DNV-RP-H102 Overview Final

16/12/2014

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DNV GL © 2014 27 November 2014 SAFER, SMARTER, GREENERDNV GL © 2014

27 November 2014Niall McLeod

OIL & GAS

An Overview of DNV-RP-H102

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DNV GL © 2014 27 November 2014

Introduction

How does DNV-RP-H102 link with other DNV rules and standards?

What is DNV-RP-H102? (high level overview)

Where do the Noble Denton Marine Assurance and Advisory Guidelines fit it?

“To establish technical guidelines and recommendations that would result in an acceptable low risk of failure for the marine operations needed during removal of

offshore installations.” – DNV-RP-H102 Objective

This is a general introduction to DNV-RP-H102

– Specifics will be discussed in detail during later presentations

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Offshore Document overview

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DNV specific;RULES

General industry use;REQUIREMENTS

General industry use;RECOMMENDATIONS


Link between RP-H102 and the “Rules”

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DNV Rules for Planning and

Execution of Marine Operations

DNV-RP-H102

Marine Operations During Removal of

Offshore Installations

Guidelines on how to apply requirements of

the rules

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Link between RP-H102 and Current DNV Offshore Standards

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VMO Standard (Replaces Rules for Planning

and Execution of Marine Operations)

DNV-RP-H102

Marine Operations During Removal of

Offshore Installations

Reference Title

DNV-OS-H101 Marine Operations, General

DNV-OS-H102 Marine Operations, Design & Fabrication

DNV-OS-H201 Load Transfer Operations

DNV-OS-H202 Sea Transports (not yet released)

DNV-OS-H203 Transit and Positioning of Mobile Offshore Units

DNV-OS-H204 Offshore Installation Operations

DNV-OS-H205 Lifting Operations

DNV-OS-H206 Sub Sea Operations


DNV-RP-H102, April 2004

Chapter 1 – Introduction

Chapter 2 – Part I – General Requirements

Chapter 3 – Part II – Operation Specific Recommendations

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Chapter 1 - Introduction


– Objective

– Clarifications

– Application

– The relationship between this RP and the rules

– Classification of objects

– Alternative methods

– Terminology and definitions

– Removal and installation - differences

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– Objective

– Clarifications

– Application






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1.3 Application

Applicable for removal of offshore structures, such as:

– Topsides

– Steel jacket structures

– Loading columns

– Subsea installations

Does not cover:

– Gravity base structures

– Removal by “single lift” vessels

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– Objective

– Clarifications

– Application






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1.5 Classification of Objects

Two types of classification for objects

– REUSE

– Objects that are to be reused

– SCRAP

– Objects that are to be safely scrapped

Classification may influence

– Limit states

– Failure modes

– Acceptance criteria

– Design factors

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– Objective

– Clarifications

– Application






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1.6 Alternative methods

RP describes practice recommended by DNV

Does not inhibit use of other approaches

If alternative methods are used it shall be documented that:

– The main objective is fulfilled

– Operational control and redundancy ≥ that obtained by following RP

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Chapter 2 – Part I - General Requirements


– Planning

– Operations

– Loads

– Load analyses

– Structural analysis and capacity checks

– Materials and fabrication

– Equipment, systems and vessels

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– Planning

– General

– Planning principles

– Documentation

– Risk evaluations and management

– Weight, CoG, buoyancy and CoB

– Operation period and environmental criteria

– Surveys

– Project specific requirements

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2.1 Planning


– Planning

– General


– Documentation




– Surveys


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2.1.2 Planning principles

Safe to Safe

– Planning and preparation to bring object from one safe condition to another

Risk management

– ALARP principle

Fail Safe

– Handled object to remain in stable and controlled condition if a failure occurs

Recovery

– Should be possible to recover the object to a safe condition

Point of No Return (PNR)

– PNR and safe conditions after passing PNR to be considered and defined.

