Bunker Oil Blending – an Inline Viscometer Application

Bunker Oil or Heavy Fuel Oil (HFO) is a residual oil of the crude oil distillation or from crackers with a high viscosity from 300 up to 30,000 cSt at 100°C. To use this HFO for marine diesel engines the bunker oil needs to be diluted to the specific viscosity, the Marine Fuel Oil (MFO), with diluents (also called cutter stocks). Usable diluents range from kerosene to visbreaker vacuum distillate, but most used are Light Cycle Oil (LCO), Heavy Cycle Oil (HCO) or slurries of the Fluid Catalytic Cracking (FCC).

Depending on the technical equipment on the ship (storage temperature, maximum pump viscosity, pre-heater temperature and injection nozzle viscosity) the specification of the MFO allows a viscosity of between 30 and 700 cSt at 50°C.

With the ViscoScope inline viscometer from Marimex (Germany) the blending process will be controlled to meet the specification reliably and accurately. As the HFO and the diluent may have different temperatures the viscosity needs to be temperature corrected to a specific temperature. The ViscoScope transmitter series VS-4450 calculate such temperature compensation according to ASTM D341. Via analogue outputs or a serial interface the measured and calculated values could be collect by a process control system.

The sensor VA-300L is mounted into the pipe after a static mixer or the pump to ensure that the fluid is well homogenised. On customers request the probe can be coated with teflon. The sensor is available with flanges from 2“ ANSI / DN50 DIN up to 8“ / DN200. Every VA-300 sensor could be provided in a intrinsically safe version for installations in a hazardous section.