Watertight bulkheads


(mohammed mokhtar) #1

Bulkhead is the watertight separation lengthening from ship’s hull to top main deck separating its interior into various divisions.
Transverse watertight bulkheads
Transverse watertight bulkheads are some of the principal transverse strength members of a ship. They are very strong in construction and responsible for maintaining the transverse form of the hull.
The forward most transverse watertight bulkhead is called the Collision Bulkhead. As its name implies, this bulkhead is the strongest bulkhead and is designed to protect the vessel in case of a collision. It is usually fitted between 0.05 and 0.075 of the length of the vessel from the forward end. The space forward of this bulkhead is the Fore peak tank. Above this bulkhead is the first hold or tank.
The After Peak Bulkhead situated aft and serves to enclose the stern tube in a watertight compartment. Other bulkheads will also be fitted on the forward and after sides of the machinery spaces.
The cargo spaces are also subdivided into smaller compartments:

[ol]
[li]Strength members: These are important contributors to the strength of the hull girder. They resist the tendency to deform the shape of the shell. In the case of longitudinal bulkheads, they contribute to longitudinal strength of the hull.[/li][li]Help to spread hull stresses over larger areas.[/li][li]Subdivision: Divides the vessel into small compartments so that in case of flooding after a collision or grounding etc. the ingress of water will be restricted to a particular compartment. Prevents progressive flooding and ultimate foundering of the vessel.[/li][li]In the case of liquid carriers, the bulkheads divide the vessel into tanks and reduce free surface effects on stability. This is especially so in the case of longitudinal bulkheads in tankers. Also, when the vessel is in motion in seaway, liquid cargoes slosh in the tanks. The bulkheads reduce the damage which could be caused due to sloshing of cargo in an open unrestricted space.[/li][li]Fire division: In case of fire in a compartment, these bulkhead help to control the spread of fire to neighboring compartments. They are specially designed to withstand high temperatures of this purpose.[/li][/ol]
In order to fulfill these functions, watertight bulkheads must extend from the bottom plating right up to the bulkhead deck (uppermost continuous deck).some exceptions are allowed however. Bulkhead plating and stiffening scantlings are adjusted according to the construction rules.
Construction of bulkheads
On older ships, bulkheads have been constructed of plates joined together and stiffened by vertical and horizontal stiffeners.
Modern shipbuilding practice and technology enables more efficient corrugated bulkheads to be constructed. Because the plates are corrugated, the bulkheads need not be fitted with stiffeners. Usually, the corrugation is vertically or horizontal for transverse bulkheads and horizontal for longitudinal bulkheads. In places where it is difficult to connect the corrugated bulkhead directly to shell plating, a flat plate with stiffening may be fitted at the sides.