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© 2017 MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO., LTD. All Rights Reserved.
MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO.,LTD
5 April 2017
Structural Design &
Construction Method for
“Apple-Shaped Liquefied
Natural Gas Cargo Tank” for
LNG Carriers
“Apple-Shaped Tank”:
Upgrade of the existing MOSS tank and
licensed by Moss Maritime a.s
as “Flexible Spherical Tank”(FST)
© 2017 MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO., LTD. All Rights Reserved. 2
CONTENTS OF PRESENTATION
1. Concept of FST (Flexible Spherical Tank) = “Apple Shaped Tank”
2. Design aspect
1. Extracting verification items in structural design for FST
2. Buckling assessment
3. Sloshing assessment
3. Construction aspect
1. New Bending process for FST
2. Construction Progress
4. Conclusion
© 2017 MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO., LTD. All Rights Reserved. 3
INTRODUCTION
MHISB has successfully developed and constructed the world’s first “Apple-Shaped Tank”*MHISB: Mitsubishi Heavy Industries Shipbuilding Co., Ltd.
“Apple-Shaped Tank” : Upgrade of the existing MOSS spherical tank and
licensed by MOSS Maritime a.s as “Flexible Spherical Tank”(FST)
“Flexible” means “with high flexibility in terms of tank shape and capacity”
Purpose of this presentation :
Introduce the excellent features of FST for the trade from U.S. to Asia
1st generation 2nd generation 3rd generation
4th generation 5th generation
6th generation: SAYARINGO
© 2017 MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO., LTD. All Rights Reserved. 5
165 to180km3 New Panamax LNGC(SAYARINGO)
MHISB has received orders for a total of 8 new generation vessels,
called as “SAYARINGO”, adopting FST
Best solution for the trade from U.S. to Asia
FST (= Apple-shaped tank)Continuous Tank cover
Lighter steel weight, Improved fuel consumption
Better terminal compatibility, Better maintainability
“SAYAENDO”
3 vessels under
construction
1st vessel: 2.5 years in service
© 2017 MITSUBISHI HEAVY INDUSTRIES SHIPBUILDING CO., LTD. All Rights Reserved. 6
Concept of FST (Flexible Spherical Tank)
Why is “SAYARINGO” the Best solution for trade from U.S. to Asia?
Panama Cannel 49m extreme
★Freeport★Cameron
★Cove point
Long haul trade
Harsh sea
North Pacific
Restricted Breadth
Compatibility with
Existing terminals
Restricted dimensions
Japan~Gulf of Mexico
One way abt.9500sm
High structural reliability for Cargo tank system
Large cargo capacity under restricted dimensions
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High structural reliability for Cargo tank system
Large cargo capacity under restricted dimensions
Concept of FST (Flexible Spherical Tank)
Ta
nk c
ove
r to
p
ab
t.4
6.9
m
155km3
Sayaendo(Stretched tank)
180km3
SAYARINGO
(FST)
180km3
Existing MOSS(Spherical tank)
Ta
nk c
ove
r to
pa
bt.4
7.0
m
Bm 48.94m
Sphere
Cylinder
Sphere
Sphere
Torus
Torus
Cylinder
Sphere
Sphere
Bm 48.94m Bm 51.9m
Sphere
One type of
MOSS tank
One type of MOSS
tank
Lower height
Low-wind resistance
Exceed the breadth
limit of Panama canal
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Concept of FST (Flexible Spherical Tank)
180km3
SAYARINGO
(FST)
Sphere
Cylinder
Sphere
Sphere
Torus
Torus
180km3
Existing MOSS(Spherical tank)
Sphere
155km3
Sayaendo(Stretched tank)
Sphere
Sphere
Cylinder
“Flexible” means “with
high flexibility in terms of
tank shape and capacity”
Center of gravity
at Lower position
Center of gravity : Lower position than the existing tank
High flexibility in terms of tank shape and capacity
Excellent sloshing property : Acceptance of Any filling level
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Extracting verification items in structural design for FST
Structural Design
Stress Assessment
Fatigue Assessment
Proving Small Leak Protection
Design Loads
Buckling Assessment
Membrane Stress Analysis by Elastic
Shell FE model
Surface Stress Analysis by Elastic
Solid FE model
Damage factor assessment
Crack penetration analysis
Leakage analysis
Internal / External overpressure
Interaction Force
Thermal Load
Sloshing Load
Buckling Strength Evaluation by
Theoretical formula
Buckling Strength Evaluation by Elastic-
plastic large deformation FE analysis
Inertia force due to ship motion
Crack propagation analysis of
Plate Through Crack
Additional verification items for FST
FSTExisting MOSS(Sphere)
Same design procedure as MOSS is applied to FST
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Buckling Assessment for FST
External Pressure
(Tank Empty)
Medium liquid level
(Seagoing)
Internal Pressure
(Pressure Discharge)
Lateral acceleration
(Seagoing)
Additional assessment for Torus and Cylindrical part.
RED : Buckling mode specific to FST
BLUE : Buckling mode similar to existing MOSS
Transverse
acceleration
Buckling of
Torus
Buckling in Sphere/Cylinder / Torus /
Buckling in
Sphere/ Cylinder
Buckling under circumferential compression
Buckling under circumferential compression
Shear bucklingExternal pressurebuckling
Buckling of
Cylinder
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Buckling Assessment for FST
Buckling test was conducted to verify the accuracy of FEM
Examined mode : Buckling in Torus part due to internal pressure
Diameters of models : 2.5m (1/20 scale)
Torus part
Cylindrical
part
Spherical part
Total
deformation
Expanding
(mode 1)
Bending
(mode 2)= +
Compression
Tension
Tension
Buckling in Torus part
Initial shape
Deformed shape
Model1 : Small radius of Torus (i.e. easy to buckling)
Model2 : Actual Shape
Verify the Accuracy of FEM
Confirm Buckling NOT occur
at Actual shape
Deformation due to internal pressure (FEM)
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Buckling Assessment for FST
FEM result by MHISB
FEM result by DNV
Buckling occurred at Torus part.
