BA 35203_04 * 3.0 * 35203_04_07_Wartung.fm 7-77
Maintenance 7
Diesel oxidation catalytic converter (DOC) with SCR catalytic
converter (option)
This exhaust after-treatment D is a closed system consisting of the diesel
oxidation catalytic converter (DOC) and the SCR catalytic converter
(SCR = selective catalytic reduction) with urea solution.
The diesel oxidation catalyst has a catalyzing surface, through which
harmful substances in the exhaust fumes are converted into non-harmful
substances. In the process, carbon monoxides and unburned
hydrocarbons are brought to react with oxygen and converted into carbon
dioxide and water. In addition, the nitrogen monoxides are converted into
nitrogen dioxides.
Temperatures of > 250°C (> 482°F) are necessary for a high efficiency.
A urea solution injected into the SCR catalytic converter reacts with the
NOx emissions contained in the exhaust fumes and reduces these to
nitrogen (N2) and water (H2O).
The control of the urea injection amount occurs via the engine electronics.
If regeneration should not be possible for different reasons, the system
indicates (by means of symbols and warning lights on the display) that
manual regeneration is necessary
– see “Monitoring of the exhaust after-treatment” on page 7-78.
If the manual regeneration is not carried out, the engine controller
activates the specified engine protection functions
– see “Monitoring of the exhaust after-treatment” on page 7-78.
➥ 1 level: Torque reduction of the diesel engine
➥ 2 level: Torque reduction + engine speed limitation
Every manual regeneration dilutes the motor oil to a small degree with
fuel.
➥ The number of manual regenerations is therefore monitored.
➥ Therefore, before an oil change, always perform a manual
regeneration of the exhaust after-treatment system – see “Manual
regeneration” on page 7-84. Then reset the maintenance counter in
the DEUTZ engine controller.
The SCR catalytic converter reacts to the faulty operation of the exhaust
after-treatment system with various warning notices.
Errors are:
► Fill level of the urea solution too low (below 15%)
► Reduced degree of efficiency of the SCR catalytic converter
► Quality of the urea solution
► System error of the SCR catalytic converter
► Crystallization in the SCR catalytic converter
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