Diesel Particulate Filters
Diesel particulate filters remove diesel particulate matter from exhaust gas. In some cases they are simply discarded when they are full, but as the typical lifespan of this disposable type is only about 30 hours it is usually more economical in the long run to choose a self-cleaning version. This self-cleaning feature (which is also known as ‘regeneration’) is critical for the reliable and effective use of a diesel particulate filter over a prolonged period.
Diesel particulate filters clean themselves by burning off the accumulated soot. When the exhaust gas is hot enough this can happen as a result of catalytic action, which is known as ‘passive regeneration’. However unless the exhaust gas temperature gets hot enough every few hours the filter will gradually become blocked and a fall-back strategy known as ‘active regeneration’ will be required. This involves the input of additional heat which may derive from burning extra fuel or the use of electrical energy. In the most sophisticated systems, active regeneration kicks in automatically without the driver even being aware it is happening, but many systems require the driver to follow a special procedure. This is difficult to enforce on hired plant and equipment.
Some diesel particle filters require the use of a special fuel additive which helps the soot to burn off. This additive is contained in a special tank and must not be confused with Adblue which is a different liquid used on many engines meeting the Stage 4 limits. Most diesel particulate filters also require the use of special lubricating oil.