Page 283 - Ship Construction.DJ Eyres 6Ed

Ch23-H8070.fm Page 272 Wednesday, October 18, 2006 7:38 AM
272 Ship Construction
foam insulation. The system is fitted with a partial secondary barrier
consisting of a drip tray under the tank and splash shields at the sides. In
accordance with its Type B notation, each tank is provided with sensors
which will detect leakage and allow timely repairs before any crack reaches
critical proportions.
Spherical tanks make poor use of available cargo space, a substantial hull
being required to house, say, 5 large spheres providing a cargo-carrying
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--- ใช้เพื่อการศึกษาเท่านั้น---
capacity of 125 000 m . Above deck the spheres are protected by substantial
weather covers.
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
MEMBRANE TANKS Two common membrane tank designs are those
developed and associated with the French companies Gaz Transport and
Technigaz. The Gaz Transport system uses a 36 per cent nickel-iron alloy
called ‘Invar’ for both the primary and secondary barriers. Invar has a very
low coefficient of thermal expansion which makes any corrugations in the
tank structure unnecessary. The Invar sheet membrane used is only 0.5 to
0.7 mm thick which makes for a very light structure. Insulation consists of
plywood boxes filled with perlite (see Figure 23.4).
The Technigaz system utilizes a stainless steel membrane system where
tanks are constructed of corrugated sheet in such a way that each sheet is
ึ
free to contract and expand independently of the adjacent sheet. This forms
the inner primary barrier and a balsa insulation and secondary barrier

Plywood boxes
‘Invar’ primary and filled with Plywood
secondary barriers Perlite Corrugated stainless
steel facing

Inner hull Fibreglass Balsa
GAZ–TRANSPORT TECHNIGAZ

FIGURE 23.4 Membrane systems