
• Establish suitability of current environmental conditions and trends for the
work programme at the particular location
• Anticipate the effects of future weather and currents
• Avoid passing close up wind or tide when on passage or when ‘dodging’ on
low power
• Two competent persons on the bridge whilst approaching and in the
Safety Zone
• Complete Safety Zone pre-entry checklists as per requirements of the
data card

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Ship/Installation Collision Avoidance
• Obtain permission from the Installation before entering the Safety Zone
• Before approach, confirm readiness to work a supply vessel in the most
expeditious manner, in a safe location and with minimum time alongside
• Approach the Installation at a safe speed and heading
• Before final approach, set-up the vessel minimum 50m from the proposed
working location in order to assess the actual environmental conditions,
motion and behaviour of the vessel
• Be aware of different handling characteristics between ‘light’ and loaded
conditions
• Do not retain vessel alongside the Installation for extended periods of
‘standby’ when not employed
• Do not retain vessel with hoses connected for extended periods when not
transferring cargo
• Be aware of the limited capability of some multirole vessels
• Move outside the Safety Zone when not required in close proximity to the
Installation
Further guidance is given in:
• OSV Code Section 7.5.2 on checks before entering Safety Zone
• OSV Code Section 8 on CRM for infield vessels
• OSV Code Section 9 for general guidance on Installation vessel operations
and 9.6 for weather side working practices
• OSV Code Appendix 11 for pre-entry checklists
• SBV Guidelines Section 2 on approaching the Installation
4.4.2

Installation/Vessel Communications

Good communications between vessels and Installations are essential to ensure
understanding of priorities and to assist in the Identification of hazards.
These should include:
• Dedicated clear radio channels or other means of communication
• An established, accessible point of contact on the Installation whenever the
vessel is working in close proximity
• Review of proposed work programmes between Installation and vessel,
taking account of the master’s specialist expertise
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Ship/Installation Collision Avoidance
• A procedure for
working conditions

constant

review

• Agreed emergency communications
which includes a safe escape route

of
plan

weather
and

conditions

contingency

and
plan,

Also refer to OSV Code Section 9.2.
4.4.3

Special Precautions – Weather Vaning and DP Installations

Floating production storage and offtake units and drill ships involve particular
marine hazards different from fixed platforms, jack-ups and anchored semisubmersibles. The peculiarities below may increase the potential for collision with
attendant vessels.
1.

With the exception of a few semi-submersible production units, they tend to
be ship shaped.

2.

Most are moored to a single point and to some extent free to rotate and
align with wind/current/tide.

3.

Some are controlled by thrusters and partially or wholly maintain position
and heading by (thrusters can interact with those of a vessel working
alongside).

4.

They may have limited reach carnage.

5.

Supply vessels may have problems adopting a weather kindly heading when
working cargo with these Installations.

Generally, such Installations are straight sided, their motion is unpredictable and
may involve unexpected thrusters wash.
Precautions for support vessels working in close proximity to such Installations
precautions include:
• Prior to setting up, vessel and Installation personnel should discuss and
understand the particular hazards of the operation
• Appreciation by vessel personnel that a weather vaning Installation may
move unpredictably
• Understanding of thruster interaction between the Installation and vessel
• Appreciation by Installation personnel that they must keep vessel advised of
any actions which could increase the potential for collision
• Contingency plans, including a safe escape route for the vessel, in the event
of a rapid change in the situation
Also refer to OSV Code Appendix 14.

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4.5 Contingency Plans
Each Installation should have in place a succinct contingency plan for
immediate actions in case of an attendant vessel collision. These actions may
include, according to location, Installation and the type of operation:
• Rapid evacuation of the Installation personnel, if required
• Rescue of the attendant vessel crew
• Dealing with a ruptured riser or pipeline
• Fire and/or explosion
• Location of sensitive seabed facilities in the vicinity of the Installation
• Shutting down production and/or pipelines
Refer to the Evacuation, Escape and Rescue Assessment guidance in the Safety
Case Regulations (SI 1992/2885). Also refer to Paragraph 2.6 of this guide.

4.6 Follow-up
Every incident or potential incident should be reported and followed up.
Only by so doing can the potential for collision be properly assessed
(refer to Paragraph 2.8). In all cases, lessons and outcome should be fed back to
Installation and vessel personnel and managements.

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5

OFFTAKE TANKERS
5.1 Introduction
In a few cases, offtake tankers load from fixed platforms but are more are often
associated with FPSO/Floating Storage Units (FSUs), transhipping and
transporting the produced crude oil to shore terminals. Transhipment may take
place via a separate loading buoy or directly from the FPSO/FSU. Having two
large vessels loaded with hazardous cargo in close proximity for extended
periods introduces obvious hazards. Any collision, even at low speed may cause
significant damage with major consequences to life, the environment and the
business of the operator.
Precautions and controls are given in detail in the UKOOA Tandem Loading
Guidelines. Further expert guidance is given in the Oil Companies International
Marine Form (OCIMF) Offshore Safety Loading Guidelines.

5.2 Assessing the Potential for Collision
Factors associated with offtake tanker operations which can affect the
probability of collision include:
• Frequency and duration of offtakes
• Whether hawser connected
• If DP, the DP class
• Whether offtakers are dedicated to the particular operation
• Relative congestion of the field
• Whether either or both vessels are thrusters controlled or free to rotate
• Whether support vessels are used for mooring and towing assistance either
for alignment or maintaining tension
Experience shows that underlying factors may include:
• Reliability of position referencing systems for DP tankers – the possibility of
references dropping out must be allowed for in risk assessment
• Standards of propulsion/control system redundancy in non-dedicated offtake
tankers and the potential for power failure and position loss
• Use of heavy fuel in some non-DP tankers again with potential for
power failure

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Ship/Installation Collision Avoidance
• Changeover from automatic to manual controls (some propulsion systems are
known to fail at full pitch and the time to regain control before significant
momentum is gained) is critical
• Differences between tanker trade and offshore DP practice; this may affect
bridge and engine room manning practices and DP tanker bridge
management – for example a tanker master normally retains control, whereas
in diving vessels dedicated DP operators man the consol; engine room
controls must be manned during offtake to allow for immediate response to
problems
• Training and familiarisation of tanker crews – again a function of the
different cultures
• Fish-tailing and surging – the tendency of FPSO/FSUs to move in a seaway
in a manner difficult to follow accurately with manual or DP control of the
offtaker; excessive movement can result in mooring failure or collision
• Thruster failure modes – as above some are known to fail at full pitch
• Main propulsion failure – if continuous running is required to maintain
mooring tension, propulsion failure may result in collision with the storage
vessel or buoy
• Pressure to continue production or transhipment – may persuade masters to
moor and remain moored in marginal conditions so as to maintain production
or offtake
These factors, the capability of the offtaker together with the operating
standards and procedures should be the subject of risk assessment for each
combination of field and offtaker.

