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Diesel Particulate Filter (DPF) Ash Cleaning

This article summarizes the most prevalent DPF ash cleaning process available.  The article presents the application of  cleaning techniques, as well as a customized approach to ash cleaning based on the specific ash properties and distribution in the DPF.

Available Cleaning Processes

A number of ash cleaning systems exist, with the most common being pneumatic-based, utilizing reverse flow of air through the DPF to blow out the accumulated material.  The frequency of filter cleaning is generally specified by the engine or equipment manufacturer, based on pre-determined maintenance intervals.  The actual frequency of DPF ash cleaning will depend on many factors including the effectiveness of an previous cleanings (i.e. amount of residual ash), engine oil consumption, and the vehicle drive cycle.

The ease with which ash can be removed form the DPF channels depends on two primary factors, namely the strength of the ash bond to the DPF walls, and the location of the ash deposits within the filter.  For most DPF applications, a large quantity of the ash is packed in the end plugs.  This type of ash is generally the most difficult to remove using conventional pneumatic cleaning approaches.  Regardless of the specific cleaning system, pneumatic approaches are limited by the fluid dynamics, which drives the flow along the path of least resistance.  As shown in Figure 1 reverse flow by-passes much of the ash plug, flowing instead around the plug and through the open portion of the channels.

 

Why is this important for DPF ash cleaning?

Not all DPF ash is the same, and not all DPFs benefit equally from the same type of cleaning process. Filters can be most efficiently cleaned and recovered when cleaning processes are selected which are designed to target the specific ash deposits present in the filter.  DPF inspection and diagnostics are a key component of any cleaning process to ensure cleaning effectiveness and track filter health.