IMO’s DE 48 addresses Guidelines on On-board Exhaust Gas Cleaning Systems and IACS UIs for the Annex VI Regulations and its NOx technical Code

At last week’s meeting of the IMO Design and Equipment Sub-committee (DE 48) two key issues were addressed relating to the forthcoming enforcement of MARPOL Annex VI (Regulations for the prevention of air pollution from ships). 

Guidelines on On-board Exhaust Gas Cleaning Systems:

The guidelines for the design and operation of acceptable on-board exhaust gas cleaning systems (scrubbers) were completed, save for the full consideration of the necessary water treatment systems. It is to be noted that Regulation 14 of Annex VI requires all exhaust gas emissions within a Sulphur Emission Control Area (SECA) to meet the requirements of the Regulation. This will also include boiler emissions. The guidelines as formulated allow two alternatives to be selected, namely:


a)     Scheme A allows for “type approval” of the equipment to be installed as defined within the Emissions Technical Manual (ETM) and complying with the SECA Compliance Certificate (SCC). The equipment also requires means to automatically record wash water pressure and flow rate at the scrubber inlet, together with the exhaust gas temperature before and after the scrubber unit.  

b)     Scheme B allows for continuous monitoring of the exhaust gases from each of the units which the scrubber serves. The tamper-proof data recording and measurement system is fully defined within the guidelines but primarily relies upon the ratio of SO2 (ppm) to CO2 (%) in the exhaust gas stream being below 65. By use of such a ratio the necessity to compensate for differing loads on the engines, and the unknown load on the boilers, is removed. 

Consideration of the IACS Unified Interpretations for the Annex VI Regulations and its NOx Technical Code.

The International Association of Classification Societies Unified Interpretations (IACS UIs) presented for consideration amounted to approximately 70. INTERTANKO had submitted a paper relating to these interpretations at the 52nd session of the Marine Environmental Protection Committee (MEPC 52) and these observations were taken into account by the group. The lack of time left some 23 UIs outstanding for consideration at the next meeting. Of the original 70 submitted, only 17 IACS UIs were accepted with the remainder being either re-drafted or deleted. The INTERTANKO observations were accepted in the main. 

See also article below “Compliance with Annex VI for all ship operators.” 

Contact: Dragos Rauta