The Norwegian Maritime Authority (NMA) has deemed a loss of oil pressure, thanks to low levels of lube oil, to be the cause of the engine failure which left Viking Sky adrift at Hustadvika, a famously treacherous stretch of Norwegian coastline.
36 of the vessel’s 1,373 passengers were hospitalized after the vessel lost propulsion and suffered what owner Viking Ocean Cruises described as a power ‘blackout’, at the same time as it was battered by heavy wind and waves, causing severe rocking motions.
While the level of lubricating oil in Viking Sky‘s tank was within pre-determined safe range, the vessel’s low-level alarm did not sound until after the vessel had hit rough seas in the area. Once the oil shortage was detected, the system cut the engines to prevent a breakdown.
The NMA’s report indicated “the heavy seas in Hustadvika probably caused movements in the tanks so large that the supply to the lubricating oil pumps stopped. this triggered an alarm indicating a low level of lubrication oil, which in turn shortly thereafter caused an automatic shutdown of the engines”.
Cruise ship owner Viking Ocean Cruises will revise its procedures on all vessels “to ensure that this issue could not be repeated”, according to their own subsequent statement “we will continue to work with our partners and the regulatory bodies in supporting them with the ongoing investigations”.
The incident outlines the importance of lubricants, the choice of which is key to incident-free ship operation. Although the difficulties are well-understood in Norway, where 0.1% sulphur emission control area (ECA) regulation has already been in place for several years, the wider industry should expect many more loss-of-propulsion (LOP) incidents in the coming years.
With relatively few vessels fitted with scrubbers, a large number will be relying on supplies of blended 0.5% sulphur fuels, which refiners have indicated will, as many expected, be inconsistent from one batch to the next in terms of viscosity, cold-flow, and other properties. In a conference last week, Jerome Leprince-Ringuet, marine fuels global solutions manager at Total, indicated that “from next year we will grade low sulphur fuels based on the sulphur content, and no longer the viscosity – there will be one grade, 0.5% sulphur, and that’s it. These fuels we produce… will very dramatically from one batch to another”.
While various low-BN lubes have been brought out to match the properties of these new fuels, the particulars of their interactions will, necessarily, represent uncharted territory. “We will of course propose a minimum viscosity, but it comes with a cost, because what is not mainstream is bespoke” Leprince-Ringuet added “most customers will not be willing to pay for a specific viscosity on top of a specific sulphur content”.
As a result of the incident on Viking Sky, the NMA has drawn up a general safety notice about ensuring a continuous supply of lubricating oil to engines and other critical systems in poor weather conditions. “This should be done in cooperation with the engine supplier and, moreover, be included in the ship’s risk assessments in the safety management system” it said.