CHAMBER A. 5S1833 - Caterpillar

The Caterpillar Clean Emissions Module (CEM) houses catalytic converters that treat exhaust gas from the engine.System Block Diagram
Illustration 1 g03860871
(1) Clean Emissions Module (CEM)
(2) Dosing control cabinet
(3) Diesel Exhaust Fluid (DEF) customer supply tank
(4) Compressed air supply
(5) Separate circuit aftercooler (SCAC)
(6) Air cleaner
(7) Turbocharger compressor
(8) Turbocharger turbine
(9) Mixing tube
(10) Selective Catalyst Reduction (SCR) catalysts
(11) Exhaust outDiesel Exhaust Fluid (DEF)
Note: Two tools are available to measure the DEF concentration. The two tools are the 431-7087 Tool Gp (Refractometer (DEF)) and the 360-0774 Refractometer (Brix). Refer to Testing and Adjusting, "Diesel Exhaust Fluid Quality - Test" for additional information.Selective Catalyst Reduction (SCR) refers to a method of treating engine exhaust in order to reduce the undesired oxides of nitrogen compounds NOx. SCR uses a catalyst which promotes a desired chemical reactions over other possible chemical reactions. The catalyst remains unchanged. Ammonia (NH3) is mixed into the exhaust, and reacts with the NOx in the presence of the catalyst to form harmless compounds (water and nitrogen). In this system, urea ((NH2)2CO) is injected into the exhaust, which quickly decomposes into ammonia under the heated conditions. Urea is used because urea is inexpensive, and does not need the special handling that ammonia requires.DEF is an aqueous urea solution (urea salt dissolved in water).A 32.5 percent (by weight) solution of DEF is required for the system.A 32.5 percent concentration has the lowest freezing point possible, −11 °C (11 °F), for this solution.A 32.5 percent concentration of urea keeps a constant concentration through freezing and thawing.DEF must be stored below 50 °C (122 °F) to delay decomposition.Note: The customer is responsible for providing primary filtering of the DEF from the customer supply tank to the dosing control cabinet. The system requires a 40 micron primary filter.Use only DEF that meets quality properties per ISO 22241-1. Using DEF that does not meet ISO 22241-1 can result in clogging of the injection nozzle.Contaminants can degrade the life of DEF related components. Care must be taken when refilling or performing service on the DEF system to minimize the introduction of contaminants. Initial operation should include a thorough system flushing with clean distilled water.Primary DEF filtration is required. Filters must be compatible with DEF and should be used exclusively with DEF. Check with the filter supplier to confirm compatibility with DEF before using any filter. The DEF system primary filter must have a maximum of a 40 micron filtration level with a Beta = 1000 (99.9% Efficient). Check with your Caterpillar dealer for Caterpillar DEF filtration offerings which may meet your application specific needsReference: Refer to Operation and Maintenance Manual, SEBU6251, "Cat Commercial Diesel Engine Fluids Recommendations" for detailed DEF cleanliness recommendations.DEF is a non-toxic source of ammonia.DEF is corrosive. Do not store DEF in a tank or use supply lines that are made of the following materials: aluminum, brass and steel. Use only corrosion resistant materials such as PVC or stainless steel. Any O-rings must be Ethylene Propylene Diene Monomer (EPDM).Clean Emissions Module (CEM)
U Style CEM
Illustration