Consider this list: a Washington state ferry ran aground; a Grumman Goose crashed shortly after takeoff; a bulk carrier with 20,000 metric tons of zinc lost all power at sea; diesel generators rolled on command but then dropped offline; and thousands of cars around Tampa stalled out.
The culprit wasn't a software fail or a ransomware attack. All these, and thousands more such mishaps, were caused by contaminated fuel.
It’s strange that something so vital as fuel is also something we rarely lay our eyes on. Fuel moves through pipes and sits in tanks until called upon. That means we need to rely on tests, best practices, and honest suppliers. Or we can wait until an engine coughs and dies.
The consequences vary from fatalities to equipment damage to very costly business expenses. According to Emerson Network Power, when data centers lose grid power and can't rely on emergency generators, losses average $7,900 per minute.
The reasons also vary. Some contaminants are natural. Consider gas-turbine power plants, which in international settings often operate on liquid fuels such as crude oil or refinery residuals. These plants can be at the mercy of creatures living in the seas millions of years ago.
Sea cucumbers – soft-bodies, glowing, slug-like creatures whose descendants still inhabit today’s ocean floors – are known for their ability to accumulate unusually high concentrations of vanadium in their tissues. As part of the ancient marine biomass that was converted over geologic time into crude oil, these organisms help explain why organic vanadium is frequently present in fuel.
When burned at gas-turbine temperatures, vanadium melts and oxidizes to form vanadium pentoxide, which is extremely corrosive to the hot-gas path. Vanadium, being oil-soluble, can't be removed upstream by water-based fuel polishing. Fortunately, compounds such as magnesium sulfonate, when injected into the fuel stream, combine with vanadium to form a compound with such a high melting point that it can't adhere to and corrode.
Boiler operators have long dealt with contaminants, but impurities in feed water claimed top of mind. One concern regarding fuel quality was the sulfur content of coal.
“It is well known to all intelligent engine drivers,” Indiana geologist E.T. Cox wrote in 1876, “that when sulfur is brought in contact with red-hot iron it causes it to fuse or lose its tenacity; thus, the sulfur from coal will destroy the grate-bars, fire-boxes, and sooner or later, the boilers themselves.”
Another concern was, and still is, the moisture content of piled coal, which, along with temperature and oxidation, can lead to spontaneous combustion.
One could look back and say coal- and wood-firing engineers had it lucky, given they had to deal with such a short list of fuel contaminants. Today's piston engines and turbines are so demanding, run so hot, and are so tight of tolerance, that the list of fuel trouble-causers is long.
Some contaminants are unwanted but almost inevitable byproducts of refining. These are catalytic fines, called “cat fines” in the trade: typically, tiny but very abrasive particles of aluminum silicate. Filters can screen out cat fines along with sand and grit, but that's not so easy with the tar-like fuels that big ships burn when at sea. It's called heavy fuel oil (HFO).
HFO is cheap because it's an unavoidable residue from refining. However, it's also very thick and contains chemicals and solids that vary with the crude oil feedstock and the specific refinery. Any operation using HFO needs to heat the container to liquefy it for pumping and combustion.
Some events are due to one useful product being erroneously added to another, yielding a blend that's not only useless but also harmful. In August 2023, a mistake at a Citgo fuel rack at the Port of Tampa in Florida sent gasoline tanker trucks to service stations with enough accidental diesel to pose engine problems for more than 2,000 gasoline-fueled cars.
I'm not a big believer in what's commonly known as Murphy's Law (“whatever can go wrong, will, and at the worst possible time”), but Murphy had his way here, since the bad blend came at the same time Tampa-area residents were desperate to gas up and flee Hurricane Idalia.
Another example of how two good products can combine to make a bad one starts with diesel exhaust fluid (DEF), an additive injected into late-model engine exhaust to cut nitrogen pollutants. DEF is a clear fluid, as is fuel system icing inhibitor (FSII), an additive for jet fuel that prevents stray water from freezing into ice crystals in fuel-handling components.
