Page 213 - Ship Construction.DJ Eyres 6Ed

Ch18-H8070.fm Page 202 Wednesday, October 18, 2006 6:58 AM
202 Ship Construction
be fitted immediately forward of the machine space, a pipe tunnel is gen-
erally fitted through them with access from the engine room. This tunnel
carries the bilge piping as it is undesirable to pass this through the deep
tanks carrying oil cargoes.

TESTING DEEP TANKS Deep tanks are tested by subjecting them to the
maximum head of water to which they might be subject in service (i.e. to the
--- ใช้เพื่อการศึกษาเท่านั้น---
top of the air pipe). This should not be less than 2.45m above the crown of
the tank.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี

Topside Tanks
Standard general bulk carriers are fitted with topside tanks which may be
used for water ballast, and in some instances are used for the carriage of
light grains. The thickness of the sloping bulkhead of this tank is determined
in a similar manner to that of the deep tank bulkheads. In present practice,
as indicated in Chapter 17, the topside tank is generally stiffened internally
by longitudinal framing supported by transverses (see Figure 17.7). Trans-
verses are arranged in line with the end of the main cargo hatchways; and in
ึ
large ships, a fore and aft diaphragm may be fitted at half the width of the
tank, between the deck and the sloping plating.

Shaft Tunnel

When the ship’s machinery is not located fully aft it is necessary to enclose
the propeller shaft or shafts in a watertight tunnel between the aft end of
the machinery space and the aft peak bulkhead. This protects the shaft
from the cargo and provides a watertight compartment which will contain
any flooding resulting from damage to the watertight gland at the aft
peak bulkhead. The tunnel should be large enought to permit access for
inspection and repair of the shafting. A sliding watertight door which may
be opened from either side is provided at the forward end in the machinery
space bulkhead. Two means of escape from the shaft tunnel must be pro-
vided, and as a rule there is a ladder in a watertight trunk leading to an
escape hatch on the deck above the waterline, at the aft end of the shaft
tunnel. Where the ship narrows at its after end the aftermost hold may be
completely plated over at the level of the shaft tunnel to form a tunnel flat,
as the narrow stowage space either side of the conventional shaft tunnel
could not be utilized. The additional space under this tunnel flat is often
used to stow the spare tail shaft. Shaft tunnels also provide a convenient
means of carrying piping aft, which is then accessible and protected from
cargo damage.