Single pull macgregor type hatch cover.pdf - Cochin University of ...

easier to handle without power assistance. Aluminium single pull weather deck covers
have occasionally been fitted in the past, sometimes experimentally. Aluminium can
be used for Ro-Ro vessel access equipment but it is usually limited to small ramps and
car decks. It is less resistant to fire damage than steel.
3.4.3 Glass Reinforced Plastic (GRP)
GRP structures are light but the modulus of elasticity of GRP is only 7 percentages of
that of mid steel and excessive deflection is a problem which invariably accompanies
its use. Additional stiffening is thus necessary, making the structure heavier and more
expensive to manufacturer. For this reason GRP has not as yet found wide application
in the construction of cargo access equipment, although development work is in
progress. GRP in ‘sandwich’ construction could be particularly suitable for covers in
refrigerated ships because insulation can be built into them during the manufacturing
process at very little extra cost, whereas the present system of insulating steel covers
is expensive and time consuming.
3.4.4 Wood
Wooden covers no longer supplied to weather decks of new cargo ships, although on
rare occasions, they are fitted in tween decks. Classification society rules lay down
scantling for beam and boards covers because of LLC requirements; in practice they
care now mainly for the benefit of repair to older ships.
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