The presence of water in diesel fuel systems causes a variety of problems. Water rusts steel and iron components, forming loose particles of iron oxide. These rust particles can quickly clog fuel filters. Micron sized and smaller rust particles may pass though fuel filters to reach injectors, scoring surfaces and ruining fuel injection spray patterns.
Standing water at the bottom of a fuel tank provides an excellent environment for a wide variety of soil bacteria, entering through tank openings and during dispensing. Fuel and water form an interface that provides a comfortable home where bacteria can feed on diesel fuel in a moist environment.
These bacteria form a slime layer that often breaks free to rapidly clog fuel filters and disperse bacteria throughout the fuel system. Living bacteria pump out acids as a waste product, further corroding and damaging fuel system components. It must be noted that water in a fuel tank that gets sloshed around or simply pumped off the bottom, leaves the tank as visible floating droplets.
Revision This is a preview of the paper, limited to some initial content. Full access requires DieselNet subscription. Please log in to view the complete version of this paper. Addition of water into the diesel combustion process is a known method to reduce NOx and, in some implementations, simultaneously reduce NOx and PM emissions.
The very notion of introducing water into the cylinder of the diesel engine may sound controversial. After all, engineers have been taking great care to accomplish the exact opposite and protect the combustion chamber from water contamination, be it from the fuel or from water condensation in intake air coolers. The controversy around water addition is founded on the observation that water droplets impinging on the cylinder walls can immediately destroy the lubrication oil film.
This danger however, although very real, is posed exclusively by liquid water. Once water is evaporated, it can no longer affect the lube oil film []. Thus, water addition methods which ensure that water droplets cannot contact the cylinder liner surface may be considered harmless.
Considering the temperatures in diesel combustion, condensation in the combustion chamber is not possible at any time. When the engine tries to inject water with the fuel, you will experience erratic idling and performance, or the engine may cut out mometarily, especially during acceleration.
Any pressure indicators will show a varying of pressure in the common rail system if you have one of those. Not only this, but you'll get either black or white smoke during engine operation. All of these are reliable symptoms of water in diesel fuel. Many newer diesel engines utilize common rail injector systems. A poor description of such a system would be that the diesel fuel is cycled through a rail system that fits over top of the pistons, with the injectors hooked into the rail.
A computer controls which injectors fire at what time, for how long, and how much fuel they're injecting. Common rail injection systems operate at very high pressures. Just because we're out of the hot and humid months doesn't mean water problems go away. Water freezes in diesel fuel when the temperature gets colder. This is true more so in small systems i. Most diesel users in the North have encountered freeze problems at some point, whether it's frozen water in the fuel line or, more commonly, frozen water in the filter and in the bowl.
The only way to keep this from happening is control the water before it gets to freezing temperature. The simplest way to control water, if it's in an above ground tank, is to drain the water off. Damage caused by ice can be hard to correctly diagnose since the ice will melt and disappear long before a lab examination can occur. Soft Solids: Water is polar. Certain chemicals in additives are polar.
Hydrocarbons are non-polar. This means that water and polar chemicals are attracted to each other. In the presence of free water, the chemical molecules will sometimes disassociate themselves from the hydrocarbon chain of the additive and combine with water molecules to form a new substance. The new material is a soft solid that precipitates out of the fuel and can rapidly clog filters or create engine deposits.
See additive stability for more information. Microbial Growth: Like most living organisms, bacteria and fungi molds need both food and water to survive. If free water is present microbial growth can proliferate, creating slimes that foul your fuel and acids that corrode your tank and fuel system.
Fuel Oxidation: Free water accelerates the oxidation process and encourages the formation of acids, gums and sediments known generally as fuel degradation products. All diesel contains some percentage of dissolved water.
The water molecules remain part of the fuel until there are too many of them. The point at which the fuel can hold no more water is called the saturation point. The quantity of water in fuel is measured in ppm parts per million. As long as the water stays below the saturation point as dissolved water it is typically not too much of an issue. Significant problems start when water separates from diesel and becomes free or emulsified water.
Emulsified water is another form of free water; the droplets are simply so small as so well mixed into the fuel that they remain suspended rather than dropping to the bottom.
There are no "droplets" when water is fully dissolved in fuel. Water can come from a wide variety of sources, some of which can be extremely difficult to control. There are several methods for measuring water content in fuel.
Some are done in a laboratory, some can be done onsite. It is important to understand the type of information these different tests can provide. Perhaps the most common method for testing for water in fuel tanks is to "dip" the tank using a special indicator paste on a long dip stick. This method is fast, easy and can be done on site, it will tell you if there is free water in the tank bottom. Water monitors sensors can be installed inline and give reliable real time results.
They measure the dissolved water content in fuel and return the relative humidity of the diesel as a percentage. This test method will not tell you how much free water there is in the tank. The Karl Fischer titration method is a laboratory test used since for determining water content in a fluid sample.
The test is highly precise and requires only a small sample size. It detects even small amounts of dissolved water, down to about 50 ppm in diesel fuel. It can measure water content both below and above saturation level dissolved and free water. In laboratory practice it can be used to determine water saturation level of fuel under different conditions. While laboratory tests are typically more precise than field tests, they can be much less accurate.
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