Scrubber factsheet- technical point of view.

With the IMO sulphur cap regulations fast approaching, we take a look at some of the issues surrounding scrubber installation?


How labour intensive are scrubbers?


The equipment is designed in a way that allows for the scrubber to operate without any interference from the crew.


Are there any operational issues facing scrubber technology?


The technical issues to be addressed should include:



1.Damper control could be an issue particularly when on dry mode, to avoid exhaust gasses becoming trapped and going back to the engine(s). Dry mode is when the engine is operating on MGO or Low-Sulphur fuel oil producing exhaust gases which do not require scrubbing, the damper control directs the exhaust gases through the scrubber by-pass and similarly, when the scrubber is out of operation for whatever reason.




  1. When the scrubber system works in closed loop, an alkali such as caustic soda (NaOH) is needed to clean the water which is held in the wash water tank. In open loop systems there is no need for such water treatment.




  1. Care must be taken to ensure sufficient supply of sea water is available for the scrubber sea water pumps, which will necessitate the additional sea chest and overboard discharge dedicated to the use of scrubber sea water.




  1. Diligent preparation is required before commencing the retrofit work in order to avoid complications. It is important that all spare parts are available for example a small part such as a $500 temperature sensor might be crucial for the operation and if not available, this could disrupt work.


What are the various options available to owners to meet the sulphur requirements?


The alternatives are: to install scrubbers so that you can continue to use the heavy fuel oil; to use a very low Sulphur fuel (VLSFO) compliant fuel; to use MGO; to use LNG or other alternative fuels.


Who are the major scrubber manufacturers? Is scrubber technology their main focus or are they amongst a wider range of product?


Wartsila, Alfa Laval and Yara Marine currently have just a combined market share of just over 50% of in terms of supplying scrubbers.


Most of the scrubber makers already make various parts for ships, the business case scrubber model is maximum 5-years old and most scrubber manufacturers are currently working on developing this technology.


What type of scrubber systems are currently being installed?


The majority of scrubbers installed are using open loop systems. Hybrid scrubbers, that allow the flexibility to operate both open and closed loop systems, account for around 22% of scrubbers installed with only 2% selecting closed loop technology.


Are closed loop systems too expensive to consider?


Equipment and installation is about 30% higher than for open loop scrubbers. This technology can only be considered if the vessels are not operating worldwide (such as vessels on specific traders eg liners and passenger vessels) but at specific ports that can accommodate the scrubber waste or vessels that have extensive port stays, to allow time for sludge disposal.


Where can receive the exhaust sludge?


The water used by the scrubbers passes into a process tank, followed by a water treatment and then a sludge tank and finally a holding tank. The end waste product for a closed loop system will be in a powder form which can be discharged upon arrival in port.


What issues can we highlight


The most important issue is that the majority of scrubbers installed are not operated because of increased consumption issues. Therefore, owners will press the ‘start’ button in the last week of December. If we also take into account that this is during the Christmas holidays and that a few thousand vessels will be switching on their equipment after an idle period. The concern is that the scrubber manufacturers will not have the sufficient manpower to accommodate requests that whilst small, could be vital to the operation of the scrubber.


How many scrubbers have been fitted?


This year we have recorded just over 1730 scrubber installations. Around 70% of these scrubber system installations have been for retrofits with the rest being installed in newbuild vessels. A year-on-year increase of 360% in terms of retrofitted scrubbers.


What type of vessels are fitting scrubbers?


According to our records, around 37% of scrubber installations has been on Bulk Carriers, 24% on tankers with the remainder being fitted on to other vessel types such as container ships, cruise ships and Gas Tankers etc.


How long does it take to install a scrubber?


The estimated off-hire time necessary to install a scrubber is approximately 35 days.


Are the yards experiencing any delays?


At the time of writing scrubber installation is taking longer than estimated by as much as a week to ten days.  


Cost/ payback period.


This depends on the size of the vessel and where the scrubber is being installed. The installation costs, minus the cost of the scrubber itself can be anything between $1.2m-%1.6m for a capesize bulk carrier.

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