SIX STEPS TO BETTER FUEL FILTRATION
Clean fuel is more important than ever with today's low-emission engines
Deborah Lockridge
Senior Editor
As emissions get lower and lower, injection pressures get higher and higher. Injection pressures as high as 30,000 psi are being used to gain more efficient combustion and lower emissions.
But to develop those high injection pressures, tolerances and clearances in the injection pump and injectors are smaller than ever. Particulate matter or contaminants in the fuel that easily passed through older mechanical systems can cause severe damage in the new systems. This is already true in the current 2002/2004 engines, and will likely be even more so in the 2007 engines.
That makes fuel filtration, and fuel cleanliness in general, more important than ever.
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1 Use the right filter
It's important to follow your engine OEM's recommendations regarding fuel filters and maintenance practices. If you're considering a replacement filter, make sure you understand how filters are sized and graded.
"Just because a filter is listed at 5 microns doesn't mean it necessarily traps all particles or contaminants that are 5 microns or bigger," says Gary Parsons, global OEM and industry liaison manager for Chevron Oronite. "First, not all particles or debris are spherical or uniform. Second, as a filter traps materials, the backpressure can increase and significantly reduce flow through the filter. The OEM knows which filter works best for a particular application. In most cases, they have run extensive tests to verify that the filter they select provides the best performance best matched to the needs of the equipment and service intervals."
Everyone is looking for ever-tighter fuel filtration, says Chris Greeson, senior technical services manager with Wix filters. But many people don't realize that there's a tradeoff involved – capacity.
The finer the filtration, the more contaminants the fuel filter catches, the faster it fills up and has to be changed.
"To counter short life, several options are available," says Steve Hardison, fuel product manager with Racor. One possibility is a larger filter with synthetic media. Another choice, he says, is a dual filter system, with a primary filter protecting the final "polishing" filter.
"Recent trends are to use a primary filter followed by a transfer pump, and then the final fuel filter," he says. "This configuration primes the fuel system, eliminating air from the system and avoiding rough idle at start-up. The tandem filters also have a long life when compared to a single filter system."
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2 Ch-ch-ch-changes
Change fuel filters at intervals prescribed in the owner's manual. Don't wait for a fuel filter to plug and impact driveability before changing it.
Of course, it's possible to get a load of dirty fuel that plugs the filter more quickly than expected, or in cold weather for ice or wax to plug the fuel filter.
"When I was in the field as a filter salesperson, I carried extra fuel filters with me in my company car," Greeson says. "When the weather got cold, I gave a lot of them away on the side of the road. I was surprised at how many over-the-road trucks don't carry extra fuel filters with them."
In fact, one of the top 10 reasons for needing breakdown service, according to the FleetNet America emergency roadside service provider, is replacement of fuel filters. You can save money and downtime by having drivers carry extra fuel filters and training them to change them properly.
Asphaltenes, which naturally occur in diesel fuel, can plug diesel filters very quickly, notes Racor's Hardison. "These tarry precipitates are always present, and the percentage in diesel fuel can be increased by engine heat. Fuel filters partially plugged by asphaltenes also remove water less efficiently. What this means is that fuel filters should be replaced according to the quality of the fuel, not the miles driven."
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3 Keep the water out
Water in your fuel system can lead to corrosion, and can reduce the lubricity of the diesel fuel and lead to higher wear rates in your fuel injection pump and other fuel system parts. Water is also a haven for filter-plugging bacteria and algae.
"Fuel/water separation has always been a challenge on diesel engines," says Wix's Greeson. "For some reason, just because of the way we store fuel, transport and handle fuel, it picks up moisture in all kinds of different ways."
That's why fuel/water separators are important. But you can't just assume that because you have one, you're protected. In order for a fuel/water separator to do its job, it must be drained regularly. "You can't look at a fuel/water separator too often," Greeson says. In some applications, such as construction, they should be checked daily. For over-the-road fleets, every time drivers fill up would be a good schedule, although Greeson acknowledges that in the real world, that may be overly optimistic. But once a week should be a minimum.
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4 Be prepared for cold weather
"Every October or November, the first time you get a cold snap, fleets call and say the fuel is gelling," says K.W. Gardner, fuels quality manager at ExxonMobil. Gardner says what's really happening in most cases is not a problem with wax crystal formation, which most people mean when they say fuel is gelling, but instead a problem with water in the fuel.
"If someone has a 20-degree night and starts having filter plugging, it's ice crystals forming, not wax," he says. It has to be about 10 degrees before wax crystals start accumulating on filters, and the use of additives can drop that temperature threshold another 15 or 20 degrees.
A good way to check whether or not it's a water problem is to take the filter out and drain it, then put it on a piece of filter paper or blotter that will absorb the fuel. If that blotter gets wet as the filter warms up, you'll know it's ice plugging the filter, Gardner says, because the ice will melt. If it's a wax problem, he says, that wax will stay in the filter.
"The obvious cure is, prior to the winter season, make sure the water is drained from the saddle tanks and the fuel delivery system," he says. And, as we mentioned above, make sure trucks are equipped with fuel/water separators and that those separators are checked regularly.
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5 In the shop
Many people tend to overlook the fact that contaminants and debris can enter the fuel system during maintenance procedures such as changing fuel filters, fuel lines or injectors. It's very important to clean the parts and the surrounding areas prior to removing and filters or parts. Try to operate in as clean an environment as possible. Use compressed air to blow dry or blow dust off parts, not a rag or shop towel. Rags and shop towels can introduce lint and fibers into the fuel system.
Racor's Hardison also suggests doing a postmortem analysis of used filters. "Open up used filters and see what the filter sub-assembly looks like," he says. "If it is black and oily, then the fuel was bad and the filter was used too long. If there is red sludge, look for a rusty fuel tank. Ideally, the used filter should look dark, but there should be no obvious thickness of contaminants."
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6 It starts with clean fuel
The biggest misconception people have is when there's a plugged filter, it's an issue with the filter," says Matt Stein, lead engineer for engine liquid filtration with Donaldson. "The filter was doing its job protecting the engine. People need to be more aware of what's going on with the fuel."
Buy fuel from reputable suppliers who practice good housekeeping with their fuel facilities and have a reasonably high turnover of fuel. If you have your own fuel supply, make sure you have a filter on the dispensing unit before it goes into the truck.
Train drivers that if a fueling location looks dirty, if it doesn't look like they change the filters on the pumps regularly, then the fuel's probably dirty, too. Drivers also should take care to ensure that the saddle tank is free of dirt and debris that could get into the tank while fueling.
Maintenance for Profit continued...
