Page 177 - Ship Construction.DJ Eyres 6Ed

Ch16-H8070.fm Page 166 Wednesday, October 18, 2006 6:57 AM
166 Ship Construction
not uncommon however for it to be extended to the ship’s side, and indi-
vidual bilge wells are then provided for drainage purposes (see Chapter 26).
In vessels requiring a passenger certificate it is a statutory requirement
for the tank top to extend to the ship’s side. This provides a greater degree of
safety since there is a substantial area of bilge which may be damaged with-
out flooding spaces above the inner bottom.
At the centre line of the ship the middle strake of the inner bottom may
--- ใช้เพื่อการศึกษาเท่านั้น---
be considered as the upper flange of the centre line docking girder, formed
by the centre girder and keel plate. It may therefore be heavier than the
other strakes of inner bottom plating. Normally a wood ceiling is provided
Figures 16.4 and 16.5).งสมุด ศูนย์ฝกพาณิชย์นาวี
under a hatchway in a general cargo ship, but the inner bottom plating
thickness can be increased and the ceiling omitted. If grabs are used for dis-
charging from general cargo ships the plate thickness is further increased,
or a double ceiling is fitted.

FLOORS Vertical transverse plate floors are provided both where the
bottom is transversely and longitudinally framed. At the ends of bottom
tank spaces and under the main bulkheads, watertight or oiltight plate
floors are provided. These are made watertight or oiltight by closing any
holes in the plate floor and welding collars around any members which pass
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through the floors. Elsewhere ‘solid plate floors’ are fitted to strengthen the
bottom transversely and support the inner bottom. These run transversely
from the continuous centre girder to the bilge, and manholes provided for
access through the tanks and lightening holes are cut in each solid plate
floor. Also, small air and drain holes may be drilled at the top and bottom
respectively of the solid plate floors in the tank spaces. The spacing of the
solid plate floors varies according to the loads supported and local stresses
experienced. At intermediate frame spaces between the solid plate floors,
‘bracket floors’ are fitted. The bracket floor consists simply of short trans-
งานห้อ
verse plate brackets fitted in way of the centre girder and tank sides (see

TRANSVERSELY FRAMED DOUBLE BOTTOM If the double bottom
is transversely framed, then transverse solid plate floors, and bracket floors
with transverse frames, provide the principal support for the inner bottom
and bottom shell plating (Figure 16.4). Solid plate floors are fitted at every
frame space in the engine room and in the pounding region (see the end of
this chapter). Also they are introduced in way of boiler seats, transverse
bulkheads, toes of brackets supporting stiffeners on deep tank bulkheads,
and in way of any change in depth of the double bottom. Where a ship is
regularly discharged by grabs, solid plate floors are also fitted at each
frame. Elsewhere the solid plate floors may be spaced up to 3.0 m apart,
with bracket floors at frame spaces between the solid floors. The plate
brackets of bracket floors are flanged and their breadth is at least 75 per cent