8 Rationale Applied for Loading Pattern Evaluation

  8.1.1 For homogeneous loading conditions, the damage to cargo tanks may have a major effect on residual stability. Outflow of the loaded cargo liquids (and less inflow of seawater) may reduce the ships' displacement and cause heel to opposite side of the damage. For alternate loading conditions the residual stability depends on the damaged cargo tank. Damage to a fully loaded cargo tank might cause reduction of the initial displacement and heel to the opposite side, but damage on an empty cargo tank might cause the opposite effect. For the damage to two adjacent cargo tanks, one filled and one empty, the total effect might be less severe due to two (partly) neutralizing effects.

  8.1.2 Partial loading of liquid cargo tanks will cause a high free surface moment when the surface does not intersect with the tank overhead and will increase the heel in case of damage. However, reductions of the initial displacement and heel to the opposite side may not be as significant. Trim to the ship as a consequence of damage can be significant due to many partially-filled cargo tanks.

 In general damage stability calculations should be performed for both ship sides. However, the damage stability calculation for one side of the ship may be accepted for symmetrical load (alternate, homogeneous, full, partial or empty), if the ship and all openings are also symmetrical and initial heel to portside or starboard is zero.

 Additional information regarding intact and damage stability matters for tank ships can be found in MSC/Circ.406/Rev.1, which also recommends application of the Guidelines for the Uniform Application of the Survival Requirements of the Bulk Chemical Code (BCH Code) and the Gas Carrier Code (GC Code) to the IBC and IGC Codes.