SEAL 2035958 - Caterpillar

To meet current emissions legislation requirements, a small amount of certain chemical compounds that are emitted by the engine must not be allowed to enter the atmosphere. The Clean Emissions Module (CEM) that is installed to the engine is designed to convert these chemical compounds into less harmful compounds.
Illustration 1 g02384560
Typical example (1) Clean emissions module (CEM) (2) Inlet connection (3) Outlet connection (4) Mounting cradle (5) Flexible exhaust pipe from engine to CEMThe Clean Emissions Module (CEM) for the engine consists of the following components.
Diesel Oxidation Catalyst (DOC)
Diesel Particulate Filter (DPF)The Diesel Oxidation Catalyst (DOC) oxidizes the carbon monoxide and the hydrocarbons that are not burnt in the exhaust gas into carbon dioxide and water. The Diesel Oxidation Catalyst (DOC) is a through flow device that will continue to operate during all normal engine operating conditions.The Diesel Particulate Filter (DPF) collects all particulate matter in the exhaust gas.A flexible exhaust pipe connects the engine to the Clean Emissions Module (CEM). Refer to Disassembly and Assembly for the correct procedure to install the flexible exhaust pipe.The solid particulate matter that is collected by the DPF consists of soot (carbon) from incomplete combustion of the fuel and inorganic ash from the combustion of any oil in the cylinder.The rate of accumulation of ash is slow under normal engine operating conditions. The filter is designed to contain all the ash that is produced for the life of the engine.The engine aftertreatment system is designed to oxidize the soot in the DPF at the same rate as the soot is produced by the engine. The oxidization of the soot will occur when the engine is operating under normal conditions. The soot in the DPF is constantly monitored. If the engine is operated in a way that produces more soot than the oxidized soot, the engine management system will automatically activate the exhaust back pressure valve to raise the exhaust temperature. The raising of the exhaust temperature will ensure that more soot is oxidized than the soot that is produced by the engine. The oxidization of more soot returns the DPF to a reduced level of soot. The exhaust back pressure valve is then deactivated when the soot level has been reduced.The engine ECM must know how much soot is in the DPF. Measurement of soot is accomplished through the following means:
Radio frequency measurement across the DPF
Calculated model based on developed engine out soot measurementsThe Electronic Control Module (ECM) uses the soot measurement information to determine if the engine operating conditions need to be adjusted in order to oxidize the soot at an increased rate.