Dry docking Q: What is Dry dock procedure? A: Before Docking Make a repair list.Contact with dry dock authoritiesagreed draught and trim.


Dry docking

Q: What is Dry dock procedure?

A: Before Docking

  • Make a repair list.
  • Contact with dry dock authorities
  • agreed draught and trim. (upright with small trim)
  • supply ships plan, including shell expansion plan showing position of appendages, inlet, discharge, echo sounders, projecting logs, bilge keels, propellers, etc., Cargo plan if any cargo on board, Any available plans from previous dry dock which might be useful.
  • confirm whether the dock is graving or floating dock, whether side shores or bilge block will be used.
  • Confirm the facilities are supplied - toilets, fire main, telephone etc.
  • Rig fenders as necessary.
  • Calculate stability condition (particularly for critical instant). Minimise free surface and secure moveable weights.
  • If possible empty fore and aft peak tanks ( unsupported weights increase hogging stress)
  • Lower derricks and cranes and ensure hatches closed.
  • Secure two means of access/escape ( eg. Gangway port forward and starboard aft)
  • Takes sounding of all spaces and record result.
  • Establish shore connection for telephone, fire line, domestic water, electric power. Secure earth return line.
  • Clarify responsibilities between ship and shore (eg. Watchman, fire patrols)
  • Arrange sanitation/toilets/waste disposal. Close/plug scuppers, overboard discharge, etc.
  • Safety store (chief mate office) any bottom plug removed.
  • Take sounding of all spaces and compare with soundings on entry ( if any difference, re-work stability condition for critical instant).
  • Check all plugs back in place.
  • Ensure all staging removed. Disconnect all utilities. Remove gangways.

P= (COT X MCTC) / LCF, {P = Reduction of TMD X TPC}

Virtual loss of GM = ( P X KM ) / W

COT= ( W X D ) / MCTC.

After Docking

Before Flooding Dock

Q: What is critical instant?

A: As the water is pumped out the vessel’s trim will reduce until the ship lands fore and aft on the blocks. The instant before this happens is known as the CRITICAL INSTANT.

Q: What is critical period?

A: The interval of time between the vessel touching the blocks aft and landing fore and aft is known as the CRITICAL PERIOD since the vessel is losing stability throughout this period.

Q: What precaution you would take while Docking with Cargo?

A: 1. Leave some water in the dock so that the vessel is still displacing water, thereby reducing the upthrust from the blocks.

2. Increase the number of lines of blocks supporting the vessel so as to spread the load. ( N.B. Blocks should always be laid in line with longitudinal bottom giders).

Q: What is Declivity?

A: The declivity of the drydock is the slop of the bottom of the dock towards the entrance ( this assist in the drainage of the dock).

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