Understanding Marine Diesel Fuel

in Fuel

Trawler and motor yacht owners love the sound of our diesels; like music to our ears. The diesel power plants are the heart of any vessel.

But problems can occur with diesel fuel stored in your trawler's fuel tanks, that will affect those diesels?

It is crucial to know what diesel fuel is to begin with. Diesel fuel is refined from crude oil. In petroleum refineries, crude oil is heated, and various hydrocarbon molecules are extracted to create the fuel. Diesel fuel is much heavier than gasoline and vaporizes much more slowly. It's often referred to as "fuel oil" because of its consistency. Oftentimes forgotten, diesel is an organic matter.

"Provide a diesel engine good fuel and it will last forever and a day." This old saying is less of an exaggeration than you might think. Repair statistics record that 90% of trawler diesel engine problems result from contaminated fuel. The promise of doing away with 9 out of 10 potential failures should put fuel-system upkeep at the top of your list.

The most frequent signals of fuel contamination in a trawler are clogged filters, and reduced engine performance. However, the lack of these circumstances does not necessarily suggest that your diesel fuel is not contaminated. In fact, it is probable that every trawler's fuel is moderately contaminated. Fuel pick-up tubes, where the engine pulls fuel from the fuel tank, generally sit about 3/4 of an inch off the bottom of your fuel tank floor. This position is designed to protect the engine from contamination that has settled to the bottom of the tank. Consequently, you may never recognize that you have a diesel fuel contamination problem until the fuel is agitated in some way - such as when you are in rough waters in your trawler.

Moisture can get into trawler fuel storage tanks in different ways - by condensation of humid outside air, during transport from refineries to distributors, by leakage through faulty fill hoses or vents and by careless handling. Water can cause injector nozzle and pump corrosion, microorganism growth and fuel filter plugging with materials resulting from the corrosion or microbic growth. Your trawler's fuel/water separators should be checked often for water and drained as necessary. In cold northern winters, ice formation in fuels containing water produces severe fuel line and filter plugging problems. Regularly getting rid of the water is the most effective means of preventing this problem; however, small amounts of alcohol may be used on an emergency basis to preclude fuel line and filter freeze-ups.

Regular diesel fuel filter exchanges and the expensive and time consuming project of cleaning diesel fuel tanks have become standard routine maintenance instead of waiting for a warning signal for diesel engine failure. Diesel fuel filter elements should give you several hundred hours or more and injectors some 15,000 hours. However, since diesel fuel is inherently unstable, solid matters begin to take shape and the gathering tank sludge will finally clog your diesel fuel filters, maybe ruin your injectors and cause diesel engines to smoke.

Diesel Fuel stored in trawler tanks for long periods (six months and more) requires special care. This diesel suffers from multiple problems that influence its quality. The presence of free water supplies the platform for microbiological growth that result in the formation of slime and acids inducing corrosion of metal surfaces such as storage tanks, pumps, injectors, etc. Left neglected this water layer will entrap sludge and become the breeding ground for microbes, fungus, yeast and more. This toxic mix produces acids that compromise the integrity of your storage tank, lines, pumps, fittings and worse, diesel machinery.

Another crucial factor leading to diesel deterioration, is mechanical stress created by heat and pressure of pumps. Since most diesel engines return substantial amounts of fuel back to the tank, it is easy to see that the engine itself adds to fuel deterioration.

Microbes in the form of bacteria and fungus are present in all diesel fuels. Extended periods of fuel storage can create ideal opportunities for microbes to grow in fuel tanks. The first suggestion of microbic contamination is mucous-like accumulations on fuel-filters. Bugs can only be removed from the fuel system by polishing or by preventing their occurrences by use of a diesel fuel pesticide such as BioBor. I highly recommend it.

Should you use diesel fuel additives? There are plenty of additives on the market today that are designed to improve the operation and efficiency of diesel fuel. I opt to use Marvel Mystery Oil. However, if you use the proper additives, you can achieve peak performance from your fuel every time.

Most trawler fuel systems have primary and secondary filtering systems installed; Racor is a good example. Every time the diesel engine is operated, the diesel is polished by filtering and returning fuel back to the storage tanks. A separate polishing system can also be installed that polishes the fuel independently of the engine operating.

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Understanding Marine Diesel Fuel

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This article was published on 2010/04/14