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Be Particular About Particulate Matter

By on July 1, 2016

by: Homer Hogg, Manager for Technical Development for TA-Petro

In 2007, the Environmental Protection Agency (EPA) introduced a set of emissions standards to be applied to on-highway diesel engines. These standards require almost zero Particulate Matter to be emitted from a vehicle’s exhaust. For most diesel engines, the addition of a Diesel Particulate Filter (DPF) and a Diesel Oxidation Catalyst (DOC) met the requirements. We are nine years down the road, and I believe the industry is still working to sort out the maintenance practices and costs necessary to successfully operate these often-misunderstood devices.

If you consider the amount of black smoke that billowed from most diesel trucks prior to 2007, it is astonishing how clean the air exiting the exhaust pipes of most modern trucks has become. The problem is that the black smoke is still present, but it is trapped in the DPF; consequently, it never reaches the atmosphere.

Pay Attention to Light

All seems to be good until that funny looking DPF light on the dash illuminates, and engine performance declines and fuel efficiency is reduced. If the DPF is not regenerated to the correct level by the on-board computer systems, or the driver does not initiate a manual regeneration cycle, the DPF light will start to flash providing a final warning. If the condition is not rectified, the red light will illuminate and the engine may derate and/or shutdown. This could result in a tow bill or very expensive roadside repair and may damage the DPF, requiring a very expensive replacement.

If the DPF becomes restricted due to normal operation, it can be removed, inspected, cleaned and placed back in service. The cleaning process varies, and is a point of much discussion and some contention within the industry. Multiple methods are available and may be required for a specific engine based on the extent of the required cleaning.

Cleaning for Best Performance

Most cleaning methods include a pneumatic process that should remove the majority of the trapped Particulate Matter and contamination trapped in the filter. To obtain a better level of cleanliness, combining air cleaning with a baking process is advisable. The combination of blowing the soot out of the filter with a high quality machine and baking will clean most filters to an acceptable level. Some operators or owners don’t have the time to take their vehicles out of service for 24 hours to allow the filter to bake and cool, so they opt for a pneumatic clean only.

At least one manufacturer requires a liquid clean for its filters, but this process typically means an exchange system, so the filter can be sent back to the engine manufacturer and cleaned in a very controlled environment. This method may provide a slightly better clean, but tends to make some customers nervous due to their good known core going into a system where they will never see it again.

What About DOC?

The DOC, which is mounted in front of the DPF, plays a critical role in the after treatment process. It is a catalyst device that heats up and helps burn excess fuel not totally burned during the combustion process. This device should be cleaned when the DPF is removed. Failure to clean the DOC could result in a contaminated DPF once the engine is restarted or may shorten the expected life of the cleaned DPF.

The cleaning equipment for DPFs and DOCs have evolved and become much more efficient resulting in lower costs and less downtime. As technicians continue to learn the techniques necessary to quickly remove and service these after-treatment devices, hopefully, it will be less painful for drivers, owners and fleet managers when that funny-looking light on the dash illuminates.

Being particular about Particulate Matter pays dividends. See your TA Truck Service Center for assistance with DPF and DOC cleaning.

HomerHoggHomer Hogg’s Maintenance Matters airs on the Dave Nemo Show (Road Dog Trucking, SiriusXM 146), 8 a.m. ET, the first and third Thursdays of each month.

Homer Hogg, Manager of Technical Development for TA and Petro, has worked as a truck technician for more than 30 years. He is ASE Master-Certified, a Daimler Certified Trainer, and a member of the Nashville Auto-Diesel College Hall of Fame.

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