What is Sequential Method of ballast water exchange and factors taken into account?

1. Stability

• Intact Stability
• Damage Stability

2. Longitudinal Strength

At any longitudinal location, a typical output of longitudinal strength includes the following:

• Calculated still-water bending moment (SWBM) and still-water shear force (SWSF)
• Maximum and minimum values of SWBM and SWSF
• Calculated still-water torsional moment (SWTM), where applicable
• Maximum permissible value of SWTM, where applicable
• Calculated SWBM and SWSF in flooding conditions, where applicable
• Maximum permissible values of SWBM and SWSF in flooded conditions, where applicable

3. Sloshing

In general, sloshing is unavoidable for a vessel using the sequential method. However, it can be controlled to within acceptable limits by restricting the sea state in which the ballast water exchange operations are conducted. Where necessary, an approach is to be proposed, subject to the approval of the Flag Administration, to establish a maximum sea state or significant wave height for partial filling of ballast tanks where sloshing occurs.

An assessment of the potential for liquid resonance in the tank as a function of the ballast water filling height. For low filling levels (less than 25%), the resonance in general is not a concern. However, confirmation is required. For filling levels greater than 50%, resonance can be an issue that may require a sea state limitation during ballast water exchange sequence.