Section 28(3) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(3)Oil tankers shall be regarded as complying with the damage stability criteria if the following requirements are met, namely:-(a)the final waterline, taking into account sinkage, heel and trim, shall be below the lower edge of any opening through which progressive flooding may take place and such openings shall include air-pipes and those which are closed by means of weathertight doors or hatch covers and may exclude those openings closed by means of watertight manhole covers and flush scuttles, small" watertight cargo tank hatch covers which maintain the high integrity of the deck, remotely operated watertight sliding doors, and sidescuttles of the non-operating type;(b)in the final stage of flooding, the angle of. heel due to unsymmetrical flooding shall not exceed 25º provided that this angle may be increased up to 30º if no deck edge immersion occurs;(c)the stability in the final stage of flooding shall be investigated and may be regarded as sufficient if the righting lever curve has at least a range of 20º beyond the position of equilibrium in association with a maximum residual righting lever of at least 0.1 m within the 25º range and the area under the curve within this range shall not be less than 0.0175 m.rad.:Provided that unprotected openings shall not be immersed within this range unless the space concerned is assumed to be flooded:Provided further that within this range, the immersion of any of the openings listed in clause (a) above and other openings capable of being closed watertight may be permitted;(d)the Central Government shall be satisfied that the stability is sufficient during intermediate stages of flooding;(e)equalisation arrangements requiring mechanical aids, such as valves or cross-levelling pipes, if fitted, shall not be considered for the purpose of reducing an angle of heel or attaining the minimum range of residual stability to meet the requirements of clauses (a), (b) and (c) above and sufficient residual stability shall be maintained during all stages where equalization is used and spaces which are linked by ducts of a large cross-sectional area may be considered to be common.
