3.7.12 Load lines should be assigned to self-elevating
units as calculated under the terms of the 1966 Load Line Convention.
When floating or when in transit from one operational area to another
units should be subject to all the conditions of assignment of that
Convention unless specifically excepted. However, these units should
not be subject to the terms of that Convention while they are supported
by the sea-bed or are in the process of lowering or raising their
legs.
3.7.13 The minimum freeboard of units which due
to their configuration cannot be computed by the normal methods laid
down by the 1966 Load Line Convention should be determined on the
basis of meeting applicable intact stability, damage stability and
structural requirements in the afloat condition.
3.7.14 Where it is necessary to assign a greater
than minimum freeboard to meet intact or damage stability requirements
or on account of any other restriction imposed by the Administration,
regulation 6(6) of the 1966 Load Line Convention should apply. When
such a freeboard is assigned, seasonal marks above the centre of the
ring should not be marked and any seasonal marks below the centre
of the ring should be marked. If a unit is assigned a greater than
minimum freeboard at the request of the owner, regulation 6(6) need
not apply.
3.7.15 Where moonpools are arranged within the
hull in open communication with the sea, the volume of the moonpool
should not be included in the calculation of any hydrostatic properties.
If the moonpool has a larger cross-sectional area above the waterline
at 0.85D than below, an addition should be made to the geometric freeboard
corresponding to the lost buoyancy. This addition for the excess portion
above the waterline at 0.85D should be made as prescribed below for
wells or recesses. If an enclosed superstructure contains part of
the moonpool, deduction should be made for the effective length of
the superstructure. Where open wells or recesses are arranged in the
freeboard deck, a correction equal to the volume of the well or recess
to the freeboard deck divided by the waterplane area at 0.85D should
be made to the freeboard obtained after all other corrections, except
bow height correction have been made. Free surface effects of the
flooded well or recess should be taken into account in stability calculations.
3.7.16 The procedure described in 3.7.15 should
apply in cases of small notches or relatively narrow cut-outs at the
stern of the unit.
3.7.17 Narrow wing extensions at the stern of
the unit should be considered as appendages and excluded for the determination
of length (L) and for the calculation of freeboards. The Administration
should determine the effect of such wing extensions with regard to
the requirements for the strength of unit based upon length (L).
3.7.18 Self-elevating units may be manned when
under tow. In such cases a unit would be subject to a bow height requirement
which may not always be possible to achieve. In such circumstances,
the Administration should consider the extent of application of regulation
39(3) of the 1966 Load Line Convention to such units, having regard
to the occasional nature of such voyages on predetermined routes and
to prevailing weather conditions.
3.7.19 Some self-elevating units utilize a large
mat or similar supporting structure which contributes to the buoyancy
when the unit is floating. In such cases the mat or similar supporting
structure should be ignored in the calculation of freeboard. The mat
or similar supporting structure should, however, always be taken into
account in the evaluation of the stability of the unit when floating
since its vertical position relative to the upper hull may be critical.