MQ Power DCA300SSJU4F3 Operation Manual page 60

60hz generators
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SELECTIVE CATALYTIC REDUCTION (SCR)
Diesel engines can be run with a lean burn air-to-fuel ratio,
to ensure the full combustion of soot and to prevent the
exhaust of unburnt fuel. The excess of air necessarily leads
to generation of nitrogen oxides (NO
pollutants, from the nitrogen in the air. Selective Catalytic
Reduction is used to reduce the amount of NO
into the atmosphere.
Diesel Exhaust Fluid (DEF) from a separate tank is
injected into the exhaust pipeline, where the aqueous urea
vaporizes and decomposes to form ammonia and carbon
dioxide. Within the SCR catalyst, the NO
reduced by the ammonia (NH
nitrogen (N
), which are both harmless; and these are then
2
released through the exhaust.
The SCR system creates a certain amount of ammonia
(NH
) that is stored in SCR catalyst. During purging
3
operations the increase in temperature at regular intervals
eleminates the stored ammonia.
The process of keeping accurate amonia storage amounts
is by counting urea injection quantities from the Dosing
Control Unit (DCU)
The SCR Purge symbol (Figure 85) will be displayed on the
ECU controller during operation when either an automatic
or forced system purge operation is in process.
The pre-alarm lamp is only ON during DOC/SCR forced
system purging and OFF during automatic system purging
ECU
Series 800 Controller
SCR PURGE
Alarm
Screen
Option
Acknowledge
Change
Figure 85. SCR Purge Symbol
PAGE 60 — DCA300SSJU4F2/F3 60 HZ GENERATOR • OPERATION MANUAL — REV. #2 (04/18/22)
), which are harmful
x
released
x
are catalytically
x
) into water (H
O) and
3
2
Engine Started
Shutdown
Pre-Alarm
Program
Exit
NOTICE
During urea DOC/SCR system purging, white smoke
may be emitted from the exhaust tailpipe temporarily
this shoud not be considered a failure. In addition the
smell of ammonia during the purging process should
not be considered a failure.
If the purging process is underway while running a light
load (0-35%) the unit may produce unusual sounds.
This should not be considered a failure or malfunction.
SYSTEM PURGING GUIDELINES
NOTICE
DO NOT perform purging in conditions where it may be
unsafe due to high exhaust temperatures.
For safe operation of equipment, the surrounding area and
the prevention of bodily harm, use the guidelines below
when system purging is required:
NOTICE
The area above and around the generator during the
purging process should be free of any type of debris,
flammable or combustible materials, as temperatures
during the purging process can reach as high
1,022 °F (550 °C).
„ DO NOT operate the unit in area with poor ventilation.
„ If operating the engine indoors, install exhaust/ventilation
equipment and ensure that there is sufficient ventilation.
„ If you begin to feel sick, stop the unit immediately and
ventilate the area.
„ Exhaust emissions from the tailpipe have a smell different
from those emitted from engines without urea SCR
systems due to the exhaust emission reduction functions
of the exhaust system.
MAINTENANCE

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