Structure Engineering Group
Gas Project Department
Offshore and Engineering Division
Gastech 2017
Development of SPB® LNG Fuel Tank
for Ships
Contents
(1)Introduction
(2)Concept Design of SPB® LNG Fuel Tank
(3)Development of the Simplified Vibration Calculation
(4)Development of High Manganese Steel
2
(1) Introduction
(1)-1 Emission Control Requirement
3
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
NOx Tier II Tier III (only ECA)SOx Global Cap 4.5% 3.5% 0.5%
ECA 1.0% 0.1%
ECA Coast of USA/Canada (from August)
Baltic Sea, North Sea Puerto Rico ,US Virgin Islands (Caribbean Sea)
CO2 EEDI Base △10% △20%
Source: Environmental Protection Agency (U.S.A.)
(1) Introduction
(1)-2 Use of LNG as Fuel
4
Advantage
- Emission Reduction
NOx: -80%
SOx: -100%
CO2: -25%
- LNG Price
Cheaper than Low Sulfur Fuel Oil
Disadvantage
- Increase Tank Space
Double in Fuel Volume
(= 1/2 density of heavy fuel oil)
Reduction of cargo volume
- Complexity of LNG fuel handling
- Undeveloped Infrastructure
Fuel Type SOx (g/kWh) NOx (g/kWh) CO2(g/kWh)
Heavy Fuel Oil 3.5% S 13 9-12 580-630
LNG 0 2 430-480
(1) Introduction
(1)-3 Feature of SPB® LNG Fuel Tank
SPB (Self-supporting, Prismatic-shape IMO type B)
In case of LNG fuel tank…..
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Assumed Problem
Tank Space
LNG handling
(pressure and temperature)
Intermediate liquid level
(sloshing problem)
Damage
(accidental, fatigue etc.)
Solution
Flexible tank shape & volume
(Best space efficiency for any size & type of ships)
Easy operation and less maintenance
(Strong against outer / inner pressure)
Any level loading without sloshing
(Eliminate sloshing phenomenon by internal bulkhead)
Robust & Reliable tank system
(Proven by robust tank concept and experience)
Hull
Tank
Support
Insulation
6
(2) Concept Design of SPB® LNG Fuel Tank
(2)-1 Concept Design Study for Container Ship
Ship’s Principal Particular
Length: app. 330.0 ~ 400.0 m
Breadth: app. 45.0 ~ 65.0 m
Depth: app. 25.0 ~ 35.0 m
Container Loading Capacity 10,000 ~ 20,000 TEU
Sea Route: Far East to Europe
Range: app. 20,000 miles
LNG Fuel Tank
Capacity: 5,000 ~ 10,000 m3
L x B x D: app. 9.0~10.0m x 35.0~55.0m x 15.0~20.0m
Arrangement: In front of Engine Room
LNG Fuel
Tank SpaceEngine Room
Trans. Section of Tank
(2) Concept Design of SPB® LNG Fuel Tank
(2)-2 Development of Cost-competitive Tank
14,000TEU container ship
Rationalization (optimization) of tank structure
- Reduction of tank weight
- Increasing of machinability and construction workability
Standardization of tank support construction
- Improvement of design and construction efficiency
(divided into three patterns by assumed reaction force)
FE modelling tool
- Efficiency and Speeding up of FE modelling
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(2) Concept Design of SPB® LNG Fuel Tank
(2)-2 Development of Cost-competitive Tank
AfterBefore
10%reduction
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14,000TEU container ship
Optimization Result of Longitudinal Girder Ring
Condition for Optimization
Target Structure Long. Girder Ring
Optimization Item Weight
Tank Material A5083-O
Tank Status Full
LNG Density 0.5 ton/m3
Vapor Pressure 0.07 MPa
Loading Condition - Static Heel Case
- Max. Trans. Acceleration Case
- Collision Case
ThicknessThin Thick
(2) Concept Design of SPB® LNG Fuel Tank
(2)-3 High Design Vapor Pressure Tank
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Approval in Principle (AIP)
JMU received an AIP for the design
procedure for increasing design
vapor pressure SPB® tank up to
0.4 MPa (4.0 barG) from American
Bureau of Shipping in January 2017.
Diesel Engine
-Typical main engine for merchant ships
-Larger exciting force of vibration than turbine engine
Location
-Close to engine room
(3) Development of the Simplified Vibration Calculation
(3)-1 Background
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Severer environment of vibration
comparing to LNG carrier, FLNG, etc.
LNG Fuel
Tank SpaceEngine Room
LNG Fuel
Tank SpaceEngine Room
(3) Development of the Simplified Vibration Calculation
(3)-2 Tank Vibration Assessment -Obtaining the Natural Frequency-
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Conventional way
FEM: Time-consuming
Simplified method
Time can be saved.
Accuracy shall be verified.
𝑓 = 0.057𝜋2
𝑙2𝐸𝐼
𝜌𝐴
𝑓 =? ? ?SPB® fuel tank
(3) Development of the Simplified Vibration Calculation
(3)-3 Tank Vibration Assessment for Container Ships
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Tank height is taller than that of other types of ship
(3) Development of the Simplified Vibration Calculation
(3)-4 Rigid Body Model (Step 1) and Elastic Body Model (Step 2)
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Simplified methodFEM
Rigid + Elastic vibration
Step 1
Rigid body vibration
Step 2
Elastic body vibration
+
(3) Development of the Simplified Vibration Calculation
(3)-5 Coupling of Step 1 and Step 2 –Actual Phenomenon-
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Simplified method
1
𝑓2 ≅1
𝑓12 +
1
𝑓22
𝑓: Natural frequency of the coupling mode𝑓1: Natural frequency of Step 1 mode𝑓2: Natural frequency of Step 2 mode
FEM
Rigid + Elastic vibration
(3) Development of the Simplified Vibration Calculation
(3)-6 Verification of the Accuracy
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The Ratio of Natural Frequency (Simplified method vs FEM)
Filling level Longitudinal vibration Transverse vibration
Full 1.06 1.18
Empty 1.05 1.14
Enough accuracy for initial planning stage.
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Effect of Higher Strength compared to other cryogenic materials
Yield Stress:
3 times as that of Aluminum
Plate Thickness : 60% of Aluminum
(Stiffener size can be reduced similarly)
Comparison with Aluminum
(4) Development of High Manganese Steel
(4)-1 Creation of New Material and Welding Material
To confirm Adequate Quality and Manufacturing Cost
- Creation of New Material and Welding Material
- Basic Test for Material Property
- Confirmation of Workmanship
(4)-2 Basic Test for Material Property
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- Fatigue Strength Analysis
- Crack Propagation Analysis
- Leakage Quantities Estimation
SPB® Tank Design
・SN curve Data
・Fatigue Crack Growth Rate Curve Data
(4)-3 Confirmation of workmanship
- workability (cutting, bending etc.)
- welding
- corrosion resistance during construction
(4) Development of High Manganese Steel
Thank you for your kind attention.
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