design of double hull tankers-gl presentation may 2005
TRANSCRIPT
25.05.20052003-12-10
25.05.20052003-12-10
What do we face in the design?
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Existing Tanker Fleet
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World Oil MovementsWorld Oil Movements
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Oil Tanker Categories
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Principal Dimensions of Tankers I
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Principal Dimensions of Tankers II
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Principal Dimension Considerations
• Breadth Limitations (Panama Canal)
• Draft Limitations (Trade Route)
Suez Canal
Malacca Straits
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A new type of VLCC is BornMALACCA-MAX
T=20.5m Cargo same as a large VLCC
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Double vs Single Hull Tankers
• We have come a long way !
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Double vs Single Hull Tankers
• Increased Strength Requirements
• Increased Stability Requirements
• Increased Cargo Temperature
• Increased Ballast Surface
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Structural Design Considerations
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Structural Design Considerations
• Longitudinal Strength (Global Bending/Shear)
• Transverse Strength (Primary Support Members)
• Buckling (In combination with above)
• Fatigue (Long Term Effect)
• Ultimate Strength (Extreme Load/Plasticity)
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Longitudinal Strength (Beam Model)
• Minimum Section Modulus (IACS Requirement)
• Static and Wave induced Bending and Shear
• Sagging and Hogging
• Sagging dominates in Full Load
• Hogging dominates in Ballast Load
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Transverse Strength (Local Loads)
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Typical Midship Section of a VLCC
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More Mid-ship Sections
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How to do it? Cavalry To the Rescue!
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POSEIDON NDComputer Supported Tanker Scantling
Assessment
• Rule Based Structural Design
• First Principle Structural Design
• Support of Plan Approval Procedure
• Condition Assessment
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Midship Section of a Suezmax Tanker Created byPOSEIDON-Plating
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It is not over yet!2nd Stage of Analysis FEA
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Model of a Suezmax Tanker without Deck and Shell Plating
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FE Model 319,000 dwt VLCC
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The bad and the ugly:Sloshing and Slamming
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SloshingCritical for:
Ltank>0.1L and/or Btank>0.5B
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SlammingCritical at Low Draft Fwd-High Speed
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Fatigue AssessmentCritical AreasCritical Areas
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Fatigue Input (In addition to Stresses)Wave Scatter
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Material Tolerance (S-N curves)
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Detailed Stress Analysis (Zooming)
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In Conclusion of Fatigue 101
• Miner Damage Accumulation Model
• North Atlantic Wave Input
• Weibull Stress Distribution
• Proper S-N curves (depend on approach)
• Satisfy Target Life (>20 years)
BUT…………
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The Fatigue Doctor: Good DetailsThe Fatigue Doctor: Good Details
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Design Proper Structural Details !Quiz:Find what is missing below
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LAST BUT NOT LEASTOperational Considerations in Design
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Ship Acoustics
• Noise prediction
• Optimisation of engine foundations
• Optimisation of structure-borne noise insulation index
• Noise measurements
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Vibrations
• Local Vibration Analysis
• Mast Vibration Analysis
• Shaft Vibration Analysis
• Vibration Level Prediction
• Analysis of coupled machinery/foundation vibrations
• Vibration measurement
Area Classification A
Passenger Cabins for instance
B Crew Accommo
dation for instance
C Working Areas for instance
Overall frequency- weighted r.m.s.-values from 1 to 80 Hz mm/s2 mm/s mm/s2 mm/s mm/s2 mm/s Values above which adverse comments are possible
143
4
214
6
286
8
Values below which adverse comments are not probable
71.5
2
107
3
143
4
Note: The zone between upper and lower values reflect the shipboard vibration environment commonly experienced and accepted
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The Big Enemy: Corrosion!
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Coatings do not last forever!
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Protection of Cargo Oil Tanks
• Pitting corrosion caused by sulphur components in combination with water
• Formation of hydrochloric acid
• Sulphur reducing bacteria
• Susceptible areas to be protected by coatings
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Where to Protect?
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Do not Forget : Eco-friendliness
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THANK YOU FOR YOUR ATTENTION!