bill robllee, drydock issues

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DRY-DOCKINGISSUES

PRESENTED BY:

Bill Robblee

MSC TECHNICAL DIVISION


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


Is The Dock Adequate?

• Dock Width > Ship’s Beam




• Dock Length > Ship’s Length –Floating docks, ship can exceed dock length




• Dock Length > Ship’s Length –Floating docks, ship can exceed dock length

• Dock Capacity > Ship’s Docking Disp.



• 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


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


Dock Loads

• Factors

–Ships displacement

–Eccentricity – distance between ship’s LCG and centroid of blocking area

–Total block area


Load per foot, fwd = W / Lkeel - 6(W)(e)/(Lkeel)2

Load per foot, aft = W / Lkeel + 6(W)(e)/(Lkeel)2


Ways to meet load per foot limit:• Use position 3 (minimum overhang)• Move LCG ship by adding ballast or shifting fuel


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


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


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.


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


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


Questions?

bill robllee, drydock issues

Education

dock loading

dock capacities

dry dock adequate

foot rating

dock loads factors

long tons

foot limit

foot gsy