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DNV GL © SAFER, SMARTER, GREENERDNV GL ©
OFFSHORE LNG
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A Technical Safety Perspective
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SYNOPSIS
The presentation will outline potential safety issues with floating FSRU and FLNG
installations, and how they are addressed in current DNVGL rules and best
practices
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DEFINITIONS
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Offshore LNG
In this presentation, ‘Offshore LNG’ covers Floating Storage and Regasification
Units (FSRU) and Floating Natural Gas Liquefaction Units (FLNG or LNG FPSO)
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Petronas PFLNG-1 – in production 4/2017
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Technical Risk
In this presentation, ‘Technical Risk’ covers operational hazards which can be
addressed by proper design of the unit and its systems
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FSRU BW Singapore
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Technical Risk – the Starting Points
CONVERSIONS
LNG Carrier
All types of tanks
Significant space constraint
Conversions are always compromises
Age of LNGC is not automatically a factor – less surprises
NEWBUILDINGS
Tanks which allow a flat top
Less space constraint
From-the-beginning-design
More common for FLNG than FSRU
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THE RISK PICTURE
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The Risk Picture
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Human Impact
Asset Impact
Environmental Impact +
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The Risk Picture
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Mechanical Damage
Fire and Explosion Damage
Cryogenic Damage
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The Risk Picture
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NG and LNG Transfer
Integrity
LNG Storage Integrity
Platform Integrity
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PLATFORM INTEGRITY
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Platform Integrity
1. Navigational Hazards
Collision between LNG Carrier and Offshore LNG Unit or between LNG Carrier and
Jetty
Collision of either with other traffic
Grounding.
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Platform Integrity
2. Mooring Hazards
Two vessels connected not only one – complicated hydrodynamics
Where is overall coordinated mooring and mooring release control? The Offshore
LNG Unit or LNGC?
Fairly complex control and communication system with several interfaces
Lots of data; metocean, line loads, GPS, separation detection, ESD…
‘Smart’ system required.
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Remora Trelleborg
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Platform Integrity
2. Loss of Gas Containment Related Hazards
Cryogenic release causing fracture of hull or
other important components
Explosion causing fracture of hull or other
important components
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Platform Integrity
3. Hull Degradation
Hull girder fatigue due to sea conditions and fixed orientation vs predominant
wave patterns
Hull corrosion due to limited maintenance (minimised shut downs and challenging
logistics) and no dry docking
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NG AND LNG TRANSFER INTEGRITY
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NG and LNG Transfer Integrity
Spillage or leakage due to hose, coupling or piping failure or operational error
– Cryogenic hazards
– High pressure (NG import/export)
– Evaporation and ignition
Venting/Flaring
– Heat Flux
Process failures
24/7 automatic software-dependent operation
SIMOPS.
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NG and LNG Transfer Integrity
Ship-to-ship transfer, especially in unsheltered
offshore locations, is sensitive to sea induced
motion or sudden large displacement, such as
caused by mooring failure
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LNG STORAGE INTEGRITY
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LNG Storage Integrity
Tank sloshing due to sea conditions and partial filling, causing dynamic pressure
peaks within the tanks, which may damage internals or rupture membranes.
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DNV GL OFFSHORE LNG RULES & STANDARDS
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DNV GL Offshore LNG Rules and Standards
This section will describe the relevant DNV GL Offshore Rules and Standards and
give some examples of how they address the risks outlined in the preceding
sections
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OFFSHORE STANDARDS
DNVGL-OS
DNVGL Rule System
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High level,
classification process,
referring to OS or
even Ship Rules
OS contain technical
requirements which are
possible to use outside a
classification context
RULES
DNVGL-RU
DNVGL-RU-OU-0103
Floating LNG
DNVGL-OS-A101
Safety Principles & Arr’ts
DNVGL-OS-E201
Oil & Gas Processing
DNV GL Offshore LNG Rules and Standards
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DNV GL Offshore LNG Rules and Standards
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FIXED
REQUIREMENTS
’PRESCRIPTIVE’
VARIABLE
REQUIREMENTS
’SAFETY
ASSESSMENT’
Challenging
Requires a process
Project Specific
Cook Book
Generic and therefore
well understood
Experience based
Enables new solutions
More confidence in
end performance
Generally acceptable safety
for standard applications
‘Sedative’
Predictable
Negotiable with some effort
Typical Rule Make-Up
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DNV GL Offshore LNG Rules and Standards
FSRU The Offshore Way
OI notation possible, with limitations to class scope
Field specific design possible
REGAS same as ships.
