Dry Dock Pocket Guides for Ship Master

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Welcome again to my blogs!

Today I will discuss safe and efficient dry dock operations as Master. This handy sheet may help you with pre-DD meetings among all ship staff also, this would cover as following:

Type of Dry Docks

There are various types of Dry Dock available in the maritime industry. Commonly used are Graving docks and Floating docks.

Mostly Graving docks are used for large-sized vessels. These types of docks are very accessible for supplying stores/spares. Dock water is restricted by locking gates, which are also known as Caisson gates. This type of dock is non-operational if caisson gates are malfunctioned.

Mostly defective / small-sized vessels use Floating docks. It is handy to change trim either by the Head/Astern, as per vessel requirement (highly useful for damaged vessels, which can’t meet DD requirement). These types of docks are not very accessible for supplying stores/spares, because of their location at sea.

Other than these there are SLIPWAY DOCK and SYNCHRO LIFT DOCK which are mostly used for very small-sized vessels. Not for conventional merchant vessels.

Caisson gate / Locking gate

Vessel is in the graving dock

Vessel entered Graving docks but water not yet pumpd out

FLOATING DOCK

Captain’s Communications with Dock Master

Following queries Master will clarify from Dock Master:

1. Is the ship-shore electrical connection for AC/ Refrigerator compatible or not?
2. The dry dock handbook is to be received prior DD.
3. Requirements of Trim, GM, Draft, UKC prior docking-undocking?
4. Dock clearance how much (each port/ Stbd side?
5. Sanitation disposal lines/ facilities
6. Garbage disposal facilities
7. Sea-water circulating methods for machinery spaces
8. Any ship-shore air line for various pneumatic tools operations.
9. The master may ask for Communication methods with dock Master – Landline & WhatsApp Number.

Air-line connection if   necessary for operating pneumatic tools

Pre-docking documentations

However, the following items are prepared by the ship’s chief officer:

• The General Arrangement Plan
• The Dry Dock Plan /The Plug Plan (incorporated into Dry Dock Plan)
• The Shell Expansion Plan (If a grounded vessel with bottom damage is being docked; shell expansion plan copies must be readily available.)
• The Ship Stability Information
• The Fire Fighting Facility Plan of the Vessel
• Rigging Plan (Cargo Vessels)
• The Tank Arrangement and Distribution of Commodities (Stowage plan – In case docking with cargo on board)
• Cargo Plan and Manifest (In case docking with cargo on board)
• Relevant Certificates
• Repair plan (DD specs).
• Gas-free Certificate (Tanker Vessels– Certificate will be issued by 3^rd party).

• Chief Officer to ensure tanks gas free- every corner of the tanks.

Statutory Stability Information

1. Ship’s general particulars

2. A metric conversion table and deadweight scale

3. Tank Arrangement (Capacity Plan)

4. General notes on stability

5. Hydrostatic particulars

6. Damage stability information (if damaged vessel)

7. Centre of gravity of all tanks

8. Details on free surface movement

9. Curves of statical stability and the Cross Curves with examples

10. Condition sheets for various options

11. Tank-sounding booklet which includes initial soundings of all tanks when the vessel took to the blocks.

Stability calculation for ‘Critical Period’

During Dry Docking Stability of the Ship is the Most Vital Concern. There are several incidents while docking/undocking due to stability. Following are a few points to help you to have a safe DD.

1. Prior to initial stability calculation, all the tank sounding is to be carried out by the Chief Officer & Chief Engineer.

Do not trust others for the same. The same record can be stored by the Master to compare the same during un-docking. Soundings must be taken for all Tanks including void spaces.

• Remove all heavy loads from the forward & aft portions of the vessel and empty the FPT / APT to avoid overhang/ bending stresses on the vessel. After the vessel is seated on the blocks, these tanks are not within the support of the blocks (due to the curvature of a ship).

• Make sure no list at all while approaching DD & especially while sitting on the blocks.  There is a high risk of getting the vessel’s appendages such as the Bilge keel dislodged, and damaging the blocks when the vessel lists in the dock.

*** Make sure that the ballast and fuel are transferred with the written consent and instructions of the dock master only***.

