Nett - Model S-Series - Diesel Particulate Filters (DPF)
From Diesel Particulate Filters (DPF)
Nett's S-Series Diesel Particulate Filters (DPF) utilize cordierite and silicon carbide wall-flow monoliths to trap the soot produced by diesel engines. The cylindrical filter element consists of many parallel channels running in the axial direction, separated by thin porous walls. The channels are open at one end and plugged at the other, forcing the particle laden exhaust gases to flow through the walls. Gases are able to escape through the pores in the wall material, but particulates are too large to escape and are trapped in the filter walls. The S-Series passive DPF relies on heat from engine exhaust to regenerate the trapped particulates. Periods with exhaust temperatures of 615-750°F (325-400°C), which are necessary for proper filter regeneration, occur on most heavy-duty diesel engine applications.
S-Series - Designs and Options
Standard models of cordierite and SiC diesel particulate filters are listed in Table 1 and Table 2, respectively. Filter sizing guidelines in the table are approximate. Sizing for particular engines and applications should be consulted with our office before ordering.
S-Series - Technology
Nett® S-Series diesel filters utilize cordierite or silicon carbide wall-flow monoliths to trap the soot produced by heavy-duty diesel engines. The cylindrical filter element consists of many square parallel channels running in the axial direction, separated by thin porous walls, as shown below.
The channels are open at one end and plugged at the other, which forces the particle laden exhaust gases to flow through the walls. Gas is able to escape through the pores in the wall material. Particulates, however, are too large to escape and are trapped in the filter walls and in the inlet channels. A proprietary noble metal catalyst is coated onto the inside surface of the filter monolith. The catalyst lowers the soot combustion temperature allowing the filter to regenerate. The accumulated soot is oxidized in the filter during regular operation of the engine. For about 25-30% of the engine operating time, the exhaust temperatures must be at least 275-300°C (530-575°F) for proper filter regeneration when ULSD (ultra-low sulfur diesel) fuel is used.
The exact temperature requirements change with engine technology, with installations on older, dirty engines requiring higher exhaust temperatures for regeneration. For example, filters installed on older off-highway engines with high DPM emissions (e.g., >= 0.30 g/bhp-hr) may require temperatures of 325-400°C (615-750°F). The regeneration also depends on other factors, such as the vehicle duty cycle, filter sizing and type of diesel fuel used. ULSD fuel (S < 15 ppm wt.) is now widely available and should be used whenever possible with any diesel particulate filter.
Nett® diesel particulate filters are available with either cordierite or silicon carbide (SiC) substrates. Cordierite substrates perform satisfactory in most heavy-duty applications with high exhaust temperatures. However, in low-temperature applications which may experience “uncontrolled regenerations”, cordierite is more susceptible for damage from high temperatures, such as melting. Silicon carbide has higher maximum operating temperature limits and better durability in high temperature applications. Disadvantages of SiC include higher weight and higher cost.
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