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The diesel particulate filter (DPF) clock has been ticking for more than two years now. Fleets that bought trucks with EPA 2007 engines will be reaching their maximum 250,000 mile service intervals soon and need to be removed from their trucks and cleaned.

"I think this has missed a lot of people," says Frank Nicholson, director of maintenance at Olathe, KS-based TransAm Trucking.

"The dealer that we have, MHC, which is one of the largest PACCAR dealers in the nation, they weren't even thinking about it until we started pushing on it," he says. "And it took me a while to think about it, so I think that the industry as a whole is just dealing with the everyday fires and I think this is just going to be Pandora's Box when it starts hitting hard and heavy.

"Due to the fact that we have so many of these DPF-equipped units on the road, I have done my share of due diligence on the subject, and see some disturbing problems."

Where are the DPF cleaners?

Disturbing is putting it lightly. TransAm bought 300 2007 trucks, and when some of them started coming due for their first-ever DPF cleaning, Nicholson immediately started running into trouble.

"We're finding that, across the country as a whole, there are not but a handful of dealers that have any idea what they're doing," he says. "And I'm speaking specifically about our specific fleet, meaning a PACCAR product with a yellow engine.

"Not every one of the distributors is going to have one of these machines, so you're stuck trying to get it cleaned only where there is one," Nicholson goes on. "And a distributor's hours may be different from a dealer, which is 24/7. So you've got to wait until that place is open to get your DPF cleaned.

"And, the knowledge (of DPFs) across the country is very, very limited; it's not as simple as rolling in, pulling the unit off, sticking it on the machine and getting it cleaned, at least not with Caterpillar."

On the contrary, Nicholson explains: when a truck is taken in for a DPF cleaning, it must first go through an active or a forced regeneration, to burn off the material in the DPF. Only then can the filter element be taken off the truck and placed in the machine for cleaning. After it's cleaned, the DPF's flow rate must be tested to make sure it matches the manufacturer's setting. If it passes, it can be reinstalled and the truck can be on its way.

But here's the catch: the truck's computer has to be reset to show that the DPF has been cleaned. "If somebody doesn't reset that and you put the DPF back on then it's done you no good," Nicholson explains. "And we know that, because the ones we've cleaned, the dealers didn't know that it had to be reset. We were actually checking them, following them, tracking them, and the fuel economy didn't get any better, and I thought,

'What the heck?' Well, after we got to digging into it, we realized that our engine manufacturer said, 'Oh yeah, by the way, this is what you've got to do.' Not even everybody at the engine manufacturer knew! We went back and got them reset, and now the fuel economy's starting to gain on these units."

Thermal Events

You may be wondering what exactly happens when a DPF reaches the ripe old age of 250,000 miles. Frank Nicholson can tell you.

"We sat through those cleaning presentations, and one vendor in particular said that while most fleets are concerned about fuel economy degradation, what they don't realize is that the farther you run these DPFs without cleaning them, (the more) you're going to start to deteriorate the DPF itself," he says. "Then you take a chance that, when you reach a point where you can't drive the vehicle anymore and you go to clean it, it's not cleanable. Not necessarily because they can't get it out, but it's had so many 'thermal events' inside the DPF that it basically breaks down the inside of the DPF and you have to replace the whole thing.

"Now you're looking at several thousand dollars to replace the DPF instead of several hundred dollars (maybe a thousand, depending on who you go to) for the cleaning."

The problem became real for Nicholson earlier this year when he had his first "thermal event breakdowns."

"Some trucks have had failures," he says, "and it's been a progressive failure, meaning that it had some injectors or turbo take a dump, and it doses that DPF with either fuel or oil, so when that happens, that's not the normal process of soot and ash that the DPF is supposed to be handling. It now has oil or fuel in it. We've had some where they have done so many regenerations and have gotten to the point where they are restricted because they're at that 250,000 mile range, and we've had to pull them off and get them cleaned.

"That needs to be factored in," Nicholson stresses. "It's not just the fuel economy, although that's a big deal, your're also damaging the DPF."

"A Sophisticated Garbage Can"

After some early missteps, Nicholson has found what seems to be a winning strategy. He has persuaded his Kenworth dealer in Olathe, MHC, to purchase DPF cleaning units from Granite Falls, WA-based FSX, Inc. a process that has recently begun.

In late June, FSX co-owner Drew Taylor spent some time at MHC, where he trained technicians from both the dealer and the trucking company on the proper use of the new DPF cleaning machine, and he offers a description of the cleaning process that is both simple and complicated:

"A diesel particulate filter--also referred to as catalyzed regenerating technology--is the heart and soul of clean diesel technology," says Taylor. "What you have here is a very sophisticated garbage can, that's about the only way I can put it. It performs a very, very vital function, and it does it very, very well. It strips and burns off most of the hydrocarbon that is found in diesel emissions, and it does a very good job of protecting you and I, the truck drivers and the community at large from this very damaging, very toxic carcinogen. But there are some wrinkles that are starting to appear, that pose a threat to the bottom lines and the balance sheets of those that rely on this equipment--the fleets--that need to be addressed."

As Taylor describes it, the DPF operates in 'out of sight, out of mind' mode, and so drivers and fleet managers don't think about the build-up of ash inside the filter until the dash indicator comes on. The DPF can inventory a great deal of ash, but in time the ash reacts with the crystalline substrate of the filter, a ceramic wall that consists of billions of small pores between 11 and 15 microns in size.

"As long as these pores remain open the DPF breathes well," Taylor explains. "The hydrocarbon enters the DPF, and impinges itself on the substrate, and because it's such a high temperature--about 750 degrees Fahrenheit--it burns off there and leaves more or less harmless gasses to pass through to the other side. As long as that process goes on, everything's fine. But there are residues from the engine oil that do not pass through, and do not burn off, that continually, at a linear rate, build up. This is the ash."

Ash contains potassium and the calcium. "Those are the real bugaboos," says Taylor, because, between them, they cause the pores in the DPF to glaze over with a glass-like substance and clog up.

"So, it's very important to get the ash out, sooner than later," Taylor goes on. "You don't want to just sit there and let it build up, or you place your whole DPF pool at risk. The fleet owner needs that like he needs two heads. He's suddenly presented with a gigantic cost that he did not anticipate as he starts to see these DPFs go down right and left.

"There's a false sense of security out there, because people think they're getting their filters cleaned by the various processes that are out there, but, unfortunately, the processes that first came on the scene leave a lot of ash behind, and this process of 'sintering' goes on unabated," he explains.

Cleaning Solution

Frank Nicholson has considered cleaning machines from the three manufacturers on the market--SPX, Donaldson and FSX--but chose FSX because their machines have been cleaning DPFs on transit buses since 2005.

At his request, MHC Kenworth has installed its first FSX unit in Olathe, and will soon be installing a unit at a Texas dealership that also serves TransAm. After that, MHC will install the units in other facilities as demand increases.

"We don't have an option," says Nicholson. "We've already had some of these units that have failed, that have been cleaned, and it's better to be proactive and have scheduled downtime than it is to have unscheduled downtime. On-time is what we're all about. We're a 100 percent refrigerated carrier, and we don't have the option to have late loads."