Buckling area
Measured point
of displacement
Buckling occurrence
Reflect to FEM
Pressure test
MODEL1
Result of FEM accurately match with Experiment
Measurement of
Imperfection
Third party evaluation
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Buckling Assessment for FST
Measured imperfection
FEM result
Buckling did NOT occur
even in twice pressure(420kPa) as
Emergency pressure discharge condition
Pressure test
MODEL2 Torus part :
No buckling deformation
Buckling did NOT occur, Because deformation
is small and linear
At max press: 420 kPa
Measurement of
Imperfection
Out-of-plane displacement(mm)
Inte
rnal p
ressu
re(k
Pa)
Buckling in Torus would never occur due to internal pressure
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Sloshing Assessment for FST
FST’s sloshing property
Gradual change of shape from MOSS(Spherical shape)
MHISB have verified if FST has the same level of
excellent sloshing property as MOSS, just to be safe
Procedure of Sloshing Assessment
1st Step: Regular wave approach
Verification of CFD Analysis
Comparison of FST & MOSS by CFD
Comparison of Exp. & CFD
2nd Step: Irregular wave approach
Third party evaluation
by DNV-GL
Evaluation by MHISB
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Sloshing Assessment : Regular wave excitation by MHISB
0.0
0.2
0.4
0.6
0.8
1.0
0 50 100 150 200
tan
k h
eig
ht/
tan
k d
iam
ete
r
impulsive pressure [kPa]
CFD results(non-spherical tank)
test results(non-spherical tank,excluding pressure spike)
Verify the accuracy of CFD
CFDEXP.
Comparison of MOSS(Sphere) & FST
MOSS(SPHERE)FST
Results of CFD SIMULATION
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80
he
igh
t /
tan
k d
iam
ete
r
impulsive pressure [kPa]
FST(CFD)amplitude:4.0m
spherical tank(CFD)amplitude:4.0m
MOSS(Sphere)
FST
Pressure: Same level as Sphere
Impulsive pressure [kPa]
Impulsive pressure [kPa]
Heig
ht
/ T
an
k d
iam
ete
r
Heig
ht
/ T
an
k d
iam
ete
r
Experiment CFD by Exp. model
Comparison : Experiment vs CFD
Analysis accuracy is verified
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Sloshing Assessment : Irregular wave excitation by DNV-GL
Screening #1 :Irregular excitation for30min.
Identify Worst Filling Ratio (H/D = 0.6,0.7)
Identify Worst Sea-state (H, T) = (15m,10.5sec)
Screening #2 :Irregular excitation for30min.
Same Volume
Sphere FST
67,500 74,300
66,350 72,490
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
100,000
Filling ratio = 0.6 Filling ratio = 0.7
Glo
bal
load
[kN
]
FST MOSS
Slo
sh
ing
lo
ad
[k
N]
Detailed Analysis:Irregular excitation for 120min.
Comparison of Sloshing load (FST vs MOSS)
Sloshing load:
Same level as MOSS(Sphere)
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Development of New Bending process for Torus part
ABC
Sphere: Only one radius
Torus: Radius of A to C are different
Necessity of many bending mold & adjusting bending load→ Lot of Time & Cost for Bending Process of Torus part
MHISB developed the Method of Bending Process by One mold & Uniform bending Load
A
C
B
Meridian dir.
Latitudinal dir.
Latitudinal dir.
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Development of New Bending process for Torus part
Meridian & Latitudinal Radii are different
Different Radii of Latitudinal dir. shall be formed
by One Mold (One radius)
Identify the optimal
Mold property & Bending procedure
FEM Simulation for Press sequence
Lati
tud
inal d
ir.
La
titu
din
al d
ir.
Press Head
Press Bed
Plate
Meridian dir.
Press location
Press
Combination setting:
Mold property
(Press Head & Bed)
Press Load
Sequence of Press
Press headPress bed
Two different radii of Mold to be applied
for Meridian & Latitudinal dir.
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Development of New Bending process for Torus part
Identify the optimal
Mold property & Bending procedure
Press experiment using the 1/20
scaled-down model die (Die A)
Bending for Actual product
Accurate shape for Target
FEM Simulation for Press sequence
(2) Measurement of Formed Shape
by 3D Laser equipment
(1) Press according to FEM simulation
Research for further improvement of
Press accuracy & Shortening time
(3) Re-simulation by using the
results of measurement
(4) Decision of Next Press condition
(5) Press, later repetition of (2) to (5)
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Construction Progress
MHISB has received orders for a total of 8 new generation vessels
FST for first vessel in SAYARINGO series : Grand Assembly Completed
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CONCLUSIONS
MHISB has developed the Apple-shaped tank (FST) as an upgrade
of the existing MOSS spherical tank.
The design & construction method for FST successfully established.
FST has the following advantage.
Inherit all excellent properties of MOSS spherical tank system
Lower height & Lower center of gravity compared with Conventional MOSS( Spherical tank & Stretched tank)
Possible to design the tank capacity flexibly responding to the need of customers
MHISB will actively continue the development of the new innovative
key technology such as FST, corresponding to the needs of
customers.