The boats cruisers use to follow their dreams, whether sail or power, usually rely on diesel fuel. It is the lifeblood of engines and generators, and often the one component that receives the least amount of care.
Microbial contamination of diesel fuel is a fact of life. It is not a matter of ‘if’, it is just a matter of ‘when’. As a general rule, whenever diesel and water come into contact in a fuel tank, microbes will start to grow. Moisture entering through the fuel tank vent and condensation inside the tank are contributors to this problem. Water is heavier than diesel fuel, and therefore accumulates at the bottom of a tank.
The water at the bottom of the diesel tank serves as a perfect medium for microorganisms to live in. And the hydrocarbons in the fuel are a tasty food source for many species of microbes. The result is a proliferation of bacteria and fungi feeding at the fuel/water interface. In addition, microbes can adhere to the tank walls and can grow fast enough to quickly coat those walls with a slime of organisms. Whether it is bacteria, mold or other fungi, unless this growth is held in check the result will be clogged filters, tank sludge and injector failure.
Inorganic debris such as rust, dust, sand and other particulates usually find their way into the fuel during the transportation and delivery process from the refinery to the fuel pump. This dirt is abrasive and causes excessive wear and tear on engine parts.
Naval architects understand this problem. Therefore, they design fuel tanks with pick up tubes many inches above the bottom of the tank. This keeps the sludge, water and particulate matter that settle to the bottom from being sucked up into the fuel supply line. Eventually the height of the contaminants will rise to a point above the pick up tube and get pumped through the fuel system and into engines or generators. The immediate result is that the primary and secondary fuel filters get plugged and engine performance drops since the engine is being starved of fuel.
The remedy is a diesel fuel maintenance program, and its cornerstone the installation of an onboard system that will polish the fuel and clean the tanks. Fuel polishing systems can be powered by direct current or alternating current, depending on the available electrical supply aboard the boat.
The best tank cleaning systems are multi-stage systems that use a variety of inline fuel conditioning and filtration technologies and don’t rely on just one process, such as a centrifuge.
The first phase of fuel polishing is to pass the fuel through a magnetic conditioner. The permanent magnets generate a very weak electrical field that separates the molecular bonds holding together the large clusters of hydrocarbon contaminants and disperses them. The next phase is a water separator and particulate filter, which removes free water, sludge, organic and inorganic matter greater than 30 microns in size.
The final step is a multi-pass filtration process which agitates the fuel and removes the organic and inorganic debris floating in the fuel, as well as any emulsified water. This extensive filtration process, also called dialysis, removes particles down to a diameter of three microns or less. To put this in perspective, a human hair has a diameter of 80 microns and particles between five and ten microns in diameter can cause problems in fuel systems.
What about Diesel Additives?
During the fuel polishing process an additive is used to dissolve the sludge and slime that accumulates on the walls and baffles of tanks. This procedure assures that mold and bacteria are removed from all tank surfaces. Once the tank is cleaned and the fuel is polished, an additional dose of fuel additive is mixed into the tank to help guard against future microbial contamination. Use of a full spectrum additive during this step will also add lubricity to the diesel fuel, prevent corrosion, reduce carbon build up and stabilize the fuel. Each time the fuel is topped off a new dose of additive is mixed with the fuel to control any contaminants in the fresh fuel.
How often should you Clean your Diesel Fuel?
At a minimum, fuel should be polished every six months. Ideally, fuel polishing should be completed every time new fuel is bunkered. Vigilance is the watchword to combat fuel contamination, and trouble-free diesel engine operation is the reward.