Page 203 - Ship Construction.DJ Eyres 6Ed

Ch18-H8070.fm Page 192 Wednesday, October 18, 2006 6:58 AM
192 Ship Construction
be reduced to three, the aft peak bulkhead being at the aft end of the
machinery space.
Of these bulkheads perhaps the most important is the collision bulkhead
forward. It is a fact that the bow of at least one out of two ships involved in
a collision will be damaged. For this reason a heavy bulkhead is specified
and located so that it is not so far forward as to be damaged on impact.
Neither should it be too far aft so that the compartment flooded forward
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causes excessive trim by the bow. Lloyd’s Register gives the location for
ships whose length does not exceed 200 m as not less than 5 and not greater
than 8 per cent of the ship’s length (Lloyd’s Length) from the fore end of
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
the load waterline. As a rule this bulkhead is fitted at the minimum distance
in order to gain the maximum length for cargo stowage. The aft peak bulk-
head is intended to enclose the stern tubes in a watertight compartment
preventing any emergency from leakage where the propeller shafts pierce
the hull. It is located well aft so that the peak when flooded would not cause
excessive trim by the stern. Machinery bulkheads provide a self-contained
compartment for engines and boilers preventing damage to these vital com-
ponents of the ship by flooding in an adjacent hold. They also localize any
fire originating in these spaces.
A minimum number of watertight bulkheads will only be found in smaller
ึ
cargo ships. As the size increases the classification society will recommend
additional bulkheads, partly to provide greater transverse strength, and also
to increase the amount of subdivision. Table 18.1 indicates the number of
watertight bulkheads recommended by Lloyd’s Register for any cargo ship.
These should be spaced at uniform intervals, but the shipowner may require
for a certain trade a longer hold, which is permitted if additional approved
transverse stiffening is provided. It is possible to dispense with one watertight
bulkhead altogether, with Lloyd’s Register approval, if adequate approved

TABLE 18.1
Bulkheads for Cargo Ships

Length of ship (metres) Total number of bulkheads
Above Not exceeding Machinery midships Machinery aft

65 4 3
65 85 4 4
85 105 5 5
105 115 6 5
115 125 6 6
125 145 7 6
145 165 8 7
165 190 9 8
190 To be considered individually