VLSFO Quality Issue Continues After 50 Days of Implementation?


IMO 2020 sulfur regulations are in practice for 50 days now. Several organizations had put tremendous amounts of groundwork & preparations for a smooth transition from the Global 3.50 % wt sulfur limit to a 0.50 % wt limit. 

Here we present Viswa Lab’s latest technical update which discusses the VLSFO quality so far based on their fuel test results. 

Quality of VLSFO

Sulfur compliance 

  • Majority of the fuels tested were within the 0.50 % wt limits. 
  • There were about 2 % of the tested fuels that had sulfur beyond the specification limit. 
  • In this case, the majority of the fuels fell within the 95% ISO 4259 confidence limit levels. 

Total Sediment 

Offspec total sediment cases are on the rise from not just ARA ports but also from Singapore & Panama. In relation to this, an increase in the number of cases is seen where offspec sediment has caused purifier sludging, filter choking and clogging of drain pipes with sludge. 

  • A few of the vessels reported purifier sludging issues after storage of fuel onboard for a few weeks. 
  • In addition, over 10 % of the fuels tested had sediment higher than 0.07 % wt. With higher sediment there is an increased tendency to deposit sludge. 
  • In cases where the sludge samples have been provided to us, the sludge was found to be predominantly asphaltenic. 

Pour Point 

  • Over 15% of the tested fuels had pour points above 20 deg C. 
  • A few cases have been reported where the fuel in the tank got frozen before the fuel was ready to be transferred. 
  • The fuels had to be heated to a higher temperature than the wax formation temperature. 
  • It is becoming important to check the wax appearance temperatures (WAT) for VLSFOs to understand at what temperature the fuels may start depositing wax. 


  • While there were a few cases of offspec catfines, over 12 % of tested fuels had catfines over 40 ppm.
  • 50% of these cases belong to fuels supplied in Asian market. 


CCAI is a parameter that has been not widely discussed in the industry as there is wide range of opinions regarding its usage. 

Here is an excerpt from an engine manufacturer about CCAI values. 

“Straight run residues show CCAI values in the 770 to 840 range and are very good ignitors. Cracked residues delivered as bunkers may range from 840 to – in exceptional cases – above 900. Most bunkers remain in the max. 850 to 870 range at the moment.” 

  • It is seen that a lot of VLSFOs are with higher CCAI’s. 
  • When checked on the Fuel Ignition & Combustion analyzer these fuels were confirmed to have poor ignition and combustion properties. 

Viswa Lab is investigating over 10 cases of premature liner wear. At this point, investigations are continuing to find if it is the acidity, ignition properties or the cylinder lube that are a cause of the problems experienced. An update on this is expected to be released shortly. 


A lot of cases have the BDN (Bunker Delivery Note) viscosity different from the lab tested viscosity and the viscosity determined onboard using the onboard viscosimeter. It is very important that the viscosity of the fuel is checked before making any changes to injection temperatures. 

Acid Number 

  • An increase in the acid number values have been noted with a lot of VLSFO supplies.
  • Over 10% of the tested cases had acid numbers greater than 0.50 mgKOH/g. 

Chemical Contaminants 

Viswa Lab had issued a technical update in December 2019 about chemical contamination of VLSFO with a very high amount of ethylene crackers and other substances in the fuel. 

Read more: VLSFO Fuels Identified With High Contamination Levels in Major Ports

This trend has continued, and fuels contaminated with ethylene crackers residue, shale oils and some unknown oxygenated compounds are still seen. 

In one of the cases the chemical contamination was so high that it reacted with the paint and rubber gaskets causing damages. Viswa Lab assures to give updates as more and more samples come in. 

Please do not hesitate to contact Viswa Lab for any further questions about this technical update or any fuel related problems. wgfuels2020@theviswagroup.com  

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Source: Viswa Group


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