A professional engineer who worked for DuPont as a consultant engineer for 28 years specializing in corrosion, Bob Tatnall is a subject matter expert on microbiologically influenced corrosion and sludge in diesel systems. He is the founder of Fuel Right, a company that produces the Fuel Right sludge/fouling/corrosion control treatment that includes different specialized variations designed to solve various types of problems that occur in distillate fuels (www.fuelright.com).
He says there are some main universal myths connected to treating diesel fuel. Here, he discusses those myths and the facts.
Myth: Good fuel quality will prevent problems.
Ultra-low-sulfur diesel (ULSD) is almost always of excellent quality when it leaves the refinery. The problem is that contamination happens during storage and transport, and this contamination is the source of many of fuel system problems.
Water - condensation and leakage - combines with common bacteria that come with the water to make sludge and biofilms - a complex aggregation of microorganisms growing on a solid substrate. The combination of biofilm and active bacteria leads to pitting corrosion.
Sludge fouling leads to plugged filters and fuel lines.
Myth: Biocides will sterilize the fuel and prevent problems.
The bacteria that form sludge and corrosive deposits are a type known as slime-forming bacteria. Just as bacteria are difficult to control in the body using antibiotics, these microorganisms are likewise difficult to control in nature using biocides.
Sometimes using a biocide triggers a reaction known as mucoid stage - sludge formation on steroids. There are cases where bacteria have been able to convert the biocide to a food that promotes growth.
Even in those cases where first treatment with a biocide seems to help, repeat or constant use of a biocide can lead to development of resistant strains. Biocides are, therefore, rarely a long term fix.
Myth: Unstable fuel is the problem so use stabilizers.
Fuel stability was a legitimate issue with yesterday's high-sulfur fuels. Today's ULSD is almost always rock-solid stable and making chemical stabilizers a waste of money.
The exception is in certain modern common rail diesel engines that impart high pressure and heat stress on the fuel, which can lead to filter plugging and black, non-slimy deposits in fuel tanks. There are chemical stabilizers that will prevent these situations but most common additives that say they stabilize fuel do not work at all against this particular problem.
Myth: Corrosion is not a problem in diesel systems.
The fact is, corrosion associated with biofilms in ULSD systems has become such a big problem that the petroleum industry has asked the ASTM (American Society for Testing and Materials) to form a task force to study causes and solutions. This insidious problem not only can cause leaking fuel lines and tanks, but also may damage tight tolerance surfaces in injector pumps, injectors and metering devices.
Laboratory studies have found that this issue can be prevented by using certain combinations of filming amine corrosion inhibitors.