Page 269 - Ship Construction.DJ Eyres 6Ed

Ch22-H8070.fm Page 258 Wednesday, October 18, 2006 6:59 AM
258 Ship Construction
Construction of the transverse bulkheads is similar to that in other ships,
the bulkhead being oiltight. Vertical stiffeners are fitted, or corrugated
plating is provided with the corrugations running either vertically or horizon-
tally. Horizontal stringers support the vertical stiffeners and corrugations,
and vertical webs support any horizontal corrugations. Further support is
provided by the vertical centre line web which is as a rule deeper on one
side of the bulkhead than on the other, unless the tank is very long and the
--- ใช้เพื่อการศึกษาเท่านั้น---
web may then be symmetrical either side of the bulkhead.
Longitudinal bulkheads which are oiltight may be conventionally stiffened
or may be corrugated with the corrugations running horizontally. Vertical
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
corrugated centre line bulkheads may be fitted. Conventional stiffening is
arranged vertically where the side framing is vertical, and arranged longitu-
dinally when the side is longitudinally framed. Vertical webs are fitted to
the longitudinal bulkhead when this is corrugated or longitudinally framed.
Corrugated longitudinal bulkheads are only permitted in ships of less than
200 m in length.

Hatchways
ึ
Oiltight hatchways provide at the exposed deck access to the tank spaces.
The openings for these are kept as small as possible, and the corners are well
rounded, circular openings being not uncommon. Coamings provided for
the openings should be of steel and at least 600mm high, and suitably fastened
steel or other approved material covers are fitted. Patent oiltight hatches are
available and approved with both steel and fibre reinforced plastic covers.
Access to any cofferdams and water ballast tanks may be by similar
hatches in the deck, or alternatively a watertight manhole may be fitted
with a cover of suitable thickness. Other openings are provided in the deck
for ullage plugs and tank cleaning, these being on the open deck, and not
within enclosed deck spaces.

Testing Tanks

Each cargo tank and cofferdam may be tested separately when complete
by filling the tank with water to a head 2.45 m above the highest point of
the tank excluding the hatchways, and by filling the cofferdam to the top
of the hatch. Water testing on the building berth or dry dock may be
undesirable owing to the size of flooded tanks which gives rise to large
stresses on the supporting material and structure. Testing afloat is there-
fore permitted, each tank being filled separately until about half the tanks
are full when the bottom and lower side shell in the empty tanks are
examined. Water is then transferred to the empty tanks, and the remainder