5.3 Minimising the Probability of Collision
Specific guidance on two-vessel offtake operations is given in IMCA document
M161 Design and Operation of DP Vessels – Two-vessel Operations.
The Dutyholder’s management must ensure:
• That only suitable vessels are chartered
• That vessel suitability is verified by persons with the necessary experience
and knowledge
• That operating methods and procedures both for the tanker and the offtake
operation are appropriate to the identified hazards of that particular location
• That the system is audited at appropriate intervals

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The various responsibilities should be set out in the JOPs as should the means of
implementing them.
5.3.1

Offtake Tanker Suitability:

Overall the vessel equipment and manning should be confirmed as suitable for
and capable of carrying out the transhipment operation in the worst conditions
anticipated.
Detailed guidance has been developed by OCIMF, Intertanko, IMCA and the
UKOOA FPSO Committee. This guidance is listed in Addendum 7 of this
document.
5.3.2

Equipment

Offtake tankers equipment should meet the following criteria:
• Propulsion, control and DP systems, where fitted, should be adequate, to
moor, remain on location and unmoor safely in the most severe operating
environmental conditions anticipated, with adequate reserve power and
sufficient redundancy
• DP offtake tankers should meet Equipment Class 2 of International Maritime
Organisation (IMO) Circular 645; in addition no known single failure mode
should cause an emergency disconnect or cause a position excursion which
necessitates emergency release of the loading hose and/or mooring hawser, if
used
• Mooring systems and equipment, if used, should be adequate, with sufficient
reserves in terms of numbers and strength, to moor up expeditiously and
remain on station in the worst anticipated operating conditions
• Where thrusters are required to run continuously to maintain mooring tension
or maintain station, sufficient redundancy of generation, propulsion, control
and fuel systems should be available
• Thrusters should normally fail to zero pitch or at last order; where thrusters
fail to full pitch, then procedures for promptly regaining control should be in
force
• Position reference systems should include sufficient redundancy and
diversity that loss or corruption of one system will not cause a loss of
position; where DP computers use a reference voting system, no two systems
should fail or be corrupted by the same fault or error; systems for identifying
failures and regaining control should be sufficiently robust
The offtake tanker should undergo an annual DP trial in the IMCA format
or similar.

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5.3.3

Manning

Provision of adequate and competent crew is critical to safe offtake operations:
• Manning should be adequate to provide sufficient alert, skilled personnel for
all critical tasks on the bridge, in engine room and on deck for the duration of
the offtake operation, including arrival and departure from the field
• Manning practices should be appropriate to the hazards involved in loss of
position; this should include at the least double manning of the bridge
(the master should not be one of the DP operators) and continuous manning
of the engine control room
• Key personnel should be properly qualified, have experience of the vessel
and offshore transhipment operations and at least have knowledge of the
particular operation or one that is similar
• Any changes of personnel should include adequate handover, overlap and
replacement by personnel of similar knowledge and experience
Detailed guidance on personnel competence is given in UKOOA Tandem
Loading Guidelines Volume 1 Appendix C – Key Personnel Competency
Matrices.
5.3.4

Vetting

The suitability of the offtake vessel should be demonstrated using an industry
standard format or system. Examples of such systems are given in Addendum 4.
The vetting process is critical when chartering non-dedicated vessels,
spot vessels or ones which are unfamiliar in the particular trade.
Despite possible time pressures, allowance must be made for the
vetting process.
5.3.5

FMEA

Tankers used for offshore offtake should be subjected to a systematic Failure
Mode and Effect Analysis (FMEA) carried out by a specialist contractor.
The report should be available to vessel personnel and made available to
potential charterers/field operators. Any deficiencies noted should be allowed
for in operating practices and procedures involving the vessel.
If any significant changes are made to generating, propulsion or control
systems, the FMEA should be repeated. Inspectors vetting a vessel should
confirm that the FMEA report is current. Annual DP trials confirm performance
against the FMEA.

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5.4 Collision Avoidance Measures
5.4.1

Operating Procedures

Succinct field-specific operating procedures should be produced and made
available to offtake tankers. Field/vessel-specific JOPs should be developed.
These procedures should cover as necessary:
• Operating parameters and constraints
• Controlling environmental conditions and decision points
• Communications provisions
• Step-by-step arrival and departure procedures
• Propulsion, control and stationkeeping requirements and methodology
including towage assistance where used
• Differences where appropriate between: fixed point (buoy) and tandem
mooring; between DP and non-DP offtakers
• Managing thruster interaction
• Abort decision points: mooring, transhipping and unmooring
• Emergency shutdown, disconnect and departure parameters and procedures
• Safe vessel escape routes
The procedures should be supported by relevant checklists at required points in
the operation. Some examples are given in Addendum 5.
Where field operations require use of a TAV, this should be covered in the
procedures. Refer to UKOOA Tandem Loading Guidelines Volume 2.
5.4.2

Contingency Planning

Each field in which offtake operations take place should have a standard
contingency plan which can be adapted to individual offtakers in consultation
with the master.
Contingency plans for regular offtakers should be included in the JOPs. At the
least, standard and specific plans should address:
• Significant offtaker propulsion or control problem during approach
• Loss of position control at any time during the operation
• Offtaker adrift, out of control, in the field

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Ship/Installation Collision Avoidance
• Loss of or high mooring tension (hawser connected operations)
• Collision or close quarters event between offtaker and FPSO
• Abort parameters
• Significant offtaker propulsion or control problem during departure
• Fire and/or explosion
• Support vessel casualty
Offtaker specific plans on both units should be confirmed by arrival checklists.
Elements of the plan should be exercised periodically with dedicated offtakers.
Refer to general remarks in Paragraph 2.6.
5.4.3

Reporting and Follow-up

It is only by accurate reporting of all incidents, near misses and close quarters
events that the industries and individual operators can properly assess the level
of risk. When collated and analysed these reports will aid implementation of
further risk reduction and control measures, where they are needed.
Field operators should implement procedures for recording all incidents
and near misses. Suitable reporting forms and systems have been developed by
IMCA and UKOOA FPSO Committee. Examples are referenced in
the Addenda.
Whenever a loss of position or more serious incident occurs the
Dutyholder should:
• Carry out an investigation, in cooperation with the vessel operator and
regulatory agency where appropriate
• Implement any lessons learned
• Repeat the risk assessment and feedback the results to involved vessels,
vessel operators and field personnel

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Addendum 1
Glossary of Terms
The following terms when used in this document have the meaning as
given below.
Attendant Vessel

A vessel with legitimate business, supporting or working
at the Installation, one with permission to enter the
Installation Safety Zone.

Close Quarters
Situation

One where a vessel is in such close proximity to another
vessel or fixed object that the navigator has to take
urgent avoiding action or where there is imminent
potential for collision

Damage Criteria
(Installation)
Catastrophic:

Damage resulting in shutdown of the Installation,
including major structural damage and/or loss of
stability, possibly resulting in evacuation and/or loss
of life.

