Section 27(1) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(1)Every oil tanker of five thousand tonnes deadweight and above delivered on or after 1st February, 2002, as defined in sub-rule (37) of rule 1A, shall comply with the intact stability criteria specified in clauses (a) and (b) of rule 27, as appropriate, for any operating draught under the worst possible conditions of cargo and ballast loading, consistent with good operational practice, including intermediate stages of liquid transfer operations and under all conditions, the ballast tanks shall be assumed slack.-.(a)In port, the initial metacentric height' GMo, corrected for the free surface measured at 0 degree heel, shall be not less than 0.l5metres;(b)At sea, the following criteria shall be applicable -(i)the area under the righting lever curve (GZ curve) shall be not less than 0.055 m.rad up to θ=30º angle of heel and not less than 0.09 m.rad up to θ 40º or other angle of flooding θf if this angle is less than 40º and additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30º and 40º or between 30º and θf if this angle is less than 40º shall be not less than 0.03 m.rad;[Note: θf is the angle of heel at which openings in the hull, superstructures or deck houses, which cannot be closed weathertight, immerse and in applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open](ii)the righting lever GZ shall be at least 0.20 m at an a angle of heel equal to or greater than 30º: ,(iii)the maximum righting arm shall occur at an angle of heel preferably exceeding 30º but less than 25º(iv)the initial metacentric height GMo, corrected for free surface measured at 0º degree heel shall be not less than 0.l5m.
