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IMO 2020 and diesel engines: powering up for a change

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Hydrocarbon Engineering,

The International Maritime Organization’s (IMO) new rules on marine fuels, which reduces the MARPOL Annex VI global fuel sulfur cap from 3.5% to 0.5%, came into effect from 1 January 2020. A prohibition on the carriage of non-compliant fuel simultaneously came into force.

The main aim of the new IMO 2020 regulation is to ensure that marine engines use a low sulfur fuel or marine distillate oils, which already comply with low sulfur regulations. The move is aimed at curbing sulfur dioxide (SOX) pollution produced by ships, and represents a significant and industry-wide event, which will likely have far reaching effects on the global shipping industry for many years to come.

SOX released into the atmosphere via a ship’s exhaust gas combines with NO2 – which acts as a catalyst – and other compounds to form sulfuric acid. This can contribute to the formation of acid rain and as a result cause damage to the quality of air, water, soil, food and life itself. It can also have a detrimental effect on the ozone layer, thereby contributing to global warming. It is therefore incumbent upon shipowners, vessel managers and crews to take the necessary steps to ensure they understand these issues, and that their vessels are provided with fuel oil that is suitable for use by marine engine power plants. If any problems arise, these must be addressed to minimise any impact.

There is an alternative option to low sulfur fuel, and that is to install post-combustion treatments such as a scrubber system to curb SOX. However, due to the large CAPEX requirement and time out of service for installation, only a small percentage of shipowners are opting for scrubbers, with most going for compliant fuels.

Fuel oils

As 2020 dawns, very low and ultra-low sulfur fuel availability has long been a concern, but it appears that suppliers have responded to the upcoming demand and supply will not be a problem. Possibly of greater concern is how long high HFSO will remain available or if the price of it will get closer to the low sulfur fuels, greatly affecting the return on investment (ROI) of those owners who opt for scrubbers.

Incompatibility of bunker stems may leave shipowners facing serious engine repairs, requiring vessels to be taken out of service and leading to a serious loss of earnings for operators. The mixing of non-compatible fuels can lead to the formation of sediment in the tanks which can block filters and purifiers. Add to that the ever-present risk of asphaltenes and cat-fines in certain fuels, and the stemming of good quality fuel and on-board management is essential if damage to the engines and fuel systems is to be avoided.

The nature and type of fuel oils that will be available are expected to differ significantly. A different mix of fuels – a variety of blends – will mean practical steps need to be taken to secure quality control. Good industry practice proposes developing a ‘bunker checklist’ to supplement the vessel’s own safety management system procedures – a list of checks and tasks from pre-bunkering through bunkering to the final completion and disconnection.

Fuel segregation between bunker sources will also become a feature of future operations until all sources of fuel can be proven to be stable, mixable and compatible with each other. Smaller bunker orders may become the order of the day to avoid mixing different fuel supplies. The monitoring of fuel will be increasingly important to avoid poor quality fuel reaching the engine, as well as running purifiers at their optimum settings, i.e. the right fuel oil temperature and the correct throughput (slow as possible). Checks by port authorities on compliance, especially in Emission Control Areas (ECA), will increase, and it will probably not be too long before on-board testing of sulfur content and emission measurement becomes the norm.

Technical challenges

Lower sulfur content in fuels will contribute to decreased levels of ‘lubricity’ in engines, contributing to increased wear and tear in fuel pumps and requiring additional maintenance of injectors as a result. These components have high tolerances, and most manufacturers of fuel pumps have already moved towards a higher material specification for their plungers, often using a diamond-like carbon coating to reduce wear. These coatings are extremely hard, corrosion resistant and have ultra-low coefficients of friction. They can also be deposited with a high-degree of control of the coating thickness.

If the decision is made to move away from high HFSO and scrubbers, the cleaning of pipes and storage tanks will need careful planning and inevitably result in substantial costs and down-time. Manual cleaning is time consuming, and again may result in down-time for the ship if not carefully planned. Recommended best practices is to flush through the system with distillate and afterwards dispose of it as waste oil. Note though that it is a very competitive supply, so it would always be prudent to consider quality and versatility as well as cost effectiveness of a potential service partner.

As stated earlier, some ships will limit the SOX air pollution by installing exhaust gas cleaning systems, also known as ‘scrubbers’. This is accepted by flag states as an alternative means to meet the sulfur limit requirement. These scrubbers are designed to remove sulfur oxides from the ship’s engine and boiler exhaust gases. A ship fitted with a scrubber can use high HFSO since the SOX emissions will be reduced to a level equivalent to the required fuel oil sulfur limit. The most likely ships to install scrubbers are the larger deep-sea vessels which have high fuel consumptions, and crucially have the space in the engine room to fit this equipment. 50 t/d seems to be an accepted cut-off point for fitting a scrubber and still obtain a reasonable ROI, say within 5 years.


What is the alternative to burning low sulfur fuel or using scrubbers? Converting engines to LNG will provide considerable reductions in fuel costs as well as reducing emissions, including SOX. It will first need to be determined if the existing engines can be converted to gas, or if new engines are required (dual fuel or pure gas). Finding space in the engine room for the storage tanks is key and, depending on whether the engines are converted to dual fuel or pure gas, there may still need to be a liquid fuel storage system as well.

Underpinning the aims of IMO 2020 is a need to improve fuel consumption for the ship operator, thereby keeping costs to an acceptable limit and reducing all exhaust gas emissions, including SOX and CO2. The implementation of advanced technologies such as ‘Eco Speed’ – a recent development in Royston’s engine/ fuel monitoring system – allows vessel operators and owners to determine the most economical speed against the best fuel consumption for any particular vessel.

There is an obvious need to pay close attention to the detail in the project management and planning of service jobs in meeting the requirements around IMO 2020. Careful review of the options (low sulfur fuel or high sulfur fuel plus scrubber or conversion to LNG) around practicalities and ROI should be made, with a project management team appointed to undertake the programme. Independent service providers such as Royston can be focused on providing a fully responsive engineering service that is geared towards meeting the specific timing, location and technical needs of a customer facing IMO 2020 compliance issues. The company can provide such project management in collaboration with the relevant engine or scrubber manufacturers, as well as providing supervision of installations and fuel system cleaning and tank segregation.

Written by Neil Graham, Technical Director of Royston.

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