Page 277 - Ship Construction.DJ Eyres 6Ed

Ch23-H8070.fm Page 266 Wednesday, October 18, 2006 7:38 AM
266 Ship Construction
The IMO International Gas Carrier Code

In 1975 the 9th Assembly of IMO adopted the Code for the Construction
and Equipment of Ships Carrying Liquefied Gases in Bulk, A.328 (IX) which
provides international standards for ships which transport liquefied gases in
bulk. It became mandatory in 1986 and is generally referred to as the IMO
International Gas Carrier Code. The requirements of this code are incorp-
--- ใช้เพื่อการศึกษาเท่านั้น---
orated in the rules for ships carrying liquefied gases published by Lloyds
Register and other classification societies.
The code covers damage limitations to cargo tanks and ship survival in
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
the event of collision or grounding, ship arrangements for safety, cargo con-
tainment and handling, materials of construction, environmental controls,
fire protection, use of cargo as fuel, etc. Of particular interest in the context
of ship construction is the section on cargo containment which defines the
basic cargo container types and indicates if a secondary barrier is required,
i.e. a lining outside the cargo containment which protects the ships hull
structure from the embrittling effect of the low temperature should cargo
leak from the primary tank structure. The cargo containment types are
described below.
ึ
INTEGRAL TANKS These tanks which form a structural part of the ships
hull and are influenced in the same manner and by the same loads which
stress the adjacent hull structure. These are used for the carriage of LPG at
or near atmospheric conditions, butane for example, where no provision for
thermal expansion and contraction of the tank is necessary.

MEMBRANE TANKS These are non-self-supporting tanks consisting of
a thin layer (membrane) supported through insulation by the adjacent hull
structure. The membrane is designed in such a way that thermal and other
expansion or contraction is compensated for without undue stressing of
the membrane. Membrane tanks are primarily used for LNG cargoes (see
Figure 23.4).

SEMI-MEMBRANE TANKS These are non-self-supporting tanks in the
load condition. The flat portions of the tank are supported, transferring the
weight and dynamic forces through the hull, but the rounded corners and
edges are not supported so that tank expansion and contraction is accom-
modated. Such tanks were developed for the carriage of LNG, but have
been used for a few LPG ships.

INDEPENDENT TANKS These are self supporting and independent of
the hull. There are three types: