It has happen sooner or later. Whether you go by the Environmental Protection Agency’s (EPA) requirement that diesel particulate filters (DPFs) need to be able to go a minimum of 150,000 miles before being cleaned, or the engine OEM’s recommendations that DPFs can go 250,000 miles between cleanings, someone, somewhere has to clean the things.
Let’s start at the start: every new 2007 truck has a DPF installed as an aftertreatment device in its exhaust. The DPF traps the particulate matter in a honeycombed filter element, preventing it from exiting with the exhaust. And that filter must be cleaned periodically. Because the cleaning equipment is so new, and so big, we wondered how the typical fleet maintenance shop will fit this new device in its workspace, and incorporate this new cleaning procedure into its existing workflow.
Donaldson Company has developed a two-stage cleaning system for DPFs, according to product manager Cory Anderson. “The first stage that we use is our pulse cleaner,” he explains. “It’s designed to remove ash and some soot from the channel walls of the DPF. It uses a high-volume pulsed air at a low pressure. The system is fully enclosed, and is an automated system. It takes 15 minutes for the cleaning process.”
Technicians will need to remove the DPF from the truck and schedule it for cleaning in their shop, then, after the 15-minute cleaning cycle, remove it from the cleaning system and reinstall it onto the truck. Every DPF Anderson has seen can be taken off the truck with quick-disc connect type clamps or is a bolted flange connection.
“Initially, what the EPA put out there as a minimum for cleaning DPFs was that the first cleaning takes place at 150,000 miles for heavy-duty trucks, although the first cleaning may not be needed until the truck has 200,000 to 300,000 miles on it,” he says. “But, if DPFs need to be cleaned before the first 150,000-mile threshold it might be the responsibility for the truck or engine manufacturer to clean it at that point.”
Donaldson has also developed a DPF Thermal Regenerator that cleans the DPF when it has become extremely plugged with unburned soot and hydrocarbons. This, the second part of Donalsdon’s system, involves a seven-hour cleaning cycle. Anderson believes this will be a tool for the shops to use when a regeneration cannot happen on a truck. “If things operate properly out in the field, the regeneration of unburned hydrocarbons and soot will occur on the truck, and what’s left is the ash,” he says. “So you would pulse-out the ash material from the DPF. If there’s a situation where you can’t thermally regenerate the DPF because the engine isn’t able to operate (example: a downed engine or turbo failure), then you would use the DPF Thermal Regenerator. The cleaning interval would be the same, whether it’s soot-plugged or ash-plugged.”
When visually inspecting the face of the DPF filter, the technicians will get an idea of which kind of cleaning will be needed. The face of the freshly regenerated filter will appear ash-like in color, Anderson says.
“I think it will really be a learn-as-you go type of a situation for the technicians as they see a light on the dash from the truck for regeneration, or a high back pressure—that will vary by truck manufacturer of how that is indicated—for when the DPF needs to be cleaned,” he explains.
A DIFFERENT APPROACH
“How far a DPF is going to go will depend on a lot of variables,” says Bill Linder, customer relations manager for SPX Service Solutions-Construction and Agriculture Markets. “It’s going to depend on how the vehicle is being used—a dump truck that’s stopping every 500 feet is probably going to clog up faster than something that’s running across the country, just because of the ability to regenerate.
“A lot of this is unknown science right now,” he says.
Adding to the unknown is that not all fleets can be counted on to switch to the new low ash engine oils, or to ultra low-sulfur diesel fuel (ULSD), simply because they have so few ‘07 engines. “That may fill the DPF with ash faster,” Linder says.
“Then there are always the events that we call ‘oops’ in the market,” he adds. “Something might happen with the DPFs—they might not regenerate the way they’re supposed to.”
Although SPX is ready with its own service tool, appropriately dubbed the Diesel Particulate Filter Cleaner, Linder fears that fleets might not be ready for DPF maintenance.
“I think there’s a lot of unknowns,” he says. “I think everyone knows—and the OEM’s have all clearly stated—that the filter needs to be cleaned, but when and how often, they’re not sure.”
Linder equates DPF cleaning to oil changes in consumer vehicles: the people who change oil more frequently than they need to, say, every 3,000 miles, may be putting in more work, but they are also better protected from breakdowns.
“I think the same thing is going to happen with the DPF Cleaner,” he says. “If the process for cleaning the filters is fairly quick (approximately 30 minutes with the SPX product), and can be done at the same time that the yearly preventive maintenance is being done on a long-haul truck, why not do it?”
Once the ash is removed from the DPFs, the only remaining issue is the removal of that ash from the cleaner itself. According to Linder, California calls the ash that must be emptied from the cleaner a hazardous waste that must be disposed of appropriately, and some other states are following suit.
Fleets that plan to clean their own filters will need to keep abreast of local disposal laws, but that may be the least of their challenges when dealing with the “unknown science” of cleaning diesel particulate filters.