Page 281 - Ship Construction.DJ Eyres 6Ed

Ch23-H8070.fm Page 270 Wednesday, October 18, 2006 7:38 AM
270 Ship Construction
TABLE 23.1

Basic tank type Cargo temperature - 10 °C and Below − 10 °C Below − 55 °C
at atmospheric above Down to − 55 °C
pressure

No secondary Hull may act as Separate
barrier secondary secondary
--- ใช้เพื่อการศึกษาเท่านั้น---
required barrier barrier required
Integral Tank type not normally allowed
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
Membrane Complete secondary barrier
Semi-membrane Complete secondary barrier
Independent
Type A Complete secondary barrier
Type B Partial secondary barrier
Type C No secondary barrier
Internal insulation
Type 1 Complete secondary barrier
Type 2 Complete secondary barrier
incorporated
ึ

very long tanks. The shape of the tanks generally prevents good utilization
of the underdeck space.

SEMI- PRESSURIZED ( OR SEMI- REFRIGERATED) TANKS The
3
capacity of semi-pressurized ships ranges up to about 5000 m the cargoes
carried being similar to fully-pressurized ships. The independent Type C
tanks are generally constructed of ordinary grades of steel suitable for a
temperature of − 5 °C and are designed for a maximum pressure of about
2
8kg/cm . The outer surface of the tank is insulated and refrigeration or
reliquefication plant cools the cargo and maintains the working pressure.
Cargo tanks are often horizontal cylinders mounted on two saddle supports
and many designs (see Figure 23.1) incorporate bio-lobe tanks to better
utilize the underdeck space and improve payload.

FULLY-REFRIGERATED TANKS The capacity of fully-refrigerated ships
3
3
ranges from 10 000 m to 100 000 m the smaller ships in the range being
multi-product carriers whilst the larger vessels tend to be single product
carriers on a permanent route. Tanks fall almost exclusively into the pris-
matic, independent Type A category with tops sloped to reduce free surface
and bottom corners sloped to suit the bilge structure. In most cases they are
subdivided along the centreline by a liquid-tight bulkhead which extends to