Title 46

SECTION 42.20-12

42.20-12 Conditions of equilibrium.

§ 42.20-12 Conditions of equilibrium.

The following conditions of equilibrium are regarded as satisfactory:

(a) Downflooding. The final waterline after flooding, taking into account sinkage, heel, and trim, is below the lower edge of any opening through which progressive flooding can take place. Such openings include air pipes, ventilators, and openings which are closed by means of weathertight doors (even if they comply with § 42.15-10) or covers (even if they comply with § 42.15-30 or § 42.15-45(d)) but may exclude those openings closed by means of:

(1) Manhole covers and flush scuttles which comply with § 42.15-40;

(2) Cargo hatch covers which comply with § 42.09-5(b);

(3) Hinged watertight doors in an approved position which are secured closed while at sea and so logged; and

(4) Remotely operated sliding watertight doors, and side scuttles of the non-opening type which comply with § 42.15-65.

(b) Progressive flooding. If pipes, ducts, or tunnels are situated within the assumed extent of damage penetration as defined in § 42.20-11 (a) and (b), progressive flooding cannot extend to compartments other than those assumed to be floodable in the calculation for each case of damage.

(c) Final angle of heel. The angle of heel due to unsymmetrical flooding does not exceed 15 degrees. If no part of the deck is immersed, an angle of heel of up to 17 degrees may be accepted.

(d) Metacentric height. The metacentric height of the damaged vessel, in the upright condition, is positive.

(e) Residual stability. Through an angle of 20 degrees beyond its position of equilibrium, the vessel must meet the following conditions:

(1) The righting arm must be positive.

(2) The maximum righting arm must be at least 0.1 meter (4 inches).

(3) The area under the righting arm curve within the 20 degree range must not be less than 0.0175 meter-radians (0.689 inch-radians).

(4) Each submerged opening must be weathertight (e.g. a vent fitted with a ball check valve).

(f) Intermediate stages of flooding. The Commandant is satisfied that the stability is sufficient during intermediate stages of flooding.

[CGD 79-153, 48 FR 38649, Aug. 25, 1983]

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