- All ships should under go drydock twice in 5 years, and time difference between two continues drydock cannot be more than 36 months.
- This comprise maintenance of the hull, propeller, rudder and other parts which are immersed in water and are normally inaccessible by ship staff at regular sailing period. Ship owners start planning their dry docking activities several months before the schedule date, because these activities take a lot of preparation and are relatively expensive.You often see that ships have to be compelled to take a very totally different route for an appropriate dry dock place, as most of the time the specified facility isn’t offered once required. This is most common with larger vessels.
- The shell plating is to be analyzed for unnecessary consumption, disintegration because of scraping or contact with the ground and for undue injustice or clasping.
- Special consideration is to be given to the association between the bilge strakes and the bilge keels.
- The clearances in the rudder direction are to be estimated. Where relevant, weight testing of the rudder is additionally required whenever regarded fundamental.
- The ocean associations and over the edge release valves and cocks and their connections to the body are to be inspected.
- The propeller, harsh shrubbery and ocean association fastenings and the gratings at the ocean gulfs are to be inspected.
- The leeway in the harsh bramble or the effectiveness of the oil organs is to be learned.
- When chain links are gone, the grapples and links are to be inspected by the Surveyor.
Types of Dry Dock
- Graving dock
- Floating dock
- Marine Rail Dock
- Marine mobile lifts
Preparations before Dry-docking
- Get ready Repair Specifications ahead of time for planning and welcoming citations
- Pipe Lines
- Structural steel recharging, for which plate thickness checking might be required.
- Overhauling of Mooring Equipment.
- Special overhauling prerequisites
- Overhauling and testing of Cargo Gear ( freight siphons if the vessel is a tanker)
- Prepare Spare Parts
- Plan and complete Hold/tank cleaning/gas liberating before appearance
- Check and affirm accessibility of unique devices, instruments and manuals ready.
- Confirm accessibility of drawings like Shell extension plan, Docking Plan, GA and so forth ready.
- Select yard dependent on vessel’s exchanging design.
- Invite citations and arrange costs.
- Issue directions to Master/Chief Engineer with respect to: Cargo/balance/fuel oil amount/conveyance, Calculation of appearance drafts and trim, Fire/Safety insurances.
Activities in Dry Dock
- Bottom Inspection/remedial activity
- Bottom painting
- Anchor link running and painting.
- Cleaning and painting of chain storage.
- Echo-sounder and speed log checks
- MGPS and ICCP checks
- Sea chests/channels cleaning/painting
- Storm valves updating
- Rudder pintle and bouncing clearances checking
- Rudder weight testing/interior painting whenever required
- Poker measure perusing (Propeller drop)
- Stern seal hole check
- Propeller cleaning/fixes whenever required.
- Tail shaft overview, whenever required.
- Bottom plugs expulsion/re-fitting as required
Safeties in Dry Dock
• Warning notices
• Fire line under strain/putting out fires apparatuses kept prepared
• Means of interchanges set up
• Usage of kitchen and WCs confined as required.
• Hot work consents/safeguards
• Earthing of vessel
Checks before/during flooding in Dry Dock
• Sea associations, ocean chests checking
• Bottom attachments fitting/spill test by vacuum
• Any other structure opening
• Removal of concealing of anodes
• Securing of rudder fittings, propeller nut/cone fitting, rope gatekeeper and net-shaper fitting
• Ensuring counterbalance/weight appropriation same as when docked
• After beginning of flooding, when the water level has risen enough to cover all shipside opening, flooding should be halted and all ship side associations checked for any spillage. Subsequent to affirming that all are agreeable, flooding is continued and the vessel skimmed.
Anchor chain inspection in Dry Dock
• During a anchor chain review, the chain links ought to be gone out on the dock floor and outwardly examined for wear and the connection breadth is estimated. Generally the upgrading of each shackle has been excluded .All anchor chains are stud chains .
• Chain connections are made of steel bar or cast steel. If there should arise an occurrence of ULCC and VLCC practically all are of cast steel.
1. Anchor shackle
2. Link shackle
4. Open link
5. Enlarged link
6. Kenter shackle
7. Anchor shackle (Crown shackle)
1) Anchor shackle Large shackle utilized for interfacing the chain link and the anchor
(2) Joining shackle As previously mentioned, shackles utilized for interfacing two chain links; if studless end connections are not given at the two closures , this shackle can’t be utilized.
(3) Kenter shackle Shackles utilized for interfacing a chain comprising of regular connections just and no closure joins. This shackle has a part development, along these lines, it very well may be utilized to associate a wrecked chain, independent of where the break has happened. It is more costly than the joining shackle; disassembling this shackle is somewhat troublesome.
(4) Swivel is joined near the anchor, it has the job of forestalling turns in the chain link because of its revolution. In the event that a swivel isn’t given in the chain, the connections in the chain might be contorted
Length and joining.
- The length of chain is characterized as the separation between within edge of the connection toward one side and furthermore within edge of the connection at another end is 27.5 m. These chains are gotten together with shackles to shape a length that agrees to the necessities of the Equipment Number. The quantity of connections in a chain is an odd number so the shackle consistently comes at a similar situation on the vagabond wheel of the windlass. To expel the bits of chain link, a swivel piece is here and there associated among anchor and the chain link. The quantity of connections in the swivel piece is significantly number
Dispose of if decrease in width surpasses 12% in the territory appeared.
swivel eyelet pivot wear out, thought to be given to substitution where the greatest horizontal development likens to 5% of the eyelet hub width.
D1 = average of measured diameter (mm) = (d1+ d2)/2
d1 and d2 measured diameters of the chain link in the area of maximum wear
DO = original diameter (mm)