Slow steaming, the practice of sailing at reduced speeds, continues to play a crucial role in lowering vessel fuel consumption and emissions. Since biofuels and new fuel blends come at higher and more volatile prices, it’s also a cost-effective strategy as the marine industry decarbonizes. When its advantages are also applied to the fuel line through automatic flow control, it can improve separation efficiency as well as fuel efficiency – and thereby cat fine protection.

Decreasing flow rate along with speed

Without a doubt, slowing vessels down is among the most effective ways of improving their energy efficiency and long-term economy. At lower speeds, the engines require less fuel. As exemplified in a CE Delft study, a 10% reduction in average speed at sea can lead to a 27% reduction in fuel consumption. This why so many vessels derate their engines to meet the requirements of the Energy Efficiency Existing Ship Index (EEXI).

Yet focusing only on fuel consumption is a missed opportunity. Fuel cleaning can also benefit – if the flow through the separators is reduced proportionately. The separator flow has traditionally been set at 100% of the engine’s maximum fuel consumption (plus an added safety margin), but few vessels today run at 100% engine capacity.

Numerous sources, including engine maker guidance, point out the benefits of reducing flow through the separators. Simply put, decreasing the feed flow increases separation efficiency, as it gives the separator more time and better conditions for removing particles. As pointed out in CIMAC paper 51, “there is a large potential for increasing the separation efficiency by applying automatic flow control in relation to the actual fuel consumption.”

Fewer cat fines with less energy spent

Automatic flow control, e.g. with Alfa Laval FlowSync, synchronizes the feed to the separators with the actual engine load. By reducing the flow to the minimum safe rate needed, it concentrates the cleaning process on less fluid, giving the fuel more time to interact with the separator disc stack. This yields cleaner fuel in the end, with more cat fines and other harmful particles removed. The longer the fuel stays in the separator bowl, the better it is for the engine.

In addition, flow control removes a significant overlap in fuel processing. If the fuel is always pumped through the system as though the engines were running at full capacity, the cleaned fuel reaching the service or day tank will be more than the engine can use. Any excess will be recirculated to the settling tank – after which, it will have to be cleaned again.

This makes automatic flow control a true win-win. Not only does it maximize cat fine removal, it also further reduces energy use by eliminating unnecessary pumping and repeated separation. As a result, it secures the maximum benefit from slow steaming.

Insurance as well as savings

The benefits of automatic flow control are anything but marginal. When applying FlowSync to the example from the CE Delft study, where a 27% reduction in fuel consumption is achieved at 10% lower average speed, separation performance improves by 10–35% depending on the particle size in the fuel. In the field, Alfa Laval experts have seen separation performance increases of 50% when speed and fuel consumption are decreased further.

Given the high costs of cat fine damage and resulting downtime, the impact of this difference on a vessel’s bottom line can rival the fuel savings achieved through slow steaming. By ensuring that fewer cat fines enter the engine, flow control protects against wear to cylinder liners, piston rings and fuel injection pumps – and potentially catastrophic damage.

Get the most benefit with a holistic approach

Automatic flow control is among the best examples of taking a holistic, adaptive approach to the fuel line. It links the result – the amount of cleaned fuel needed by the engine – back to the beginning of the process, creating conditions for more effective cat fine removal while using less energy.

There are still more ways to improve the fuel line setup, such as running separator systems in parallel, which can reduce flows even further. The best way to take advantage of them is to work with a partner whose equipment and deep insights cover all fuel line aspects. Alfa Laval has been at the forefront of fuel line applications for more than 100 years, and we’re ready to help you achieve the most efficient and effective engine protection. Simply contact our fuel line experts.