Annex 9 – Guidelines
for Technical Assessment in Conjunction with Planning for Enhanced
Surveys of Bulk Carriers
These guidelines contain information and suggestions concerning
technical assessments, which may be of use in conjunction with the
planning of enhanced surveys of double skin bulk carriers. As indicated
in 5.1.6, the guidelines are a recommended tool which may be invoked
at the discretion of the Administration, when considered necessary
and appropriate, in conjunction with the preparation of the required
2 Purpose and Principles
2.1.1 The purpose of the technical assessments
described in these guidelines is to assist in identifying critical
structural areas, nominating suspect areas and in focusing attention
on structural elements or areas of structural elements which may be
particularly susceptible to, or evidence a history of, wastage or
damage. This information may be useful in nominating locations, areas
holds and tanks for thickness measurement, close-up survey and tank
2.1.2 Critical structural areas are locations
which have been identified from calculations to require monitoring
or from the service history of the subject ship or from similar or
sister ships (if available) to be sensitive to cracking, buckling
or corrosion which would impair the structural integrity of the ship.
2.2 Minimum requirements
However, these guidelines may not be used to reduce the
requirements pertaining to thickness measurement, close-up survey
and tank testing contained in annexes 1 and 2 of part B and in paragraph
2.7, respectively, which, in all cases, should be complied with as
As with other aspects of survey planning, the technical
assessments described in these guidelines should be worked out by
the owner or operator in co-operation with the Administration well
in advance of the commencement of the renewal survey, i.e., prior
to commencing the survey and normally at least 12 to 15 months before
the survey's completion due date.
2.4 Aspects to be considered
2.4.1 Technical assessments, which may include
quantitative or qualitative evaluation of relative risks of possible
deterioration, of the following aspects of a particular ship may be
used as a basis for the nomination of holds, tanks and areas for survey:
.1 design features such as stress levels on various
structural elements, design details and extent of use of high-tensile
.2 former history with respect to corrosion, cracking,
buckling, indents and repairs for the particular ship as well as similar
vessels, where available; and
.3 information with respect to types of cargo
carried, use of different holds/tanks for cargo/ballast, protection
of holds and tanks and condition of coating, if any.
2.4.2 Technical assessments of the relative risks
of susceptibility to damage or deterioration of various structural
elements and areas are to be judged and decided on the basis of recognized
principles and practices, such as may be found in references 2, 3
3 Technical Assessment
3.1.1 There are three basic types of possible
failure, which may be the subject of technical assessment in connection
with planning of surveys; corrosion, cracks and buckling. Contact
damages are not normally covered by the survey planning since indents
are usually noted in memoranda and assumed to be dealt with as a normal
routine by surveyors.
3.1.2 Technical assessments performed in conjunction
with the survey planning process should, in principle, be as shown
schematically in figure 1. The approach is basically an evaluation
of the risk in the following aspects based on the knowledge and experience
.1 design; and
3.1.3 The design should be considered with respect
to structural details, which may be susceptible to buckling or cracking
as a result of vibration, high stress levels or fatigue.
3.1.4 Corrosion is related to the ageing process,
and is closely connected with the quality of corrosion prevention
systems fitted at new building, and subsequent maintenance during
the service life. Corrosion may also lead to cracking and/or buckling.
126.96.36.199 Damage experience related to the ship
in question and sister and/or similar ships, where available, is the
main source of information to be used in the process of planning.
In addition, a selection of structural details from the design drawings
is to be included.
188.8.131.52 Typical damage experience to be considered
will consist of:
184.108.40.206 This information may be found in the survey
reports and/or the owner’s files, including the results of the
owner’s own inspections. The defects should be analysed, noted
and marked on sketches.
220.127.116.11 In addition, general experience should
be utilized. Also, reference should be made to reference 2, which
contains a catalogue of typical damages and proposed repair methods
for various structural details on single skin bulk carriers. Reference
should also be made to reference 3, which contains catalogues of typical
damages and proposed repair methods for double hull oil tanker structural
details which may to some extent be similar to structural details
in double skin bulk carriers. Such figures should be used together
with a review of the main drawings, in order to compare with the actual
structure and search for similar details that may be susceptible to
damage. In particular, chapter 3 of reference 3 deals with various
aspects specific to double hull tankers, such as stress concentration
locations, misalignment during construction, corrosion trends, fatigue
considerations and areas requiring special attention, while chapter
4 of reference 3 addresses experience gained on structural defects
in double hulls (chemical tankers, OBO carriers, ore/oil carriers,
gas carriers), which should also be considered in working out the
18.104.22.168 The review of the main structural drawings,
in addition to using the above-mentioned figures, should include checking
for typical design details where cracking has been experienced. The
factors contributing to damage should be carefully considered.
22.214.171.124 The use of high-tensile steel (HTS) is
an important factor. Details showing good service experience where
ordinary, mild steel has been used may be more susceptible to damage
when HTS, and its higher associated stresses, are utilized. There
is extensive and, in general, good experience, with the use of HTS
for longitudinal material in deck and bottom structures. Experience
in other locations, where the dynamic stresses may be higher, is less
favourable, e.g., side structures.
126.96.36.199 In this respect, stress calculations of
typical and important components and details, in accordance with relevant
methods, may prove useful and should be considered.
188.8.131.52 The selected areas of the structure identified
during this process should be recorded and marked on the structural
drawings to be included in the Survey Programme.
184.108.40.206 In order to evaluate relative corrosion
risks, the following information should generally be considered:
.1 usage of tanks, holds and spaces;
.2 condition of coatings;
.3 cleaning procedures;
.4 previous corrosion damage;
.5 ballast use and time for cargo holds;
.6 risk of corrosion in cargo holds and ballast
.7 location of ballast tanks adjacent to heated
fuel oil tanks.
220.127.116.11 Reference 4 gives definitive examples
which can be used for judging and describing coating condition, using
typical pictures of conditions.
18.104.22.168 The evaluation of corrosion risks should
be based on information in both reference 2 and reference 4, as far
as applicable to double-side skin construction, together with relevant
information on the anticipated condition of the ship as derived from
the information collected in order to prepare the Survey Programme
and the age of the ship. The various holds, tanks and spaces should
be listed with the corrosion risks nominated accordingly.
3.2.3 Locations for close-up survey and thickness
22.214.171.124 On the basis of the table of corrosion
risks and the evaluation of design experience, the locations for initial
close-up survey and thickness measurement (areas and sections) may
126.96.36.199 The sections subject to thickness measurement
should normally be nominated in tanks, holds and spaces where corrosion
risk is judged to be the highest.
188.8.131.52 The nomination of tanks, holds and spaces
for close-up survey should initially be based on highest corrosion
risk, and should always include ballast tanks. The principle for the
selection should that the extent is increased by age or where information
is insufficient or unreliable.