Intact Stability Criteria Lecture Notes

Introduction to Intact Stability Criteria

• Definition: Stability criteria when the vessel is in intact (watertight) condition.
• Source: International Intact Stability Code 2008, adopted by IMO on 4th December 2008 (Resolution MSC 267 85).
• Purpose of Codes:
  • Protect the ship, cargo, persons on board, and the environment.
  • Ensure safe operation and minimize risks.

Structure of Intact Stability Code 2008

• Divided into:
  • Introduction
  • Part A: Mandatory criteria
  • Part B: Recommendations and guidelines
• Came into force: 1st July 2010.
• Applicable to:
  • Ships and marine vehicles of 24 meters in length and above.
  • Types: cargo ships, passenger vessels, fishing vessels, special purpose ships, etc.

Key Elements of Intact Stability Code 2008

• Capsizing Prevention:
  • General precautions against capsizing.
  • Negative GM (metacentric height) leads to capsizing.
• Criteria Addressed:
  • Metacentric height (GM)
  • Righting lever (GZ)
  • Weather criteria (wind and rolling)
  • Effects of free surfaces and icing
  • Watertight integrity
• Operational Aspects:
  • Information for the master, stability booklets, and heavy weather procedures.

Intact Stability Criteria for Various Vessels

General Cargo, Tankers, and Passenger Ships

• Initial GM Requirement: Not less than 0.15 meters.
• Righting Lever (GZ):
  • At least 0.20 meters between 0.15 and 30 degrees heel.
  • Maximum GZ must occur at greater than 30 degrees but not less than 25 degrees.
• Area Under GZ Curve:
  • Not less than 0.055 meter radian up to 30 degrees.
  • Not less than 0.09 meter radian up to 40 degrees.
  • Not less than 0.03 meter radian between 30 degrees and angle of down flooding.

Container Ships (>100 meters length)

• Initial GM: Not less than 0.15 meters.
• Righting Lever (GZ):
  • Minimum 0.033 meters at 30 degrees heel.
  • Maximum GZ at least 0.042 meters.
• Area Under GZ Curve:
  • Not less than 0.009 meter radian up to 30 degrees.
  • Not less than 0.016 meter radian up to 40 degrees.
  • Not less than 0.006 meter radian between 30 degrees and angle of down flooding.
  • Not less than 0.029 meter radian up to angle of down flooding.

Ships Carrying Timber Deck Cargoes

• GM: Not less than 0.1 meters at all times.
• Maximum GZ: At least 0.25 meters.
• Area Under GZ Curve: Not less than 0.08 meter radian up to 40 degrees or the angle of flooding.
• Limiting Angle of Heel: 16 degrees under steady wind.

Cargo Ships Carrying Grain in Bulk

• Initial GM: Not less than 0.30 meters.
• Angle of Heel due to Shift of Grain: Not greater than 12 degrees.
• Residual Area:
  • Not less than 0.075 meter radian up to 40 degrees or angle of flooding.

Conclusion

• The Intact Stability Code 2008 provides essential guidelines and criteria for various types of vessels to ensure safety and prevent capsizing.