A potentially deadly mistake occurs in jet-fuel trucks that have a reservoir for the ice inhibitor FSII. Those diesel-powered trucks also have a separate DEF reservoir. Both fluids are clear and come in five-gallon containers. If a worker accidentally pours DEF into the ice-inhibitor reservoir, the urea-based DEF will form crystalline deposits that block filters and fuel lines, even in small amounts. Because the inhibitor is injected at the fuel truck's nozzle in such systems, sampling the truck's jet-fuel tank won't reveal the contamination. And the risk is real. A 2023 Federal Aviation Administration (FAA) bulletin about several DEF-caused aviation mishaps said: “In all cases, the affected aircraft experienced in-flight operational malfunctions, such as un-commanded in-flight engine shutdown, resulting in emergency landings.”
One benefit of icing-inhibitor blends is their anti-microbial quality. While it may seem odd that bacteria and fungi can survive in tanks of jet fuel and diesel, they actually thrive in the interface between fuel and the water that sits at the bottom of a tank. It's so common that fuel experts call those critters HUM (hydrocarbon-utilizing microorganisms) bugs. In any storage tank that's been in service for a while, there'll be water below the fuel as it vents to the atmosphere, and air brings humidity and condensation. More water may enter with a top-off from the supplier.
This deep, dark colony at the bottom of the tank, typically clustered around a stringy fungi called Cladosporium resinae, turns out to be slime that excels at clogging filters, injectors, and fuel lines. The HUM bug caused an engine shutdown that ran the Walla Walla ferry aground on Bainbridge Island, Washington, in 2023.
According to those who specialize in the care and feeding of mission-critical diesel generators, the fuel should be sampled and the machines run under load at frequent intervals. And they warn that the late addition of a biocide won't get rid of the goo already produced by earlier bacteria and fungal colonies.
Microbial colonies are accidental. Other contamination is probably traceable to bad actors doing business between the source and the end-user. Hundreds of ships refueling at Singapore and Houston in 2018, 2020, and 2022 reported damage from contaminated bunker fuel … contaminants that ordinary quality checks didn't detect. Phenol, styrene, and chlorinated compounds came up in later tests. Some ships had to proceed under reduced power, and a few suffered a complete blackout. Engine shutdowns in a crowded channel, near a reef, or in a harbor are a serious matter.
While the container ship MV Dali's deadly crash into the Francis Scott Key Bridge near Baltimore, Maryland, in 2024 wasn't due to fuel contamination, it does show how shutdowns leave a massive ship at the mercy of momentum, current, and wind.
Sometimes the precise cause of fuel contamination is unclear. After a Cessna airplane crashed after a takeoff in 1985, killing the pilot and all 16 skydivers on board, National Transportation Safety Board investigators found discolored fuel, so heavily contaminated it was black rather than the proper amber, in the right-side tank. The pilot had been warned of sugar contamination and a clogged fuel filter three days earlier but had continued flying. Some news sources pointed to sabotage, but that couldn't explain why the pilot disregarded timely alerts from his mechanic and an FAA inspector.
It remains unclear what went wrong in 2019, when almost $3 billion worth of crude oil was dispatched by the Russian pipeline company Transneft to Eastern Europe. Companies on the receiving end found it contaminated with such high levels of chlorinated organics that it was unusable unless greatly diluted.
Most ships burn the gummy, tar-like heavy fuel oil when at sea. HFO isn't commonly used to run gas-turbine power units. However, fuel contamination can still be an issue for units that rely on lighter liquids and gases. The owner of Hawaii's Hamakua Energy Plant has filed suit for damages arising from 2024 incidents involving two gas turbine units that burn biodiesel, alleging contaminated fuel. One turbine required $4.9 million in repairs.
Heat recovery steam generator operators have less to worry about from contaminated fuel than the gas turbines that feed them, since they run on turbine exhaust rather than fuel, but a contamination issue can arise even so. In 2008, RS Norek and TD Newbound documented a case of serious damage to a gas turbine and its heat recovery steam generator’s (HRSG) first-stage nozzles, concluding that an emulsion impurity in the fuel gas, and then exhausted into the HRSG, was probably responsible.
“All of my clients are continually concerned about the quality of the gas they are receiving and have to pay very close attention to pressures, filters, etc., as the pipeline suppliers too often send moisture, crud, and other contaminants along with the gas,” said Bob Sansone, CEO of the Power Gen & Construction Practice.
Think of it this way: Your organization may regard itself as fool-proof, but is it fuel-proof?