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

Figure 3.3 Detailed analysis of the structure of a 120,000 tdw bulk carrier
Source: Cargo Access Equipment for Merchant Ships.
It has been suggested that, since hatchways are always closed by hatch covers,
the latter ought to be designed to contribute to the strength of the hull girder. This is
however not practical as the devices securing the cover to the coamings would have to
be excessively robust, and any deformation due to the loading of the vessel in port
could lead to the covers becoming jammed and thus impossible to open. Moreover, to
make a significant contribution to vessel’s strength, the covers would have to be
considerably stronger and heavier than at present, and this could introduce operational
difficulties.
Hatch coamings can be designed to contribute to the longitudinal strength of
the ship but there can be problems associated with this. If it is decided to use the
coaming in this way, they must be continuous over the midship portion of the ship and
properly tapered at the forward and after into account in calculating the midship
section modulus, according to classification society requirements.
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