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Wednesday, October 17, 2018


The 5th session of the IMO’s sub-Committee on Bulk Liquid and Gases (BLG5) did not achieve too many of its initial goals. Before the meeting, it was perceived that that this session would be dedicated to conclude most of the revision of MARPOL Annex I. A brief revision of the discussions and the problems regarding this process are given below.

Progress report on the revision of Annex I

Since the entry into force of MARPOL 73/78 on 2 October 1983, there have been numerous amendments to Annex I, resulting in a complicated set of regulations and unified interpretations. In many cases it is difficult, and sometimes confusing, for end users to comprehend the requirements.

One of the major difficulties that has arisen in developing the revised Annex I is the treatment of the different structural requirements for tankers of different age groups, which in the current Annex I, is difficult to follow.

The main features of the revised Annex are as follows:

  1. The requirements for machinery spaces of all ships have been allocated to a separate chapter (Chapter 3).
  2. The requirements for cargo areas of oil tankers have been allocated to a separate chapter (Chapter 4).
  3. The new Annex I in general would apply to both New and Existing ships; Part A of Chapter 4 deals with the construction requirements of oil tankers, existing ships are subject to the current Annex I under the Grandfather clause of the new Annex I.
  4. The numbering system has been decimalised.
  5. The definition of Prior Annex I has been kept, since several regulations of the New Annex I require references to the Current Annex I.
  6. The proposed new term “Generation of Ships” has been replaced by the term “Ships constructed on or after a certain date” in line with the practice of relevant conventions.
  7. References to dedicated clean ballast tanks (CBTs) have been deleted since these are not applicable to new ships which will have segregated ballast tanks (SBTs).
  8. The requirements of the Enhanced Surveys (Resolution A 744 (18) have been allocated to a separate regulation (Regulation 7), taking into account the importance of the matter.
  9. The requirements of the Reception Facilities have been arranged in three sections in Chapter 6.
  10. The Unified Interpretations and its Appendices need to be examined and amended as appropriate in line with the revised Annex I.

During the meeting a number of documents offering comments and further editorial amendments were considered.  Indeed the sub-committee went through all the papers and agreed that because of the complicated nature of the current Annex I, the revised Annex I may not have solved all the problems and in some cases, it could be said it has created some new problems!  Therefore three Options for the revision of Annex I are now to be considered.  They are as follows:

Option 1)   To continue the development of the revised Annex I, with the understanding that this will be the new Annex I and there will be a need for the current Annex I defined as the Prior Annex I.

Option 2)  To develop a revised draft of Annex I incorporating all the requirements in the present Annex I and all the proposed amendments, both editorial and substantive;  this revised draft Annex I, when adopted by the MEPC, will replace the current Annex I in its entirety.

Option 3)  To prepare a set of amendments to the current Annex I without changing the structure and the numbering of regulations.

Option 3 appears to be outside the terms of reference of the committee and so will be discarded.  In IMO this week there appeared to be a consensus on progress in the manner proposed in Option 2.

Probabilistic Methodology for Outflow Analysis

Since MARPOL Annex I regulation 13F was enacted, all new takers have been built with double hulls. However, not all of the designs seem to be providing a minimum acceptable protection against outflow in case of contact accident. Consequently, IMO has decided to replace the current regulations in MARPOL Annex I for assessment of outflow (regulations developed long before the double hull feature was adopted) with a new probabilistic methodology which is aimed to ensure an environmentally sound tanker design.

This is probably the single substantial change to MARPOL Annex I regulations and is thus dealt with separately. The new regulation is drafted and final calculations and evaluations need to be done. We would therefore invite any tanker operator, member of INTERTANKO to make such an evaluation of their new designs. A worksheet will shortly be made available..

The important issues are: all VLCCs with 3 cargo tank across and a double hull (bottom and side) clearance of at least 3.0 or 3.2 metre would comply with the rules. On the Suezmax size and lower, there would be a need for a longitudinal partition of the cargo tanks (a 2-tank across arrangement) with clearance of 2.8 m (Suezmax) and 2.2 or 2.5 metre (Aframax).

The difficult question would be for newly built OBOs. BLG5 recognised the problem, but it was thought that an increased double hull clearance as compared with the current OBO designs should allow the new buildings of this type to comply. Operators who have an interest in OBO new building projects will be also requested to check the new draft regulations’ impact.

Revision of MARPOL Annex II

BLG5 only discussed the future pace of this process. It appears that in November an inter-sessional meeting of the IMO’s ESPH working Group will be able to evaluate 215 chemical cargoes, of which new hazard profiles would be concluded by GESAMP. In such a case, the next BLG session (February 2001) would probably be able to start a serious analysis of the substantial amendments to the revised MARPOL Annex II (e.g. 3 versus 5 categories in which chemicals should be grouped)

Application of MARPOL to FPSO and FSUS

BLG5 agreed to form a Correspondence Group on this issue which should:

  • collect information on the current operations of the FPSO/FSUS and the different national legislations
  • identify different types of FPSO/FSUS and find out whether any categorisation would be needed and thus which categories should be subject to the BLG/IMO work
  • address a document submitted by IACS (BLG 5/10) which sums up different MARPOL Annex I regulations and express views on the extent to which each of these regulations may or may not apply to FPSO and FSUS.

Members interested in these developments are encouraged to contact INTERTANKO and enrol themselves into this correspondence group. The conclusions and possible developments will be discussed at BLG 6 in February 2001 in London.

For any questions or clarification, please contact Dragos Rauta at the INTERTANKO office in Oslo (; or direct line +47 2212 2685)

This article can also be found under the Technical Section