Diesel particle filter cleaning
In the diesel particulate filter purification is a chemical or mechanical and / or thermal cleansing carried out by specific service providers or garages. Clogged diesel particulate filters (DPF) can be exchanged for new DPFs or repaired by means of diesel particulate filter cleaning.
causes
All automobile manufacturers use so-called wall-flow filters in their original equipment. The collected soot is burned about every 500 to 1,000 km by the so-called regeneration, which is triggered by the engine control with its sensors. However, the incombustible ash will accumulate over time. Depending on the vehicle model and type of diesel particulate filter, diesel soot particle filters (DPF) are clogged with incombustible ash after a mileage of around 120,000 to 180,000 km. In some cases, soot clogging occurs earlier (e.g. when driving frequently in city traffic or when driving on serpentines ). The steadily growing mountain of ash also increases the exhaust back pressure and thus fuel consumption. In extreme cases, the particle filter full of ash can generate such a high exhaust gas back pressure that the exhaust system is torn from the engine block if the internal electronics have not completely switched off the engine beforehand. Replacing an old DPF with a new one is extremely costly, depending on the model. The prices including installation range from around 1,500 euros to 4,500 euros for special import models. Alternatively, DPF cleaning processes are offered. The providers promise that it is significantly cheaper to clean a particle filter than to replace the filter.
Procedure
Heat
There are different DPF cleaning methods. By heating the filters over a longer period of time at a constant temperature in an oven, all impurities in the narrow channels should be loosened. The remaining soot is also burned. The filter is then blown out or washed out. The cleaned filters should last as long as new filters if all associated engine parts ( EGR valve, sensors , air mass meter , turbocharger , valves, etc.) are in perfect, functional condition. In contrast to new filters, however, no mileage is guaranteed for cleaned DPFs.
Compressed air
When cleaning with compressed air, there is no need to separate the housing or use harmful chemicals. Only a non-toxic, drinkable aerosol is fed into the cleaning process for a maximum of one minute. This process removes soiling such as soot, ash or oil ash deposits. Since the housing does not have to be separated with this type of cleaning, a weakening of the filter housing by welding seams and sandblasting is avoided. After cleaning with compressed air and aerosol, the filter is dried well below the firing temperature. The flow behavior is then checked and recorded in a protocol. This process removes almost 100% of the soot and ash residues.
Dry snow
The DPF cleaning process using dry snow (solid carbon dioxide CO 2 ) is especially effective for cleaning larger filters if both front sides of the filter are open. This process also works without the housing having to be separated. The cleaning then usually only takes 10 to 45 minutes. According to the supplier, the filter should be cleaned almost completely in a manner that is gentle on the material. There is no further waste, only the removed amounts of soot and ash remain. Closed truck filters and other large filters are also cleaned with compressed air and non-toxic aerosol without the housing being separated.
Chemical cleaning fluids
In addition, there is the particle filter cleaning using chemical liquid solutions. A distinction must be made between cleaning soot and cleaning ash.
Strictly speaking, the cleaning of soot is the same as the regeneration by the engine. The cleaning fluid is sprayed into the DPF. During a subsequent longer journey, the soot is then completely burned off due to the regeneration that starts. The temperatures in the filter can rise so high as a result of the chemical reactions that occur that the filter is damaged or, in extreme cases, even destroyed.
When cleaning ash, the filter is rinsed against the direction of flow with a special cleaning liquid, which rinses the ash out of the filter material and out of all channels.
Ultrasonic
The DPF can be cleaned when it is installed in the vehicle by means of ultrasonic processes using special piezo elements that are attached to the filter from the outside. For this purpose, a suitable cleaner is introduced into the diesel particulate filter from the outside and the particulate filter is excited via a special frequency, whereby the soot / ash is released and flushed out via the exhaust system.
criticism
Most DPFs are coated - cleaning can damage this precious metal coating. In addition, the cleaning is not 100% successful, so some of the ash remains in the filter. Furthermore, there is a not inconsiderable proportion of rejects from the filter elements due to microcracks or defective cell areas after long initial mileages. In order to rule this out completely, the filter elements would have to be checked individually. With almost 100 wall ducts with a cross-section of around 2 × 2 mm, which are then 300 or 400 mm long, this represents a not inconsiderable effort.
On the subject of coating aging / poisoning, the Federal Motor Transport Authority (KBA) stipulates, for example, when retrofitting DPF, that the previous oxidation catalytic converter must not be older than five years or not longer than 80,000 km. Problem-free DPFs are full of ash after 90,000 km at the earliest and therefore have longer service lives.
When removing the filter, the piping, the screw connections, the sensors and the existing oxidation catalytic converter - especially if it is mechanically non-detachable connected to the filter element by a welded connection - can be destroyed or damaged. Then there are additional costs. All reputable DPF cleaning companies expressly point out this problem.
In 2018, the ADAC conducted a survey among automobile manufacturers as to whether mechanical or chemical cleaning of the particle filter could be recommended. Not a single car manufacturer has recommended these cleaning methods or cleaning agents. The use of additional additives has also not been approved by a single automobile manufacturer. The automobile manufacturers and their sellers also point out that they will not be responsible for any damage that is causally related to filter cleaning or the use of additives. For this reason, any vehicle guarantee or liability for material defects is void. This also applies expressly to any consequential damage and irregularities resulting therefrom.
swell
- adac.de: Particle filter cleaning instead of replacement? last updated December 2018
- Damage to diesel particulate filters after cleaning with liquids as of October 31, 2015
- Cleaning the particle filter DPF
- DPF cleaning - New cleaning technology from GCSTech March 2017
Individual evidence
- ↑ Procedure FilterMaster for cars and FilterMaster for trucks and more. Retrieved May 22, 2017 .
- ↑ Procedure FilterMaster for cars and FilterMaster for trucks and more. Retrieved May 22, 2017 .
- ↑ Methods of soot particle filter cleaning , in: Auto Bild , accessed on April 1, 2017.
- ↑ adac article from December 20, 2018