Contingency planning

– Identify possible contingency situations and prepare plans or actions

Proven methodologies

– Design and planning based on well proven principles, techniques, systems and equipment. Use of new technology should be qualified

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2.1 Planning


– Planning

– General


– Documentation




– Surveys


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2.1.5 Weight, CoG, buoyancy and CoB

Preferably weight and CoG should be determined by weighing

Weighing may not always be possible

– Establish based on:

– Data from construction and installation of platform

– Information gathered by operator during lifetime of platform

– Confidence level of estimates to be considered

– Conservative inaccuracy factors may be insufficient

so should also consider:

– Extreme positions of CoG and CoB

– Object weight equal to lowest possible

weight

– Buoyancy equal to maximum feasible

buoyancy

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2.1 Planning


– Planning

– General


– Documentation




– Surveys


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2.1.6 Operation period and environmental criteria

Operations can be defined as unrestricted or restricted

– Could impact on safety and cost

– Should be defined early in planning process

Methods given in rules for defining environmental design loads consider duration of operation

– For unrestricted operations less than 5 days reduction in design wind speed and wave height found by pure statistical methods could be considered

– Magnitude of reductions need to be agreed with all parties (including MWS)

– Proven reliability of forecasts

– Available contingency procedures

– Consequences of exceeding defined environmental conditions

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2.1 Planning


– Planning

– General


– Documentation




– Surveys


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2.1.7 Surveys

Systematic survey program to be made and verified

Due consideration paid to scheduling

– Information needs to be received early enough to be included in planning but not be too old to be reliable

Main scope of survey is to:

– Confirm original design data still valid

– Gather required data not available from

documentation

– Check all relevant items i.e. dimensions,

possible obstructions

– Identify items that could represent a safety risk

Conservative assumptions to be made on design basis data not verified by survey

Inaccuracies in applied survey methods to be considered by applying contingency factors

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– Planning

– Operations

– Loads

– Load analyses




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2.2 Operations


– Planning

– Operations

– General

– Operation reference period

– Operational limiting criteria

– Forecasted and monitored operational limits

– Weather forecasting

– Organisation

– Preparation and testing

– Status of object

– Marine operations manual

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2.2 Operations


– Planning

– Operations

– General





– Organisation




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2.2.4 Forecasted and monitored operational limits

Uncertainty in monitoring and forecasting to be considered

– Recommended that this is done using an “alpha” factor

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Operational Period [h]

Wave/response monitoring (Mon.)?Weather forecast level A (WF-A)?

1<Hs≤2 2<Hs≤4 2<Hs≤4

TPOP ≤ 6 Mon. = yes 0.9 1.0 1.0

TPOP ≤ 12 Mon. = yes and WF-A = yes 0.82 0.92 0.97

Mon. = yes or WF-A = yes 0.75 0.84 0.88

Mon. = no and WF-A = no 0.68 0.76 0.80


Mon. = yes or WF-A = yes 0.69 0.78 0.83

Mon. = no and WF-A = no 0.63 0.71 0.75


Mon. = yes or WF-A = yes 0.62 0.70 0.74

Mon. = no and WF-A = no 0.56 0.64 0.67


Mon. = yes or WF-A = yes 0.56 0.65 0.69

Mon. = no and WF-A = no 0.51 0.59 0.63


2.2 Operations


– Planning

– Operations

– General





– Organisation




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2.2.5 Weather forecasting

Categorisation of forecast levels based on operational sensitivity

– Level A for weather sensitive offshore operations with TR>24hrs

– Level B for weather sensitive offshore operations with TR<24hrs

– Level C for non weather sensitive offshore operations and inshore operations

Forecast is acceptable to start marine operations if all items are within operational criteria for complete operational reference period TR

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– Planning

– Operations

– Loads

– Load analyses




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2.3 Loads


– Planning

– Operations

– Loads

– General

– Permanent loads – G

– Variable functional loads – Q

– Environmental loads – E

– Accidental loads – A

– Deformation loads – D

– Weight and CoG estimates/calculations

– Marine growth

– Buoyancy

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2.3 Loads


– Planning

– Operations

– Loads

– General

– Permanent loads – G

– Variable functional loads – Q

– Environmental loads – E

– Accidental loads – A

– Deformation loads – D

– Weight and CoGestimates/calculations

– Marine growth

– Buoyancy

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2.3.7 Weight and CoG estimates/calculations

Characteristic value of weight should be taken as “expected weight”

– Maximum or minimum expected weight

– Best estimate multiplied or divided by contingency factor

Contingency factor to be found by:

– Identify best estimate weight (BE)

– Estimate by reasonable conservative assumptions the maximum or minimum expected weight (MW)

– Calculate the weight contingency factor as MW/BE

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Description of weight control system/weight calculation method

Part of Object

WCF

Weighing with tolerance < ± 3% All 1.0

Weighed weight at installation and weight control during lifetime

All 1.05

Estimated weight, see Pt. 1 Ch. 3 Sec.3.5.2 for objects where no modifications during the lifetime has taken place

All 1.1

Review of as built drawings including all modifications during the lifetime and thorough inspections to verify drawings

