DRYDOCKING 101

LAY PERIOD OF SHIP IN THE DRY DOCK

Dry docks are located in various locations convenient for ships to utilize in order to accomplish maintenance which cannot be performed waterborne. Such maintenance may be planned, as in the case of interim drydocking, or may be corrective to make specific repairs. Since interim drydockings are scheduled during upkeep periods, a great deal of maintenance will be performed in dry dock that could be done just as easily alongside the pier. Most drydocking routines require inspection of the underwater hull and hull appurtenances and provide for corrective action based on the inspection.

It must be recognized that the extent of services provided by the dry dock will vary from drydocking to drydocking depending on the type of dry dock, the class of ship drydocked, the anticipated duration of the drydocking, the work scheduled to be performed, and the ship’s systems to be incapacitated during drydocking.

Assigned Responsibilities

  1. Dry dock personnel:
  2. Drydocking and undocking the ship
  3. Providing dry dock services while in the dry dock
  4. Installation of temporary connections.
  5. Installation and maintenance of gangways.
  6. Rigging.
  7. Crane services as requested, rigging and unrigging brows, etc.
  8. Dock Master:
  9. Regularly walk-thru of the dry dock basin.
  10. Regularly check for blocking and shoring stability, ensuring there have been no drastic changes.
  11. Observe that safety precautions are being utilized by all personnel in and around the dry dock and ship.
  12. Calculation of weight shifts, additions and removals to ensure the vessel stays within safe limits of stability.
  13. Responsible for the safety of the vessel until the completion of the undocking evolution.
  14. Ship personnel:

The ship’s preparation for interim drydocking starts well before the drydocking date with the submission of work requests for various services required in dry dock. The latest Docking Report and the latest corrected Docking Plan must be furnished to the Dock Master with information on the desired docking position in sufficient time to prepare the basin prior to the drydocking.

Once in the dry dock, the ship is responsible to ensure that temporary lifelines, webbing, stanchions, etc., are promptly and properly installed topside. Besides the ship’s underwater surface, the following items normally are inspected at interim drydockings:

  1. Rudder and stern plates
  2. Shaft(s), bearings and propeller(s)
  3. Main shaft seal
  4. Main ballast tanks and free flooding spaces
  5. Sea valve and sea chest hull strainer plates
  6. Zincs (impressed current cathodic protection system anodes)

In addition, ship personnel are usually required to furnish line handlers during drydocking and undocking; and to help connect services.

Final Note

“Prior to undocking, the commanding officer/master of a ship shall report to the Dock Master any material changes in the amount and location of weights on board which have been made by the ship’s force while in dry dock, and shall ensure, and so report, that all sea valves and other openings in the ship’s bottom are properly closed. The level of water in the dock shall not be permitted to rise above the keel blocks prior to receipt of this report. The above valves and openings shall be tended during flooding of the dock.”  (…more)

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