Annex II

The revised annex includes a number of other significant changes. Improvements in ship technology, such as efficient stripping techniques, has made possible significantly lower permitted discharge levels of certain products which have been incorporated into Annex II. For ships constructed on or after 1 January 2007 the maximum permitted residue in the tank and ist associated piping left after discharge will be set at a maximum of 75 litres for products in categories X, Y and Z – compared with previous limits which set a maximum of 100 or 300 litres, depending on the product category.

Alongside the revision of Annex II, the marine pollution hazards of thousands of chemicals have been evaluated by the Evaluation of Hazardous Substances Working Group, giving a resultant GESAMP2 Hazard Profile which indexes the substance according to ist bio-accumulation; bio-degradation; acute toxicity; chronic toxicity; long-term health effects; and effects on marine wildlife and on benthic habitats.

As a result of the hazard evaluation process and the new categorization system, vegetable oils which were previously categorized as being unrestricted will now be required to be carried in chemical tankers. The revised Annex includes, under regulation 4 Exemptions, provision for the Administration to exempt ships certified to carry individually identified vegetable oils, subject to certain provisions relating to the location of the cargo tanks carrying the identified vegetable oil.

Transport of vegetable oils
The MEPC also adopted a resolution on Guidelines for the transport of vegetable oils in deep tanks or in independent tanks specially designed for the carriage of such vegetable oils on board dry cargo ships. The guidelines have been developed to allow general dry cargo ships that are currently certified to carry vegetable oil in bulk to continue to carry these vegetable oils on specific trades. The guidelines will take effect on 1 January 2007.

Consequential amendments to the IBC Code
Consequential amendments to the International Bulk Chemical Code (IBC Code) were also adopted at the session, reflecting the changes to MARPOL Annex II. The amendments incorporate revisions to the categorization of certain products relating to their properties as potential marine pollutants as well as revisions to ship type and carriage requirements following their evaluation by the Evaluation of Hazardous Substances Working Group. Ships constructed after 1986 carrying substances identified in chapter 17 of the IBC Code must follow the requirements for design, construction, equipment and operation of ships contained in the Code.

Solidifying
1. in the case of a substance with a melting point of less than 15°C which is at a temperature of less than 5°C above ist melting point at the time of unloading;
or
2. in the case of a substance with a melting point of equal to or greater than 15°C which is at a temperature of less than 10°C above ist melting point at the time of unloading.

High-Viscosity Substance means a noxious liquid substance in Category X or Y with a viscosity equal to or greater than 50 mPa.s at the unloading temperature. The properties of the solidifying or high viscosity substance should be obtained from the shipping document.

Persistent floater means a slick forming substance with the following properties:
– Density: ≤ sea water (1025 kg/m3 at 20°C);
– Vapour pressure: ≤ 0.3 kPa;
– Solubility: ≤ 0.1% (for liquids) ≤ 10% (for solids); and
– Kinematic viscosity: > 10 cSt at 20°C.

As of Jan 2021  persistent floaters can be identified by the entry 16.2.7 in column o of chapter 17 in the IBC Code.

Within the Antarctic area (south of latitude 60° S , any discharge into the sea of Noxious Liquid Substances or mixtures containing such substances is prohibited.

Additional washing requirements before cargo tank can be used for ballast water. Mandatory for cargo tanks having contained substances of category X or Y if solidifying or high viscous

Before filling the cargo tank with ballast water following subsequent wash in addition to the prewash has to be applied:

– a complete cycle of the cleaning machine(s) for ships built before 1 July 1994 or

– a wash with a water quantity not less than calculated with “k” = 1.0 for ships built on or after 1 July 1994

Condition for discharge of this ballast water:

1. Distance from Land > 12 nautical miles

2. Water depth > 25 metres

Washing with a recycled washing medium may be adopted for the purpose of washing more than one cargo tank. In determining the quantity, due regard must be given to the expected amount of residues in the tanks and the properties of the washing medium and whether any initial rinse or flushing is employed. Unless sufficient data are provided, the calculated end concentration of cargo residues in the washing medium shall not exceed 5% based on nominal stripping quantities.

