Diesel particulate filters are designed to trap diesel particulate matter and soot, keeping them out of diesel exhaust and out of our air and environment.
Over time DPFs fill up, and need to be cleaned. As the filters become clogged, their performance deteriorates. It’s a lot like the filter on a vacuum cleaner — it works great when it’s clean and new, but it gets clogged, and becomes worse over time.
The process of cleaning a DPF is often referred to as “Regeneration” because it renews the filter to function properly, as it did when it was new and clean.
There are several ways to clean diesel particulate filters, to keep them functioning properly. Some regeneration methods occur onboard automatically. Other regeneration or cleaning methods are performed off-board, with the DPF removed from the vehicle.
Passive regeneration
Passive regeneration is an automatic DPF cleaning process that is designed to occur during normal vehicle operation.
Passive regeneration occurs naturally while the vehicle is being driven. Passive regeneration uses the heat of the exhaust gasses to burn away off the accumulated soot in the DPF.
Active regeneration
Active regeneration is similar to passive regeneration, but uses additional heat above and beyond that which is generated during normal driving operation.
Active regeneration raises the temperature of the exhaust gasses, which helps to burn off the soot in the filter. Active regeneration processes vary depending on the engine, make and model.
Active regeneration often uses additional diesel fuel to achieve higher temperatures.
Manual regeneration
Manual DPF regeneration requires a manual initiation of the regeneration process. This often achieved using a button or switch in the vehicle. Manual regeneration often requires a vehicle to be parked, but this varies depending on the engine and vehicle specifications.
Off-board regeneration
Off-board DPF regeneration is performed after a DPF is removed from a vehicle.
The DPF is then cleaned, usually using specialized equipment, including:
- “Air blade” cleaning to remove large amounts of soot and diesel particulate matter
- Soaking in an aqueous DPF solution
- High-temperature baking in a specialized kiln to burn away soot
- Ultrasonic cleaning in a specialized machine which removes the last stages of soot and particulate matter
Regardless of the method used, the goal of cleaning a diesel particulate filter is always to remove accumulated soot and restore the filter to its full operating capacity.