Posted on July 31, 2018
Righting (and heeling) levers of stability are determined by dividing the righting (or heeling) moment by the ship’s displacement. In intact condition, the displacement to choose for that division is unambiguously that of the loading condition under consideration. In damage stability, the choice is not that obvious. However, the standard suggested by the relevant regulations has conventionally been “Constant displacement”, so that has always been the standard choice in PIAS. For some time now an alternative choice is also available — as presented in “MSC.1/Circ.1461, guidelines for verification of damage stability requirements for tankers” and “IACS 110 Guideline for Scope of Damage Stability Verification on new oil tankers, chemical tankers and gas carriers” — i.e. “Intact displacement minus liquid cargo loss”. The choice between these two alternatives is now available as a setting in PIAS, please consult the manual for more details.