1 Damage to side shell, externally through contact
with docksides or tugs and, internally from impact by cargo dislodging
equipment during discharge, can result in initiating fractures and/or
fatigue of the structure. In single side-skin bulk carriers, bulkheads,
trunks and ballast tank boundaries, can present "hard spots" that
concentrate forces where the change in construction occurs (e.g. longitudinal
to transverse framing). This may lead to undetected fractures.
2 Internal degradation through corrosion may be
accelerated through chemical action from certain cargoes. Welds in
particular may be subject to "grooving" corrosion, in which the material
forming the weld corrodes at a faster rate than the plating to which
it is attached. Fatigue failure may result due to loss of cross-sectional
area in the plating joints.
3 In ballast holds, sloshing forces due to partially
filled spaces (such as may occur when changing ballast for environmental
reasons) may result in damage to the structure. This damage may go
unnoticed if it is in inaccessible positions. Sloshing is also a known
cause of secondary damage after a space has become flooded.
4 Damage to bow plating such as is possible through
impacts associated with swinging or loosely stowed anchors may cause
an initiating fracture or fatigue in bow shell plating that could
lead to failure and subsequent flooding. Internal integrity of forward
spaces (that are usually used for ballast and/or stores) is therefore
of vital importance. Corrosion degradation will seriously reduce the
ability of plating and stiffening to withstand the forces to which
it will be subjected. In larger ships, partially filled forepeak tanks
may set up destructive sloshing forces unless the tank structure is
designed for this.
5 External forces - horizontal and/or vertical
- may cause hatch cover dislodgement. The cargo hatchway, if it loses
its protection in this way, is a major access for water ingress and
a serious threat to the integrity of the hull.