9.1.3 Vessels Subject to Damage Stability Requirements
Vents and overflows of vessels subject to damage stability requirements are to be terminated above the equilibrium water line in the damaged conditions. Automatic means of closure are to be fitted to the outlets of vents whose intersection with the deck is below the equilibrium water line. Such means are also required for those vents whose outlets will be submerged in the range of residual stability beyond the equilibrium where such range is required by the applicable damage stability criteria.
9.3 Tank Vents
9.3.1 General Requirements (1 July 2012)
Except for comparatively small compartments that are not fitted with a fixed means of drainage, vent pipes are to be fitted to all tanks, cofferdams, voids, tunnels and compartments which are not fitted with other ventilation arrangements. In all vessels, the structural arrangement in double- bottom and other tanks is to be such as to permit the free passage of air and gases from all parts of the tanks to the vent pipes. Each tank is to be fitted with at least one vent pipe which is to be located at the highest part of the tank. Vent pipes are to be arranged to provide adequate drainage under normal conditions. No shutoff valve or closing device that can prevent the venting from a tank is to be installed in vent piping.
9.3.2 Vent Pipe Height and Wall Thickness
9.3.2(a) Exposed to weather. Vent pipes on decks exposed to the weather are to have the following heights: