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| Illustration 1 | g06382814 |
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(1) Diesel Exhaust Fluid (DEF) injector
(2) Selective Catalytic Reduction (SCR) system (3) SCR mixing tube (4) Diesel Oxidation Catalyst (DOC) (5) Diesel Particulate Filter (DPF) (6) Exhaust intake connection (7) Exhaust outlet connection | |
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| Illustration 2 | g06382836 |
The first filter media that exhaust gas is exposed to is the DOC, a flow through style filter. The DOC oxidizes hydrocarbons, carbon monoxide, and soluble organic fractions as the exhaust gas flows through the filter. There are two temperature sensors, one at the inlet of the DOC canister, and one at the outlet of the DPF. These two sensors are used to make sure DOC is hot enough to oxidize efficiently. The DPF outlet temperature is also used by ECM to know that the exhaust leaving the DPF and entering the SCR.
The DPF is a catalyzed ceramic filter which traps particulate matter (soot). The trapped soot is cleaned from the DPF through a catalytic reaction by heating the filter through a process called regeneration. The inlet section of the DPF cannister contains the DPF inlet pressure sensor, and DPF delta pressure sensor. The DPF Inlet Pressure sensor is used to measure the backpressure being generated by the DPF. The delta pressure sensor is used to measure soot collected in the DPF. The delta pressure sensor is measuring the pressure drop across the DPF. Since the delta pressure sensor is measuring flow resistance across the DPF, the sensor will also detect ash loading.
Once the exhaust gas flows through the DPF, the exhaust gas enters the SCR mixing tube where Diesel Exhaust Fluid (DEF) is injected for the SCR. After the exhaust gas flows through the DPF, the gas enters the SCR. The DEF injected prior to the SCR, mixes with exhaust gas in SCR to reduce Nitrogen Oxides (NOX). DEF contains deionized water and urea, which turns to ammonia when heated. The ammonia reacts with the SCR catalyst to convert NOX into harmless nitrogen and water vapor. At the inlet of the SCR cannister is the SCR inlet temperate sensor. This sensor is used to make sure that the temperature is hot enough in the catalyst for DEF dosing to occur.
Compact Clean Emissions Module (CEM)
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| Illustration 3 | g06239572 |
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(1) Diesel Exhaust Fluid (DEF) injector
(2) Selective Catalytic Reduction (SCR) system (3) SCR mixing tube (4) Diesel Oxidation Catalyst (DOC) (5) Diesel Particulate Filter (DPF) (6) Exhaust intake connection (7) Exhaust outlet connection | |
A flexible exhaust pipe connects the engine to the Clean Emissions Module (CEM). The CEM contains the Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and the Selective Catalytic Reduction (SCR) systems. The CEM contains several mechanical and electrical components that reduce various exhaust emissions emitted from the engine. All the systems on the CEM are controlled by the engine ECM. Exhaust gases entering the CEM flow through the DOC first, then the DPF and SCR.
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| Illustration 4 | g06239584 |
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(1) SCR Outlet Temperature
(2) Exhaust Differential Inlet Port (3) Exhaust Differential Outlet Port | |
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| Illustration 5 | g06258346 |
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(4) DOC Inlet Pressure Port
(5) DOC Outlet Pressure Port (6) DPF Inlet Temperature (7) DOC Inlet Temperature | |
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| Illustration 6 | g06239590 |
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Air Flow through CEM Package | |
The first filter media that exhaust gas is exposed to is the DOC, a flow through style filter. The DOC oxidizes hydrocarbons, carbon monoxide, and soluble organic fractions as the exhaust gas flows through the filter. There are two temperature sensors, one at the inlet of the DOC canister, and one at the outlet. These two sensors are used to make sure DOC is hot enough to oxidize efficiently. The DOC outlet temperature is also used by ECM to know that the exhaust leaving the DOC, and entering the DPF, is hot enough for regeneration to begin. There also two ports on the DOC that can be used to hook up a delta pressure sensor for troubleshooting.
Once the exhaust gas flows through the DOC, the exhaust gas enters the SCR mixing tube where Diesel Exhaust Fluid (DEF) is injected for the SCR. Before the SCR, exhaust gas enters the DPF. The DPF is a catalyzed ceramic filter which traps particulate matter (soot). The trapped soot is cleaned from the DPF through a catalytic reaction by heating the filter through a process called regeneration. The inlet section of the DPF cannister contains the DPF inlet pressure sensor, and DPF delta pressure sensor. The DPF Inlet Pressure sensor is used to measure the backpressure being generated by the DPF. The delta pressure sensor is used to measure soot collected in the DPF. The delta pressure sensor is measuring the pressure drop across the DPF. Since the delta pressure sensor is measuring flow resistance across the DPF, the sensor will also detect ash loading.
After the exhaust gas flows through the DPF, the gas enters the SCR. The DEF injected prior to the DPF, mixes with exhaust gas in SCR to reduce Nitrogen Oxides (NOX). DEF contains deionized water and urea, which turns to ammonia when heated. The ammonia reacts with the SCR catalyst to convert NOX into harmless nitrogen and water vapor. At the inlet of the SCR cannister is the SCR inlet temperate sensor. This sensor is used to make sure that the temperature is hot enough in the catalyst for DEF dosing to occur.
Engine Throttle Valve and HC Dosing Regeneration
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| Illustration 7 | g06258348 |
| (1) Engine Throttle Valve | |
Mostly, regeneration is achieved passively, which means no added fuel to achieve regeneration. This is achieved by an engine throttle valve. The engine throttle valve is a butterfly valve located between the charger cooler outlet and the inlet manifold. This valve is the primary means of regeneration. The engine throttle valve is controlled by the ECM and is used to restrict the flow of air into the inlet manifold and the combustion chamber. This restriction increases the exhaust gas temperature and is used to control the DOC and SCR temperature to ensure emissions compliance in all operating conditions.
If passive regeneration cannot be achieved due to low temperature, load, or speed, then the use of active regeneration is needed. Active regeneration is the means of injecting a small quantity of fuel into the exhaust stream to create the heat needed to oxidize soot in the DPF, and decrease sulfur in the SCR. This fuel injection process is called In Cylinder Dosing (ICD). The engine throttle valve will always be activated as well when ICD regeneration is occurring to aid in temperature increase.
To regenerate the DPF at the right time, the ECM must know what the soot and sulfur levels are. The soot input is a function of delta pressure measurement across the DPF, and calculated soot model based on developed engine out soot measurements. Sulfur percentage is determined from a calculation based on operating conditions over time. There is no direct sulfur measurement. The information gathered from these inputs is converted into a percentage of soot and sulfur. The percentages can be viewed through Cat® Electronic Technician (ET).
Soot - 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 operating conditions of the engine do not increase temperature enough to oxidize the soot, the engine throttle valve will activate to raise temperature once soot reaches a certain level. If the engine throttle valve cannot achieve the required temperature, and soot increases to a critical level, ICD regeneration will trigger.
Desulfation - The DOC catalyst and SCR catalyst will accumulate sulfur. This will affect the efficiency of both catalysts. A software strategy based on engine fueling and catalyst temperatures determines how much sulfur build-up there is over time. Once sulfur is above a threshold, an ICD regeneration will trigger.
DEF Deposits - The SCR catalyst will accumulate Diesel Exhaust Fluid (DEF) deposits from the fluid being injected to reduce NOx emissions. DEF deposit accumulation will affect the efficiency of the SCR catalyst. Under normal engine operating conditions the SCR should get hot enough that the DEF deposits burn off. If the SCR does not get hot enough, and software strategy determines deposits are increasing, an ICD regeneration will trigger.
De-crystallization - If the temperature at the DEF injector is not hot enough, DEF crystallization will occur. This is a process where DEF crystallizes, causing the DEF injector not to function correctly. Under normal engine operating conditions the DEF crystals should get hot enough to burn off from DEF injector. But if DEF pressure is not increasing when desired, an ICD regen will trigger to remove DEF crystals.
HC Evap - Hydrocarbons can accumulate in the DPF when operating at cold exhaust temperatures. If engine idles long enough at cold temperature, the engine throttle valve will activate to raise temperature and evaporate hydrocarbons.
Regeneration Action Strategies
The soot and sulfate level percentages are generated by the ECM and used in determining when regenerations are required. They are also used to determine when to trigger speed/load requests, lamps, diagnostics, and shutdown strategies related to regeneration.
Speed/Load Requests for Soot - When the soot level reaches 90% and engine is idling, the operator will get a pop-up on display panel indicating that speed must be increased to perform the regeneration. When the soot level reaches 100%, the operator will get a pop-up on display panel indicating that load must be increased to perform the regeneration. At 110% soot, the operator will get a pop-up on display panel indicating that it is urgent the load is increased to perform the regeneration.
