DIESEL FUEL QUALITY: BUG ZAPPERS

With prices in the stratosphere and dancing around like a comet, you’d think fleets would be doing anything and everything to mitigate the exorbitant cost of fuel. Surcharges on the freight bill. Incentives for drivers to run efficiently. More precise route plans. The haranguing of fuel suppliers — and commodities brokers — to effect some predictability on pricing. Which is why the lack of attention to fuel quality is so mind-boggling.

Fleet supervisors dutifully break out a test kit to monitor the condition of their engine coolant, and routinely hire labs to analyze their oil. Yet most don’t think of checking their fuel for water and other contaminants, notes John Clevenger, director of global product management for Fleetguard, even though “it’s the primary cause of most on-vehicle problems.”

So you have a choice. You can take steps to improve the quality of the fuel you put into your tank, or you can add filtration on your truck to snare particles before they cause harm. Or both.

THE JOB OF FUEL FILTERS

Of all the contaminants that can cause problems in your engine, water is the most common. It gets into the fuel as warm air condenses on the cold metal walls of your tanks, or from poor housekeeping practices. Much of it settles to the bottom of the tank where it can be drained. Emulsified water, however, stays suspended in the fuel. That’s how it enters the fuel lines, fuel pump, and injectors, where it can cause corrosion and component failure.

“Water is not a good lubricant,” says Fleetguard’s Clevenger. “It’s worse with today’s low-sulphur fuel, because sulphur is the best lubricant in fuel. So you’re taking away the lubricating ability of the fuel, and at the same time the water in fuel is not lubricating.” The reduced lubricity can cause close-tolerance assemblies like plungers to seize up. Water can even blow the tip off an injector.

Water also is a problem because microbes, fungus, and bacteria can live there and feed on hydrocarbons in the fuel. These bugs can quickly plug a fuel filter, and maybe that’s the lesser of two evils; if they pass through, they can damage the fuel pump and injectors.

Asphaltenes are a contaminant that can be a special problem in newer engines. These black, tar-like contaminants are naturally present in diesel fuel, but they separate out of the fuel as it’s heated and cooled repeatedly, which happens on new engines that use the fuel to help cool the injectors. They are a common reason for filter plugging.

Fortunately, fuel filters trap most contaminants before they can do damage. Eventually, though, they become restricted and plugged. If they plug sooner than expected, chances are the problem is dirty fuel, not the filter. The worst thing you can do to address problems with filter plugging is to switch to a more “open” filter. It won’t plug as fast, but really you’re just pushing the problem down the road, when you face hundreds of dollars for injector replacement or thousands for a complete engine overhaul.

BULK STORAGE

Fuel can easily become contaminated in storage tanks, so if you have your own, take precautions to keep it clean. Sediment and other solids can get into tanks during the fuel transport and transfer process, or through tank breathers without proper filtration. Corrosion in the fuel tank is another culprit. Also, the fuel you have delivered probably isn’t as clean as you think. For example, you’ll never know what percentage is water — 2 per cent is not unheard of — unless you test it.

Testing, however, can be confusing. There are dozens of things you can test for, such as cetane, viscosity, sulfur content, water, sediment, density, cloud point, ash, distillation, and lubricity. Testing runs the gamut from simple, do-it-yourself kits that let you check for water or biological contamination on-site to independent labs where you can pay several hundred dollars for an exhaustive analysis.

If you’re concerned about contamination, the main things to test for are water, sediment/particulates, and perhaps biological contamination. Cetane is also a good idea. The American Society for Testing and Materials publishes voluntary specifications for such tests. It has a standard, D975-03, which prescribes the required properties of diesel fuels at the time and place of delivery.

It’s all well and good to install filters on your storage tanks, but you have to make sure those filters are kept in place and changed. Some companies have discovered filter media pulled out by employees who are impatient with having to change filters frequently, or with slower flow rates. This can be addressed through education, and also by spec’ing systems that accommodate high flow in the first place.

An often-overlooked source of fuel contamination is the tank “breather.” Diesel fuel tanks “breathe” from day to night, expanding and contracting as they heat and cool. So whatever is airborne in the evening hours will be drawn into the diesel fuel.

ON THE TRUCK

As the pressures in the fuel system have increased, engine manufacturers are calling for finer filtration, but they have taken various approaches in deciding how much filtration to require. Caterpillar is using a 2-micron secondary filter, while Cummins is using a 10- or 15-micron filter, depending on the engine. Other engine makers fall in between those two extremes.

“Something that is unique to fuel filters is they have a very wide operating range depending on the application,” says Chris Boesel, senior product manager for commercial vehicle filtration at Fram. “A primary fuel filter can be as wide open as 40 microns, while the secondary filters on Caterpillar engines are down to 2 microns. So put on a filter that’s designed for that application.”

If you don’t, he says, the filter can plug faster or allow damaging particles to get past it.

Many truck owners go beyond the standard filter, opting for additional filtration or fuel/water separation. Different fleets use fuel/water separators in different ways, notes Kathy Edge, marketing manager for Racor.

“A lot of fleets want it as their tightest filtration system,” she says. “They may want a 2-micron or 10-micron element in it, and rarely change their final filter, letting the fuel/water separator do the work. Other fleets use the water separator as a primary filter, with say a 30-micron element in it, and the on-engine filter as the secondary filter.”

Consider the ease of draining when spec’ing a separator. Donaldson, for instance, has a “twist and drain” system that makes it easy to accomplish with a 180-degree turn forward and back. Whether you decide to add fuel/water separators or other filters may depend on your duty cycle.

If you’re trading in your trucks every three years while they’re still under warranty, sticking with the OEM’s recommendations is probably fine, says Fleetguard’s Clevenger. “But if you’re keeping your trucks longer, the more you’ve done to minimize component wear, the better you’re going to be from a fuel system maintenance cost standpoint after the warranty runs out.”