Diesel Hygroscopic

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DIESEL 101

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According to a

study performed

by the University

of Idaho in 1994,

it is estimated

that Low Sulfur

Diesel degrades

as much as 26%

in the first 28

days.

DIESEL 101 | REFUEL SYSTEMS

Diesel fuel is an organic compound that is used, not only

as a combustible, but also as a coolant and lubricant.

THE NATURE OF DIESEL

Made up of thousands of hydrocarbons, diesel fuel begins

to deteriorate as soon as it is produced. Today's ultra low

sulfer diesel fuel actually deteriorates at a faster rate

than traditional diesel fuel produced ten years ago due to

advances and changes in refining technology and

environmental requirements. This accelerated

degradation results in greater challenges when trying to

maintain fuel quality over time and can lead to

emergency/back-up generator failures.

Understanding how diesel fuel degrades and the factors

that contribute to its breakdown is essential to eliminating

single points of failure and protecting the critical

infrastructure on which we rely.

Equally important are the several factors that contribute to diesel fuel contamination.

These include:

Repolymerization and Oxidation

These are natural processes by which the diesel molecules lengthen and bond to produce

varnishes and insoluble gums. These particles then drop to the bottom of the tank to form

asphaltene (also known as diesel sludge).

Hygroscopicity

Low sulfer and ultra low sulfer diesel fuel is highly hygroscopic: it readily absorbs water

from moisture in the air. Water contamination in diesel fuel is of particular concern as it

can lead to the corrosion of steel components and the promotion of microbial growth.

Increased use of additives and the introduction of biodiesel, for the management of

mandated fuel sulphur reductions, have dramatically increased surfactant levels in diesel.

Surfactant levels are the measurement of the tenacity in which the emulsified water and

fuel molecules bond together. This change in fuel surfactancy has given rise to consistent

failures of congenital separation and coalescence media used to separate water from

diesel fuels.

Microbial Growth

Microbial growths that naturally occur in diesel can form a layer of organic debris that

adheres to the walls and bottom of the storage container as fuel ages. The growths survive

and flourish by living in or around the water line and feeding on the rich hydrocarbons

present in the asphaltene layer. Adding fresh fuel to a contaminated fuel supply

accelerates the development of these growths. Growths that break away from the sides

and float freely in the fuel can unexpectedly clog fuel lines or filters during emergencies.

These factors taken alone or together can interfere with the durability and performance of

back-up and emergency generators, and back-up systems as a whole

University of Idaho scientists have conducted tests to determine the timeline and

percentage of degradation of stored diesel fuel #2. The results of this testing indicated that

petroleum diesel fuel #2 degraded 26% after just 28 days of storage.

Just as hydrodesulphurization produced unforeseen side effects in diesel fuel lubricity,


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additives and biodiesel create a less obvious, but equally dangerous unintended outcome:

failure of existing fuel-water separators. In short, ULSD blends containing sufficient

lubricity additives to pass wear requirements, and ULSD blends containing biodiesel,

create conditions where commercial fuel-water separators fail to remove 40-100% of

fuel-entrained water. The insidious aspect of this side effect Is that there is no way for an

operator to know it is happening. - - Christine Stanfel - PhD - Ahlstrom Filtration - LLC

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Diesel Hygroscopic