Operation
9270−1/A1
Winterthur Gas & Diesel Ltd.
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2.2 SCR Heating-up with Exhaust gas (Tier II)
For operation conditions, the SCR temperature must be equal to or more than
T
Minimum
Exhaust
Gas
(see Table 2). The SCR system uses hot exhaust gas to get the
applicable operation temperature, see Fig. 4.
The engine operates in Tier II mode to prepare for the heating-up. An urea solution is
not injected. In this mode, valve V1 is fully open. Valve V2 is fully open to let the
exhaust gas flow the SCR reactor. Subsequently, valve V3 is part-closed to let the
exhaust mass flow through the SCR reactor. Thus, the mass exhaust flow increases
gradually the temperature of the SCR reactor to prevent thermal force and thermal
problems.
The SCR reactor can have an external heater. This heater can be manually activated.
Note: If Tier II mode is selected, the operator can set to on the external heater. If
Tier III mode is selected and the engine is stopped, the control system
automatically sets to on the external heater.
Load changes can cause sudden changes in scavenge air pressure.
The system can operate the valve V4 to adjust the exhaust gas temperature and to
decrease sudden changes in scavenge air pressure.
The remaining valves stay closed.
Engine
V1
V2
V3
V7
V4
Turbocharger
SCR Reactor
Air pipes − flow
Exhaust pipes − no flow
Exhaust pipes − flow
WCH03722
Fig. 4: SCR Heating-up with Exhaust Gas
2016−11
Selective Catalytic Reduction System
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