lng sloshing for new designs, new operations and new trades
TRANSCRIPT
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LNG sloshing for new designs, new operations and new trades
GastechBilbao, March 16th 2005
Wouter Pastoor, Tom Østvold, Eirik Byklum, Sverre Valsgård
Hydrodynamics & Structures
Det Norske Veritas
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Sloshing structural response
Contents
Market developments → DNV Sloshing R&D
LNG sloshing loads
Market developments → DNV Sloshing R&D
LNG sloshing loads
Sloshing structural response
Sloshing guideline
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Market developments & interests
Partially filled tanks
Rapid increasing fleetIncreasing carrier sizes
More trading in severe environmentsAlternative propulsion
and machinery
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Alternative propulsion
and machinery
R&D focus at DNV
Partially filled tanks
Rapid increasing fleetIncreasing carrier sizes
More trading in severe environments
DNV R&D
SLOSHING
SLOSHING CLASS NOTES
VIBRATION /PROPULSION
SLOSHING /FATIGUE /
ICE OPERATION
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Market developments – Focus on LNG sloshing
Offshore (off)loading
Increasing carrier sizes More trading in severe environments
Spot tradingMilk run Floating terminal
LNG Sloshing Challenges
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Sloshing
What is the problem?
Sloshing causes fluid loads which needs to be assessed
Structural integrity issues (ultimate & fatigue loading):
• Containment system
• Pump tower and supports
• Hull structure
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Sloshing is not new but …
• no stringerdecks!
• no webframes!
• no long. bulkheads!
Typical double-hull tanker LNG carrier
• LNG tank is large and smooth without sloshing “suppressors”
• Different structures, which means different ‘failure modes’
• Different consequences upon a penetration
• Different response dynamics
• Different repair possibilities
• Different repair price
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Filling level restriction for unrestricted operation
10% of tank length
70% of tank height
Present filling restrictions for LNG carriers up to 150.000 m3 capacity
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Market developments – Focus on LNG sloshing
Offshore (off)loading
Increasing carrier sizes More trading in severe environments
Spot tradingMilk run Floating terminal
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Filling level restriction for unrestricted operation
10% of tank length
70% of tank height
Present filling restrictions for LNG carriers up to 150.000 m3 capacity
For partially filled operation a wave height restriction needs to be
determined
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LNG Sloshing challenges from the market
Implications for a Class Society?
Update rules?
Issue new rules?
Develop a methodology!NEW COMPETENCE FIRST!
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Membrane tanks - sloshing
Present qualification basis
• Structural tests + calculations of containment system, sub-assemblies and materials for ultimate and fatigue loading
• Large experience with membrane containment systems in ships over past decades
• Primary and secondary membrane (~hardware safety factor)
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New competence?
Why a focus on new competence?
Rapid pace of new designs and new operations
Extend of the present qualification basis
Sloshing experimental and numerical R&D
LNG sloshing methodology
Assess these new designs and new operations.
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LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
LOADS
STRENGTH
FULL-SCALE
MEASUREM.
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LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
LOADS
STRENGTH
FULL-SCALE
MEASUREM.
![Page 16: LNG sloshing for new designs, new operations and new trades](https://reader030.vdocument.in/reader030/viewer/2022012423/61775bee2d72a0529901cb22/html5/thumbnails/16.jpg)
LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
LOADS
STRENGTH
FULL-SCALE
MEASUREM.
![Page 17: LNG sloshing for new designs, new operations and new trades](https://reader030.vdocument.in/reader030/viewer/2022012423/61775bee2d72a0529901cb22/html5/thumbnails/17.jpg)
LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
LOADS
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Sloshing Loads – 6 experimental sloshing phases
scale = 1:70scale = 1:20Instrumented “Pump tower”
1. Filling level & sea state severity
2. Variation of load footprint area
3. Effect of ship speed
4. Scaling study
5. Long-term load distribution
6. Pump tower tests
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Experimental set-up
• scale = 1:20
• 138.000 m3 LNG carrier
• No. 2 tank
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Example sloshing issue - scaling
Scaling of sloshing model experiments
scale = 1:70scale = 1:20
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Scaling of sloshing impacts
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.01 0.10 1.00Scaled gas-liquid density ratio
Fro
ud
e-s
ca
led
pre
ssu
re
Small tank (1:70)Vacuum
Near vacuum
Light gas
Air-1 atm
Heavy gas
Scaling of sloshing model experiments
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Scaling of sloshing impacts
Scaling of sloshing model experiments
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.01 0.10 1.00Scaled gas-liquid density ratio
Fro
ud
e-s
ca
led
pre
ssu
re
Large tank (1:20)
Small tank (1:70)Vacuum
Near vacuum
Light gas
Air-1 atm
Heavy gas
Air-1 atm
Heavy gas
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Numerical sloshing simulation?
