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Incorporating Clean Shipping International

ADVICE ON SCRUBBER SELECTION FROM GARD

Thursday, October 25, 2018 

Norwegian insurer Gard, in its latest ‘Insight’ publication, has issued advice to shipowners considering the scrubber option for compliance with the IMO 2020 sulphur emissions regulations.

Gard says that owners need to consider all available options – including lower-sulphur or alternative fuels - before deciding which would be best for their particular needs. Shipowners should undertake a proper assessment of the risks involved and should not only consider the cost element but any operational and safety issues. For example, in the case of compliant fuels, safety issues would be fuel oil stability, compatibility, combustibility, leakage and exposing fractures in pipes which are not apparent when using thicker HFO, whereas some of the operational issues would include heating requirements, tank segregation, change in cylinder oil, changing certain engine parts and lower power output. 

The current demand for exhaust gas cleaning systems (scrubbers) means that some major manufactures are reporting long lead times for installation and shipowners are having to turn to other suppliers to ensure compliance by 1 January 2020. But whichever scrubber is chosen, owners must consider installation and operating costs, structural compatibility (including the space available for the system), the vessel’s trading pattern, alkalinity of the water, and any requirements for additional substances such as caustic soda or magnesium oxide.

Owners or their managers may need to carry out an assessment of any additional power needed in order to run the various scrubber related installations such as feed water and circulation pumps, dosing units, exhaust fans and monitoring equipment. In addition, there must be sufficient power to counter the back pressure produced by the scrubber unit, which may be considerable, thereby, in theory, marginally increasing GHG emissions. Also, it must be verified that the back pressure limits are not exceeded else the NOx emissions may be adversely affected.

Wash water from scrubbers is highly corrosive, and the effects are aggravated by high temperatures of exhaust gases. Materials and coatings for scrubber towers, internal piping, valves and waste storage tanks must reflect this need. However, little can be done to improve resistance to corrosion in the overboard distance piece which is located between the scrubber overboard discharge valve and ship shell plating. Due consideration must be given to durability, regular inspection and likely need for underwater repair to such parts.

Vessels using open loop scrubbers may not be able to trade freely as some ports or states may prohibit the discharge of wash water, in spite of the discharge meeting international standards. Hybrid or closed loop systems may therefore appear to be better options for trading in these areas. 

Scrubbers can break down or malfunction.  Should this happen, owners would need to notify both the flag and port states immediately. This will be perceived as a temporary non-compliance and the vessel would not be in immediate breach of the regulations. The vessel would, however, be expected to change over to compliant fuel immediately. If this is not available, the vessel must carry out repairs at next port or use bunker compliant fuel. Difficulty in repairing scrubber units whilst the vessel is located in remote regions should be anticipated. 

It is important that the crew is given training in not only operating the scrubber unit, handling sensitive control and monitoring systems and carrying out maintenance, but also safe handling of the chemicals used and scrubber waste. 

Gard concludes that whichever route an owner selects on the road to IMO 2020 compliance, the final selection should only be made following a proper study and full knowledge of the pros and cons of each option, achieved through dialogue with manufacturers, technical experts, charterers, bunker suppliers and classification societies.

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