Structural 1.05

Review of as built drawings and records of history

Structural 1.1

Well documented installation weights and thorough inspections

Equipment and accessories

1.1

Documented installation weights not available, but thorough inspections

Equipment and accessories

1.2

Calculated based on that all possible members/ tanks are flooded

Entrapped water

1.0

Calculated according to NORSOK, see 2.3.8

Marine Growth

1.0

Estimated based on surveys Marine Growth

1.2




– Planning

– Operations

– Loads

– Load analyses




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2.4 Load analyses


– Planning

– Operations

– Loads

– Load analyses

– General

– Friction

– Characteristic loads

– Sensitivity studies

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2.4 Load analyses


– Planning

– Operations

– Loads

– Load analyses

– General

– Friction

– Characteristic loads

– Sensitivity studies

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2.4.2 Friction

If documented a reduction in the design load may be considered

– Relevant for seafastening

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Surface 1 Surface 2 Condition μ

Steel Steel Wet 0.0

Steel Steel Dry 0.1

Steel Timber (wood) Wet 0.2

Steel Timber (wood) Dry 0.3

Steel Rubber Wet and Dry 0.3




– Planning

– Operations

– Loads

– Load analyses




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2.5 Structural analysis and capacity checks


– Planning

– Operations

– Loads

– Load analyses


– General

– Design considerations

– Method

– Failure modes

– Design loads and conditions

– Design analysis

– Structural resistance

– Accept criteria – general

– Accept criteria - SCRAP

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– Planning

– Operations

– Loads

– Load analyses


– General


– Method

– Failure modes


– Design analysis




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2.5.4 Failure modes

Failure mode is relevant if:

– Considered possible

– Anticipated consequences cannot be disregarded

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2.5.4 Failure modes

Failure mode is relevant if:

– Considered possible

– Anticipated consequences cannot be disregarded

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Elements or objects and operations as indicated

Failure Mode Limit state group(s) and accept criteria (ref.)

Jackets & piled subsea structures after the piles are (partly) cut

Overturning – on bottom stability ULS/FLS – No overturning 1)

All objects transported on seagoing vessels Overturning of cargo ULS – No uplift 2)

All vessels and self floating objects Loss of hydrostatic/ dynamic stability ULS and ALS – See Pt.1 Ch.2Sec.4

REUSE all operations Unacceptable damages ULS/FLS/SLS – See 2.5.8

SCRAP all operations Excessive deformations ULS/FLS – See 2.5.9

SCRAP all lifts Dropped load ULS – See 2.5.9, 2.7.2 and 2.7.3

All lifts in water Slack slings; DAF > 2.0 ULS 3) – No slack, DAF 2.0

Seafastening Sliding of object ULS – See 2.7.4

Seafastening Overturning of object ULS – See 2.7.4

Seafastening Unacceptable cracks FLS – See 2.7.4

Grillage Unacceptable damage to transport vessel ULS – See 2.7.4

Guides and bumpers Exceeding “allowable” stresses Not relevant for design according to the rules but see 3.3.5

Guides and bumpers Excessive deformations Fulfilment of functional requirements to be documented

1) Neither caused by excessive uplift nor soil or structural failure2) See 2.7.4 for guidance note3) This check is often done without load (safety) factors. i.e. a SLS case. This is not acceptable as the only check to verify

that DAF ≤ 2.0

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– Planning

– Operations

– Loads

– Load analyses


– General


– Method

– Failure modes


– Design analysis




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2.5.9 Accept criteria - SCRAP

Acceptable in ULS to consider large plastic deformations and failure of single members if documented:

– Structure will not transform into a mechanism i.e. collapse

– Failure of critical members/components will not occur when considering any possible redistribution of loads

– Possible redistribution of loads will not overload

supporting equipment or structures

– FLS does not represent a relevant failure mode

considering that a limited number of cycles could be

critical if large deformations are allowed

– Any possible SLS specified by the owner is satisfied

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– Planning

– Operations

– Loads

– Load analyses




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2.6 Materials and fabrication


– Planning

– Operations

– Loads

– Load analyses



– General

– Existing materials

– Selection of new materials

– Tolerances

– Assembly and welding

– Weld inspection

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– Planning

– Operations

– Loads

– Load analyses



– General



– Tolerances


– Weld inspection

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2.6.2 Existing materials

Existing materials to be documented based on:

– Original fabrication documentation

– Material testing

– If neither available minimum material strength

properties as considered possible to be

assumed

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– Planning

– Operations

– Loads

– Load analyses



– General



– Tolerances


– Weld inspection

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2.6.3 Selection of new materials