*** Critical Period and Calculations ****

Now I will try to explain stability matters till the vessel is resting on the blocks. The Dock Master will advise you on Trim & Minimum GM requirements. According to that Chief Officer has to calculate the ‘P’ force to ensure positive GM after fully resting on the Block.

When coming into Dry Dock (Stability matters):

• Once the sternpost is touching the block, the UP-THRUST forces start to act against the sternpost.
• At this moment part of the ship’s weight gets transferred to the keel blocks, so the vessel will suffer loss on her GM.

• The time interval between the sternpost landing on the blocks and the ship taking the blocks overall is referred to as the CRITICAL PERIOD.

• The vessel must have a positive effective GM that is to be maintained throughout the critical period.

• If not vessel may heel over, slip off the blocks when there is an external force acting and heel the ship.

*** CALCULATIONS: ‘P’ – FORCE***

*** CALCULATIONS: Loss of gm***

There are two methods to calculate the virtual loss of GM during critical periods. Details are as follows:

Method 1 – GG1: Weight transferred

This can be calculated by following the formula:

Method 2 – MM1: Buoyancy transferred

•When the vessel comes in contact with the blocks, it is assumed that there is a transfer of buoyancy ‘P’ to the keel blocks.

•Hence there is a reduction in KM while the weight and KG remain constant.

This can be calculated by following the formula:

Exercise:

A vessel with LBP 120m is going to dry dock at the following conditions in seawater. Draft forward is 3.5m and aft is 4.0m, distance sueing point (AP) to F is 57.5m. Her displacement is 4600 tonnes, MCTC is 86 t-m and TPC 15.45 Calculate.

i.The amount of up-thrust force (P) at the end of the Critical Period?

ii. Loss of GM / Final GM.

Solutions:

The vessel comes to the dry dock with an initial trim of 0.5m by the stern.

The vessel will then change her trim from 0.5m by the stern to 0.5m by the head when the Critical Period is completed.

Therefore Change of Trim required at the end of the Critical Period is 0.5m or 50cm by head, vessel will be at even keel drafts.

** Calculation of ‘P’ Force **

P = COT x MCTC / d

    =  50 x 86         /  57.5

P = 74.8 tonnes

** Virtual loss of GM Calculations **

Method 1 – GG1 method

GG1 = P x KG

             W – P

         = 74.8 x 7.2

            4600 – 74.8

GG1 = 0.119m

So, Residual GM = 0.8 – 0.119 = 0.681m

Method 2 – MM1 Method

MM1 = P x KM

                  W

           = 74.8 x 8.0

                  4600

MM1 = 0.130m Virtual loss of GM (MM1) method…

So, Residual GM = 0.80 – 0.130 = 0.670m

CONCLUSION:

•The virtual loss of GM is NIL as the vessel has zero trim.

•The loss is increased as the trim increases.

•Maximum trim is dependent upon the initial GM.

Various log book entries / Paper Works

Officers will assist to Master as follows:

• While on deck, assist the bridge by providing all clearances from the navigational obstructions in proximity.

• Basically, the deck officer is the “eyes and ears” of the master during critical operations such as making entry into the dry dock. The master will rely on the officers for accurate reporting and advisories.
• The bridge equipment is adequately used and switched off as and when the ship’s power is isolated.
• Mooring stations are properly manned by having competent personnel for all the rope work.

• Local tide tables & immediate weather reports for dock entry are to be readily available for immediate use.

Logbook Entries:

For all legal and record purposes, a distinctively routine docking operation should be included in the ship’s logs. A typical logbook account should cover all aspects of docking for various activities. This is a critical operation, so, Master should discuss various entries with BTM officers earlier. Following are some entries which to be logged down:

The deck logbook and engine logbook should be appropriately recorded with –

➢ Times of operations and details of tugs involved

➢ Time when Entry into the docks

➢ Times and details of the relevant engine movements

➢ Record of the shore men (if boarded the vessel for mooring /

      assisting in dock entry)

➢ Time of first lines ashore etc.

➢ Times when lines passed, taut and cleared

➢ Gates closing/opening in case of the ‘Graving Dock’

➢ Times and operations related to flooding / emptying the dock

➢ Times when the vessel rests or clears the keel blocks

➢ Access-way attached to the vessel after residual water is cleared   from the dock

➢ Times of Pilot’s embarked and disembarked

➢ All other operations and tasks undertaken during the stay of the vessel in the dock are to be recorded and provided to the company office as necessary

Paperwork / Files for DD:

• Prepare a separate file for the blank landing report, which will be filled and signed by the chief officer (C/O) and the shore in-charge when any part from the ship’s deck is landed ashore for repairs or checks.
• Make a separate file to collect all the invoices of spares received during dry dock.