Severe:

Damage affecting the integrity of the Installation
sufficient as to require repair in the immediate or short
term (up to one month).

Moderate:

Damage requiring repair in the medium (up to 6 months)
or longer (over 6 months) term.

Minor:

Damage not affecting the integrity of the Installation.

Dutyholder

The Dutyholder is the person who has the legal
responsibility for the Safety Case and for implementing
the health and safety responsibilities associated with it.
In the case of a fixed Installation, it is normally the
operator. For a mobile Installation, it is normally the
owner/manager. The Dutyholder is defined in the
Management and Administration Regulations (MARs).

Errant Vessel

A vessel which has failed to take avoiding action on
approaching a fixed or moored Installation or has failed
to respond to communications from the Installation or its
attendant vessel(s); a vessel which poses or appears to
pose a threat of collision with the Installation or its
attendant vessels.

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Add 1-1

Ship/Installation Collision Avoidance
Incident

Collision or unintentional contact between vessel
and Installation.

Installation

An offshore unit engaged in exploration for or
exploitation of hydrocarbons resources. May include
fixed platforms, mobile drilling units (floating or
self-elevating), floating production or Floating
Production Storage and Offtake (FPSO) units.

Major Accident
Hazard (MAH)

Near Miss

A hazard with the potential for serious personal injury
resulting from: fire/explosion or the release of a
dangerous substance; major damage to the structure or
loss of stability; other hazard with the potential for five
or more casualties. A Major Accident Hazard (MAH) is
defined in the Safety Case Regulations (SCRs). The
principle hazards are summarised in the ‘Purpose and
Scope’ of this document.
Circumstances which could have escalated into an
incident and/or circumstances which require activation
of emergency response procedures on the Installation.
For attendant vessels a near miss may include:
• A loss of position control which if uncorrected could
have resulted in a collision
• An offtake tanker incident with the potential to cause
a collision
• Activation of emergency procedures related to
collision risk on the Installation
• Location-specific near miss parameters developed by
Dutyholders
For passing vessels:
• A Safety Zone infringement is a vessel passing within
500m of the Installation
• Failure of an approaching vessel, with Closet Point
Approach (CPA) <500m to respond to calls from the
Emergency Rescue and Recovery Vessel (ERRV)
or Installation
• Activation of emergency procedures
Installation such as a precautionary muster

Glossary
Add 1-2

on

the

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Ship/Installation Collision Avoidance
Offtake Tanker
(or Offtaker)

A tanker used for exporting produced oil from offshore
fields via loading buoys, subsea connections or direct
from storage vessels. Normally specially modified
and equipped.

Passing Vessel

A vessel on passage to somewhere else, one that should
keep clear of the Installation Safety Zone.

Safety Zone

The 500m radius exclusion zone established around all
active surface Installations and some subsea Installations
in the UK sector. In the case of floating storage units, it
may be extended to include the swinging area of vessel
and any tandem moored offtaker.

Support Vessel

An attendant vessel with specific duties at the
Installation such as supply, towage, standby, diving etc.

Traffic Density

The following values give a comparison of densities in
the UK Sector:
Low
Low to Medium
Medium to High
High

<1,000 passing vessels per year
1,000 to 5,000 vessels per year
5,000 to 20,000 vessels per year
>20,000 vessels per year

The degree of concentration of traffic into narrow
channels should also be taken into account when
comparing the densities.

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Addendum 2
Promulgation and Detection – Passing Vessels
Location
Type
1.

2.

Fixed
platform,
open
location

Mobile
Installation,
open
location

Traffic
Density
Light

Light

Promulgation
• Advance notices
to mariners

Detection
• ERRV radar

• Marking on
charts

• Clear surveillance
and reporting
responsibilities

• Standard
markings

• Maintain alertness by
regular exercises

• Advance notices

• ERRV radar

• Navigation
warnings before
and during time
on location

• Installation radar if
available and manned

• Standard
markings

• Clear surveillance
and reporting
responsibilities

Additional
Precautions
• Obscured sectors
covered during
close standby
• Clearly understood
joint coverage
arrangements

• Obscured sectors
covered during
close standby
• Clearly understood
arrangements for
any joint coverage

• Maintain alertness by
regular exercises
3.

NUI

Moderate

• Advance notices
to mariners

• ERRV radar when
manned

• Clearly understood
arrangements for
any joint coverage

• Marking on
charts

• Coverage from
nearby Installation if
available

• Responsibilities
clearly understood

• Radar surveillance
from platform
transmitted to ERRV

• Clearly understood
arrangements for
any joint coverage

• Marking on
charts

• AIS detection

• Responsibilities
clearly understood

• Standard
markings

• Consider extra bridge
watchkeepers

• Standard
markings
• Consider racon
4.

Fixed
platform
near busy
traffic route

Moderate

• Advance notices
to mariners

• Risk assess any
multirole coverage

• Consider racon

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Add 2-1

Ship/Installation Collision Avoidance

5.

Location
Type

Traffic
Density

Promulgation

Detection

Additional
Precautions

Mobile
Installation
near busy
traffic
route.

Moderate

• Advance notices

• Radar surveillance
from Installation
transmitted to ERRV

• Clearly understood
arrangements for
any joint coverage

• AIS detection

• Responsibilities
clearly understood

• Navigation
warnings before
and during time
on location
• Standard
markings

• Consider extra bridge
watchkeepers

• Risk assess any
multirole coverage

• Consider racon
6.

Mobile
Installation
in busy
traffic area
or near
traffic node

Moderate
to heavy

• Advance notices
• Navigation
warnings before
and during time
on location
• ‘Securite’
messages from
ERRV

• Radar surveillance
from Installation
transmitted to ERRV
• AIS detection

• Dedicated ERRV
coverage
• Responsibilities
clearly understood

• Extra bridge
watchkeepers

• Standard
markings
• Consider racon
7.

NUI in
busy traffic
area or near
traffic node

Moderate
to heavy

• Advance notices
to mariners

• As the previous point
when manned

• Marking on
charts

• Dedicated coverage
from nearby
Installation or ERRV
preferred

• Standard
markings; racon
• Any special
precautions per
consent to locate

Note:

• Clearly understood
responsibilities and
hierarchy on
nearby Installation/
ERRV

• Consider extra bridge
watchkeepers

Any detection systems required by the above should be properly maintained
hence reflecting their importance.

Promulgation and Detection – Passing Vessels
Add 2-2

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Addendum 3
Systems Audits
The Dutyholder should routinely and regularly audit the collision avoidance system.
Auditors, either internal or external should have sufficient independence to
objectively review working of the systems. They should report directly to the
appropriate level of management.
The formats which follow are intended as templates for auditing arrangements at
individual Installations and fields. They are not definitive and should be adapted to
local requirements.

1

SYSTEM MANAGEMENT (ALL SITUATIONS)
Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

1.

Manager responsible for collision avoidance
assurance nominated?

2.

Internal/external Auditor nominated?

