The IMO’s Marine Environment Protection Committee (MEPC) has published a review on the quality of marine fuels supplied, following a year since the introduction of the 0.50% sulphur cap.
In the document MEPC 76/5, the ISO committee in charge of marine fuel standard ISO 8217 provides an overview of the characteristics of very-low-sulphur fuel oil (VLSFO) supplied and used from January to June 2020.
The data shows that 2020 RM VLSFOs in comparison with 2018 HSFOs generally have lower viscosity, lower density, lower MCR and lower CCAI, higher net specific energy and a higher pour point, all of which, as anticipated before, point to VLSFOs in general tending towards being paraffinic in nature and having better ignition and combustion properties in comparison with HSFOs.
Compared to HSFOs, VLSFO characteristics show a wider viscosity distribution and generally lower viscosity and density. Combined with the possibility of a higher pour point, a greater awareness of the fuel properties as loaded, with regard to managing storage, treatment and onboard fuel handling temperatures is required.
The North of England P&I Club provided a list of key findings from the review:
- The average viscosity of a VLSFO is 105 cSt (at 50°C), much lower than traditional 380 cSt ‘high-sulphur’ residual fuels
- A broader range of viscosities – from as low as 10 cSt to over 380 cSt
- A higher risk of instability – ‘Total Sediment’ tests show a noticeable increase in the percentage of samples exceeding the specification limit of max. 0.10% (by mass)
- The average density of a VLSFO is 936 kg/m³ (in 2018 the average density for a ‘high-sulphur’ residual fuel oil was 988 kg/m³)
- Average sulphur content 0.45% (by mass)
- Cat fine content at slightly lower levels (18.2 mg/kg) compared with 2018 ‘high-sulphur’ residual fuel oils (22.3 mg/kg), with fewer samples found off-spec
- Increase in net calorific value (41.7 MJ/kg) compared with 2018 ‘high-sulphur’ residual fuel oils (40.3 MJ/kg)
- VLSFO products are tending to be more paraffinic in nature with higher pour points – presenting an increased risk of wax formation and solidification if correct temperatures are not maintained.
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