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Diesel Particulate Filters (DPF)
Background
Level III
Diesel Particulate filters have been in use on non-road machines since the early 80’s and within the automotive industry since mid 90’s. Diesel engines during combustion of the fuel/air mix produce a variety of particles generically classified as diesel particulate matter due to incomplete combustion. The composition of the particles varies widely dependent upon engine type, age, duty cycle, fuel used and the emissions specification that the engine was originally designed for.
Diesel engine emissions were not regulated until 1987, The California Heavy Truck rule was the first introduced capping particulate emissions at 0.60 g/BHP Hour. Since then progressively tighter standards have been introduced for both On-Highway (Road) and Off- Highway (Non-Road) diesel engines.
While particulate emissions from diesel engines were first regulated here in the United States, similar regulations have also been introduced in Europe, and around the world. Europe, having the greater usage of Diesel Engines, has also adopted a new and different stance on factory supplied technology. Instead of using a DPF for Particulate reduction the European vehicle / engine manufacturers have focused on Reducing the amount of fuel used and increasing the oxygen within the combustion process. This has increased Nox emissions thus driving the need for the Selective catalyst Reduction (SCR) technology being adopted. The driving factor of this is of course the price of fuel, and even today our European partners pay 3 to 4 times the value for the same amount of Diesel.
While no jurisdiction has made filters mandatory, the increasingly stringent emissions regulations that engine manufactures must meet mean that eventually all on highway diesel engines will be fitted with them. Neither the American 2007 heavy truck engine emissions regulations or the European Union 2007 automobile regulations have been met without filters.
Off Highway diesel engines are now also regulated and with the introduction of localized Directives this will increase the need for additional DPF’s.
As of July 2006 the California Air Resources Board (CARB) is looking at introducing regulations that will require retrofit of all diesel engines operating in the state by the year 2013. Similarly, the Environmental Protection Agency (EPA) is reviewing similar directive / mandates. Other Countries, States, government agencies are doing this as well, and a variety of retrofit programs have already been established here in the United States. (Air Quality Management Districts)
Diesel particulate filters are sometimes called DPF’s or Wall Flow Filters, this is a device designed to remove diesel particulate matter or soot (ranging in sizes from PM 10 down to PM 2.5, this is the actual size of the particulate) from the exhaust gas (pollutants) of a diesel engine. Wall-flow diesel particulate filters usually remove 90% or more of the soot, and can at times (heavily loaded condition) attain soot removal efficiencies of close to 100%. A diesel-powered vehicle equipped with functioning filter will emit no visible smoke from its exhaust pipe. The days of using engine smoke to determine engine faults no longer will exist. (Blue smoke oil problems, white smoke water / head gasket problems etc.)
In addition to retaining the particulate, a method must exist to clean the filter. DET’s DPF’s are designed to burn off the accumulated particulate, either through the use of a catalyst Technology (Passive), or through an Active Regenerating Technology
Commonly known as "filter regeneration," and referred to as Active systems, Fuel sulfur levels will also determine which "regeneration" strategy best suits the application as all DPF’s are sensitive to Sulfur levels. The introduction of improved regulations and more focus on alternative fuels such as bio-diesel. Please note all DET’s DPF’s are able to work with Bio diesel but before doing so DET request that you involve our engineering team as by doing so my invalidate your warranty.
Unlike Diesel Oxidation Catalysts which are a flow-through device, a DPF cleans exhaust gas by forcing the gas to flow through the filter. There are a variety of diesel particulate filter technologies on the market. Every filter is designed around similar requirements:
- Fine filtration (Future requirement will be Nano Particles.)
- Minimum Back Pressure
- Product longevity
A typical Summary of Technologies with regards to California Air Resources Board verified Diesel Emission Control Strategies (VDECS) program.
DOC- Level 1 device
POC – Level 2 device
DPF - Level 3 Device
Filter Applications and Usage
A properly designed filter will have little effect on fuel usage, however improper installation can be catastrophic, which is why automotive and truck engine manufacturers have avoided the use of filter technology until now.
Maintenance
All DPF’s (Filters) require maintenance unlike Diesel Oxidation Catalysts. Engine and fuel oil ash builds up on the surface of the inlet face of the filter, and will eventually clog the pores. The clogging in turn increases the pressure drop (Backpressure) within the filter / exhaust system. It is essential that the jointing / connection method can withstand the higher pressures and that they don’t leak.
It is vital that a DPF is maintained inline with our directive. If the unit is not then the exhaust back pressure will increase, and the engine will use more fuel. As the back pressure increases the temperature will also increase which may affect engine condition and will run the risk of permanently damaging the DPF. It is therefore recommended that a maintenance agreement is put in place when ordering your specific device. For further details visit please visit www.dieselemissioncleaningservices.com
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