Auditor should not be part of
the Installation operations
department.

3.

Does Auditor report directly to nominated Manager
on effectiveness of collision avoidance system?

Auditor should have direct
access to appropriate
management level without
filtering by operations
management.

4.

Has an agreed Policy Statement been developed and
issued to Line and Installation Managers?

Should be endorsed by senior
management.

5.

Do Line and Installation Managers understand the
purpose and principles of collision avoidance?

Auditor should take samples of
level of understanding.

6.

Are there sufficient personnel within the organisation
with the necessary marine competence?

7.

Are vessel operators and mobile unit operators fully
integrated into the system? Do they understand the
principles of collision avoidance?

Review with vessel operators
and crew.

8.

Are evacuation and rescue arrangements adequate and
appropriate to the risks?

Check contingency
arrangements in event
lifeboats lost/damaged.

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Installation/Field

No

Dutyholder

Activity

Responsible
Person

9.

Have joint arrangements (eg for shared ERRV
coverage or when Dutyholder does not arrange
support vessels) been agreed? Are they understood by
line/Installation managers?

10.

Is there a robust system for vessel/Installation
personnel to feed concerns to the management?

11.

Is there an effective system for reporting collision
incidents and near misses?

12.

Do Installation and vessel personnel understand the
importance of reporting near misses?

13.

Are incidents and near misses analysed, trends
actioned and lessons fed back to operating personnel
and vessel personnel?

2

Audit/Review Period

Comments
Who arranges and charters
ERRVs?

PASSING VESSEL PROCEDURES
(ALL SITUATIONS)
Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

1.

Are reporting lines to responsible Manager clear?

3.

Has the probability of a passing vessel collision
been assessed?

4.

Are the means of detecting and communicating with
an approaching vessel appropriate to the risk at the
particular location? Are they maintained properly?

Refer to Addendum 2.

5.

Are the means of promulgating the Installation’s
presence adequate and appropriate to the
probability of collision and potential consequences
at the location?

Refer to Addendum 2.

6.

Do OIMs, Installation and vessel personnel
understand the risks and the purpose of the collision

Auditor should take samples of
level of understanding.

Systems Audits
Add 3-2

There should be clear lines
from the Manager responsible
for implementing passing
vessel arrangements.

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Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

avoidance system?

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Ship/Installation Collision Avoidance

Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

7.

Are there location-specific collision
avoidance procedures?

8.

Do the procedures address situations when sectors are
obscured during close standby and when a single
ERRV covers more than one Installation?

Are the responsibilities clearly
understood?

9.

Are the procedures reviewed with the ERRV/guard
vessel and other support vessels during routine visits?

Ensure that vessel personnel
understand their
responsibilities.

10.

Who will review the procedures during these visits?
How does he/she report any concerns to management?

Include regular and spot
/relief vessels.

11.

Do support vessels understand the importance of
passing vessel surveillance?

12.

Who charters ERRV/guard vessel?

13.

When the Dutyholder does not charter ERRVs and
other support vessels, how does he ensure suitability
for surveillance?

14.

Is there a robust system for vessel/Installation
personnel to feed concerns to the management?

15.

Are contingency plans developed for responding
rapidly to the threat of collision? Are they
exercised regularly?

Systems Audits
Add 3-4

Each Installation crew and
each vessel crew should be
exercised twice per year.

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3

ATTENDANT VESSEL ARRANGEMENTS
(ALL SITUATIONS)
Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

1.

Are reporting lines to responsible Manager clear?

There should be clear lines of
reporting and responsibility.

2.

Is there a robust system for ensuring the suitability of
support vessels for the Installation/location and the
adequacy and competency of the crews?

What are performance
standards for inspections?

3.

Who is responsible for ensuring suitability of vessels
and competence of crews? How does he/she report to
management?

4.

How are vessels confirmed suitable before
employment?

Check inspection
performance standards.

• Term chartered vessels
• Pool vessels
• Relief vessels

• Spot vessels
5.

Who charters support vessels? Do they understand
the importance of vessel suitability in collision
avoidance terms?

6.

When the Dutyholder does not charter ERRVs and
other support vessels, how does he ensure suitability?

7.

Do all support vessels hold field/ Installation
data cards?

8.

Are there location-specific collision
avoidance procedures?

9.

Are the procedures reviewed with the all support
vessels during routine visits?

10.

Who will review the procedures during these visits?
How does he/she report any concerns to
management?

11.

Do OIMs, Installation and vessel personnel
understand the risks of vessel platform collision and
the importance of good communications?

Discuss with personnel.

12.

Do all support vessels complete a pre-entry checklist
before approaching Installation? How is this
recorded?

Check records.

Issue 1 February 2003

Identify person responsible
for issuance.

Systems Audits
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Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

13.

Do Installation personnel dealing with support
vessels have sufficient marine understanding for the
task?

Check qualifications
and experience.

14.

Do Installation personnel recognise that frequent
visits and weather side working increase
collision risks?

Discuss with personnel.

15.

Are support vessels released promptly on completion
of task and not kept standing by unnecessarily?

Check procedures and
actual activity.

16.

Do ERRVs and other vessels ‘dodge’ in safe areas in
relation to wind and current?

17.

Have contingency plans been developed to respond to
serious incidents? Are they exercised regularly ?

18.

Do contingency plans address rescue of
vessel personnel?

4

OFFTAKE TANKER ARRANGEMENTS
(FIELD SPECIFIC)
Installation/Field

No

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

1.

Are reporting lines to responsible Manager clear?

There should be clear of
responsibility and reporting.

2.

Person responsible for auditing the system nominated?

Auditor should report to
senior management.

3.

Is there a robust system for ensuring the suitability of
offtake tankers for the location and the adequacy and
competency of the crews?

Procedures and performance
standards for vetting.

4.

Who is responsible for ensuring suitability of vessels
and competence of crews? How does he/she report to
management?

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Installation/Field

No
5.

Dutyholder

Activity

Audit/Review Period

Responsible
Person

Comments

What system/format is used for ensuring suitability
before employment:
Offtake tankers
Crews

6.

Who charters offtake tankers? Do they understand the
importance of vessel suitability and crew competence?

What is the relationship with the
Dutyholder?

7.

How is the suitability of spot or relief
offtakers verified?

8.

Are Joint Operations Procedures (JOPs) in use for each
specified offtaker?

9.

Are the JOPs developed/ reviewed with vessel operators
and personnel?

10.

Are other support vessels eg TAVs used? How is their
suitability and crew competence verified?

11.

Have contingency plans been developed for
emergencies? Are personnel familiar with them?
Are the plans exercised regularly?

12.

Do OIMs and personnel and support vessel crews
understand the potential for offtake collisions and the
importance of good communications?

13.

Do all offtakers complete a pre-entry checklist before
approaching Installation? How is this recorded?

Check records.

14.

Do Installation personnel dealing with offtakers have
sufficient marine understanding for the task?

Check experience.

15.

