Chapter 17 - Discharging and Loading of Portable Tanks on Board
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Chapter 17 - Discharging and Loading of Portable Tanks on Board

 To ensure the safe handling of all cargoes to and from portable tanks which form part of the vessel or remain on board, under all normal operating conditions and foreseeable emergency conditions, to minimize the risk to the vessel, its crew and the environment, having regard to the nature of the products involved.

17.1 Preamble

17.1.1 The present Code applies only in the case of bulk carriage involving transfer of the cargo to or from its containment. The carriage of dangerous goods in packaged form is regulated under SOLAS chapter VII Part A and should comply with the relevant requirements of the IMDG Code. The IMDG Code is also applicable for environmentally hazardous substances in packaged form under MARPOL Annex III. Provisions of 4.2.1 of the IMDG Code provide that: "Portable tanks shall not be filled or discharged while they remain on board."

17.1.2 The current operation practice is to carry portable tanks in two ways:

  • .1 Offshore portable tanks and their contents are loaded and offloaded to the offshore installation by the use of a crane, in which case the IMDG Code applies; or

  • .2 Offshore portable tanks and portable tanks are loaded with their contents onto a vessel by crane or filled while on board and used as deck tanks in a "deck spread". Then the contents are pumped to the offshore installation or to the seabed. These tanks can also be used to receive backloads from the installation and will be secured to the deck, in which case the cargo is shipped under the present Code.

17.2 General

17.2.1 This chapter applies when using offshore portable tanks and portable tanks allowed under 5.2.2.

17.2.2 A portable tank, for the purpose of this section, means a multimodal tank used for the transport of dangerous goods of class 1 and classes 3 to 9. The portable tank includes a shell fitted with service equipment and structural equipment necessary for the transport of dangerous substances. The portable tank should be capable of being filled and discharged without the removal of its structural equipment. It should possess stabilizing members external to the shell, and should be capable of being lifted when full. It should be designed primarily to be loaded onto a vehicle or vessel and should be equipped with skids, mountings or accessories to facilitate mechanical handling. Road tank-vehicles, rail tank-wagons, non-metallic tanks and intermediate bulk containers are not considered to fall within the definition of portable tanks.

17.2.3 The provisions of this chapter should apply in conjunction with all other provisions of the present Code.

17.2.4 Chemicals, including blending additives, transported in portable deck tanks which are considered to fall outside the scope of 1.1.9 may be carried in limited amounts in accordance with provisions acceptable to the Administration. The aggregate amount of such chemicals which may be transported should not exceed 10% of the vessel's maximum authorized quantity of products subject to the present Code. An individual tank should contain not more than 10 m3 of these chemicals. The discharge of these chemicals into the sea from OSVs is prohibited.

17.3 Arrangement of deck spread

17.3.1 All pumping equipment, processing equipment, pipework, valves and hoses should be compatible with the substances being transferred.

17.3.2 Pipework connecting deck spread tanks to bulk tanks within the cargo area of the vessel should have two valve separation and should comply with the provisions of chapter 6 of the present Code.

17.3.3 In addition to the cargo segregation required by chapters 3 and 4, the general stowage and segregation requirements given in chapter 7 of the IMDG Code should apply. The segregation requirements may be relaxed subject to approval by the Administration.

17.3.4 Cargo tank vent systems of portable tanks allowed under 5.2.2 should be to the satisfaction of the Administration, taking into account the requirements of chapter 6 of the IMDG Code.

17.3.5 Arrangements of products with a flashpoint not exceeding 60C, toxic products and acids should comply with the provisions in chapter 4, as applicable.

17.3.6 Deck spills should be kept away from accommodation and service areas by means of a coaming of suitable height and extension.

17.4 Shipment of cargo in portable tanks used as deck tanks

17.4.1 A procedure for the carriage of portable tanks should be completed and submitted to the Administration or any organization recognized by it, for consideration and approval prior to arranging the deck spread. A model format for the procedure is set out in appendix 3.

17.4.2 The portable tank should be physically secured to the vessel, in accordance with the vessel's cargo securing manual to prevent loss in the event of an incident while at sea. The arrangements for securing the portable tanks to the vessel should be of such strength as to withstand the forces likely to be encountered during the voyage to and from the area of operation.

17.4.3 The portable tank(s) and pumping system should be monitored regularly on the sea passage to ensure the physical security of the portable tanks.

17.4.4 The pipework and valves should be secured to prevent movement.

17.4.5 The loading and unloading of the portable tanks should not be undertaken at the same time as other deck cargo is being handled.

17.4.6 Portable tank(s) should be filled through a manifold system.

17.4.7 Discharge into the sea of portable tank contents, residues, tank washings, or other residues or mixtures containing such substances, is prohibited. Any discharges of residues and mixtures containing noxious liquid substances should be to port reception facilities.


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