DRYDOCKING
Objectives
• General
• Reasons for Dry docking
• Choosing a dry dock
• Types of Docks
• Dry dock various operations
Dry Dock
• Dry dock schedule is established from the
date of building
• To satisfy survey requirements
• To ensure vessel remains in the class
• conduct and update essential
modifications and repairs
Reasons to Dry Dock
• Routine scheduled dry-docking to
coincide with classification needs
• Exceptional circumstances like damage
• New vessel may need to dock after
maiden voyage to adjust propeller.
Dry Dock Operations
• Hull Cleaning
• Ship Names, Load lines and draught
marks
• Chain Locker Cleaning and Inspection
• Bow Thruster Units
• Propellers
• Stern tube
• Gas freeing (Tankers)
Choice of Dock
• Capacity of dock
• Dock availability
• Time, efficiency and reputation
• Dry Dock Facilities
• Administration
• Docking after emergency incident
Choice of Dock
• Plate storage
• Workshops
• Store Supply
• Labour
• Transport operations
• Medical and First aid facilities
• Economy
Dry Docking Methods
• Graving Dock
• Floating Dock
• Synchro Lift Dock
Graving Dock
The Graving Dock
• A permanent dock built in stone or
concrete.
• Accessible at one end from the sea by
which vessels enter inward for the
purpose of repair, inspection or
cleaning.
• The seaward end is closed off by a dock
gate.
The Graving Dock
• Advantages
– Permanent facilities
• Dock Admin
• Local Labour source
• Regular shore supplies
• Disadvantages
– Can not be trimmed to accept any kind of
damaged vessel
The Graving Dock
• The floor of the dock is flat, but is
constructed on a slight incline.
• The incline,“Declivity of the Dock”, tends to
assist drainage of the flood water. when
the dock is being pumped dry.
Floating Docks
Floating Docks
• Because of their generally restrictive size,
have a tendency to cater for the smaller
tonnage and specialist type vessels.
• The feasibility of the floating dock to be
towed into alternative locations is a distinct
advantage
Floating Dock
Floating Dock
Synchro-Lift Dock
• Most modern style of docking
• Allows multiple vessels to dock at a single
time
Synchro-Lift Dock
• Advantages
– Multiple dockings possible
– Workforce is available across the dock
– Working constraints and time schedule are
independent to individual ships
Synchro-Lift Dock
• Disadvantages:
– Lifting capacity of up to limited
– Only used for small vessels
– Can not dock a loaded vessel
– Continuos maintenance of the Platforms,
lifting winches required etc
Preparations for dry dock
1. All tanks, spaces clean – tanker gas free.
Tanks full or MT.
2. Cargo RoB (details). DG’s documented
3. Moveable weights secured.
4. Derricks/cranes/g’way secured.
Preparations for dry dock
5. Arrangements for
• Fire protection
• Water
• Power
• Watchmen/security
• Access
• Garbage disposal
• Communications
• Toilets/sewage disposal
Preparations for dry dock
6. Establish work to be performed by crew
• Additional work to be carried out by 3rd
party contractors – radar/charts/VDR etc
• Arrangements for storing (deck/ ,E/R
catering)
• Permit to work, hot work, gas free.
Documents
1. Repair list (inc items for mod)
2. Standard dry dock job list
– painting, shell cleaning, marking anchor cable…
3. G.A. plan
4. Fire fighting plan
5. Shell exp plan
6. Rigging plan – lifting gear to be overhauled
7. Stability info (GM, tank info) Draft, trim.
8. Manhole, plugs & anodes plan
9. All certificates
FF – responsibilities?
1. Under construction?
• Ship builder
2. Under repair?
• Ship owner – unless responsibility delegated to
repairers in writing – who pumps water? terms
known
3. At sea?
• Owner through Master
4. In port?
• Owner through Master – if fire brigade called then
Chief Fire Officer or could be Port Authority
Legal aspects to consider before
enter dry dock?
1. Survey requisitions for certificates
• Safety Construction, Safety Equipment,
Radio, Pax Ship Safety, Loadline
• Certificate of Class
2. Fresh water tanks – 5 year testing
3. A ship to comply with all usual
regulations
• Musters and drills
• Safe access
Docking stresses
• Upward thrust from below the keel
caused through lower blocks.
• Ships weight to cause a downward and
outward stress
• Incorrect placing of the blocks can and
do cause damage
• It is unlikely to have permanent
extensive distortion in short period of
dry docking.
Docking stresses
• Longitudinal strength member provide
positive compensation against dry dock;
– Longitudinal frames
– Girders
• Athwartships framing tends to stiffen the
body of the ship and resist distortion
when on blocks
Dry dock Departure operations
1. Plugs are in (rudder)
2. Non-return v/v’s in place
3. Inlet/discharge pipes are in place
4. Gratings/baffles in place. Nuts wire
locked.
5. Propeller shaft replaced
6. Plating intact
7. Stability (checked)
Dry dock Departure operations
8. Mooring lines out
9. Anchors correctly stowed
10. Disconnect all services
11. Check Dock is cleaned prior to flooding
12. Transducer cover must be clear.
Movie Time…..!
• ( Singapore Dry dock)
• Floating DrydockCruise Ship -1
• Floating Drydock Cruise Ship -2
• Ship lift
Exercise
• Chief officer’s duties before and
entering the dock
• Chief officer’s duties before and after
departing the dock
• Dry docking operations
