By-Pass or Open systems

1. By-Pass or Open systems I was asked to describe all common technology available on the market for reduction of particulate matter in diesel exhaust. Describing open or by-pass filter solutions is the most difficult part of this presentation. The reason is obvious: there are open or bypass systems on the market with rather interesting features and others with no efficiency at all. The problem is that these systems are difficult to distinguish from each other and their efficiencies in real traffic conditions are difficult to prove and extremely different from each other . Therefore I suggest readers of this document, and in due cause purchasers or legal and environmental advisers to be extremely careful and selective when selecting these systems as possible solutions for improvement of particulate matter emissions by retrofitting these systems. By pass or open systems are designed, developed, installed to reduce partly the PM emissions while avoiding engine stops due to clog up of the DPF systems. These systems are no Diesel Particulate Filters in the sense where all the exhaust gases are traveling true a mechanical filtering medium. They are offered as “the solution” for retrofit without problems. In reality many open or bypass filter systems have a very insignificant effect in city traffic were diesel particulate filters are having their most important task. Back to overview Diesel Particulate filters

2. By-Pass or Open systems These “open filters” are trapping some soot particulates which is positive in general. On the other hand loaded with soot a bypass, or open gap will let all the soot particulates pass true the systems to avoid power losses due to high pressure drop. A secondary effect is the ash which is passing true the system. This is a huge economical advantage because it makes these systems free of maintenance. Nevertheless in many cases these ashes contain products or components that should not be spread in the environment. Because of the very broad spectrum of driving patterns and with the knowledge that the efficiency depends very much on the driving patterns efficiency verifications of these kind of systems in real traffic is rather complex Conclusion about by-pass or open systems For long distance trucks a well designed and good open filter technology is applicable with a reasonable to good effect varying from 20 up to 60%. For pure city traffic these systems will completely inefficient because they will hardly regenerate. Conclusion, some of this open systems have a global positive effect going from 15 to 60% and their integration in retrofit could have a a positive effect. Prudence for “fake” filters is absolutely required though. There are retrofit systems in the market without catalytic coating or any other regeneration method or technology. These open or bypass systems without catalytic coating will only be loaded once (example just for one test cycle to pass an emission approval) and will stop being efficient after very short period of few hours. These systems should be banned completely in the market and for sure not be called Diesel particulate filter. Back to overview Diesel Particulate filters