One year on since the shipping industry transitioned to very low sulphur fuel oil (VLSFO) and vessel owners are encountering more handling issues and engine problems than had been expected.
During Riviera’s Fuel testing in a new age webinar, on 26 November 2020, Innospec technical services engineer for marine fuel specialties Joshua Townley said there have been more engine failures and issues since the industry-wide switching to VLSFO took place.
“No one anticipated the increases in engine damage,” said Mr Townley. “Some are still suffering ongoing issues, with most damage occurring when using higher density fuels with high viscosities.”
Of all the issues and faults encountered in 2020, almost 60% are from separation failure, with another 18% from blocked filters, 14% engine damage, 7% solids in storage tanks and the rest from cold flow (or low viscosity at low temperature) issues.
“There have been more fuel handling problems on ships, especially with lower viscosity VLSFOs, mostly through blocked filters and separation failure,” said Mr Townley.
Engine problems include piston ring breakage, injector failures, liner wear and scavenge fire.
Fuel handling issues can include purifier breakdowns and fuel starvation, while storage issues can involve excessive sludge, wax formation and comingling of different fuels with varying chemical composition and qualities.
“No one anticipated the increases in engine damage”
“Separation failure is seen across all density ranges, most commonly at lower densities,” said Mr Townley. “Engine damage occurs when using higher density fuels and solids in tanks seen above densities of 940 kg/m3 and filter blocking is seen across all density ranges,” he explained.
Some of the reasons for handling issues and engine problems come from the higher paraffinic (alkane) content or single-chain hydrocarbons in VLSFO compared to HFO.
“Typical blend ratios of modern residual marine fuels show a much higher proportion of the saturate (paraffinic) component in combination with aromatics (such as benzene), which are structurally dissimilar, causing separation and instability,” said Mr Townley.
“Paraffins are prone to rapid oxidation when heated, or drop out as wax in low temperatures,” he said.
This leads to cold flow issues and deterioration of VLSFO over time. Lower aromatic content in VLSFO means asphaltenes begin to agglomerate and increase in size, forming sludges in tanks and attributing to poor combustion,” said Mr Townley.
He said additives, such as Octamar, will prevent oxidation of paraffins and reduce growth of asphaltenes.
Intertek Lintec global technical manager Tracy Wardell said some of the problems shipowners have faced with VLSFO is down to where they bunker.
She said some issues come from regional differences in VLSFO quality and attributes including viscosity, density, pour point and flash point.
“Ships have to cope with variable bunkers and costs,” Ms Wardell said. “There are many instances where the fuel did not conform and there were then issues on board.”
To date this year there have been issues with piston ring failure and cylinder liner damage, deterioration of rubber seals, deposition of solids on cylinder heads and unusual fuel odours.
There are continuing problems with sludging during purification and microbial contamination.