Vessel

VESSEL IMPACT

1 Scope

This section provides guidance for the assessment of safety case content with respect to vessel

collisions, from hazard identification through to consequence determination, including risk

management measures. Interfaces with other sections are identified.

2 Assessment of Adequacy of Demonstration

The evaluation of risk that might stem from each major accident hazard is to be assessed by

identification of the factors that might result in an adverse combination of a hazard source and an

initiator [causal chains], together with identification and evaluation of escalation paths that might

result [consequence chains].

Two broad hazard sources can be identified and divided into a number of different vessel types

thus:

• Attendant vessels

• Passing vessels

For a major accident to be realised, these Hazard Sources need an Initiator. For vessel collisions,

the following broad categories of Initiator are proposed:

• Positioning Failure

• Navigational Failure

• Procedural Failure

• Human Error

Evaluation of risk will need consideration of the likelihood and consequence factors:

• Frequency

• Consequence

The usual measures are employed in controlling the hazard:

• Inherent Safety

• Prevention through

• Procedures

• Personnel

• High Visibility

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Source of Hazard Initiators Risk Evaluation Risk Management

Measures

Performance

Standards

• Incident Reporting and Analysis

• Detection

• Control through

• Quality Assurance

• Operating envelope

• Procedures

• Fenders/barriers

• Mitigation

• Platform ESD system

• Pipeline subsea ESD valve

• Shock resistant plant

• Physical protection

• Structural integrity

• Robustness

• Redundancy

• Reserve strength

• Double hulls

• Emergency Response

3 Depth of Assessment

This section gives guidance on the depth of assessment required to determine the adequacy of the

demonstration that measures have been or will be taken to ensure compliance with the relevant

statutory provisions.

Where relevant sections of the safety case are consistent with the good practice identified in the

assessment sheets, there will usually be no need for an assessor to probe into the details of the

application of this practice. However, this may be a suitable issue to follow-up through inspection.

4. The assessor should examine the adequacy of the hazard identification, risk evaluation and

management in conjunction with the contents of the Categorisation Table below:

Vessel Impact

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HS1 - Loss of

Integrity

• Structure

• Process

• Pipelines

• Wells

G1 - Attendant and

Passing Vessels

Frequency Inherent Safety

HS2 - Fatalities

of Workforce

G2 - Failures

• Positional

• Navigational

• Procedural

• Human Error

F4 - Subsea

Facilities,

Exclusion zone

F1 - Likelihood

Factors (including

historic data)

Prevention

F5 - Verification,

Testing and

Inspection

F6 - SBVs,

Communcations

and Procedures

F7 - SBVs, Visual

& Radar, Platform

Mounted Radar,

Automated

Systems

F8 - Procedures

[including Vessel

Contracting and

Suitability,

Platform

Operations,

Inspections,

Marine

Operations and

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HS1 Loss of Integrity, Process, Pipelines, Wells

HS2 Fatalities of Workforce

Combined

Operations]

Consequences

F2 - Loss of

Integrity to

Installation

Systems

[structural,

process,

pipelines, wells]

F3 - Fatalities to

Workforce

Mitigation

F9 - Physical

Protection

F10 - Robust

Structure, Plant

and Equipment

1. Confirmation should be obtained that the risks to the workforce, integrity of the structure, the

topside process and safety related equipment, pipelines and wells from all foreseeable attendant

and passing vessel collisions are or will be controlled to ensure compliance with the relevant

provisions. This is achieved by a multidisciplinary approach using assessment sheets contained in

the relevant sections.

2. There are likely to be differing company standards used in demonstration and each should be

examined for equivalence with general ALARP principles.

3. Relevant Legislation, ACOP and Guidance includes:

• Offshore Installations (Safety Case) Regulations 2005

• Offshore Installations and Wells (Design and Construction, etc) Regulations 1996

• Assessment Principles for Offshore Safety Cases [APOSC]

4. Specific Technical Issues:

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G1 Attendant and Passing Vessels

For passing vessels there should be time to take some form of emergency action and assessment

should, in the main, be carried out in line with that in Section 10 Emergency Response. Attendant

vessels may provide a more instantaneous vessel collision and hence it is expected that

appropriate robustness is built into the installation engineering and safety systems.

