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Cordierite |
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The most common filter is made of Cordierite (a ceramic material) Cordierite filters provide excellent filtration efficiency and are (relatively) inexpensive. They have thermal properties that make packaging them fo r installation in the vehicle relatively simple. A coupe of major drawbacks are that cordierit e has a relatively low melting point another words goes from a solid to a liquid. (around 2000° Fahrenheit / 1100° Celsius) and cordierite substrates have been known to melt down during filter regeneration along with them being extremely fragile, thus the need for a robust good canning process. Melting is mostly an issue if the filter has become loaded more heavily than usual, such as excessive lube or fuel oil, excessive idling etc, it is more of an issue with Passive systems than with Active systems, unless there is a system break down. |
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Cordierite filter cores are designed simular to that of a catalytic converter cores but they have the alternate channels plugged. With the introduction of the plugs it forces the exhaust gas to flow through the wall and the particulate collects on the inlet face. GRAPHIC |
| Silicon Carbide (SiC) |
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The second most popular filter material is silicon carbide is a ceramic compound of silicon and carbon , or SiC. It has a higher melting point (4500 °F / 2500 °C) than cordierite, however it is not as stable thermally, making packaging an issue, again the canning process and filter substrate matting material are essential DET has this covered, by not only using the highest and best materials on the market but also by using our Patented Canning Process. |
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The substrate is made up of small SiC cores which are of single pieces, while larger cores are made in segments, these are separated by a special cement so that heat expansion of the core will be taken up in part by the cement, and not all by the matting. SiC cores are usually more expensive than cordierite cores, however they are manufactured in similar sizes, and one can often be used to replace the other. |
Some of our SiC filters have different cell porosity and cell density thus they have the ability to withstand greater soot loading. As technology is moving on the two materials are becoming more alike, but with regards to SiC consideration has to also be given to its greater weight then Cordierite, thus making application engineering a little more difficult. |
Silicon carbide filter cores also look like catalytic converter cores that have had alternate channels plugged - again the plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face. |
| Metal Fiber & Mesh Filters |
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Metal fibers are becoming more and more common, they have been traditionally been used as partial devices but in recent months more alternatives are being developed for the use as filters using a process defined as sintering, DET’s is also working with technology but to date it is not commercially available. Other alternatives have been wire mesh based or corrugated wrapped layers of metal foils making them the monolith / substrate.Suchcores have the advantage that a current can be passed through the monolith to heat the core for regeneration purposes.Metal fiber cores tend to be more expensive than cordierite or silicone carbide cores, and generally not interchangeable with them as they are not truly a trap. |
These devices can also be used as pre filter devices to aid flow and dispersion of particulates into a filter substrate. |
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