• Make a separate checklist for fire rounds by duty officer/ AB. Specially closing round is to be taken by the Chief Officer only. Click to download :

• Make a separate file to collect all the Timesheets of shore technicians during dry dock.

• Master / Chief Engineer can prepare a daily meeting file, where meeting agenda/discussion results would be logged in.

• Make a separate log file to note down valve operations in the deck (fire line or ballast line). Whenever anybody operates a valve (opens or closes), he/she should record it in this log file along with the date, time and current position of the valve (open/close).

• Prepare a separate “Isolation log file” to include the date, time and the machinery isolated, so as to ensure that it is brought back to normal when the dry dock is completed.

• A separate file with all kinds of work permit forms (blank) to be arranged and kept ready. Prepare two portions on it, one for shipboard permits, and another portion for the DD safety officer’s issued permits.

• Bottom Survey / inspections

As per SOLAS (S74/CI/R12 (ii)) bottom survey is to be carried out within 2-3 years (range) and at least two times in any renewal period. Where the vessel is ‘more than 15 years old’, the survey is to be carried out every 2 – 2½ years (range) if the vessel is coated with high resistant paint coatings.

The following are the key points for the bottom survey:

* The void spaces, cofferdams, cargo tanks/holds, seawater and freshwater ballast tanks, fuel oil tanks, etc. to be opened up and surveyed. Annual Inspection report to be made (if situation requires).

* The vessel’s side plating and bottom are to be visually examined by the surveyor in order to complete the ‘Hull Surveys’.

Bottom sea valves (high sea chests, low sea chests, forward sea chests, Draft valves etc.) are to be overhauled and presented to the surveyor for inspections and survey purposes.

 Safety practices during DD including Quick tips.

* The echo sounder sensor is to be protected by covering it with a thick rubber joint before cleaning and painting.

* Marine Growth Preventive System (MGPS) anodes to be replaced.

* All the bottom sensors are to be covered before blasting/ painting.

* Medical aid, Fire-fighting and rescue facilities are readily available at all times.

* Prepare spot Risk Assessment and discuss it among the ship staff.

Tank Plugs: Removal of the tank plugs is carried out by the shore personnel as listed in the initial job list. Proper storage, replacement and removal of all tank drain plugs are to be counted by the chief officer.

While refitting the plugs the area is to be cleaned off grit and other particles that can damage the threads of the plug. Lead is used as a packing material that is to be applied before ‘screwing-in’ the plug. Make sure the plug is secured tightly in place using the appropriate tool. Cement is finally applied to the plugs in order to make sure the area is leakproof.

• sea-chest gratings

All sea-chest gratings are to be opened up and missing bolts are to be ordered and replaced if any.

• Tail shafts are to be surveyed and poker gauge readings are to be taken
• The tail shaft leak test to be witnessed by the responsible.
• Spacer ring/ stern tube seal to be renewed if required/ any leakage.
• The poker gauge is placed between the last and second last stern tube seals (aft- near the propeller). The reading is taken at every dry dock and recorded. A hole is provided on top of the seal which is closed by a plug. This plug is removed, the poker gauge is inserted and a reading taken.

Following photographs for your better understanding:

* Keep clean bilge tanks, floors, and decks to avoid fire hazards.

* All the emergency lighting and emergency generator systems are to be tried and tested beforehand. Emergency Generator will be used at least once during the docking period.

* Split the onboard staff into groups so as to oversee/administer the jobs carried out by the yard gangs.

* Ensure to paste warnings and caution signs inside the accommodation stating “not to throw anything in the toilet with vacuum system” in English and if possible also in the local language.

* Prepare separate files for empty landing reports to be used in the dry dock

* All mooring ropes are to be kept in rope locker, except the ones necessary for docking stations.

* All stores (nut-bolts, spanners), cabins and compartments inside the accommodation are to be locked and the keys are to be kept with the respective crew members and responsible officers.

