Dry Docking

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Before entry:

• Check the stability of the vessel, especially during critical period.

• Check the vessel at required draft.

• No list.

• Prepare mooring lines.

• Unused mooring lines stowed.

• Standby for dock master and dock mooring gang.

• Proper flags displayed as required.

• Free surface effects minimum.

• Movable weights to be secured.

• Ship power, fire main, fresh water, telephone connections to be ready.

• Logs off/ retracted.

• Off echo sounders.

• Overboard discharges to be shut.

• Gangway/ accommodation ladders to be stowed.

• Anchors stowed and secured.

• Crews standby to assist moorings as required.

While entering:

Times of the followings to be logged down:

• When vessel enters dock.

• When the gate closed

• When pumping out commenced.

• When vessel sewed

• When pump out completed.

After vessel docked:

Tanks and bilge soundings throughout the vessel.

Records to be kept with copy to dock‐master.

Hull high pressure wash as the level goes down.

Initial inspection of the hull to be done as soon as possible:

• The extend of the hull damage if any.

• The extend of the rudder and propeller damage

• Suitable and efficient shoring arrangements

• Suitable and efficient keel blocks

Plugs to be removed, if draining of the tanks to be required.

All removed plugs to be in safe custody of C/O.

Bridge equipments, gyro shut down, heading recorded.The preparation of a vessel for dry docking

a) Arrange a meeting with the heads of departments. Inform them about the dry docking plan. Inform them about:

• The dry dock, particulars of dry dock, if any, expected date of dry dock etc.

• Instruct the chief engineer / chief officer to prepare a comprehensive dry docking and repair list.

• Arrange another meeting with the head of the departments to go through the repair list respectively.

• Determine which repairs can be done onboard by ship’s personnel.

• Check there is no overlapping of repairs between various departments.

• Recompile repair list of both departments.

b) Prepare an official repair list, include proper photocopies of plans or diagrams of parts to repair.

c) Send the repair list to office. Also send the list of repairs to be done by ship’s personnel.

d) Ensure all plans are onboard.

e) Approved list from head office will be send back to the ship.

f) Heads of departments to have copy of repair lists.

g) Send docking plan to dry dock for preparation of dock.

h) Heads of departments to brief crew members regarding dry dock repairs.

i) Safety committee also to be involved regarding dry dock repairs.

j) The surveys due and to be done in dry dock.

k) Required preparation for surveys.

l) Any modification to be carried out.

m) Order the necessary stores, materials for repair jobs by ship’s crew.

n) Ask to company for extra officer if deem necessary.

o) Assign duties for officers and brief them about safety and security of the vessel and maintaining efficient watch at all times.

• For chief officer, overall supervision of deck work list, safety and organization of crew for dry dock and survey.

• For 2nd officer, supervision of hull cleaning and painting and to keep watch under c/o’s instruction.

• For 3rd officer, in charge for safety while in dry dock and to keep watch under c/o’s instruction.

• Designate personnel for fire patrol and gangway watch.

• Designate personnel for filling FW and disposal of garbage.

p) Instruct c/o to brief the crews on general safety requirement, dock and regulations to be followed and procedures to be taken in case of emergency / accident.

q) Stability of the ship to be calculated before entering. Following things to be considered:

• The GM of the ship, maximum loss of GM during critical period.

• Vessel to be stable throughout the process.• Trim of the ship should be adequate.

• Vessel should be upright.

• Amount of ballast, FW, FO, cargo onboard and their distribution.

r) Cranes to be stowed to avoid obstruction to dry dock cranes. High antennas to be lowered.

s) Lifebuoys to be removed from deck to avoid over painting.

t) Off‐hire time and position to be ascertained and logged (if time chartered).

Plans required in dry dock

For dock master:

• Docking plan.

• Cargo stowage plan (If docking with cargo).

• Reports from last dry dock.

Following plans to be kept ready:

• Fire plan.

• Midship section plan.

• General arrangement plan.

• Capacity plan.

Contents of a docking plan:

• Position of bulkheads

• Position of main structural members.

• Rise of floor (if any).

• Position of plugs.

3. Critical Period, Critical instant, formula for loss of GM

Critical instant or Critical moment

• It is the moment just before the vessel takes blocks overall.

• The upthrust of bilge block acts on the stern frame.

• The upthrust is maximum at this moment.

• It can be calculated by following formula:

Pmax = MCTC X t / l

MCTC = Moment to change trim by 1 cm.

t = Trim in cm.

l = Distance of CF from AP.

• It is called critical instant because maximum loss of GM occurs at this instant.

• If GM becomes negative, the ship may capsize or slip from block

Critical period

The period since the keel first touches the block until the vessel takes blocks overall.

An upthrust is caused by the blocks, denoted by “P”.

P at any instant can be calculated by the following formula:P = TPC X Change in mean draft in cm.

P is maximum at the instant before vessel takes blocks overall. It can be calculated as:

P = MCTC X t / l { t = trim in cm, l = dist of CF from AP}

Due to the upthrust, the vessel reduces its GM.

The G moves UP, thereby GM is reduced.

M moves down to M’, thereby GM is reduced.

Shift of G (Center of gravity) or M (Transverse metacenter) may be calculated as:

• GG’ = (P X KG)/(W ‐ P)

• MM’ = (P X KM)/W

• The danger is, due to subsequent loss of GM, the vessel may lose positive stability and may capsize.

• Maximum loss of GM to be calculated beforehand.

• It is dangerous if negative GM occurs in dry dock.

If negative GM occurs in dry dock

• The vessel will lose positive stability.

• She may capsize.

• She may slip off from the blocks.

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