Question

With reference to dry docking define the responsibility of the 2nd engineer

Prior to dry dock

Whilst the vessel is in DRYDOCK

Prior to flooding and leaving the dock

DRY DOCKING

Types of dock - Graving (from graved, to carvc out), Floating, Slipways and marine   railways for small ships.

BEFORE ENTERING DRYDOCK

Arrangements to maintain essential services must be made.

Cooling diesel generators

Fresh water may be piped on board run through sea water coolers to waste, but this is
expensive.   On some ships, a pipeline is provided so that on removing blanks and opening
valves, sea water coolers may be circulated from ships fresh water tanks and back to
tanks.  Under these conditions generator jacket temperatures must be carefully observed
and fresh water tanks changed over before the temperature becomes dangerously high.
For lighting and drydock power requirements, radiator or air cooled emergency generators
are often adequate.                                                                           

Shore Electrical Supply

Check the drydock supply is compatible with the ships phasing voltage and frequency. A cable is put on board and connected to the ship's supply.   Some ships are provided with a terminal box for this purpose (on deck or at top of engine room).   If no provision has been built in, connect shore cable to main bus bars.   It may be easier to connect to emergency generator bus bars and feed back to main bars.   Ship's engineers should know the most convenient terminal point before entering dock and the appropriate lengtii of cable needed to reach it.

Auxiliary Condenser

The auxiliary condenser is normally sea water cooled.   In drydock, the auxiliary range steam is passed up the funnel to atmosphere (operation: open atmosphere valve; close auxiliary condenser valve) and this is done just as dock starts to pump out.

Refrigerator

Sometimes the chief steward arranges for frozen food to be sent ashore to cold storage Check in advance to see if the refrigerator is needed,   if it is, shore water must be piped to the condenser and discharged overboard to waste.

Fire protection

 Fire connection made as soon as possible to the international fire connection and any sprinkler system connected to a shore supply of water.

Information required

Gas free certificates must be obtained for any empty fuel tanks, etc. that are to be worked in dry dock. Before entering the dock, all tanks and bilges are sounded and recorded. Any transferring considered necessary should be carried out. A dry docking condition is known and a dry docking plan available for ship and dock staff.  Since tank soundings just prior to dry docking are logged, any fuel and water consumed in dock and its effect on trim and heel may be determined from data supplied by the shipbuilder. Tables of hydrostatic data and loading tables for compartments are available. The ship generally leaves the dock in the same conditions as it enters.

ENTERING DRYDOCK     

The ship should be upright and trimmed slightly by the stern, empty of cargo, with minimum free surface in the tanks.  The ship is lined up over the keel blocks by permanent marks on the dock gates and head, or by plumb lines. As the dock is pumped out, the ship should land on the aft keel blocks first. As the dock water is lowered, the load on the after block and the reaction on the stern of the ship increases until the ship is just about to touch all along the blocks. At this instant, just before grounding all along the length of the keel, is the most critical time with regard to stability.  The load on the after keel blocks is a maximum at this point.   As soon as the ship comes down on the keel blocks, side shores (if necessary) are fitted, aligning with bulkheads or frames.   Modern docks with automatic side blocks do not require side shores. Toilet facilities are arranged (generally toilets on board will be closed) if not, arrangements are made to suit dock staff.   

IN DRYDOCK

A ship is dry docked as required for a docking survey, or as required to repair damage due to grounding or collision, nevertheless, ships are often docked annually.

The purposes of drydocking are:- 

(i) To clean the hull of marine growth Hull fouling increases the ship resistance, reduces its speed and increases fuel consumption, (ii) Classification Societies Hull Surveys. Docking and special surveys are required to maintain a ships 'class'

HULL INSPECTION

All underwater parts of the hull are inspected for damage and corrosion. Distortion of the underwater hull can be observed. If a dent is discovered, an inspection of the inside of the ship to determine internal damage should be carried out. Serious dents must be repaired, minor dents are left. All repairs and any dents left should be logged. Distorted; bilge keels should be faired and their attachment to the hull checked.

Corrosion

All cathodic protection systems should be checked for security of attachment and worn sacrificial anodes should be renewed if necessary. Particular attention should be paid at the forefoot, at the after end in way of the stern frame and on twin screw ships around propeller 'A' brackets, for corrosion and cracks. Attention should be given to edges of welds, which may suffer corrosion attack.

Rudder and propeller        

Remove the drain plug at the bottom to check the rudder is watertight and no water is entering. The rudder is mainly supported by an internal carrier bearing (a hardened steel disc may also be fitted at the bottom of some rudders).   Check the rudder wear down (maximum about 19 mm) at the tiller (steering flat).  In cases of excessive wear down               

renew the carrier bearing (and disc if fitted). Check pintle clearances, security of palm couplings and condition of the stock (cracks).  The propeller should be examined for erosion (cavitation), cracks and bent blades. CP blade bolts and cone connections should be checked.

Underwater Valves

All underwater valves (injections and discharges) should be examined. Valve grids and ship's boxes should be examined from the dock bottom to ensure the grids are clear and secure, and then from the engine room, etc. to see the attachments to the hull are sound; the valve seats tight (hammer test) and the valve lids and seats free of scores and pits. Always check the valve spindles are free to turn in their bridges. Always check each valve overhauled by shore labour before it is boxed up.   It is good practice to list all underwater valves before entering dry dock and then tick off each one overhauled, in this way none are missed.

Anchors and Cable

Ranged on the dock floor (special survey) for examination. Corrosion and wastage is excessive if greater than 11%, in which case defective lengths are removed, as also would be the case if cracks in individual links are found.   Joining shackles are parted and also checked. When re-assembling the pins require re-sealed with a lead pellet.

LEAVING DRYDOCK

When all repairs are completed, preparations are made for flooding the dock.   All under water fittings are checked to sec they are satisfactorily boxed up and all double bottom tank drain plugs checked to ensure they are replaced and properly tightened, (note the position and number of tank drain plugs from docking plan and then tick off each one as it is checked) Tank drain plugs are usually the responsibility of the First Mate but some companies require the Chief Engineer to share the responsibility.  Before flooding, soundings are taken, so that any adjustments to heel and 'trim required (due to modifications, fuel burnt or flood water cleared, etc.) can be made. Should the ship be in a poor stability condition when lifting off the blocks, severe strain and damage or even capsize may occur. 

On flooding the dock, engine room staff should stand by as follows:-

An engineer either, side of the engine room to check underwater fitting. If there are underwater fittings in separate compartments, these should be covered.

An engineer standing by the stern tube to watch for leaks. Packed stern glands should be hardened up evenly all around if leaks show.

A man should stand by any hull repairs whilst flooding of dock takes place. (Dock officer holds engine room officer machinery spaces)

The Chief Engineer should always tour the engine room at this time.  Any leaks should be reported to the Chief Engineer immediately.

FINAL REMARKS

Dry docking is a shared responsibility - dock staff, deck and engine room. Close liaison and an exact knowledge of who does what is required. This varies between companies, but in general, marine engineers are responsible for.

Propellers and shafting, rudders and fixings, corrosion plates and any impressed current system fitted, all ships side valves, fuel tanks and tanks in way of engine room, all electrical, water and steam services.