The recycled washing medium shall only be used for washing tanks having contained the same or similar substance.

A quantity of washing medium sufficient to allow continuous washing shall be added to the tank or tanks to be washed.

All tank surfaces shall be washed by means of a rotary jet(s) operated at sufficiently high pressure. The recycling of the washing medium may either be within the tank to be washed or via another tank, e.g. a slop tank.

The washing shall be continued until the accumulated throughput is not less than that corresponding to the relevant minimum quantity of water (see formular).

Solidifying Substances and substances with viscosity equal to or greater than 50 mPa.s at 20°C shall be washed with hot water (temperature at least 60°C) when water is used as the washing medium, unless the properties of such substances make the washing less effective.

After completing the tank washing with recycling the washing medium shall be discharged and the tank thoroughly stripped. Thereafter, the tank shall be subjected to a rinse, using clean washing medium, with continuous drainage and discharged to a reception facility. The rinse shall as a minimum cover the tank bottom and be sufficient to flush the pipelines, pump and filter.

The minimum quantity of water to be used in a prewash is determined by the residual quantity of noxious liquid substance in the tank, the tank size, the cargo properties, the permitted concentration in any subsequent wash water effluent, and the area of operation. The minimum quantity is given by the following formula: Q = k * ( 15 * r exp 0.8 + 5 * r exp 0.7 * V / 1000 )
where

Q = the required minimum quantity in m3

r = the residual quantity per tank in m3. The value of r shall be the value demonstrated in the actual stripping efficiency test, but shall not be taken lower than 0.100 m3 for a tank volume of 500 m3 and above and 0.040 m3 for a tank volume of 100 m3 and below. For tank sizes between 100 m3 and 500 m3 the minimum value of r allowed to be used in the calculations is obtained by linear interpolation.

For Category X substances the value of r shall either be determined based on stripping tests according to the Manual, observing the lower limits as given above, or be taken to be 0.9 m
.
V = tank volume in m3

k = a factor having values as follows:

Category X, non-Solidifying, Low-Viscosity Substance, k = 1.2

Category X, Solidifying or High-Viscosity Substance, k = 2.4

Category Y, non-Solidifying, Low-Viscosity Substance k = 0.5

Category Y, Solidifying or High-Viscosity Substance k = 1.0

The table below is calculated using the formular with a k factor of 1 and may be used as an Easy reference.

Cargo residues of substances with a vapour pressure greater than 5 Kpa = 0,05 bar at 20°C may be removed from a cargo tank by ventilation.

Before residues of Noxious Liquid Substances are ventilated from a tank the safety hazards relating to cargo flammability and toxicity shall be considered. With regard to safety aspects, the operational requirements for openings in cargo tanks in SOLAS 74, as amended, the International Bulk Chemical Code, the Bulk Chemical Code, and the ventilation procedures in the International Chamber of Shipping (ICS) Tanker Safety Guide (Chemicals) should be consulted.

Port authorities may also have regulations on cargo tank ventilation.

The procedures for ventilation of cargo residues from a tank are as follows:

1. the pipelines shall be drained and further cleared of liquid by means of ventilation equipment;

2. the list and trim shall be adjusted to the minimum levels possible so that evaporation of residues in the tank is enhanced;

3. ventilation equipment producing an airjet which can reach the tank bottom shall be used. Figure 7-1 could be used to evaluate the adequacy of ventilation equipment used for ventilating a tank of a given depth;

4. ventilation equipment shall be placed in the tank opening closest to the tank sump or suction point;

5. ventilation equipment shall, when practicable, be positioned so that the airjet is directed at the tank sump or suction point and impingement of the airjet on tank structural members is to be avoided as much as possible; and

6. ventilation shall continue until no visible remains of liquid can be observed in the tank. This shall be verified by a visual examination or an equivalent method.