10.6 Dry-docking
Describe
- Preparation of repairs list
- Hull cleaning, inspection, blasting, painting
- Precautions before flooding the dock
- Measurement of rudder and propeller drop
- Ship’s plans
- Steel renewals and thickness measurements
- Floating Dry Dock, critical period
- Precautions to be taken in case vessel to be dry docked with damaged condition
Preparation of Repairs List:
Before dry-docking, a thorough inspection of the vessel is conducted to identify any necessary repairs or maintenance. This inspection involves examining the hull, machinery, equipment, and systems.
Based on the inspection findings, a repairs list is prepared, detailing the required repairs, replacements, or upgrades.
The repairs list serves as a guide for prioritizing and planning the repair work during the dry-docking period. It ensures that all necessary repairs are addressed efficiently.
Hull Cleaning, Inspection, Blasting, Painting:
Prior to dry-docking, the vessel's hull is cleaned, removing marine growth, barnacles, and other contaminants.
Once cleaned, a detailed inspection of the hull takes place. This inspection involves examining the condition of the hull structure, coatings, anodes, and any other components.
If necessary, hull blasting may be performed to remove old paint and corrosion.
Following blasting, the hull is properly primed and painted with suitable marine coatings to provide corrosion protection.
Precautions Before Flooding the Dock:
Before flooding the dry dock, certain precautions must be taken to ensure safety and proper docking:
The vessel's stability must be carefully assessed to ensure it can safely rest on the blocks or keel supports within the dry dock.
All personnel must be clear of the dock area to prevent any accidents during the flooding process.
Communication and coordination between the dock operators and vessel's crew are essential to ensure a smooth and safe docking process.
Measurement of Rudder and Propeller Drop:
During dry-docking, the rudder and propeller drop measurements are taken to assess their condition and alignment.
Rudder drop refers to the vertical distance between the rudder reference point and the waterline when the vessel is supported on the blocks or keel supports.
Propeller drop refers to the vertical distance between the propeller reference point and the waterline in the same supported condition.
These measurements help determine if any adjustments or repairs are needed to maintain proper alignment and performance.
Ship's Plans:
The dry-docking period is an opportunity to update the ship's plans and documentation.
The vessel's plans, including general arrangement, stability, electrical, and machinery plans, may be revised to reflect any modifications or upgrades made during dry-docking.
Updating the ship's plans ensures accurate and current information is available for future operations, maintenance, and emergency situations.
Steel Renewals and Thickness Measurements:
During dry-docking, steel renewals may be necessary to address corroded or damaged structural components.
Thickness measurements are taken on the hull and other steel structures to assess their condition and determine if any steel renewals are required.
These measurements are typically conducted using ultrasonic testing or other approved methods to ensure compliance with the required thickness standards.
Floating Dry Dock, Critical Period:
If a floating dry dock is used for dry-docking, the critical period refers to the specific time when the vessel is lifted out of the water and rests on the blocks or keel supports within the dry dock.
During this critical period, proper support and stability of the vessel must be ensured to prevent any hull deformations or damage.
Adequate ballasting of the dry dock and monitoring of the vessel's positioning are essential during this phase to maintain stability and prevent any accidents or hazards.
Precautions to Be Taken in Case Vessel Is to Be Dry Docked with Damaged Condition:
If a vessel is to be dry docked with a damaged condition, additional precautions need to be taken to ensure safety and proper repair:
The extent and nature of the damage should be thoroughly assessed to determine if it is safe and feasible to proceed with dry-docking.
Stability calculations should be reevaluated to account for the damaged condition and potential changes in the vessel's characteristics.
Proper temporary repairs or reinforcements may be required to stabilize the damaged areas and ensure the vessel's safe docking.