Speed/Load Requests for Sulfate - When the sulfate level reaches 90% the operator will get a pop-up on display panel indicating that load must be increased to perform the regeneration. At 120% sulfate the operator will get a pop-up on display panel indicating that it is urgent load is increased to perform the regeneration.
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| Illustration 8 | g06239627 |
EMIL Lamp - The Emission Malfunction Indicator Lamp (EMIL) will be illuminated when a code related to removal, tampering, or loss of function of the DPF becomes active.
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| Illustration 9 | g03749907 |
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DPF Lamp | |
DPF Lamp - The DPF lamp will be illuminated when soot or sulfate levels reach 90%.
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| Illustration 10 | g03749894 |
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Check Engine Lamp (CEL) | |
Check Engine Lamp (CEL): Slow Flash - The amber warning lamp will be illuminated and flash at a slow rate whenever soot is greater than 110%. A 3719-16 fault code will become active. The DPF lamp will remain on with the warning lamp. The amber warning lamp will be illuminated and flash at a slow rate whenever sulfate is greater than 120%. A 7504-16 fault code will become active. The DPF lamp will remain on with the warning lamp.
Check Engine Lamp (CEL): Fast Flash - The amber warning lamp will be illuminated and flash at a fast rate whenever soot is greater than 120%. A 3719-0 fault code will become active. The DPF lamp will remain on with the warning lamp. The amber warning lamp will be illuminated and flash at a fast rate whenever sulfate is greater than 140%. A 7504-0 fault code will become active. The DPF lamp will remain on with the warning lamp.
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| Illustration 11 | g03749898 |
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Red stop lamp | |
Red Stop Lamp: Solid Flash - The red stop lamp will be illuminated solid whenever soot or sulfate reaches 140%. At 140% soot, a 3715-31 fault code will also become active. At 140% sulfate a 7504-0 fault code will become active. The DPF lamp will remain on with the stop lamp.
Forced Engine Idle/Shutdown Strategy - When the soot level reaches 120% a 3719-0 code will become active and the engine will drop to idle after 5 minutes. Three minutes later the engine will shut down. The engine may be restarted, but will only run for 5 minutes before dropping to idle, and again shutdown 3 minutes after that. Once a regeneration is started, the engine will not shut down. Code will reset and engine will go back to normal operating conditions once soot drops below 110%.
When the soot level reaches 140%, the engine will become 100% derated and have a 3715-31 code active. Regenerations can no longer be performed and the DPF must be replaced. The engine will idle for 3 minutes before shutting down. The engine may be restarted but will only run for 3 minutes at a time until DPF is replaced and codes are reset.
When the sulfate level reaches 140%, a 7504-0 code will become active and the engine will drop to idle after 5 minutes. Three minutes after dropping to idle the engine will shut down. A regeneration must be performed immediately to remove sulfur from the SCR. Once regeneration is started, the engine will not drop to idle or shut down in 3 minutes. The 7504-0 code will reset and engine will return to normal operation once the sulfate level drops below 120%.
Regeneration Operating Criteria
Regenerations are automatic and designed so that little to no input is needed from the operator. Regeneration can run within the entire operating window of the machine. Regeneration is accomplished by activating the engine throttle valve or ITV, and is activated automatically by the ECM when required. However if the engine is idling for long periods, or not being operated as designed, exhaust temperatures may not get high enough for regeneration to occur. When attempting to do a regeneration at low speed conditions, such as idle, the operator may be informed through the display panel to increase speed or load.
The temperature sensor at the DOC outlet continuously monitors the temperature at the DOC outlet, which also tells ECM what the DPF inlet temperature should be. The SCR inlet temperature sensor continuously monitors the temperature at the inlet of the SCR. As the temperature changes, the signals from the DPF and SCR inlet temperature sensors are sent back to the ECM. The ECM can then determine if the engine throttle valve, or ICD regeneration is necessary to maintain the desired DPF and SCR inlet temperatures. The DOC outlet temperature being desired depends on the type of regeneration triggered by ECM.
Aftertreatment Configuration Parameters
The aftertreatment system can be configured differently to suit the operation that the system is being used in. Configurations are also needed to assure the correct CEM is connected to the correct engine. The available configurations and the functions are the following:
Factory Installed Aftertreatment #1 Identification Number
This configuration contains the serial number of the CEM that is attached to the engine. This configuration is automatically programmed during initial assembly of the CEM to the engine. If this parameter needs reentered, the serial number can be found on the identification plate attached to the CEM.