The Cleaning Crew

TransAm Trucking opens the 'Pandora's Box' of DPF cleaning

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."

In the end, Nicholson felt the most comfortable with the FSX machine because it uses "Knife Technology," in which an air knife blows through every single one of the 6,000 tubes in a DPF, from both sides of the unit. To Nicholson it's all about the efficiency of the filter after it's been cleaned.

"That's another thing that I think most people don't realize: if they don't pay attention to what they're really doing and don't do their homework and find out how efficient that (cleaning) device is before they get that DPF put back on, there are several different things that could be affected," he says. "One is fuel economy. Two is the second life of that DPF--in our case, it's a 200,000-250,000 window of life--but if it's not cleaned to 90 percent or better efficiency, we're not going to get that; in fact we'll get far less, in the second life. And then third, if it's not cleaned properly, you're going to get more of these thermal events that are happening, and then you have to look at not just cleaning the DPF but having it replaced."

How Clean Is Clean?

Would you be able to tell if a DPF was really clean? There are ways to tell, and, according to both Nicholson and Taylor, a DPF should never be returned to a truck without first being fully tested and certified.

"A service provider must have three things, to be able to successfully service a fleet," says Taylor. "He's got to first and foremost be able to clean to OEM spec'. That means you've got to hit all 6,000 holes, from both directions. And you've got to clean them to as close to OEM spec' as you possibly can. In our case, it's been proven that we're into the high '90s on that score, if we get the filter early in its life-cycle.

"The second thing is, you've got to be able to apply that level of cleaning to all the different shapes and sizes and makes of DPF that are out there, both on- and off-road, and do it with a fingertip control," he says. "If you end up with a technology that varies widely and wildly, from how it cleans a small filter versus how it cleans a large filter, you really don't have anything because it's inconsistent.

"The last thing is, you've got to be able to certify that level of recovery, to the degree that your customer knows that he's got a good chance of an excellent service life at a certain level."

The FSX testing and certification process follows a three–step system, starting with a simple visual inspection for defects. The visual inspection is continued during the first couple minutes of the pneumatic cleaning process with a unique diagnostic feature that will identify broken cell walls. According to Taylor, most of the ash builds up on the outer edges of the DPF, so the pneumatic cleaning can be focused there with the custom cleaning feature.For the second step, the filter must be tested on a flow tester to compare its airflow to that of a new, clean DPF. "You're able to take a dirty DPF, put it on there, see what kind of a flow profile you have, and then, after you've put it through a Stage One pneumatic cleaning, place it back on and see what kind of flow recovery you've got," says Taylor.

"The third step is what we call a mechanical certification," he continues. "That's where we plot by the hours on a clock around the outside edges of the DPF, and we'll drop a round, stainless steel pin into the cell and we'll get a mechanical measurement of how much open area we have versus how much closed area we have down the depth of that cell. That's something that we do on a spot basis. Once we've done that, we have a very good idea of what kind of condition this DPF is in.

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