5. Other Related Assessment Sheets in this Section are:

F1 Likelihood Factors [including historic data]

F2 Loss of Integrity to Installation Systems

F3 Fatalities to Workforce

F4 Subsea Facilities, Exclusion Zone

F5 Verification, Inspection, Testing

F6 SBVs, Communications, and Procedures

F7 SBVs visual and radar, platform mounted radar, automated systems

F8 Procedures - including Vessel contracting, vessel suitability, platform, operations,

inspections, marine operations & combined operations

F9 Physical protection

F10 Robust Structure, plant and equipment

6. Cross-Referenced Sections and Sheets are:

Sheet 2.2.1.G14 Boat Impact

Sheet 2.2.2.G5 Collision/Grounding

Sheet 2.2.4.F8 Ship Collision

Section 2.4.3 Human and Organisational Factors

Section 2.1.2 Risk Assessment (including Human Vulnerability)

1. Confirmation should be obtained that the all foreseeable attendant vessels have been identified

and that particular passing vessels that may be in the vicinity of the installation have been

identified.

2. The adequacy of vessel identification process can only be assessed on an individual basis.

Typical vessels may include:

• Attendant vessels

• Standby vessels

• Supply vessels

• Multi-purpose vessels

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• MODUs

• Semis

• Jack-ups

• Drill ships

• Accommodation units

• Shuttle tankers

• Heavy lift vessels

• Anchor handling vessels

• Diving support vessels

• Survey vessels

• Well intervention vessels

• Tugs

• Barges

• Multi-role vessels [standby and supply]

• Pipe lay

• Counter pollution vessels

• Passing vessels

• All of the above [when headed for other installations]

• Merchant vessels, including:

• Ferries

• Fishing craft

• Pleasure crafts

• Naval craft

• Submarines

Further consideration will be required where installations are located in known shipping routes.






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G2 Failures: Positional, Navigational, Procedural, Human Error

None


None


None

1. For a major accident to be realised, the collision of passing and attendant vessels is caused by

a failure on those vessels. For vessel collisions, the following broad categories of Initiator are

proposed:

• Positioning Failure

• DP failure

• Mooring failure

• Extreme weather

• Installation moves

• Weather vaning

• Navigational Failure

• Watchkeeping failure

• Navigation equipment failure

• Navigation aids failure

• Mechanical failure

• Control system failure

• Power failure

• Procedural Failure

• Incorrect/Inappropriate

• Not correctly applied

• Human Error

• Commission/Omission/Fatigue

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Specific assessment and guidance on these failures for passing vessels are outside the scope of

this document. However, some control can be expected on reducing the risk for initiators for

attendant vessels.

• OGUK Guidelines for Ship/Installation Collision Avoidance, OP013,2010

• OGUK Common guidelines for safe management of offshore supply and anchor handling

operations (North West European Area) – Issue 2, OPO20, 2009

• Offshore operations notice no 14, Guidance on Coast Protection Act 1949 - consent to locate

and the marking of offshore installations, 2009

• Offshore operations notice no 61, Management of collision risk - Radio communication

between offshore installations, their standby vessels and merchant ships, 2003

2. The above guidelines are generic in nature and treatment of the initiators for individual

platforms and platform layouts should be assessed.






Initiators for attendant vessels will be vessel, company and installation specific. Assessment should

seek out this information.

5. Other Relevant Assessment Sheets in this Section are:

F5 Verification, Testing & Inspection

F6 SBVs, Communications, and Procedures

F7 SBVs Visual and Radar, Platform Mounted Radar, Automated Systems

F8 Procedures - Including Vessel Contracting, Vessel Suitability, Platform Operations,

Inspections, Marine Operations & Combined Operations

6. Cross Referenced Sections and Sheets are:

Section 2.2.2 Stability - Maritime Integrity

Section 2.2.3 Position Keeping – System failures

Section 2.3.4 Emergency Response


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F1 Likelihood Factors (including historical data)


F3 Fatalities to Workforce

1. Confirmation should be obtained that the likelihood of vessel collisions has been derived from a

recognised model or from a local marine traffic survey.