Do procedures recognise the operating differences
between DP and non-DP offtakers?

16.

Are the procedures for monitoring and controlling
hawser tension in non-DP oftakes satisfactory?

17.

Is the manning of the bridge consol and engine rooms
during DP operations adequate and satisfactory?

18.

Is there a robust system for vessel/Installation personnel
to feed concerns to the management?

20.

Do Installation and vessel personnel understand the
importance of reporting near misses?
What reporting system/format is used?

21.

Are incident and near misses lessons discussed with and
fed back to Installation and vessel personnel?

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Issue 1 February 2003

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Addendum 4
Vessel Suitability and Inspection Formats
1

COMMON MARINE INSPECTION
DOCUMENT – UKOOA
Standard document for assessing offshore support vessels, developed by
UKOOA in association with other stakeholders. Valid for up to one year unless
significant changes occur in the interim. It includes general sections common to
all offshore support vessels plus type-specific appendices.
The format can be obtained from UKOOA or IMCA (refer to Addendum 11).

2

FITNESS-FOR-PURPOSE INSPECTION
When a vessel is chartered for a specific project or task then a
fitness-for-purpose inspection is recommended. This should cover at least:
• The specific task or project
• Currency of standard inspections such as CMID, the IMCA DP annual
inspection, FMEA etc as appropriate
• Adequacy and redundancy of the vessel propulsion and control systems for
the project in anticipated operating conditions
• Adequacy of specialised equipment for the project
• Adequacy and competency of vessel personnel for the project
• Certification status, particularly for lifting gear

3

IMCA DP ANNUAL INSPECTION
This involves a comprehensive set of trials, carried out annually by specialists to
confirm the operability of dynamically positioned vessels. It is recommended
for all DP vessels from survey vessels through to the highest rated
diving/construction vessels and offtake tankers. It confirms currency of the
FMEA report.
The M139 format is available from IMCA, refer to Addendum 11 for contacts.

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4

SHIP INSPECTION REPORT PROGRAMME
(SIRE)
This is a comprehensive inspection document for various classes of tankers
including bulk oil, chemical and gas carriers. Recommended for initial fitness
for purpose assessment of offtake tankers, combined with the annual
DP inspection where relevant.
The SIRE document is published by Witherby and Co on behalf of OCIMF
(refer to Addendum 11 for contacts).

Vessel Suitability and Inspection Formats
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Addendum 5
Field Checklist
1

PRE-FIELD ENTRY
(OSV CODE APPENDIX 11)
1.1 Vessel
1.

Weather conditions are suitable.

2.

All required propulsion, control and back-up systems are operational.

3.

Master and crew are sufficiently rested.

4.

Deck crew are briefed and correctly dressed.

5.

Vessel’s programme has been advised/agreed.

6.

Communications with the Installation are working.

7.

Internal communications on vessel are working.

8.

Bulk transfer procedures have been agreed.

9.

Full details of cargo discussed/agreed.

10. Notification has been given and received of any expected helicopter
movements.

1.2 Installation
1.

The required working zone alongside is clear of other vessels.

2.

All non-essential overside discharges in the working zone have been stopped.

3.

Standby vessel has been briefed on the operation.

4.

Installation personnel are sufficiently rested.

5.

Deck crew and crane driver are briefed.

6.

Weather limitations have been considered.

7.

Vessel’s programme has been advised/agreed.

8.

Crane limitations have been advised to Master.

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9.

Permission given to offload during diving operations.

10. Bulk transfer procedures have been agreed.
11 Full details of cargo discussed/agreed.
12. Underwater/waterline obstructions which could cause a hazard to the
vessel notified.

2

OSV/FPSO CHECKLIST (OSV CODE
APPENDIX 14)
2.1 Introduction
This checklist details checks and exchange of information to be carried out by
the master of the support vessel and the OIM (or his representative) of the
FPSO. The list is in addition to any other checklists completed prior to entry
into the Safety Zone.

2.2 FPSO Supplementary Checklist
No

Check

Completed
Yes/No

1.

Risk assessment of all operations is to be carried out prior to operations
commencing. To be completed by the Vessel Master, OIM and Crane Operator.

2.

FPSO to confirm its heading and that the heading will not alter or be altered
during supply vessel operations.

3.

OIM to confirm motion of the FPSO in current conditions eg:
• FPSO roll (degrees)
• FPSO roll (period)
• FPSO pitch (degrees)
• FPSO heave (metres)

4.

A general exchange of information regarding the disposal of cargo to be
offloaded to the FPSO and back loaded cargo to be received by the OSV.

5.

A general exchange of information regarding ‘hose work’ to be conducted.
This will include the method of lowering the hose to the OSV and available
space for this to be carried out safely. Where practicable sufficient deckspace
must be available or be cleared so that the OSV crew have a safe area in which
to handle the hose.

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6.

Confirmation from the OSV Master to any particular limitations on crane
operations or special conditions affecting normal operation of the crane.

7.

Information from the OIM as to any particular limitations on crane operations
or special conditions affecting normal operation of the crane.

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3

OFFTAKE TANKER CHECKLISTS
Most field operators use a standard checklist. The formats below are generic
lists designed for offtake tanker use at Single Point Moorings (SPMs) or in
tandem loading. They are not definitive and should be adapted to local use.
Arrival Checklist

Vessel:

Loading Point:

Date:

Up-to-date charts of largest scale in use

Offtaker/Installation contingency
plans confirmed

All hazards located and marked on charts

Telemetry links (if applicable)
established and tested

No go areas marked on charts

Slow down way points established and
understood

Passage plan to loading point agreed and
in effect

Approach and pick-up plan discussed
and agreed with control room and
support vessel

Field operating manual/JOPs etc read
and understood

Deck machinery operational

Tidal and current data available and checked

Deck crew to stations

Current weather suitable, forecast checked

Pick-up gear tested, inspected and
operational

Under keel clearance (including squat)
established

Stern towing system (if used) ready

Appropriate Bridge Team assembled and
briefed

Required lights/signals
exhibited/available

Abort position/circumstances established and
understood by Bridge Team

Emergency towing system(s) visually
examined and ready for use

Escape routes identified and understood

Anchors cleared for use

Main and auxiliary propulsion operational

Permission to enter Safety Zone from
control room

Auxiliary generators and steering operational

Watchkeeping arrangements and
responsibilities for loading understood

Engine room checklist completed

Approach and pick-up plan discussed
and agreed with control room and
support vessel

Appropriate Engine-room Team assembled
and briefed

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Arrival Checklist
Vessel:

Loading Point:

Date:

All navigation, communications and control
systems checked and operational
Bridge Team duties assigned
Main and auxiliary propulsion tested in
both directions
Steering gear tested over full range
All required navigation and control systems
operational
Power distribution system in correct mode for
DP operations
DP system (if fitted) operational
DP operators (if applicable) identified,
responsibilities understood
All radio systems tested operational
Contact made with loading point control room
Contact made with any support/assist vessels
Master:

