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The
Maritime and Coastguard Agency (MCA) recommends owners to fit hull
stress monitoring systems on bulk carriers of 20,000 dwt and above.
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Owners are
invited to ensure that hull stress monitoring equipment is compatible
with the VDR fitted and that all monitored data can be transmitted to
the VDR.
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It is
essential that the assigning authority for the International Load
Line Certificate to be consulted regarding the installation of the
hull stress monitoring system and the determination of maximum
permissible stresses and accelerations.
SYSTEM
SPECIFICATION :
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Long-based
gauges for strain measurements, located on the main deck at different
positions along the ship’s length, to detect stresses during
loading, unloading or navigation taking due account of temperature
effects. The gauges for strain measurement should be located on the
main deck in way of each cargo hold and, if necessary, at the
location where the maximum hull girder wave bending stress can be
expected. They are to give information on the wave induced stresses
and the mean value of still water stresses. By analyzing an offset to
a mean value, an indication of water ingress into the holds can also
be provided.
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One
accelerometer for measuring vertical accelerations at the bow.
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Two
accelerometers for measuring roll and sway, suitably located at the
centre line of the ship. The accelerometers will give the vertical
and transverse motion of the ship. By analyzing the frequency ranges
of the signals from the vertical gauge, slamming information can also
be provided.
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A
microprocessor to be used that can interpret sensor signals and
compare these with the allowable levels approved by the
Administration. To verify intermediate and final stages of loading
and unloading operations, the HSMS can be linked to the loading
calculator. The system visual and audible indications to indicate
high stress or motion levels approaching threshold values.
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A graphical
display, supplemented by digital display as appropriate, suitable for
the presentation of the censor information, taking due account of the
importance of the human interface.
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An
electronic data storage to be used for recording device suitable for
accumulating statistical information for feedback purposes.
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Means for
ensuring the integrity of the data are to be incorporated. Checks of
the total system have to be done at intervals as agreed by the
Administration.
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The
hardware and the software of the monitoring system should be approved
by the Administration.
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All
appropriate officers should be fully trained with regard to the use
and limitations of the monitoring system.
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