Sterol glucosides and monoglycerides are natural materials found in biodiesel (FAME) derived from plants. Once they have precipitated out of the fuel, these compounds will not readily dissolve back into solution with the bulk fuel unless the temperature is raised to around 40°C. Precipitation of sterol glucosides and monoglycerides is accelerated at lower temperatures, but, as experienced in 2019, can also occur at typical ambient temperatures during summer months.
After much discussion with industry partners and further research, FAST concluded that the most likely cause of the spate of fuel filter blocking issues was the agglomeration of these FAME component precipitates. Fuel Testing
Approximately 15% of the fuels tested were in poor condition by appearance alone - they had free water and sediment visible and microbiological growth was observed.
It was concluded that filter blocking may have been due to microbiological growth and/or particulate and water contamination resulting from poor storage conditions.
As the fuel filter blocking issues became more widespread and fuel samples were continually being received without any obvious or consistent divergence from specification, FAST began to routinely measure the particle count distribution. FAST exocet ® Fuel Additive Field Trials
FAST supplied dispersant-containing fuel additives for customers to carry out field trials with end users who were experiencing serious fuel filter blocking issues.
The field trials were immediately successful and exocet® Sludgebuster became the first additive recommended to treat the problem.
It also became apparent during 2019 that, those customers who had been routinely using exocet® Gas Oil Supreme prior to the FAME content increase, did not experience any fuel filter blocking issues even though their near neighbours were. exocet® Gas Oil Supreme, exocet® Gas Oil Conditioner and exocet® Diesel Supreme became the additives recommended to prevent the problem by routine addition to the bulk fuel.Additional Laboratory Testing
Samples that had been received in August 2019 were re-visited in December. Some were now found to be hazy in appearance, having been recorded as “clear & bright” initially. This indicated a solid material was precipitating out of the remaining fuel sample.exocet ® Fuel Additives
FAST’s exocet® fuel additives containing dispersants and deposit control additives which lead to free-flowing fuel are: exocet ® Sludgebuster
exocet ® Diesel Supreme
exocet ® Gas Oil Supreme
exocet ® Gas Oil Conditioner XO1258GO
These exocet® additives will treat and prevent filter blocking problems caused by recipitated biodiesel (FAME) particulates. FAST recommends the use of a 10µm filter on all bulk storage tanks.The Economics - Replacement Filters vs. Fuel Additives
exocet® fuel additives, at the recommended dose rates, add around one penny to the price of a litre of fuel.
In this context, we ask you to consider the following:
- the price of new fuel filters for your vehicles
- the price of new filters for your bulk fuel storage tanks
- the labour charge to change these filters
- the number of times fuel filters were changed during the peak of the crisis
- the cost of downtime: people, lost production
No matter what your volume of fuel use, using fuel additives regularly is far more cost-effective than continually replacing filters.The information above is an extract from the recently published Fast exocet Biodiesel, Particles and filter blocking report. If you would like a copy of the full report please contact the AF Fuel department who will be more than happy to assist.