Date:

Departure Checklist
Vessel:

Loading Point:

Date:

Disconnect sequence and departure track agreed
and advised to support vessel and control room

DP operators (if applicable) identified,
responsibilities understood

Cargo/ballast operations completed

All radio systems tested operational

Deck machinery operational

Abort position/circumstances established
and understood by Bridge Team

Deck crew to stations

Commencement of disconnect operations
agreed with control room

Emergency towing systems ready for use

Support vessel advised

Charts of largest scale in use

Radios tested and on correct channels

All hazards located and marked on chart

Electronic navigation systems
correctly set up

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Ship/Installation Collision Avoidance

Departure Checklist
Vessel:

Loading Point:

Date:

No go areas marked on chart

Clocks synchronized

Outward passage plan agreed and in effect

Telephones/speakers tested

Field operations/JOPs etc read and understood

Whistle tested

Tidal and current data available and checked

Required lights/shapes
exhibited/available

Current weather suitable, forecast checked

Required flags exhibited/available

Escape routes and safe anchorages identified
Vessel/Installation contingency plans confirmed
Under keel clearance (including squat)
established
Main and auxiliary propulsion operational
Auxiliary generators and steering
gear operational
Engine room checklist completed
Appropriate Engine-room Team assembled
and briefed
All navigation, communications and control
systems checked and operational
Bridge Team duties assigned
Steering gear tested over full range
Power distribution system in correct mode for
DP operations
DP system (if fitted) operational
Master:

Field Checklists
Add 5-6

Date:

Issue 1 February 2003

Ship/Installation Collision Avoidance

4

COLLISION AVOIDANCE FLOWCHART
(SBV GUIDELINES APPENDIX 3)

Monitor all traffic within a suitable range

No
Does the vessel have a projected CPA of <2nm?

Yes
Monitor vessel closely

No

Does the vessel have a projected CPA
of <1nm at 6nm off Installation?
Yes
Continue monitoring vessel. Inform OIM.
Attempt radio contact with vessel.

Is radio contact made with vessel?

Yes

No
Monitor situation closely and continue attempts to contact vessel.
Inform OIM. Call off close standby. Initiate emergency response.
Attempt to intercept vessel and warn-off by all available means.

No

Does vessel still pose a collision risk?
Yes
Update OIM and prepare for potential Installation evacuation.
Continue to monitor situation.

Note: This flowchart uses distance to determine
alert/decision points. Time to CPA is recommended in
practice.

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Addendum 6
Installation Data Cards
All offshore fields and Installations in the UK sector are required to produce a
data card which includes:
• Location
• Marine hazards of the Installation/field
• Communications details and procedures
• Pre-entry checklists required before entering Safety Zone
• Marine coordination
• Crane and bulk transfer arrangements
This is an essential tool in the Installation/vessel information exchange and
ensures that the vessel is aware of the hazards and peculiarities of the location.
(refer to Section 7.5.1 of the OSV Code).
The Dutyholder is responsible for providing visiting vessels with the data card.
(refer to OSV Code Section 2.2).
An example of a data card is given in Appendix 7 of the UKOOA OSV Code.

Issue 1 February 2003

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Addendum 7
Incident and Near Miss Reporting Formats
Below are examples of such formats which should be consulted for possible
use where appropriate. Contact the individual organisation to access the format, refer
to Addendum 11.
1.

EERVA ‘Warning Off’ Report

2.

Safety Zone Infringement Report OIR 13

3.

IMCA Stationkeeping Incident Report Form:
• Thruster-assisted vessels
• DP vessels

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Addendum 8
References Including Relevant Codes and Regulations

1

2

3

HEALTH AND SAFETY AT WORK
1.

Health and Safety at Work Act 1974

2.

Statutory Instructions (SIs):
• 1992/2885

Offshore Installation (Safety Case) Regulations

• 1995/743

Offshore Installation (PFEER) Regulations

• 1996/913

Offshore Installations and Wells (Design and
Construction etc) Regulations

• 1995/3163

Reporting of Injuries, Death and Dangerous
Occurrences Regulations

3.

Health and Safety Management Systems Interfacing (UKOOA)

4.

Successful Health and Safety Management, (HS(G) 65)
UK Health and Safety Executive October 1993.

COLLISION RISK MANAGEMENT (CRM)
1.

Advice to Inspectors – Collision Risk Management (PBN 00/06), UK
Health and Safety Executive March 2000.

2.

Effective Collision Risk Management for Offshore Installations
(OTO 1999 052), Health and Safety Executive, January 2000.

GENERAL
1.

Task-based Risk Assessment – Step Change in Safety.

2.

Management of Emergency Response for Offshore Installations (UKOOA)

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Ship/Installation Collision Avoidance

4

PASSING VESSELS
1.

Automatic identification of ships
• SOLAS Regulation V/19
• IMO Draft Resolution A22/9 Annex 2

5

6

ATTENDANT VESSELS
1.

Guidelines for the Safe Management and Operation of Offshore Support
Vessels (UKOOA/CoS).

2.

Guidelines for the Safe Management and Operation of Vessels Standing By
Offshore Installations (UKOOA/ERRVA/IADC/BROA).

3.

Guidelines for the Survey of Vessels Standing By Offshore Installations
(UKOOA/ERRVA/IADC/BROA).

4.

Safety Interface Document for DP Vessel working near an offshore
platform (IMCA, M125 1997).

FPSO/FSUS AND OFFTAKE TANKERS
1.

Offshore Safety Loading Guidelines (OCIMF, 1999):
• Section 6 Joint Operations Manuals

2.

Risk Minimisation
(Intertanko 2000).

Guidelines

3.

Guidelines for the
(IMCA, M103 1999).

Design

4.

Supplement for Two Vessel Operations (IMCA, M161 2001).

5.

Quantified Frequency of Shuttle Tanker Collisions during Offtake
Operations (IMCA Report M150 February 1999).

and

References including Relevant Codes and Regulations
Add 8-2

for

Shuttle

Operation

Tanker
of

DP

Operations
Vessels

Issue 1 February 2003

Ship/Installation Collision Avoidance
6.

