Answer
Incompatibility & Sludge Formation: VLSFO blends are highly aromatic or paraffinic. Mixing different batches can trigger severe incompatibility, leading to asphaltene precipitation, which blocks purifiers, filters, and fuel lines.
Cat Fines (Aluminium and Silicon): Blended VLSFOs often carry elevated levels of highly abrasive catalytic fines. If purifiers are not operated in optimum configurations with minimized throughput, cat fines will cause rapid, catastrophic abrasive wear on fuel pumps, injectors, and cylinder liners.
Waxing and Pour Point: Paraffinic VLSFOs have high pour points. If tank heating temperatures drop below the pour point the fuel will solidify/wax, choking suction lines.
Microbiological Growth: Increased hydro-treatment during refining makes these fuels more prone to bacterial contamination when moisture is present in storage tanks.