Diesel particulate filters (DPFs) play an important function in an exhaust system and, consequently, neglecting to maintain these filters properly can lead to significant and costly repairs. The DPF system itself is an exhaust after-treatment device that is purposefully designed to trap exhaust by-products, such as soot, to reduce emissions from a diesel vehicle.
For a DPF to continue working in the way it should, built-up soot produced from the exhaust system is periodically burned off to regenerate the filter. This regeneration process prevents harmful exhaust emission and the black smoke that is common for diesel vehicles.
What is DPF regeneration?
The key to maintaining a DPF system is to ensure it can continue to regenerate itself when it fills with soot. Two types of automatic DPF cleaning procedures are expected to happen; passive regeneration and active regeneration.
Passive regeneration occurs as the vehicle is being driven normally. Inside the after-treatment device, the exhaust passes over a diesel oxidation catalyst then will pass through the diesel particulate filter. The passive regeneration process happens naturally when the heat in the engine builds up to a point where the soot combines with oxygen to create carbon dioxide and passes on through the filter.
Another output that the DPF captures is ash. As ash is already a by-product of combustion, no amount of heat from the engine can convert it. Consequently, ash will inevitably build up over time to the point where the filter has to be physically removed and cleaned. Passive regeneration does not always keep the DPF clean throughout the workday, so the filter may have to undergo active regeneration.
Active regeneration occurs when the engine is not creating enough heat, once the soot level reaches a certain point, so the engine injects fuel into the exhaust stream. The injected fuel is oxidised by the oxidation catalyst which helps the soot convert to carbon dioxide.
Both active and passive regeneration happens automatically. However, a prominent sign that active regeneration is occurring is a high exhaust temp light, as the exhaust gas temperature could reach 800℃.
When operating conditions do not allow for DPF cleaning to occur by active or passive regeneration, an operator activated parked regeneration may be necessary. For this to take place, an operator will bring the engine to operating temperature and initiates the parked regeneration by activating the dash controls. The vehicle must remain parked during this process.
What causes a blocked DPF?
Blocked DPFs are often caused by short journeys at low speeds as the system is unable to clean itself. DPFs may fail sooner if they are not well maintained due to poor servicing. Additionally, filter blockage can be caused by the use of the wrong type of oil, performance modifications or using low-quality fuel.
The MK Equipment Services team is made up of qualified mechanics, boilermakers, exhaust fitters and welders who all deliver superior workmanship. Contact the team at MK Equipment Services today on (07) 3272 9519 if you have any questions regarding our heavy vehicle services or if you would like to discuss a DPF or exhaust system related maintenance.