UKOOA Tandem Loading Guidelines:
• Background Report:
– Appendix E Generic Performance Standards for Shuttle Tankers
• Volume 1:
– Appendix B Performance Standards
– Appendix C Loss of Position and Failure Event Reports
– Appendix D Offtake Tanker Key Personnel Competency Matrices
– Appendix E Station Keeping Incident Report Form
• Volume 2:
– Towing Assistance including Performance Standards and Crew
Competency

Issue 1 February 2003

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Ship/Installation Collision Avoidance

Addendum 9
Passing Vessel – Ship Collision Assessment
1

ROUTE DATABASES
COAST gives the position of the shipping routes utilised by shipping in UK
waters and the North Sea, the volumes of traffic, the size and speed of vessels
using each route, and the width of the routes. It was developed by CorrOcean
Safetec for UK Health and Safety Executive, DTLR and UKOOA. The main
data sources used include:
• Port data provided by LMIS (Lloyds Maritime Information Services)
• Offshore traffic surveys carried out by standby vessels
• Platform and coastal-based radar systems
• Information from offshore operators (standby, supply, shuttle tanker details)
• Information from ferry operators
• Vessel passage plans
• Deep sea pilot route details
The main information contained in the database is:
• Route waypoints
• Route standard deviations
• Distance of route to a user-defined position
• Bearing from user-defined position to route
• Volume of traffic on each route
• Vessel type distribution on each route (merchant, offshore, tanker, ferry)
• Size distribution of vessels on each route
The programme may also be linked to a graphical output package that allows
the identified routes to be automatically plotted on Admiralty Raster Charting
Service (ARCS) hydrographic charts.
There is a similar shipping traffic database ‘ShipRoutes’ which has recently
been developed by Anatec and accepted by DTLR.

Issue 1 February 2003

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Add 9-1

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2

COLLISION MODELS
There are several commercial ship/Installation collision models that can be used
to calculate the frequency of a passing vessel colliding with an Installation.
Those currently available and the organisations which developed them include:
• CRASH

DNV

• COLLIDE

CorrOcean Safetec

• COLRISK

Anatec

• MANS

MSCN (Netherlands)

In part, the collision models use data contained in the shipping traffic database
to predict the frequency of a ship/Installation collisions. It is important that the
model uses traffic data which is accurate for the existing or proposed location of
the Installation under consideration.
In general the models calculate collision frequency from:
• The annual number of vessels passing the location on particular shipping
routes and their respective proximity to the location
• The probability of a vessel being on collision course with the Installation
• The probability that the vessel fails to recover from its collision course
• The probability that the Installation or ERRV fails to attract the vessel’s
attention in time to avoid collision
• Collision risk reduction measures at the field
Validation of the COLLIDE model predicted 3.77 powered collision up to 1995
and 0.69 drifting vessel collisions. In the same period there were three actual
powered collisions and no drifting collisions. The parameters used by some
these models have been modified to fit the model’s predictions to historical
incident data.

Passing Vessel – Ship Collision Assessment
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Addendum 10
Vessel Impacts – Guidance on Loads and
Consequences
1

INTRODUCTION
This addendum gives a brief overview of impact energies to be used in
assessing consequences and directs the user to appropriate references to be used
in calculating the effects of vessel impact on the Installation. It also identifies
gaps in current knowledge in evaluating the effect of vessel impact on topside
equipment. The text applies to fixed as well as floating Installations.

2

LOAD/IMPACT ENERGY
The following text applies to the impact of attendant vessels with fixed
platforms (such as jackets and jack-ups) and compliant Installations such as
articulated columns, semi-submersibles and Tension Leg Platforms (TLPs).
They do not apply to shuttle tanker collisions. Energies to be used in
FPSO/shuttle tanker collisions are discussed in Paragraph 3.3.
Since 1988, it has been standard practice to design for an impact energy
of 14MJ for sideways impact and 11MJ for bow or stern impact (References 3,
4, 11, 12, 15).
These values are based on attendant/support vessels of 5000t displacement
moving at 2m/s. The added mass is assumed to be 0.1 for bow or stern contact
and 0.4 for side impact. The impact energy is in the form of kinetic energy of
the moving vessel together with its added mass. For smaller or larger vessels,
the modified impact energy E in MJ can be calculated using the following
equation:

E =

1
(M + a )
2

v

2

Where: M = the displacement in tonnes
A = added mass of vessel (0.1M for bow or stern impact and 0.4 for
side impact) and
V = velocity of impact in m/s
Note:

For new designs the Norwegian Petroleum Directorate (NPD)
Regulations (Reference 14) requires that M and V to be assumed to be
not less than 5000t and 2m/s respectively.

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Impact velocity of 2m/s is based on probable velocity achieved during
erroneous operation or drifting in significant wave height of 4m.
On impact, the vessel and platform will absorb part of the energy as they deform
elastically and plastically (and in fracture if there is such failure). The rest will
remain as kinetic energy when the vessel and part of the fixed platform move
together. At the end of the event the energy spent in elastic deformation will be
converted to kinetic as the vessel rebounds. The rebound is largely due to the
global bending of fixed platform. In the case of floating units, rebound is
less significant.
Plastic deformation and fracture can affect structural integrity – and buoyancy/
stability in the case of floating units. They can also affect the integrity of
the equipment supported by the affected members or located behind them.
As the platform bends and then rebounds, the accelerations at deck level can be
significant and equipment can be affected. The following paragraphs briefly
consider the effects of vessel impact on structural integrity, equipment and
buoyancy/stability.

3

STRUCTURAL INTEGRITY
3.1 Fixed Structures
Assessment of structural damage due to impact is normally calculated using the
force indentation curves developed by Det Norske Veritas (DNV). They are
presented in References 4 and 5. A more recent set of curves are presented in
Reference 16. These references also provide guidance in using the curves. They
were developed for an impact of a 5000t vessel with infinitely stiff vertical
cylinders of 1.5 and 10m diameters. Even though the applicability of these
curves is limited, they are still being used widely. Unless it is certain that the
use of these of these curves and the analysis method used provides conservative
results, it is prudent to ensure that the energy absorbed by the Installation is not
less than 4MJ (Reference 11).
Detailed methods for calculating damage to leg or braces of jacket structures
can be found in References 4, 16 and 19. The methods described in these
references can also be applied to jack-up units. Techniques specifically
developed for jack-ups can be found in References 5 and 6.

3.2 Semi-Submersibles and Tension Leg Platforms
The information given in References 4, 5 and 16 are also useful in evaluating
the damage to semi-submersibles and TLPs. The columns are the areas most
vulnerable to collision with attendant vessels. These columns generally have
higher energy absorption capacity than jackets or the legs of jack-ups. However,
structural damage can also affect marine integrity by allowing water ingress
Vessel Impacts – Guidance On Loads and Consequences
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and/or causing damage to pipes essential for marine operations. Additionally,
collision with bracings should not be discounted.

3.3 FPSOs
Analysis of recent collision incidents between shuttle tankers and FPSOs
indicate that impact energy of 40MJ is foreseeable. The curves presented in
References 4, 5 and 16 cannot be used in designing or checking for collision
damage.

4

CONSEQUENCES
4.1 Equipment which can be Damaged or Affected by Collision
• Impacted directly:
– Riser, Emergency Shutdown (ESD) valves and in rare cases, conductors
are vulnerable in some fixed Installations
– Deck equipment located close to possible impact zones is vulnerable in
some FPSOs
– Hull of an unladen shuttle tanker which projects above the deck of an
FPSO as it approaches
• Equipment supported or shielded by a member damaged by vessel impact:
– Risers supported or shielded by chords or braces can be affected by large
deflection or failure of the latter
• Excessive deflection or relative displacements of equipment supports as a
result of structural damage
• Accelerations due to vessel impact sufficiently high to cause damage to
equipment supports, the equipment itself or its controls

4.2 Potential Consequences of Equipment Damage
• Escape of hydrocarbons
• Loss of power
• Loss of control
• Loss of stability/buoyancy
• Loss of emergency systems, such as fire fighting or emergency power

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• Degradation of EER systems
Often a combination of these consequences occur.

