4.2.1.1 For spaces used for salt water ballast,
an overall survey of representative spaces selected by the surveyor
should be carried out. If such inspections reveal no visible structural
defects, the examination may be limited to a verification that the
protective coating remains efficient.
4.2.1.2 Where POOR coating condition, corrosion
or other defects are found in salt water ballast spaces or where protective
coating was not applied from the time of construction, the examination
should be extended to other ballast spaces of the same type.
4.2.1.3 In salt water ballast spaces other than
double bottom tanks, where a protective coating is found in POOR condition
and it is not renewed, or where soft coating has been applied, or
where a protective coating was not applied from the time of construction,
the tanks in question should be examined and thickness measurements
carried out as considered necessary at annual intervals. When such
breakdown of coating is found in salt water ballast double bottom
tanks, where a soft coating has been applied, or where a coating has
not been applied, the tanks in question should be examined at annual
intervals. When considered necessary by the surveyor, or where extensive
corrosion exists, thickness measurements should be carried out.
4.2.1.4 In addition to the requirements above,
areas found to be suspect areas at the previous renewal survey should
be overall and close-up surveyed.
4.2.2.1 An overall survey of all cargo holds,
including close-up survey of sufficient extent, minimum 25% of frames,
should be carried out to establish the condition of:
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.1 shell frames including their upper and lower
end attachments, adjacent shell plating, and transverse bulkheads
in the forward cargo hold and one other selected cargo hold; and
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.2 areas found to be suspect areas at the previous
renewal survey.
4.2.2.2 Where considered necessary by the surveyor
as a result of the overall and close-up survey as described in 4.2.2.1,
the survey should be extended to include a close-up survey of all
of the shell frames and adjacent shell plating of that cargo hold
as well as a close-up survey of sufficient extent of all remaining
cargo holds.
4.2.3 Extent of thickness measurement
4.2.3.1 Thickness measurement should be carried
out to an extent sufficient to determine both general and local corrosion
levels at areas subject to close-up survey as described in 4.2.2.1.
The minimum requirement for thickness measurements at the intermediate
survey are areas found to be suspect areas at the previous renewal
survey.
4.2.3.2 Where substantial corrosion is found,
the extent of thickness measurements should be increased in accordance
with the requirements of annex 10.
4.2.3.3 The thickness measurement may be dispensed
with provided the surveyor is satisfied by the close-up survey, that
there is no structural diminution and the protective coating, where
applied, remains effective.
4.2.3.4 Where the protective coating in cargo
holds, as referred to in the explanatory note below, is found to be
in GOOD condition, the extent of close-up surveys and thickness measurements
may be specially considered by the Administration.
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Explanatory note:
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At the time of new construction, all internal and external
surfaces of hatch coamings and hatch covers, and all internal surfaces
of the cargo holds, excluding the flat tank top areas and the hopper
tanks sloping plating approximately 300 mm below the side shell frame
and brackets, should have an efficient protective coating (epoxy coating
or equivalent) applied in accordance with the manufacturers recommendation.
In the selection of coating, due consideration should be given by
the owner to intended cargo conditions expected in service. For existing
bulk carriers, where owners may elect to coat or recoat cargo holds
as noted above, consideration may be given to the extent of the close-up
and thickness measurement surveys. Prior to the coating of cargo holds
of existing ships, scantlings should be ascertained in the presence
of a surveyor.