For materials in temporary structures

– Design temperature should be defined based on season and location

– For materials to be welded offshore a SMYS ≤ 355 MPa is recommended

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Selection criteria for structural category

Examples for typical structures involved in removal operations

Recommended Structural Category

Insp. Cat.See DNV-OS-C101

Failure Consequence Structural Part DNVSee DNV-OS-C101

NORSOKSee NORSOK-N-004

Substantial and the structure possesses limited residual 2)

strength

Complex joints 1) • Padeyes and other lifting points• Seafastening elements without

redundancy• Spreader bars

Special DC1 – SQL1 I

Simple joints and members

Primary (Special) 3)

DC2 – SQL2 (SQL1) 3)

Not substantial as thestructure possesses residual 2) strength

Complex joints 1) • Structures for connection of mooring and towing lines

• Grillages• Redundant 2) seafastening elements



II

Simple joints and members



Any structural part where failure will be without substantial consequences

• Bumpers and guides• Fender structures• Redundant 2) (parts of) grillages

Secondary DC5 – SQL4 III

1) Complex joints means joints where the geometry of connected elements and weld type leads to high restraint and to triaxialstress pattern

2) Residual strength (redundant) means that the structure meets requirements corresponding to the damaged condition in the check for ALS, with failure in the actual joint or component as defined in the damage

3) Selection where the joint strength is based on transference of tensile stresses in the through thickness direction of the plate

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– Planning

– Operations

– Loads

– Load analyses



– General



– Tolerances


– Weld inspection

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2.6.6 Weld inspection

Normally final inspection and NDT of welds shall not be carried out before 48 hours after completion

– Materials with SMYS of ≤355 MPa could be reduced to 24 hours

– When weld inspection is on critical path minimum waiting time may be reduced

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Inspection Category

Minimum extent of NDE

Minimum waiting time before NDE

Visual NDT 1) SMYS 2)

355 MPaSMYS>355 MPa

I 100% 100% 24 hours 3) 48 hours 5)

II 100% 20% 4) Cold weld 3) 24 hours 5)

III 100% 5% 4) Cold weld 3) 24 hours 5)

1) Test method to be selected according to the type of connection, see DNV-OS-C401 (Ch.2 Sec.3 Table C1)

2) SMYS to be defined according to the specification for the actual material used and not according to the minimum required design value

3) The NDT could start when the weld is cold, but it is recommended to wait as long as practicable

4) An increased % rate shall be evaluated if defects are found and/ or weld conditions and precautions, see 2.6.5, are not fully satisfactory

5) The use of PWHT (post weld heat treatment) could (will) reduce the required waiting time

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– Planning

– Operations

– Loads

– Load analyses




53


2.7 Equipment, systems and vessels


– Planning

– Operations

– Loads

– Load analyses




– General

– Cranes

– Equipment with certified WLL (SWL) or MBL

– Seafastening and grillage

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– Offshore crane lift operations

– Subsea operations

– Back-loading offshore

– Transport from offshore locations

– Onshore transfer

– Dismantling

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3.1 Offshore crane lift operations



– General

– Loads

– Lifting equipment

– Design conditions, structures

– Lift points

– Lift operation

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3.1 Offshore crane lift operations



– General

– Loads

– Lifting equipment

– Design conditions, structures

– Lift points

– Lift operation

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3.1.4 Design conditions, structures

For design of pad eyes and other structural elements additional design factors should be applied

Tolerances which may result in an excessive lateral load component or skew loads should be avoided

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Element Category 1) γc

Lift points including attachments to object 1.3

Lifting equipment (e.g. spreader frames or beams, plate shackles)

1.3

Main elements supporting the lift point 1.15

Other elements of lifted object 1.0

Elements not contributing to the overall structural integrity of a lifted object that will be scrapped – (SCRAP), see 1.5

≤ 0.8 2)

1) γc is meant to account for severe consequences of single element failure. Categorisation of elements according to the table above should hence duly consider redundancy of elements

2) Any factor γc could in principle be agreed with the owner of these elements

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– Dismantling

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3.2 Subsea operations




– General

– Load cases

– Design loads

– Trapped water

– Preparations and operations

– Subsea cutting

– Verification of cutting

– Soil resistance

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– General

– Load cases

– Design loads

– Trapped water


– Subsea cutting


– Soil resistance

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3.2.4 Trapped water

Possible effects of trapped water during lifting out of water should be considered