4.3 Assessing the Potential Consequences
In order to assess the potential consequences of vessel impact, deck
accelerations, the vulnerability and tolerance of various equipment to
accelerations, deflections and the relative displacements or rotation of their
supports should be known.
Investigation of accelerations due to vessel impact on three jacket structures is
reported in Reference 10. The accelerations varied between 0.1 to 0.9g
depending on the structure and location of impact on the deck. There are no
validated, simplified methods to calculate deck accelerations. Finite element
models developed for strength analysis are often used. Some such models may
not be suitable for dynamic loads. Failure to consider the softening effects of
impacted area could also produce unreliable results.
Accelerations significantly greater than 0.1g can cause problems for equipment.
There are no suitable guidelines available to assess the vulnerability of offshore
equipment to such accelerations.
A ‘walkdown’ study (Reference 9) can identify equipment, which is obviously
vulnerable to lateral loads or accelerations. It cannot identify all potential
problems. In the cases below, ALARP principles should be applied to decide
whether any modifications or further detailed investigations are justified or not.
1.

When:
• Equipment vulnerability is not fully understood or
• Consequences of failure are not obvious

2.

When assessing the risks due to equipment failure, if
• Levels of accelerations are not known accurately or
• Providing robust equipment appears to be difficult or
• Acceleration levels can not be reduced

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5

REFERENCES
1.

Amdahl, Jorgen and Eberg, Ernst: Ship Collision with Offshore Structures,
Structural Dynamics-EURODYN’93 Moan et al (eds) 1993 Balkema
Rotterdam, ISBN 90 5410336 I.

2.

Dubbers, R.A.W: A Dynamic Approach to Ship Impact Assessments,
Structural Dynamics – EURODYN’93, Moan et al. (eds) 1993 Balkema,
Rotterdam, ISBN 90 5410336 1.

3.

Det Norske Veritas: Safety Principles and Arrangements (January 2001).

4.

Det Norske Veritas (Veritec): Design Guidance For Offshore Steel
Structures Exposed To Accidental Loads (August 1988).

5.

Det Norske Veritas: Strength Analysis of Main Structures of Self-eleveting
Units, Classification Notes No 31.5 (February 1992).

6.

Det Norske Veritas: Investigation of the Impact Resistance of Jack-ups,
Health and Safety Executive (OTO 98-033).

7.

EATEC Limited: Blast and Shock Induced Vibrations in Offshore Jacket
Installations. Health and Safety Executive (OTH 94 430) 1995 ,
ISBN 0-7176-0937-5.

8.

Ellinas, C E and Walker, A C: Damage on Offshore Tubular Bracing
Members, IABSE rolloquium (Copenhagen 1983).

9.

EQE International Limited: Development of Walkdown Procedures and
Pilot Study for the Assessment of Topsides Equipment Subject to Blast
Induced Vibrations (OTH 93 415).

10. EQE International Limited: Strong Vibration Working Group Phase II JIP:
Final Report, Report No 179-04 R-05 Issue 1 (25 May 2000).
11. Health and Safety Executive: Offshore Installations: Guidance on Design
Construction and Certification (4th Edition Consolidated Edition)
March 1993, ISBN O 11 882116 4.
12. J P Kenny: Protection of Offshore Installations Against Impact, Health and
Safety Executive (OTI 88 535) 1988, ISBN O 11 412927 4.
13. Lloyds Register for Shipping: Boat Impact Study, Health and Safety
Executive (OTH 85 224).
14. Norwegian Petroleum Directorate: Regulations Relating to Load Bearing
Structures in the Petroleum Activities 1998.
15. Norwegian Technology Standards Institution: Norsok Standard, N-003.
Revision 1, February l999, Action and Action Effects.

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Add 10-5

Ship/Installation Collision Avoidance

16. Norwegian Technology Standards Institution: Norsok Standard, N-004
Design of Steel Structures, Design Against Accidental Loads (December
1998).
17. Ronalds, B F: Vessel Impact Design for Steel Jackets (OTC 6384) 1990.
18. Visser, W: Resistance of Jack-up Conductors to Boat Impact, Health and
Safety Executive (OTO 98 029).
19. Visser, V (Pim): Ship Collision and Capacity of Brace Members of Fixed
Steel Offshore Platforms, Health and Safety Executive, OTO Report 2002.

Vessel Impacts – Guidance On Loads and Consequences
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Ship/Installation Collision Avoidance

Addendum 11
Contacts
1

UK OFFSHORE OPERATORS ASSOCIATION
Second Floor
232-242 Vauxhall Bridge Road
London SW1V 1AU
UK
www.oilandgas.org.uk

2

UK HEALTH AND SAFETY EXECUTIVE
Publications:
Health and Safety Executive Books
PO Box 1999
Sudbury
Suffolk CO10 2WA
Tel: +44 (0)1787 881165
OTO research reports:
Health and Safety Executive
Research Strategy Unit
Bootle
Merseyside L20 3DL
Fax: +44 (0)151 951 3098
Chemicals and Hazardous Installations Division:
Health and Safety Executive
Lord Cullen House
Fraser Place
Aberdeen AB25 3UB
Tel: +44 (0)1224 252500
www.hse.gsi.gov.uk

3

MARITIME AND COASTGUARD AGENCY
Spring Place
105 Commercial Road
Southhampton SO15 1EG
UK
www.mcga.gov.uk

Issue 1 February 2003

Contacts
Add 11-1

Ship/Installation Collision Avoidance

4

IMCA
International Marine Contractors Association
Carlyle House
235 Vauxhall Bridge Road
London SW1V 1EJ
UK
www.imca-int.com

5

EMERGENCY RESCUE AND RESPONSE
VESSELS ASSOCIATION
ERRVA Limited
PO Box 1385
Calne
Wilts SN11 8XP

Tel:

+44 (0)1249 816618

www.errva.org.uk

6

OIL COMPANIES’ INTERNATIONAL
MARINE FORUM (PUBLICATIONS)
Witherby & Co
32-36 Aylesbury Street
London EC1R 0ET
UK

Tel:
Fax:

+44 (0)207 251 5341
+44 (0)207 251 1296

www.witherbys.com

7

INTERTANKO
International Association of Independent Tanker Owners
Bogstadveien 27B
PO Box 5804 Majorstua
0308 OSLO
Tel: +47 2212 2640
Norway
Fax: +47 2212 2641
www.intertanko.com

8

STEP CHANGE IN SAFETY
www.stepchangeinsafety.net

Contacts
Add 11-2

Issue 1 February 2003