* Chief Officers and Chief Engineers must make sure that the ship’s staff are well aware of the presence of dock workers onboard and that the tools given to them are taken back after the job is completed.

* Draft marking and ship side marking are to be compared with previous markings. It is recommended to take some photographs immediately after docking, so that you will not miss any markings.

* Check ship hulls for any bendings/holes/ damaged plates, if any, discuss the matter with the Superintendent at the earliest.

* Never rely on the shore staff, the shipboard safety officer must verify safety parameters for each operation.

* Paint and Sample locker inspections to be carried out hourly (Duty AB can be nominated for the same)

* Rig Fenders must be provided around the vessel before entering the dock.

* Plug and lock all upper deck scuppers to decrease the risk of pollution.

* Make sure every frequently that safe working culture is maintained onboard.

* All retractable appendages such as the speed logs, stabilizer fins etc. are stowed away inside the hull prior to entering the dock.

* During the process of removal of deck plates, gunwales, ladders, gratings, floor plates and handrails, the repair yard must take sufficient safety measures. It is also mandatory to correctly secure and reinstall these items once the repair work is completed.

** Very important- Open railing may cause fall from the ship and die.**

* ETO to check Earthing wire fitting and bonding, Ship to be electrically grounded to shore earth.

* Ensure that the paint including primer is available onboard for various areas/renewal areas on deck. Ensure that the paints and chemicals used are tallied for when and how they get consumed.

• Usually, LSA/FFA services (annual / 5 yearly / 10 yearly) are carried out in the Dry dock. Make sure things are tallied prior to landing and counter-signed on the landing reports.
• During DD overhauling, renewal of brake bands and test of mooring winchs are highly advisable. Change gear oil also if due in the near future (as per PMS).

CO2 total flooding system door must be locked to prevent accidental actuation. Key must be in the common area and are to be known to senior officers.

Real-life incident- Collected from A book published by Marine Insight.

* Escape routes should be clearly marked/obstruction-free at all times, CE to make sure such at all times.   

* Inspection and re-packing of all underwater stuffing boxes.

* If the Funnel is to be painted, use heat-resistant or high-temperature paints or those as specified in the vessel painting scheme.

* Ship staff maintenance plans are to be prepared which could include as following:

1. Deck seals, cofferdams, pump room floors cleaning.

2. All cargo line pressure tests and issue certificates
3. Ballast line pressure test and issue certificates
4. Heating line pressure test and issue certificates
5. Bunker line pressure test and issue certificates
6. Foam line pressure test and issue certificates
7. Compressed air line pressure tests and issue certificates
8. Tank cleaning line pressure test and issue certificates
9. Vapour return line pressure test and issue certificates
10. Fire Line pressure test and issue certificates
11. Fresh water tank cleaning, and inspections with inspection report
12. All ballast Tanks cleaning, and inspections with inspection report
13. All void spaces cleaning, and inspections with inspection report
14. Main deck- support deck piping and after replacement of various angle bars, pipes, fittings etc. cleaning & painting.
15. Various valve activation, rust removal and paint.
16. Paint the lifeboat, and rescue boat and mark again.
17. Removal of rust, and maintenance of fore and aft masts as required.
18. Replace poor mast stays.
19. Accommodation area two wings and bridge deck frame paint. Accommodation outside area Paint.
20. Cleaning of antenna, painting Monkey Island and Aft mast.
21. Open and close the cover of the ballast tank and replace the gaskets.
22. Replace drip tray railing ropes/ chains
23. End-to-end replacement of mooring ropes (as required) and renewal of mooring ropes (as required).
24. All fire/foam hydrants are to be dismantled and repaired/replaced one by one.

 25. Replace and maintainance of the various vent heads all over the ship.

Special checks by ship staff including Anchor, Hull painting, Cathodic Protection / Anodes, Rudder, Propeller etc.

Ranging Anchor Chain Cables for Inspection:

The ranging of the cables can be achieved by means of a power-driven vehicle, which would tow the chain in flakes alongside the floor of the DOCK.

Slipping the Bitter End

The slipping arrangement is usually carried out in the presence of a surveyor. It is conducted by lowering the end of the anchor cable completely using a wire rope arrangement or a dock crane.

Hydro-blasting and Hull Painting

Grit blasting, one of the most commonly used blasting methods, is efficient but expensive as it requires additional cleaning up. Dust formed during this method is then hosed down using fresh Water.

