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November 26, 2012 8:00 AM, EST

Opinion: 7 Ways to Keep Water Out of Diesel Fuel

This Opinion piece appears in the Nov. 26 print edition of Transport Topics. Click here to subscribe today.

By Joe Fazio

Director of Fleet Sales

Bell Performance

Anyone who works with diesel fuel — stored or otherwise — knows that water comes with the territory. Water can cause problems all year round, but when the weather turns colder, you can get new problems, as well as amplifications of other issues.

Here are seven “must-knows” about diesel plus water, including the tell-tale symptoms of water in diesel fuel. They all can save you headaches:

1. Water in diesel fuel can wreck fuel quality.

When you store diesel fuel, it undergoes chemical reactions that may turn the diesel fuel quality south. There are two main classes of chemical reactions that do this:

n Oxidation reactions happen when the fuel is exposed to oxygen (or oxygen-bearing substances).

n Hydrolysis reactions happen when the fuel is exposed to water.

Both cause chain reactions to happen in the fuel, which becomes darkened and fouled with gums, varnishes and sludge.

2. Water is the most important determiner of whether your tank stays microbe-free.

Bacteria and fungi in fuel are a nasty problem that turns up too many times, and once they’re in the fuel and multiplying, these microbes are difficult to remove.

Water is the essential element microbes need to establish themselves and multiply because they live in the water-diesel interface.

A tank with little water in it is at less risk for developing this problematic situation — and by problematic, I mean that once they’re in the fuel, the microbes are producing acids that wreck fuel quality, corrode tanks and clog filters. And they’re staying put until you spend extra money getting rid of them with a biocide.

3. Biodiesel blends are just as prone to the effects of water as straight diesel, if not more so.

Many companies are switching to 2% or 5% biodiesel blends, and in many states, you can put as much as 5% biodiesel into diesel without having to label it as such.

Biodiesel may reduce exhaust emissions, but it doesn’t help with water issues, and in some ways brings greater potential for water-based problems in biodiesel compared with regular ultra-low-sulfur diesel.

Because water contributes to instability, you need to recognize that the bio-based portion of the blend will have its own stability issues because it is more prone to instability caused by water. What’s more, microbes love feeding on biodiesel more than regular diesel. That means it’s even more important to keep water under control in tanks you know to contain even a small percentage of biodiesel.

4. You need to be able to recognize that you have water in your diesel.

Beyond the issues of darkened fuel and microbes, there are performance indicators that can speak clearly to water problems. When the engine tries to inject water with the fuel, you’ll experience erratic idling and performance, or the engine may cut out momentarily — particularly during acceleration. Any pressure indicators will show a varying of pressure in the common rail system if you have one. What’s more, you’ll get either black or white smoke during engine operation. These are all reliable symptoms of water in diesel fuel.

5. Newer diesel engines have more water problems than older ones.

Many newer diesel engines use common rail injector systems. 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. If you get a little bit of water in them, it can cause big problems — not the least of which is blown injectors.

6. Winter brings its own set of water problems.

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. Most diesel users in northern climates have encountered freezing 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 to control the water before it gets to freezing temperature.

7. There are cost-effective options for controlling water.

The simplest way to control water in an aboveground tank is to drain the water off. But users of underground fuel storage (such as gas stations or large, centralized fleet locations) can’t do that.

They can use water-coalescing filters, but those have to be changed.

There are fuel additives available from various manufacturers to help control water, however. These tend to fall into emulsifying and demulsifying-type options. An emulsifier will cause water to combine with the diesel fuel in tiny particles (micelles) that are suspended in the fuel until it passes through the injectors and into the combustion chamber for disposal.

For more significant water problems, a number of manufacturers also provide a chemical technology that absorbs water into phase with the fuel so that it is seamlessly bound into the water and does not drop out.

Whatever you decide to do this winter, stay on top of your water issues. By doing so, you’ll reduce unnecessary maintenance costs and preserve the life of your assets.

Bell Performance, Longwood, Fla., manufactures commercial grade treatments for diesel, ethanol, gasoline, fuel oil and power plant fuels.