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Off shore
LNG carrier
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DNV GL Offshore LNG Rules and Standards
FLNG
OI notation possible, with limitations to class scope
Field specific design possible
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Off shore
LNG carrier
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DNV GL Offshore LNG Rules and Standards
The Bow Tie Analysis
Barrier Management as approach
Addresses both prevention (technical and procedural barriers) and recovery
(mitigation and prevention of escalation)
Uses the hazard identification results as input
Conventional hazards and technical barriers are covered by the class rules
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DNV GL Offshore LNG Rules and Standards
Navigation Hazards
Side impact protection
Exclusion zone (operational measure)
POSMOOR class notation; site specific mooring analysis, system component
certification.
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DNV GL Offshore LNG Rules and Standards
NG/LNG Handling Hazards
No-spill QCDC couplings
Emergency release System (ERS)
Protection against brittle fracture of primary structure
Extended Hazardous Areas and protection against ignition of gas
Fire and gas detection and protection of ventilation inlets to accommodation
Process Shut-Down (PSD) and Emergency Shut Down (ESD)
Process Blow Down
Protection against heat flux from flaring
SIL-2 requirement on control systems, optional software systems assurance
SIMOPS procedures.
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Comprehensive requirements
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DNV GL Offshore LNG Rules and Standards
Hull and Tank Containment Integrity Hazards
Site specific fatigue analysis
Sloshing analysis and tank configurations designed for sloshing limitation
Corrosion prevention and mitigation (DNVGL RP exist).
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DNV GL Offshore LNG Rules and Standards
Mooring Hazards – monitoring and control
Philosophy, data acquisition and system integrity
ERS for one or two vessels
POSMOOR class notation for offshore locations.
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DNV GL Offshore LNG Rules and Standards
Environmental Hazards – spillage and ambient sea cooling
Structural requirements to different types of tanks
Transfer systems technology qualification and certification
Vessel separation detection system
Closed loop evaporation options.
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DNV GL OFFSHORE LNG CAPABILITIES
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This section will briefly trace DNV GL history in marine LNG and describe its
general capabilities in supporting offshore LNG design and operations
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DNV GL Offshore LNG Capabilities
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1962 20171979 2017
DNV GL has been
part of defining the
LNG industry
First
classification
society to
publish rules for
gas carriers in
1962
First newbuild FLNG – DNVGL
classed PFLNG Satu
First conversion FLNG –DNVGL
classed Golar Hilli
Development of Rules for
Barge Mounted LNG Plant
Guidelines and criteria for floating
LNG FPSO and terminals
20041991
Latest
revision
of FLNG
rules
Spadeadam test facility
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DNVGL has been at the forefront of LNG technology since before the 1960’s
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Strategy FeasibilityConcept / preFEED FEED EPCI
Installation & Commissioning
Operations & Life Extension
Decommis-sioning
Environmental impact assessment
Safety risk management (Hazid, Hazop, QRA, safety case)
Project risk management
Due Diligence
Technology qualification
Verification
Inspection
PSID
Owners engineer
RAM
Concept/pre FEED Studies
Debottle.
AIM
AiP Classification
Validation/Verification/Certification
Consultancy
Regula
tory
Com
pliance
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DNV GL Forms of Engagement with Floating LNG Projects
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DNVGL have reviewed all
the major liquefaction
systems
DNVGL have reviewed/qualified all the
major LNG transfer systems
DNVGL have approved all the major LNG
containment system designs and
configurations
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DNV GL Review of LNG Related Technologies
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HAZID
HAZOP
SIL / LOPA
SRS And SIL
Verification
RAM Study
QRA
EERA
Ship Collision Study
Dropped Object
Study
Vibration and Noise
Study
Fire Analysis
Structural Fire
Response
PFP Optimization
Flare & Vent Study
Dispersion and Gas
Detector Analysis
Explosion Analysis
Fire/blast Walls
Hot Exhaust Gas
Study
Wind Turbulence
Study
Dimensioning
Accident Load
Cryogenic Spill
ProtectionPCP Optimization
DNV GL Capability in LNG Related Safety Studies
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What about novel technology?
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DNV RP A203 – Qualification of Technology
Trelleborg Floating Hose
Technip ALLS
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