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FOBAS introduces Sediments & Wax Precipitation Point test for VLSFO

05 Dec 2019

The Lloyd’s Register Fuel Oil Bunkering Analysis and Advisory Service (FOBAS) on Wednesday (4 December) introduced an additional testing parameter for low viscosity VLSFO (very low sulphur fuel oil) bunker fuel due to operational concerns.

The SWPP (Sediments & Wax Precipitation Point) test is recommended to be performed where fuels viscosity fall between 20 & 100 cSt (@ 50 Degrees Celsius).

Observations from analysis investigations and feedback from a number of clients have identified that certain blends have produced excessive sludge at the separators, with the potential to cause blockages and fuel transfer and handling difficulties, according to FOBAS.

These fuel oils are generally heated to the advised purifier temperature and the flow settings adjusted corresponding to the viscosity and density of the fuel. Issues occur if the fuel precipitates wax and sediment at the operating temperature.

“Our investigations revealed that such fuels contain high temperature melting wax or sediments, which require elevated purifier inlet temperatures compared to the recommended temperature for the corresponding fuel viscosity,” it states.

“Keeping the temperature below a SWPP (Sediment & Wax Precipitation Point) temperature risks the generation of excessive wax at the purifier.”

More complex refining processes and the use of available and suitable blend stock have added a fresh complexity for ship operators to be alert to, says FOBAS.

Quality characteristics are already showing a much wider range of viscosities being supplied for the same ordering specification, which raises the need to be very aware of the characteristics of the fuel being supplied, but remaining still within the ISO 8217:2017 limits.

The increased use of hydrocracking processes is leading to the rise of more paraffinic (more waxy) diesel fuels which may precipitate wax when the fuel temperature (ambient and storage) drops below the measured parameter of CFPP or equivalent.

With the potential increase in paraffinic blends, the SWPP test would provide critical operational information to help set an optimum fuel temperature to avoid problems with the transfer and at the fuel purifiers.

Photo credit: FOBAS
Published: 5 December, 2019


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