MULTIQUIP WHISPERWATT Series Operation Manual page 59

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; 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
eliminates the stored ammonia.
The process of keeping accurate ammonia storage
amounts is by counting urea injection quantities from the
Dosing Control Unit (DCU).
The SCR Purge symbol (Figure 83) 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 SCR forced system
purging and OFF during automatic system purging.
ECU
Series 800 Controller
SCR PURGE
Alarm Screen
Option
Acknowledge Change
Figure 83. SCR Purge Symbol
DCA400SSI4F/DCA400SSI4F3 60 HZ GENERATOR • OPERATION MANUAL — REV. #3 (04/18/22) — PAGE 59
), 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 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 (0–30%) 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 an 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.
„ Due to the exhaust emission reduction functions of the
exhaust system, exhaust emissions from the tailpipe
have a different smell from those emitted from engines
without urea SCR systems.
MAINTENANCE