Bill robllee, drydock issues

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Bill robllee, drydock issues

  1. 1. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven DRY-DOCKING ISSUES PRESENTED BY: Bill Robblee MSC TECHNICAL DIVISION
  2. 2. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Critical Issues • Is the dry dock adequate? –Determined during Tech Evaluation of proposal –Checked at time of docking • Accurate determination of docking condition –For use in docking calculations
  3. 3. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Is The Dock Adequate? • Dock Width > Ship’s Beam 
  4. 4. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven
  5. 5. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Is The Dock Adequate? • Dock Width > Ship’s Beam  • Dock Length > Ship’s Length  –Floating docks, ship can exceed dock length
  6. 6. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven
  7. 7. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven
  8. 8. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Is The Dock Adequate? • Dock Width > Ship’s Beam  • Dock Length > Ship’s Length  –Floating docks, ship can exceed dock length • Dock Capacity > Ship’s Docking Disp. 
  9. 9. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Is The Dock Adequate? • Dock’s rated linear load/foot > loading from ship? –Both floating and graving docks have a maximum load per foot rating given in long tons per foot
  10. 10. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Dock Loads • Determined by –Trapezoidal Load Method –Moment Area Method • Both methods assume ship is infinitely stiff • Uniform keel blocking, use trapezoidal • Moment Area method based on eccentrically loaded column theory
  11. 11. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Dock Loads • Factors –Ships displacement –Eccentricity – distance between ship’s LCG and centroid of blocking area –Total block area
  12. 12. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Load per foot, fwd = W / Lkeel - 6(W)(e)/(Lkeel)2 Load per foot, aft = W / Lkeel + 6(W)(e)/(Lkeel)2
  13. 13. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Ways to meet load per foot limit: • Use position 3 (minimum overhang) • Move LCG ship by adding ballast or shifting fuel
  14. 14. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Approximate Dock Loads • T-ATF: 12 tons per foot • T-ARS: 20 tons per foot • T-AO: 45 tons per foot (ballasted) • T-AO: 47 tons per foot (light ship) • T-AOE: 45 tons per foot (ballasted) • T-AOE: 48 tons per foot (light ship) • T-AKE: 64 tons per foot
  15. 15. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Dock Capacities • Cascade General, Dry Dock 3 –26,000 tons, 46 tons per foot • GSY –30,000 tons, 50 tons per foot (anticipated rating) • BAE TITAN –52,534 tons, 60 to 70 tons per foot • BAE OLD DOMINON –14,000 tons, 28 tons per foot
  16. 16. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven In-dock Period • Changes to dock loading while in dock: –Removing ballast –Removing anchors and chain –Removing props, rudders, shafts • Effect on dock loading must be considered.
  17. 17. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven The Docking Condition • Displacement and LCG –From ship’s drafts • Vertical Center of Gravity –From ship’s loading –Includes “ghost weight” to make CargoMax displacement equal to displacement from drafts
  18. 18. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven The Docking Condition • “Ghost Weight” – unaccounted weight –Unaccounted light ship weight changes –Unaccounted loads (spares, cargo, etc) • Pier side condition, corrected to as read drafts –Adjustments , as required, for acceptable docking condition
  19. 19. Military Sealift CommandMilitary Sealift Command Mission-focused, Value-drivenMission-focused, Value-driven Questions?

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