CHIEF ENGINEER Unit 12 Classification Q3

A special hull survey is a comprehensive inspection conducted by a classification society surveyor to assess the overall structural integrity and condition of a ship’s hull and associated components. It is typically carried out at five-year intervals and requires the vessel to be dry-docked.

During a special hull survey, the following items would be inspected:

Hull Structure:

• External Hull: Thorough visual inspection of the entire hull, including plating, welds, seams, and appendages like bilge keels and docking brackets.
• Internal Structure: Examination of the internal framing, bulkheads, floors, and other structural members, often requiring the removal of insulation or paneling for access.
• Thickness Measurements: Ultrasonic thickness measurements are taken at various locations on the hull plating to assess its thickness and remaining strength. This helps identify areas of corrosion or thinning that may require repairs or renewals.
• Close-up Survey: Detailed inspection of specific areas of concern, such as those identified during the visual inspection or thickness measurements, using techniques like magnetic particle testing or dye penetrant testing to detect cracks or other defects.
• Cargo Holds and Tanks: Inspection of cargo holds, ballast tanks, and other internal spaces to assess their condition and structural integrity. This may include checking for corrosion, leaks, or damage to coatings.

Other Components:

• Rudder and Propeller: Inspection of the rudder, propeller, and associated shafting and bearings for signs of wear, damage, or corrosion.
• Sea Valves and Through-hull Fittings: Examination of all sea valves, through-hull fittings, and overboard discharge valves for proper operation, tightness, and corrosion.
• Anchoring and Mooring Equipment: Assessment of the condition and functionality of anchors, chains, mooring lines, and other deck equipment related to anchoring and mooring operations.

Additional Checks:

• Stability: Review of the ship’s stability calculations and documentation to ensure compliance with the required stability criteria.
• Load Line Markings: Inspection of the load line markings on the hull to verify their accuracy and visibility.
• Documentation: Verification of the ship’s certificates, drawings, and other documentation related to the hull and its construction.

Outcome of the Survey:

• Renewal of Class: If the ship is found to be in satisfactory condition and complies with the classification society’s rules, its class notation will be renewed for another five-year period.
• Recommendations for Repairs or Renewals: If any deficiencies or areas of concern are identified, the surveyor will issue recommendations for necessary repairs, renewals, or further inspections. The ship’s class may be suspended or limited until these actions are completed.

Overall, the special hull survey is a critical process that ensures the continued structural integrity, safety, and seaworthiness of a vessel. It’s a comprehensive inspection that helps identify and address potential issues before they escalate into major problems, promoting maritime safety and protecting the marine environment.

A continuous hull survey is a method of inspecting and maintaining a ship’s hull structure by spreading out the required surveys and inspections over a period of time, typically five years, rather than conducting one large survey at the end of that period.

1. Main class hull surveys – DNV

How it works:

• The hull is divided into sections or zones.
• Each section is assigned a specific survey interval within the five-year cycle.
• The ship’s crew, under the supervision of the Chief Officer or a designated officer, conducts regular inspections and thickness measurements in the assigned sections.
• A classification society surveyor periodically verifies the crew’s findings through confirmatory surveys.

Time intervals:

• The entire hull is surveyed over a five-year period.
• Each section of the hull is surveyed at least once within that period, typically during annual or intermediate surveys.
• The specific intervals for each section can be adjusted based on the ship’s operational profile, areas of high stress or corrosion risk, and the classification society’s requirements.

Application:

• The continuous hull survey involves the following activities:
  • Visual inspections: The crew conducts regular visual inspections of the assigned hull sections, looking for signs of corrosion, cracks, deformation, or any other damage.
  • Thickness measurements: Ultrasonic thickness measurements are taken at predetermined points on the hull plating to monitor its thickness and identify any areas of significant wastage or corrosion.
  • Record keeping: Detailed records of all inspections and thickness measurements are maintained and made available to the classification society surveyor.
  • Confirmatory surveys: The classification society surveyor conducts periodic confirmatory surveys to verify the crew’s findings and assess the overall condition of the hull.
  • Repairs and renewals: Any necessary repairs or renewals are carried out based on the survey results, ensuring the hull remains in a satisfactory condition throughout the five-year cycle.

Benefits of Continuous Hull Survey:

• Reduced downtime: By spreading out the surveys, it minimizes the time the ship needs to be out of service for inspections and repairs.
• Cost-effectiveness: It can be more cost-efficient as it reduces the need for extensive dry-docking periods.
• Improved maintenance: It encourages a more proactive approach to hull maintenance as the crew is regularly involved in inspections.
• Enhanced safety: Regular inspections and timely repairs help maintain the hull’s structural integrity, reducing the risk of accidents or failures at sea.

Challenges and Considerations:

• Crew competence: The ship’s crew must be adequately trained and experienced to carry out the inspections and thickness measurements effectively.
• Record keeping: Accurate and detailed record keeping is essential for the success of the continuous hull survey.
• Classification society oversight: The classification society plays a crucial role in verifying the crew’s findings and ensuring the overall integrity of the hull.

Overall, the continuous hull survey is a valuable tool for maintaining the structural condition of ships, promoting safety, and optimizing maintenance practices.