To ensure that arrangements and procedures are provided to control potential
accumulation of hydrogen sulphide, an explosive atmosphere, and other potential hazards
backloaded from the installation.
16.1 Preamble
16.1.1 Backloading of contaminated bulk liquids could present a threat to human health
and to the marine environment.
16.1.2 Contaminated backloads should therefore be:
16.2 General
16.2.1 Unless expressly provided otherwise, this chapter should apply to new and
existing vessels.
16.2.2 The provisions of this chapter should apply in conjunction with all other
provisions of the present Code.
16.2.3 For the carriage of contaminated backloads, the requirements in chapter 17 of the IBC Code should apply as described in 16.4.4.
16.2.4 Contaminated bulk liquids should not contain traces of hydrogen sulphide
(H2S) prior to or during loading of the cargo.
16.2.5 Even if the test carried out before backloading indicates that H2S is
not present and that the contaminated bulk liquid has a flashpoint exceeding 60°C, a
separation of the chemical components may occur during the voyage, resulting in a
release of H2S and a corresponding lowering of the flashpoint to 60°C or
less.
16.2.6 H2S detection equipment should be provided on board vessels carrying
contaminated backloads prone to H2S formation. It should be noted that
scavengers and biocides, when used, may not be 100% effective in controlling the
formation of H2S.
16.2.7 Contaminated bulk liquids should not contain radioactive materials which are
subject to the applicable requirements for such materials.
16.3 Documentation
16.3.1 In lieu of the cargo information specified in 15.2.3, the shipper and/or owner of
the contaminated bulk liquids should provide the master or his or her representative
with information as required in 16.3.2 prior to backloading.
16.3.2 Information concerning the contaminated bulk liquid should be confirmed in
writing using the appropriate analysis form. An example of the analysis form is set out
in appendix 2. The information concerning the contaminated bulk liquid should at least
include:
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.1 a sample description;
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.2 descriptions of the components of the mixture, name, concentration and Material
Safety Data Sheet (MSDS), if available;
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.3 flashpoint (ºC);
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.4 hydrogen sulphide (H2S) level (ppm);footnote
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.5 lower explosive limit (LEL) level (%);
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.6 oxygen level (%);
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.7 pH;
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.8 bulk specific gravity (kg/m3);
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.9 water content (% volume);
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.10 oil content (% volume);
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.11 solids content (% volume);
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.12 date and time of the analysis;
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.13 details of any treatment to remove or prevent the formation of H2S;
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.14 any other relevant information; and
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.15 conclusions of the test results, including confirmation that the components of
the mixtures are compatible.
16.4 Operation
16.4.1 Responsibilities
16.4.1.1 The master should not accept loading of any contaminated bulk liquid which is
not properly documented in accordance with 16.3.
16.4.1.2 The master should ascertain whether the contaminated bulk liquid is within the
safe limits of the vessel and tanks, especially with regard to the flashpoint of the
specific liquid, before backloading commences.
16.4.1.3 The responsibility for ensuring that cargoes are properly prepared for carriage
on board the vessel rests with the shipper and/or owner of the cargoes concerned.
16.4.2 Carriage requirements
16.4.2.1 Contaminated bulk liquids should be carried in accordance with the applicable
minimum carriage requirements for contaminated bulk liquids specified in chapter 17 of
the IBC Code or the latest edition of the MEPC.2/Circular.
16.4.2.2 In addition to the provisions in 16.4.2.1, H2S and LEL gas detection
is required for carriage of contaminated bulk liquid as follows:
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.1 fixed vapour detection instruments with audible and visual alarms to indicate
H2S and LEL levels exceeding 5 ppm and 10%, respectively, installed
in the venting system of the relevant tanks; and
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.2 portable instruments for all personnel on the working deck.
16.4.3 H2S precaution
16.4.3.1 Contaminated bulk liquid should be discharged from the vessel as soon as
possible, preferably at the first port of call.
16.4.3.2 The need to clean the dirty tanks should be reviewed on each voyage to minimize
the risk of biological activity and H2S build up from any residue.
16.4.3.3 Prior to backloading to a dirty tank, the potential for biological activity
resulting in H2S in the dead volume and sludge should be considered. The
offshore analysis of the previous contaminated bulk liquid should be compared with
analyses of a sample representative for the liquid when unloading.
16.4.3.4 If H2S or flammable vapour is detected during loading of
contaminated bulk liquids the transfer should be stopped immediately.
16.4.3.5 Vessel-specific procedures for measures to be taken when H2S is
detected during loading, transport, discharge and cleaning of contaminated bulk liquids
should be included in the vessel's safety management system.
16.4.4 Contaminated backloads
16.4.4.1 Based on the information contained in 16.3.2, the entry for "offshore
contaminated bulk liquid P" in chapter 17 of the IBC Code should be used for backloads that:
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.1 are pollutant only and do not present any safety hazardsfootnote or where the pre-backloading tests do not indicate
any safety hazards (the backload may contain components with safety hazards, as
long as they are so diluted that the final mixture presents no safety hazard);
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.2 have a flashpoint greater than 60°C; or
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.3 do not have the potential to become more hazardous during transport.
16.4.4.2 Based on the information contained in 16.3.2, the entry for "offshore
contaminated bulk liquid S" in chapter 17 of the IBC Code should be used for backloads that:
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.1 have been treated to remove or prevent breakout of H2S;
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.2 are expected to present both pollution and safety hazards or where the initial
pre-backloading tests indicate a potential or actual safety hazard;
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.3 may contain substances with a flashpoint not exceeding 60°C;
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.4 have the potential to become more hazardous during transport; or
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.5 are to be backloaded to a dirty tank the content of which has not been
analysed.