• Use of software, ‘COAST, CRASH, COLLIDE, MAN’

• Shipping surveys

• Historic data

2. Where the hazard identification process listed above has not been used, judgement as to the

adequacy can only be assessed on an individual basis.

Further consideration will be required on an installation specific basis.

• Installation location, particularly when sited near known shipping routes

• No dedicated standby vessel

• Vessel control and speed

• Point of contact with installation

• Vessel orientation






None


None


None

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1. Confirmation should be obtained that all consequences of a vessel collision have been

considered. The consequences may involve many disciplines and a multidisciplinary approach

should have been used.

2. Where a multidisciplinary approach has not been used, the adequacy should be judged by

examining the completeness of the technical consequences documented.






• Injuries to people

• Direct contact

• Strong vibration

• Loss of structural integrity

• Direct contact


• Large relative deformation

• Loss of stability

• Direct contact


• Large relative deformation

• Loss of position

• Direct contact

• Loss of containment

• Loss of other safety critical equipment

• Loss of EER


F9 Physical Protection

F10 Robust Structure, Plant and Equipment


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F4 Subsea Facilities, Exclusion Zone

F5 Verification, Testing and Inspection

Sheet 2.2.2.G5 Collision/Grounding

Sheet 2.3.4.F8 Ship Collision


Section 2.1.2 Risk Assessment (including Human Vulnerability)

7. Lead Assessment Section for this Sheet:

OSD5.5

8. Team responsible for authoring and updating this sheet:

OSD5.3

1. Confirmation should be obtained that, where appropriate in design cases only, subsea facilities

have been considered in the concept selection thus providing inherent safety by eliminating the

need for surface facilities. Where surface facilities are provided confirmation should be obtained

that the safety system acknowledges the management of appropriate exclusion zone.

2. Not applicable.





4. Specific technical issues:

None


None


Section 2.4.1 Wells – Risk evaluation and management


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1. Confirmation should be obtained that procedures and equipment for the prevention of collisions

follow the requirements of the recognised guidance/codes of practice below:

• OGUK Guidelines for Ship/Installation Collision Avoidance 2010

• OGUK Emergency Response & Rescue Vessel Survey Guidelines – Issue 5, HS009, 2008

• OGUK Emergency Response & Rescue Vessel Management Guidelines – Issue 4, HS008,

2008

• OGUK Common Guidelines for the Safe Management of Offshore Supply and Anchor

Handling Operations (North WestEuropean Area) – Issue 2, OP020, 2009

• Guidance & ACOP to the Offshore Installations (Prevention of Fire & Explosion &

Emergency Response) Regulations 1995 (L65)

• Further guidance can be obtained from:

• OTO 1999 052 Effective Collision Risk Management for Offshore Installations

• Offshore Operations Notice ON61 Management of Collision Risk – Radio communication

between offshore installations, their standby vessels and merchant ships, 2003

2. Where standard or guidance other than that listed above has been used, judgement as to the

adequacy of the detection system can only be assessed on an individual basis.

Alternative/additional measures may be required for other types of field arrangement or when

standby vessel sharing is agreed.






None


F7 SBVs Visual & Radar, Platform Mounted Radar, Automated Systems

F8 Procedures [Including Vessel Contracting, Vessel Suitability, Platform Operations, Inspection,

Marine Operations and Combined Operations]




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F6 SBVs, Communications and Procedures

9. Confirmation should be obtained that procedures and equipment for the prevention of collisions

follow the requirements of the recognised guidance/codes of practice below:

• UKOOA Guidelines for Ship/Installation Collision Avoidance 2003

• UKOOA Guidelines for Survey of Vessels Standing by Offshore Installations 2001

• UKOOA Guidelines for the Management & Operation of Vessels Standing by Offshore

