Diesel Fuel Contamination

Maintaining diesel fuel quality, preventing diesel fuel contamination and assuring cleanliness has never been easy. To give you an idea of how long the industry has been dealing with this issue, a Caterpillar Operators Manual published 90 years ago stated “dirt and water causes 90 percent of all the problems with diesel fuel systems.”

Diesel contam.In 2006, the U.S. Environmental Protection Agency mandated the shift from low sulfur to ultra low sulfur diesel (ULSD), reducing sulfur in the fuel from 500 parts per million (ppm) to 15 ppm.  After the transition to ULSD people started complaining about higher than normal corrosion in diesel fuel storage tanks, fuel dispensing pumps and related piping configurations.

One of the concerns with ULSD fuel was lack of lubricity. The cheapest way to remove sulfur during refining involves hydrotreating, a process that removes sulfur and cetane by treating it with hydrogen. Unfortunately, hydrogen is highly reactive and also reduces the lubricity, or lubrication properties, of the end-product.

Sulfur serves as a lubricating medium and the reduction of that sulfur (from 500 ppm to 15 ppm) causes a reduction in lubricity.  After numerous complaints, refiners started adding lubricity additives to the process to compensate. Many people who service equipment still complain of evidence of poor lubricity, especially in older engines

Diesel is a perishable commodity

Even if everything else is managed correctly, when you store diesel over time, chemical reactions can compromise the fuel’s quality and cleanliness. There are two main types of chemical reactions. One is oxidation, which occurs when the fuel is exposed to oxygen or oxygen-bearing matter. The second reaction is hydrolysis, which occurs when the fuel is exposed to water.

Both reactions produce chain reactions within the fuel, resulting in a fuel that appears darker in color and more translucent. Contaminates produced under these conditions include varnishes, gums and sludge that separate out of the fuel and settle.

Most all diesel fuel, including ULSD, has a shelf life from three to six months. This can be extended by adding stabilizers, restricting water intake through proper storage, filtration and restricting heat.  But diesel is far more susceptible to water solubility issues than gasoline.

Water + diesel = microbes and sludge

The presence of water in diesel fuel also adds to the problem of microbial growth.  Fungus, mold and other types of bacteria can flourish and use diesel fuel as a food source. The residue and resulting bonding from this bacteria damages fuel quality, clogs filters and can lead to equipment failure.

Diesel sludgeDiesel fuel will always contain a certain level of water content. The objective is to keep this water content within suitable limits, which is well below the saturation point. Since some water is inevitable, one solution is a routine treatment of fuel storage tanks with a biocide treatment program to kill tank bacteria microbes.

Filter to ISO fuel cleanliness specs

Note, however that this fuel may pass through three or more storage tanks where contamination can occur before it reaches your equipment. Because of this scenario, it is absolutely critical that the equipment owner address fuel filtration at the inlet and outlet of any storage tank within their operation. The goal for fuel cleanliness entering and exiting a bulk fuel tank (stationary or mobile) should meet ISO Code 4406 for contamination.

With proper filtration, this spec can be achieved. The recommended ISO values for Code 4406 are 18/16/13. For example: An ISO cleanliness code of 18/16/13 refers to the following: 18 = 4 micron particles, 16 = 6 micron particles, and 13 = 14 micron particles. Adding filtration at the inlet and outlet points just makes sense. It directly impacts fleet reliability and repair costs.

New rules will make fuel quality even more important.

On July 13, 2015, federal regulators formally published their Phase 2 GHG (Green House Gas) Emissions Reduction Proposal that will tighten greenhouse-gas emissions for trucks, improve their fuel economy and regulate trailer efficiency for the first time.

The tougher standards for medium and heavy-duty trucks would not be phased in until 2021 through 2027, but unless there is a drastic re-design of the diesel engine and its fuel injection system, clean fuel will become even more important in trucks than it is today.

Via Equipment World

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