Tuesday, Mar 13, 2018 at 11:29
There are raging arguments about whether the latest Ultra Low Sulphur diesel is more prone to water emulsification, or not.
I have seen some Steel Tank Industry experts argue it is a load of BS - but the majority of fuel and filtration experts, claim otherwise.
Even amongst the experts, there is still a lot of poor understanding about fuel and water emulsion, combustion, and the ingredients of diesel fuel.
The change in chemistry of the ULS diesel also resulted in a reduction in Interfacial Tension (the ability of two liquids to repel each other).
A lower Interfacial Tension allows the fuel and water molecules to bind together more tightly.
This results in a diesel/water emulsion with much smaller molecules of water held in the emulsion.
In addition - to counter the severe reduction in fuel lubricity caused by the removal of the sulphur, Lubricity Improvers are added to diesel today - along with detergents, rust preventatives, anti-wear additives, and combustion-improvement additives.
All these additives ASSIST in creating a better diesel/water emulsion, as
well!
This is because ALL of these ADDITIVES are SURFACTANTS.
Surfactants have one major property - they reduce the surface tension of water molecules, thus allowing the molecules to be absorbed better.
You see the surfactant properties of detergents in action, when you have a greasy surface with water droplets sitting on it.
The water droplets are large, because they have high surface tension, due to the grease.
Once you add detergent to the greasy surface, this reduces the surface tension of the water molecules, and they then form very much smaller droplets, and are totally absorbed into the EMULSION of the water, the detergent and the grease.
Not one of the current fuel filters on the market - despite their claims - will extract the water from the emulsion in ULS diesel - simply because the water molecules are too tiny to be filtered, and too tightly held in the emulsion.
There is only one filtering process that removes these tiny water particles from the ULS emulsion - and that process is called "coalescing filtration".
A coalescing filter utilises glass fibre or poly meltspun fibres to produce filtering surfaces that effectively alter and lower the angle that the tiny water droplets approach the filtering media.
The physics of this process are complex - but essentially, the reduced angle of approach by the tiny water particles results in much better water removal from diesel/water emulsions.
Coalescing filtration involves bulky filtration units that are generally unable to be fitted to smaller road vehicles, because of their physical size.
There are units available for trucks, but I have not seen any available for 4WD's.
They may be available, but I haven't come across them.
By far the finest and most accurate "write-up" about the emulsion problem of ULS diesel, is in the link below.
This very detailed and lengthy explanation is courtesy of a filter manufacturer.
Fuel filtration - protecting the diesel engine.
Cheers, Ron.
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