Bulkheads. These are steel divisions across the vessel either transversely or fore and aft. The functions of bulkheads are:
1.To increase the safety of a ship. By dividing a ship into separate watertight compartments, the damage in case of collision may be confined to one compartment. Should one compartment be flooded, the bulkheads must be strong enough to withstand the pressure of water, so that the adjacent compartments remain dry.
2.To separate the engine room from the cargo holds or cargo tanks.
3.To increase the transverse strength of a vessel
4.To reduce the risk of fire spreading from the compartment of outbreak to the other compartments.
The number of watertight bulkheads of a cargo vessel depends upon the ship’s length and design and the Rules of the Classification Society which covers the vessel. The Rules generally require that a “collision bulkhead” is fitted forward, between 5 and 8 per cent of the vessel’s length from the forward end of the load waterline. Fifty per cent of the damage caused in a collision occurs at the forward end of the vessel and this strong bulkhead is expected to prevent the water from flooding cargo compartments. Rules also require a minimum of three others if the machinery space is amidships or two if the machinery space is aft. These are to separate the machinery space from the cargo spaces and also an afterpeak bulkhead to provide subdivision at the extreme after end of the vessel. The propeller shaft passes through the afterpeak tank, which is also used for housing parts of the steering arrangements and for containing either fresh water or ballast. The number of bulkheads required by Classification Societies increases with the size of the vessel, mainly to produce additional transverse strength and increase the amount of subdivision for watertight integrity.