CFD for sloshing:
• Impact pressures are very difficult to predict (or impossible?)
• Velocities to calculate pump tower loads is possible
• Global sloshing loads for sloshing-ship motion coupling is possible
CFD – Computational Fluid Dynamics?
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LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
STRENGTH
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Structural strength studies
1. HAZID – failure mode identification
2. Failure mode evaluation
3. Lab tests of materials and sub-assemblies
4. Calibration of FE models
5. Capacity determination
6. Develop strength assessment procedure
Dynamic strength
A
p
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Membrane Cargo Containment Systems
MARK III
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Membrane Cargo Containment Systems
MARK III
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Test examples – 1 of 3
Ultimate strength and fatigue tests of a MkIII sub-assembly
(failure investigation of the foam)
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Membrane Cargo Containment Systems
GT NO96
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Membrane Cargo Containment Systems
GT NO96
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Test examples – 2 of 3
Ultimate strength and fatigue tests of plywood plates on shear failure
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Test examples – 3 of 3
Dynamic buckling (inertia effects)
Temperature strength effects
h=23cm, t=9mm,
-2.00E+01
-1.00E+01
0.00E+00
1.00E+01
2.00E+01
3.00E+01
4.00E+01
5.00E+01
0.00E+00 5.00E-03 1.00E-02 1.50E-02 2.00E-02 2.50E-02 3.00E-02
Time
Lo
ad
[M
Pa]
t=0.625ms
t=1.25ms
t=2.5ms
t=5ms
t=10ms
t=50ms
23cm, 12mm, t=2.5ms
-10
0
10
20
30
40
50
0.00E+00 1.00E-03 2.00E-03 3.00E-03 4.00E-03 5.00E-03 6.00E-03
Time
Lo
ad
[M
Pa]
temp variation
no temp variation
Buckling ofplywood plates (NO96)
FE Analyses
Buckling strength criteria
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5
Slenderness
σu/σ
f
FEM, uniform load
Test, uniform load
Test, part load
Johnson-Ostenfeld
Elastic-Plastic
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LNG sloshing developments
Sloshing tests:• filling level & heading• sea severity• impact area• vessel speed• scaling• pump tower loading• fatigue loading
LNG sloshing technical studies at DNV 2003-…
CFD validity studies
SLOSHING LOADS
Structural tests
STRUCTURAL STRENGTH
Sloshing sensor qualification
Installation detailing
FULL-SCALE MEASUREMENTS
FE calibration & analyses
HAZID-Failure mode analysis
Verified LNG sloshing Class Note
LNG sloshing Class Note (2005)
Measuring campaign
Measurement analysesAcceptance criteria
Capacity determination
Sloshing load and structural strength assessment scheme
LOADS
STRENGTH
![Page 34: LNG sloshing for new designs, new operations and new trades](https://reader030.vdocument.in/reader030/viewer/2022012423/61775bee2d72a0529901cb22/html5/thumbnails/34.jpg)
DNV Class Note
ObjectiveGuidance to assess LNG sloshing:
• larger carrier designs
• partial filling on specified trading route
• partial filling while off-loading
• floating terminals
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DNV Class Note
Sloshing?
ApplyClass Note
Approval request
Approvalyesno
Limit State Analysis & Specifications
Design & operationalconditions
Sloshing Analysis
Loads
MkIII, NO96, CS1
no
yes StrengthAssessment
Structural SafetyAssessment
Report
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DNV Class Note – Application oriented
Sloshing?
ApplyClass Note
Approval request
Approvalyesno
Limit State Analysis & Specifications
Design & operationalconditions
Sloshing Analysis
Loads
MkIII, NO96, CS1
no
yes StrengthAssessment
Structural SafetyAssessment
Report
• offshore (off)loading
• large LNG carriers
• spot trading / milk run
• receiving terminal
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LNG sloshing for new designs, new operations and new trades
GastechBilbao, March 16th 2005
Wouter Pastoor, Tom Østvold, Eirik Byklum, Sverre Valsgård
Hydrodynamics & Structures
Det Norske Veritas