Installations 2001

• UKOOA Guidelines for the Safe Management & Operation of Offshore Support Vessels 2002

• Offshore Installations (Prevention of Fire and Explosion, and Emergency Response)

Regulations 1995 ACOP & Guidance L65

• Further guidance can be obtained from:











None



F8 Procedures [Including Vessel Contracting, Vessel Suitability, Platform Operations,

Inspection, Marine Operations and Combined Operations]




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F7 SBVs, Visual and Radar, Platform Mounted Radar, Automated Systems

1. Confirmation should be obtained that detection equipment, operation and procedures follow the

requirements of the recognised guidance/codes of practice below:


• UKOOA Guidelines for the Management & Operation of Vessels Standing by Offshore

Installations 2001

• L65 Guidance & ACOP to the Offshore Installations (Prevention of Fire and Explosion, and

Emergency Response) Regulations 1995

Further guidance can be obtained from:


• OTO 97 058 Performance of Standby Vessel Radar

2. Where standards or guidance other than that listed above has been used, judgement as to the





Offshore Installations (Safety Case) Regulations 2005

Offshore Installations and Wells (Design and Construction, etc) Regulations 1996

Assessment Principles for Offshore Safety Cases [APOSC]


None



F6 SBVs, Communications & Procedures

F8 Procedures [Including Vessel Contracting, Vessel Suitability, Platform Operations,

Inspection, Marine Operations and Combined Operations]



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F8 Procedures (including Vessel Contracting, Vessel Suitability, Platform Operations,

Inspections, Marine Operations and Combined Operations)


1. Confirmation should be obtained that the control of collision risks follow the requirements of the

recognised guidance/codes of practice below:


• UKOOA Guidelines for the Safe Management & Operation of Offshore Support Vessels 2002

• UKOOA Guidelines for Survey of Vessels Standing by Offshore Installations 2001

• L65 Guidance & ACOP to the Offshore Installations (Prevention of Fire and Explosion, and

Emergency Response) Regulations 1995

Further guidance can be obtained from:











None



F6 SBVs, Communications & Procedures





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F9 Physical Protection

1. Confirmation should be obtained that all Safety Critical Elements [SCEs] within zones

vulnerable to impact from attendant vessels are properly protected against damage due to direct

impact, large relative deformations and strong vibrations. Examples of such SCEs are:

• Risers [possibly including associated ESD valves]

• Conductors

• Caissons

• Escape routes and other EER related items

There is no specific guidance about what constitutes adequate protection, although some of the

analysis techniques used in Section 3 Loss of Structural Integrity may be used to demonstrate

strength through design.

2. Due to the lack of guidance at present, adequacy can only be assessed on an individual basis.

Further consideration will be required where damage to SCEs is tolerated on the basis that other

safeguards are in place. This may require discussion with other topic teams.






None




Section 2.2.1 Loss of Structural Integrity

Section 2.3.1 Loss of Containment - Process

Section 2.3.2 Loss of Containment - Pipelines

Section 2.4.1 Wells – Risk evaluation and management


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F10 Robust Structure, Plant and Equipment

1. Confirmation should be obtained that the safety critical plant and equipment in the installation

can sustain the large displacements and strong vibrations resulting from reasonably foreseeable

collisions from attendant vessels [see Section 3 Loss of Structural Integrity].

For structures there is limited authoritative guidance in this area:

ON 27 Status of Technical Guidance on Design, Construction and Certification

Also two main methods are currently available:

• Qualitative – through techniques such as Walkdown

• Quantitative – by structural analysis coupled to survival criteria for the plant and equipment

2. Due to the lack of guidance at present, adequacy can only be assessed on an individual basis.






None


F2 Loss of Integrity of Installation Systems


Section 2.2.1 Loss of Structural Integrity

Section 2.3.1 Loss of Containment - Process

Section 2.3.2 Loss of Containment - Pipelines

Section 2.4.1 Wells - Risk evaluation and management

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Documents

Vessel