FAQ – Diesel Particulate Filter Cleaning (DPF)
What is the purpose of DPFs?
DPFs are used to contain soot caused by exhaust emission and other particulate matter. By trapping soot and ash from the diesel vehicle, these filters reduce harmful emissions.
What is DPF regeneration?
Regeneration is the process of combining heat and oxygen to burn the soot trapped by the DPF. By burning the soot, it is converted to carbon dioxide which passes freely through the filter. The main form of regeneration is called passive regeneration. When conditions do not allow for passive regeneration, the next step is active regeneration. If neither forms of regeneration are accessible to clean the filter, manual regeneration or cleaning is necessary to restore the DPF back to proper condition.
There is no special equipment needed for passive regeneration as it happens during typical engine operation. The process occurs when the engine heats to a degree which burns off soot. The soot combined with exposure to oxygen at high heat creates carbon dioxide. Converted to a gas, the soot can then pass through the DPF, resulting in a cleaner DPF. This process occurs naturally under normal load conditions, but not all engines undergo the speed and load conditions necessary for passive regeneration.
Like passive regeneration, active regeneration does not require any extra equipment or external action. When conditions do not allow a diesel engine to generate enough heat for passive regeneration, soot builds in the DPF. The next step the engine takes to remove soot from the DPF is called active regeneration. When the soot builds to a certain level in the DPF, the engine subsequently injects raw fuel into the exhaust stream. The fuel reaches the diesel oxidation catalyst (DOC) where it is oxidized to create the level of heat necessary to burn the soot off the DPF.
In the event conditions prevent both passive and active regeneration from occurring, manual regeneration is necessary to facilitate the cleaning of the filter. This process is usually required after long periods of idling. As the truck is parked, the operator or a technician manages the parked regeneration by using the dash controls to bring the engine to proper heat for regeneration. It is important to note, not all trucks have the capability to enact parked regeneration for the DPF.
Why do DPFs need to be cleaned?
Conditions may prevent regeneration from being accessible or regeneration may not be enough to clean the filter. In this event, the DPF will require a manual cleaning. Once the soot and ash are removed, the filter will be able to operate properly once more.
What is the process of cleaning a DPF?
To begin cleaning, the filter needs to be removed and assessed. Using proper protective equipment, the technician cleaning the filter will then use compressed air to blow out blockage. After removing as much as possible, water will be sprayed through the filter to disturb stubborn build up. Finally, chemical cleaners may be applied to ensure a thorough cleaning. Once the filter is clean and fully dry, it is ready to be used again.