KING CITY, Ont. -- There’s more than one way to skin a cat, and as it turns out, the same can be said for the cleaning of diesel particulate filters (DPFs).
Lee Abrahamson of Assegai Automotive was at the Transportation Maintenance and Technology Conference, where he discussed a method of cleaning the particulate filter without removing it from the vehicle. Typically, DPFs are removed and then cleaned on-site or sent to a third-party vendor for cleaning, which removes about 90% of ash but can cost $300-$600, plus three hours of labour for removal and reinstallation of the filter.
Another method involves cleaning the filter while it remains attached to the truck, often done in conjunction with a fuel injector flush service, Abrahamson explained. The exhaust inlet side pressure sensor, located on the inlet side of the DPF filter housing, is removed. A DPF cleaner nozzle gun with a special attachment is inserted and then used to inject a cleaning solution. The engine is then started and run at a fast idle. The DPF cleaning fluid is injected into the DPF and forced through the cordierite galleries using the exhaust pressure from the fast-idling engine.
The In Situ DPF cleaning process takes about an hour, Abrahamson said, but saves three hours since the filter doesn’t have to be pulled from the truck.
Still, he added, “prevention is better than the cure.” Abrahamson spoke of a premium diesel booster additive that can be added to the diesel fuel to drastically reduce DPF cleaning intervals.
Matt Fairbairn, fleet manager with Powell Contracting, is a fan of the Forte diesel booster additive. He said adding it to the diesel at a 400:1 (diesel-to-additive) ratio has eliminated stationary DPF regeneration requirements on the company’s truck fleet.
“We have taken 10-15 trucks out of the fleet and taken the filters off and examined them, and the filters are spotless,” he said. Beforehand, Powell had a major issue with frequent stationary regenerations on its fleet of trucks, which serves road construction sites.
Fairbairn wasn’t sure if the additive is OEM-approved.
Norm West of DPF Cleaning Specialists also stressed the importance of including DPFs in a preventive maintenance program. Connections should be inspected regularly and the sensors checked for resistance.
“If you get a temperature sensor that goes out of range, you’re either never going to regenerate or you’re always going to regenerate. When you get into a problem like that, have a look at the sensor. Take a probe and check the ohm rating on the front and back sensor and if it’s not within 5-10%, there’s something wrong, so change sensors,” West advised.
Filter media should also be inspected for damage caused by thermal events.
West said few fleets inspect their DPFs frequently enough, noting the EPA mandates a minimum of 4,500-hour cleaning intervals, but every duty-cycle is different.
“Some guys are able to run 6,000 hours and some only get to 2,000 hours, that’s the spread,” he said.
The diesel oxidation catalyst (DOC) too, should be inspected for anything abnormal, such as the caking of black soot along its surface. Clean the DOC as required, West added.
“The general rule is to clean the DOC every second DPF cleaning,” he said.
As far as cleaning intervals are concerned, West said “You can always wait too long to clean your DPF but you can’t clean it soon enough.”