LNG sloshing for new designs, new operations and new trades
Transcript of LNG sloshing for new designs, new operations and new trades
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
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
Market developments & interests
Partially filled tanks
Rapid increasing fleetIncreasing carrier sizes
More trading in severe environmentsAlternative propulsion
and machinery
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
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
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
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
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
Market developments – Focus on LNG sloshing
Offshore (off)loading
Increasing carrier sizes More trading in severe environments
Spot tradingMilk run Floating terminal
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
LNG Sloshing challenges from the market
Implications for a Class Society?
Update rules?
Issue new rules?
Develop a methodology!NEW COMPETENCE FIRST!
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)
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.
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.
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.
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.
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
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
Experimental set-up
• scale = 1:20
• 138.000 m3 LNG carrier
• No. 2 tank
Example sloshing issue - scaling
Scaling of sloshing model experiments
scale = 1:70scale = 1:20
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
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
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?
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
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
Membrane Cargo Containment Systems
MARK III
Membrane Cargo Containment Systems
MARK III
Test examples – 1 of 3
Ultimate strength and fatigue tests of a MkIII sub-assembly
(failure investigation of the foam)
Membrane Cargo Containment Systems
GT NO96
Membrane Cargo Containment Systems
GT NO96
Test examples – 2 of 3
Ultimate strength and fatigue tests of plywood plates on shear failure
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
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
DNV Class Note
ObjectiveGuidance to assess LNG sloshing:
• larger carrier designs
• partial filling on specified trading route
• partial filling while off-loading
• floating terminals
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
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
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