dnv-rp-h102 overview final
TRANSCRIPT
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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
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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 GL © 2014 27 November 2014
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
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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DNV GL © 2014 27 November 2014
Chapter 1 - Introduction
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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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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Chapter 1 - Introduction
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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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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Chapter 1 - Introduction
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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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
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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Chapter 2 – Part I - General Requirements
Chapter 2 – Part I - General Requirements
– 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
Chapter 2 – Part I - General Requirements
– 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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2.1.2 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
Chapter 2 – Part I - General Requirements
– 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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2.1.5 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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DNV GL © 2014 27 November 2014
2.1 Planning
Chapter 2 – Part I - General Requirements
– 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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2.1.6 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
Chapter 2 – Part I - General Requirements
– 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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2.1.7 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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Chapter 2 – Part I - General Requirements
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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2.2 Operations
Chapter 2 – Part I - General Requirements
– 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
Chapter 2 – Part I - General Requirements
– 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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2.2.4 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
TPOP ≤ 24 Mon. = yes and WF-A = yes 0.76 0.86 0.91
Mon. = yes or WF-A = yes 0.69 0.78 0.83
Mon. = no and WF-A = no 0.63 0.71 0.75
TPOP ≤ 48 Mon. = yes and WF-A = yes 0.68 0.77 0.81
Mon. = yes or WF-A = yes 0.62 0.70 0.74
Mon. = no and WF-A = no 0.56 0.64 0.67
TPOP ≤ 72 Mon. = yes and WF-A = yes 0.62 0.71 0.76
Mon. = yes or WF-A = yes 0.56 0.65 0.69
Mon. = no and WF-A = no 0.51 0.59 0.63
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2.2 Operations
Chapter 2 – Part I - General Requirements
– 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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2.2.5 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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Chapter 2 – Part I - General Requirements
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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2.3 Loads
Chapter 2 – Part I - General Requirements
– 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
Chapter 2 – Part I - General Requirements
– 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
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Chapter 2 – Part I - General Requirements
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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2.4 Load analyses
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– General
– Friction
– Characteristic loads
– Sensitivity studies
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2.4 Load analyses
Chapter 2 – Part I - General Requirements
– 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
DNV GL © 2014 27 November 2014
Chapter 2 – Part I - General Requirements
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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2.5 Structural analysis and capacity checks
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– General
– Design considerations
– Method
– Failure modes
– Design loads and conditions
– Design analysis
– Structural resistance
– Accept criteria – general
– Accept criteria - SCRAP
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2.5 Structural analysis and capacity checks
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– General
– Design considerations
– Method
– Failure modes
– Design loads and conditions
– Design analysis
– Structural resistance
– Accept criteria – general
– Accept criteria - SCRAP
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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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2.5 Structural analysis and capacity checks
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– General
– Design considerations
– Method
– Failure modes
– Design loads and conditions
– Design analysis
– Structural resistance
– Accept criteria – general
– Accept criteria - SCRAP
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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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Chapter 2 – Part I - General Requirements
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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2.6 Materials and fabrication
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– Materials and fabrication
– General
– Existing materials
– Selection of new materials
– Tolerances
– Assembly and welding
– Weld inspection
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2.6 Materials and fabrication
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– Materials and fabrication
– General
– Existing materials
– Selection of new materials
– Tolerances
– Assembly and welding
– 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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2.6 Materials and fabrication
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– Materials and fabrication
– General
– Existing materials
– Selection of new materials
– Tolerances
– Assembly and welding
– 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
Primary (Special) 3)
DC3 – SQL2 (SQL1) 3)
II
Simple joints and members
Primary (Special) 3)
DC4 – SQL3 (SQL1) 3)
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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2.6 Materials and fabrication
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– Materials and fabrication
– General
– Existing materials
– Selection of new materials
– Tolerances
– Assembly and welding
– 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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Chapter 2 – Part I - General Requirements
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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2.7 Equipment, systems and vessels
Chapter 2 – Part I - General Requirements
– Planning
– Operations
– Loads
– Load analyses
– Structural analysis and capacity checks
– Materials and fabrication
– Equipment, systems and vessels
– General
– Cranes
– Equipment with certified WLL (SWL) or MBL
– Seafastening and grillage
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Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– 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
Chapter 3 – Part II – Operation Specific Recommendations
– 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
Chapter 3 – Part II – Operation Specific Recommendations
– 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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Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– Dismantling
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3.2 Subsea operations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– General
– Load cases
– Design loads
– Trapped water
– Preparations and operations
– Subsea cutting
– Verification of cutting
– Soil resistance
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3.2 Subsea operations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– General
– Load cases
– Design loads
– Trapped water
– Preparations and operations
– Subsea cutting
– Verification of 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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3.2 Subsea operations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– General
– Load cases
– Design loads
– Trapped water
– Preparations and operations
– Subsea cutting
– Verification of 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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3.2 Subsea operations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– General
– Load cases
– Design loads
– Trapped water
– Preparations and operations
– Subsea cutting
– Verification of 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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Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– Dismantling
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3.3 Back-loading offshore
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– 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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3.3 Back-loading offshore
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– 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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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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3.3 Back-loading offshore
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– 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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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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DNV GL © 2014 27 November 2014
Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– Dismantling
73
DNV GL © 2014 27 November 2014
3.4 Transport from offshore locations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– 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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3.4 Transport from offshore locations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– 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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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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3.4 Transport from offshore locations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– 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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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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Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– Dismantling
79
DNV GL © 2014 27 November 2014
3.5 Onshore transfer
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– General
– Skidding or trailers
– Lift-off
– Crane lifting
– Moorings
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3.5 Onshore transfer
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– 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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Chapter 3 – Part II – Operation Specific Recommendations
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– Dismantling
83
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3.6 Dismantling
Chapter 3 – Part II – Operation Specific Recommendations
– Offshore crane lift operations
– Subsea operations
– Back-loading offshore
– Transport from offshore locations
– Onshore transfer
– 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