– Considerable increase in crane hook load

– Unacceptable tilt of lift due to change in CoG

– Reduced lift stability due to free surface effects combined with changed CoG

If necessary structure should be perforated before the lift in order to reduce the effect of trapped water

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– General

– Load cases

– Design loads

– Trapped water


– Subsea cutting


– Soil resistance

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3.2.6 Subsea cutting

Should primarily be planned to be performed by WROV

If cutting after PNR redundancy and back up equipment must be considered

Following cutting platform must comply with unrestricted conditions

– Strength

– On bottom stability

– Unless cut out section

immediately removed

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– General

– Load cases

– Design loads

– Trapped water


– Subsea cutting


– Soil resistance

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3.2.7 Verification of cutting

Prior to lifting requirement to verify cut has been achieved

Verification method should be evaluated

– Documented reliability

– Importance of accurately verifying cut

In some cases two independent methods of verification may have to be used

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– Dismantling

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3.3 Back-loading offshore





– General

– To deck of crane vessel

– To deck of transport vessel

– Dynamic set down loads

– Guiding systems

– Temporary securing

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– General




– Guiding systems


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3.3.4 Dynamic set down loads

Both horizontal and vertical set down loads to be documented

Various methods could be applicable

– Simplified (conservative) calculations

– Advanced analysis i.e. time domain

– Model tests

– Combination of above

Method should be selected based on:

– Operational criticality

– Structural margins

– Acceptance criteria

Method should consider:

– Transport vessel motions

– Crane vessel motions

– Crane lowering speed…

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– General




– Guiding systems


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3.3.5 Guiding systems Rules imply dynamic design loads need to be calculated

Normal practice for installation guides and bumpers is to use empirical “static” design loads i.e. %age of objects weight

Calculation of dynamic design loads recommended for set down on transport vessel (Rules approach)

Empirical method could be used for set down on crane vessel deck and for “lift-out” guides

Size, layout and design should be detailed considering:

– Functional requirements

– Strength requirements (Plastic deformations could normally be allowed)

– Operational procedure

– Maximum calculated relative movements

– Maximum calculated or allowable tilt

– Uncertainties in dimensions

– Final position tolerances

– Any requirement for guides to act as temporary seafastening

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– Dismantling

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3.4 Transport from offshore locations






– General

– Transport (design) criteria

– Manuals and procedures

– Transport on crane vessel

– Ship transport

– Barge transport

– Self floating transport

– Seafastening procedure

– Stability

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– General




– Ship transport

– Barge transport



– Stability

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3.4.2 Transport (design) criteria

Weather routing may be allowed for TR ≤72 hours provided:

– Ample contingency time

– Minimum documented transit speed with most unfavourable operational environmental conditions

– Estimated contingency transit time considering

– Available backup

– Redundancy of propulsion system(s) / tugs

For TR >72 hours transit should be unrestricted

Heading controlled transport may be allowed

– Transport shall sustain head and quartering seas

– All sea directions not included in ULS should be considered as ALS

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– General




– Ship transport

– Barge transport



– Stability

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3.4.6 Barge transport

Transport on an unmanned barge shall not commence until seafastening is complete

Towing force shall be sufficient to maintain zero speed in open sea and 1.0m/s in coastal, narrow or shallow waters:

– Sustained wind speed – 20m/s

– Head current velocity – 1.0m/s

– Significant wave height – 5.0m

Above may be relaxed based on tow restrictions or seasonal environmental data

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– Dismantling

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3.5 Onshore transfer







– General

– Skidding or trailers

– Lift-off

– Crane lifting

– Moorings

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3.5 Onshore transfer







– General

– Skidding or trailers

– Lift-off

– Crane lifting

– Moorings

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3.5.5 Moorings

Mooring of transport vessel during onshore transfer

– 10 year return period seasonal condition

– Any one line broken condition shall be complied with

– Stand by tugs may compensate a deficient mooring system

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– Dismantling

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3.6 Dismantling







– Dismantling

– General

– Offshore dismantling

– Onshore dismantling

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What about Noble Denton Marine Assurance & Advisory Guidelines?

Ongoing process of alignment of legacy DNV and GL rules and standards

– Noble Denton guidelines form part of this

Identify significant discrepancies

Update both sets removing significant discrepancies

Issue cover document explaining any continuing differences

– Users should select one set to use - not cherry pick

Work towards producing harmonised DNV GL documents

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SAFER, SMARTER, GREENER

www.dnvgl.com

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Niall [email protected] 289 184

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DNV-RP-H102 Overview Final

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