0327337 JOHNSON SHIFT ROD, Long

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 2 g06086348
(1) Exhaust out
(2) Outlet mixer
(3) Catalyst brick
(4) Service door
(5) Swirl mixer
(6) Flapper mixer
(7) Mixing tube
(8) Urea injector
(9) Exhaust inCEM Operation
The exhaust gas exits the engine and enters the mixing tube, where the DEF is injected into the exhaust stream.The DEF decomposes into ammonia and water.The mixture of exhaust and ammonia travels through the SCR.The ammonia reacts with the NOx in the exhaust stream at the SCR catalyst to produce water vapor and nitrogen.Dosing Control Cabinet
Illustration 3 g06306395
(1) SCR controller
(2) Wiring harness
(3) Wiring harness connector to CEM
(4) AC power in
(5) Breaker
(6) Air purge solenoid valve
(7) Air outlet to CEM
(8) Air inlet
(9) DEF inlet
(10) DEF outlet to CEM
(11) Wiring harness connector to engine ECM
(12) Service tool connector
(13) DEF pumpThe dosing control cabinet controls the following:
Rate of DEF flow to the injector
Compressed airCompressed air is used for the following:
Assist in the atomizing of the liquid DEF during injection into the exhaust stream
Shield the liquid DEF in the injector from the exhaust heat until spraying, so that no crystallization occurs which could plug the injection nozzle.
Purge the DEF line to the injector during shutdown in order to prevent crystallization of DEF resulting in a clogged nozzle or failed control valve.Compressed Air Supply to Dosing Cabinet
In general the air supplied to the dosing cabinet needs to be frree of contaminates, or large quantiles of oil. Water in the compressed air can lead to component failure if exposed to freezing temperatures. An oil water separator is recommended. Air pressure must also be available even when the SCR system is not actively dosing to cool the DEF injection lance. Additional air is potentially required after the engine shuts down to complete the DEF purge process and continue to cool the DEF injection lance after engine shut down.Oil can foul the catalyst and prevent the necessary chemical reactions from occurring. Sediment in the airline can plug the injection system.The SCR system will use up to 255 L/min (9 SCFM) at 482 kPa (70 psi). The system contains an air regulator with a maximum rating of 1069 kPa (155 psi) inlet pressure.To avoid clogging the air system with oil and/or sediment from piping, use a coalescing filter/separator that is 90 percent effective rated for 1069 kPa (155 psi) and 849.5 L/min (30 CFM).Air lines must be sized and routed so pressure loss across the line is no greater than 7 kPa (1 psi) with air delivery at 345 kPa (50 psi) and 255 L/min (10 SCFM).Dosing Control System
The purpose of the dosing control system is to meter DEF into the exhaust stream.The dosing control cabinet houses an Electronic Control Module (ECM) that provides the controlling logic.The desired rate of DEF injection is determined via a closed loop system, utilizing NOx sensors for feedback. The sensors measure the level of nitrogen oxides (NOx) entering the CEM and in the exhaust gas exiting the CEM.If the NOx sensor indicates high NOx in the exhaust outlet, the closed loop system will request an increase of the DEF flow rate.DEF flow rate is increased by increasing the frequency of the Pulse Width Module (PWM) signal to the dosing pump.The