How old is your kerosene?
What does concern Julia is that fact that the UK is now buying ships full of kerosene that may have been floating around the world for some time. “With less control over its quality and its source, are we importing problematic fuel?” she asks. “As the fuel ages en route, it could lead to larger molecules resulting in poor char values.
“When tested char values of imported fuel were as high as 25.2mg/kg,” said Julia. “On the other hand, a fresh sample manufactured at a UK refinery had a char value of 1mg/kg.” Typical char values taken from kerosene samples at fuel distributor’ premises were an acceptable 6.5mg/kg.
Part of the kerosene specification still involves a 24-hour burning IP10 test to determine the fuel’s char value. “This basic test is certainly not 21st century science but it remains part of the spec,” said Julia. “With the burnt bit of the wick scraped off and measured, it’s very subjective. The capability to find out what molecules cause char probably exists, but with kerosene used as heating oil being a very small part of a vast kerosene market for aviation fuel, checking out its properties is well down the pecking order.”
Kerosene used as aviation fuel has a different burning process which does not produce char.
Variable specifications
Variable kerosene specifications may have an impact on the one million plus appliances in which it is burnt here in the UK but when compared with the 31 million commercial flights per year that rely on aviation fuel quality, it is a drop in the ocean. With the performance of aviation fuel critical, the Energy Institute and Joint Inspection Group have recently produced a Standard to assist all parties in the maintenance of aviation fuel quality, from its point of manufacture through to delivery to airports.
With nothing of this magnitude linked to kerosene, what advice would Julia give to distributors who may face increasing queries over kerosene quality?
“Influenced by more imported material, fuel quality is certainly more variable. When distributors buy kerosene, char values are not always checked but this may become increasingly important to those with a high percentage of domestic customers. I would ask to see a fuel specification sheet and ask your fuel supplier whether the kerosene has been tested.
Storage conditions
“Kerosene is obviously affected by its storage conditions with neglect causing many of the problems we saw in the fuel samples. I’ve seen the source of some filthy fuel – very old tanks with prolific bug infections – lids left off and condensation running down the walls. Tank owners need more encouragement to ensure tanks are cleaned out and properly maintained. Although it’s an additional cost – and no one wants to pay more – a tank maintenance scheme is a good idea, especially if it stops the heating going off!”
FAST has its own AGA which has trialed biokerosene. “We know that our AGA is beautifully set up,” said Julia. “No matter how we try to choke it, we really struggle to coke it up. Again if an appliance – boiler or tank – is correctly installed, serviced and maintained it generally performs well. Many fuel issues can be managed but people need to buy into good housekeeping,” added Julia.
The FAST range now features over 40 fuel additives of which Exocet Cooker, Exocet Kerosene Lubricity Additive, Exocet Premium Heating Oil – with and without fragrance – are specifically for the kerosene market.