Sand used for blasting is relatively softer than the grits. Due to the hazards of ‘Grits” & ‘sand” blasting, a newer method known as “High-Pressure Hydro-blasting” has been developed. This method improves the blasting operations by increasing efficiency, reducing health hazards and allowing better work ergonomics.

* Make sure you have covered all the openings e.g. Hydraulic winches, motors, crane motors, LB engine motors, and accommodation access doors prior to blasting.

* The lower region of the ship from the boot topping to the keel is almost always in danger from electrochemical corrosion, especially the aft area containing the propeller.

Hull Painting (In short elaboration):

Boot Topping Region: It is the surface area of the outside hull plating located between the light and load waterlines of the vessel. The hull area near the water line has to be coated with paints of different compositions which can withstand regular wear.

Superstructure: It is defined as any structure which extends above the ship’s main deck.

Top sides: Paintwork areas of the ship’s hull that is located above the waterline.

Initially, they will blast the ship’s hull. The superintendent is to decide the extent of the blast (in %) and the master is to discuss the same with the Chief officer. Nowadays, most of the DD is using cherry pickers to blast the upper portions instead of staging.

After completion of blasting, inspection is to be done by the Chief officer and Master. The same is to be discussed during the DD meeting (normally morning hours).

Upon confirmation, they will apply primer, then touch up and finally will apply Anti-fouling paint. The paint supplier will provide an anti-fouling certificate, based on which Flag/ class will issue IAFC.

Anti-fouling Paints: They are special paints, defined as a toxic composition applied to the vessel’s bottom to prevent marine growth such as barnacles and weeds that could affect a vessel’s performance.

CATHODIC PROTECTION / ANODES

If the propeller is efficiently bonded to the ship’s hull by means of the shaft, then the propeller becomes the `cathode’ and the steelwork of the

rudder and the stern frame areas become the anode of a large corrosive cell, the salt water being the electrolyte solution establishing the completion of the galvanic corrosion cell.

This stern area of the hull is mainly prone to corrosion because of the mechanical actions which produce turbulence, vibrations and the erosion of paint coverings.

Shielding the stern area and supplementary hull features, which are prone to excessive corrosion and galvanic attack, is achieved by using of

`Sacrificial Anodes’. These anodes are made with noble metals such as aluminium, zinc or magnesium.

The anodes are positioned around the stern frame areas including the rudder structure in sufficient numbers so as to offer adequate cathodic protection.

The number of anodes depends on size of the ship, hull paint coating and material of the propeller.

The anode is sleeve welded to the hull to make a successful electrical contact. The anodes slowly waste away and are therefore required to be replaced in every dry dock.  

The anode is sleeve welded to the hull to make a successful electrical contact. The anodes slowly waste away and are therefore required to be replaced in every dry dock.  

Impressed Current System:

Impressed Current System: This system works by supplying a controlled amount of DC to submerged surfaces using highly reliable mixed metal oxide anodes and zinc reference electrodes.

This electrical current is constantly monitored and regulated by the system itself to prevent the electrochemical action of galvanic corrosion.

The corrosion-resistant anodes are insulated from the hull and kept completely immersed in seawater, thus completing the electrical circuit.

The hull then becomes Cathodic (electron receiver) in an electrolytic cell, efficiently preventing the ferrous ions from passing into the solution by subsequently protecting the hull.

A direct current (D.C) supply of up to 10 volts (30 volts maximum for extreme cases) is usually required along with an adaptable device incorporated in order to differ the voltage for altering conditions, e.g. Higher voltage is necessary in warm waters, where paintwork has

Deteriorated, when the vessel is making way or when the ship is in fresh water or dock water.

The voltage for the system needs to be maintained within fine limits. If set on high, alkali generation would occur which would leave the paintwork of the hull open to attack. If lesser voltage is applied, the protection provided turns out to be ineffective.

Precautionary checks before flooding the docks

The chief officer and chief engineer are jointly responsible for checking the underwater hull openings, before the flooding of the dry dock.

This includes:

➢ Sewer storm valves

➢ Tank drain plugs

➢ All sea valves and sea chests

Throughout re-floating, the engineering staff shall be stationed at the engine room to ensure that there are no leakages. Similarly, the chief officer will ensure the condition of all the deck tanks.

Following are the points to be carefully examined before flooding the dry dock:

➢ All departments in charge should confirm that the repairs assigned under their departments are completed successfully followed by tests and surveys

➢ Check the rudder plug and vent. Also, check if the anodes are fitted back on the rudder

➢ Check Impressed Current Cathodic Protection System (ICCP) anodes are fitted in position and the cover is removed

➢ Check anodes are fitted properly on the hull and the cover is removed (If ICCP is not installed)

➢ Check if all sea inlets and sea chest gratings are fitted

➢ Check echo sounder and logs are fitted and their covers removed

➢ Check if all the plugs of double bottom tanks are secured

➢ Check all external connections for shore water supply, sewage disposal pipe etc. are removed

➢ Check if the propeller and rudder are clear of any obstruction

➢ Check inside the ship if all repaired overboard valves are in place

➢ Check the area near the stern tube propeller shaft for any kind of leakages

➢ The cables for the ICCP anode fixed in the hull are carried into the engine room via water-tight ducts. Ensure no water leakage is there and the duct manhole door opening in the engine room is shut

➢ Secure any moving item inside the engine room and deck

➢ Check the soundings of all tanks and match them with the value that is obtained prior to entering the dry dock

➢ Ensure the emergency generator is in ready condition to start manually

➢ If there is any load shifting that can lead to a change in the ship’s stability, inform the dock master

➢ Go through the checklist again and the satisfactory checklist is to be finally signed by the master

➢ Master must sign the authority for the flooding certificate

➢ Once dry dock flooding is in process, a responsible engineer/officer should go to the bow thruster and steering gear room to check

the water tightness if any repair is performed on this machinery system

➢ When dock flooding reaches the overboard valve level, stop the process and check the valves and the stern tube for leakages

➢ Shore power cables will be removed once the cooling water is available for suction in the generator system

➢ If required, use emergency generator power before starting the main generator to avoid a long blackout period

➢ Instructions must be given to all crew members to stay vigilant while undocking.

They must continuously keep checking the water tightness of the ship throughout the process

➢ If a crew member finds any kind of water leakage, same must be informed immediately to the chief officer or department in charge

as he/she will ask the dock master to stop flooding immediately Ordering a navigator to prepare the ship movement from the dock

➢ Canceling shore leave and posting the sailing board

➢ Placing engine room and respective personnel on standby

➢ Conducting checks on all navigation equipment

➢ Making significant entries into the deck and official logbooks

➢ Ensuring all hatch covers are closed and watertight integrity of the uppermost deck maintained

➢ Ensuring the anchors and cables are correctly stored onboard the vessel. The ship’s officer, accompanied by the dock manager, will ensure that none of the materials, vehicles or personnel are left behind in the dock before commencing the flooding/re-floating operation.

Relevant manpower is provided for safely disconnecting all power and pipelines at the correct time.

The chief officer must take a full set of tank sounding and ensure that a sufficient supply of fresh water, lubricating oil and fuel is taken on board before departing.

A complete stability check of the ship is to be carried out to ensure that acceptable ‘GM’ is achieved once the ship is clear off the blocks.

This stability check is the sole responsibility of the ship personnel and a comparison should be made between the entry soundings when the vessel was last afloat and the first `on the block soundings’ taken when the ship became `sewn on the blocks’.

Linesmen and marine pilots need to be present on standby during the time of departure. The ship’s crew thereafter would be placed as stand-by at fore and aft to tend to the moorings.

Tugs, pilots and wharf labour are mostly ordered well in advance of the day of departure.

Ultimately the shore gangway must be landed ashore, once the dock personnel have cleared the ship.

Once the vessel floats and is clear off the blocks, the dock manager should note the ship’s draughts and forward it to the chief officer.

Finally, the master would need to sign the ‘Authority to Flood’ certificate once he is satisfied with the completion of the docking specifications provided by the Dry Dock Authority.

Following the completion of this certificate, the flooding of the dock shall commence. Proper communication must be maintained between the ship and the dock so that immediate actions are taken to stop flooding if any leakage is detected.

Appreciate your patience to read this long and boring article, hope you will be highly benefited from this. Put your comments if you have any queries/ recommendations.

Bon Voyage

– Marine Legends