JLG 1850SJ, Руководство по обслуживанию и ремонту, Страница: 112 / 712

SECTION 3 - CHASSIS & TURNTABLE
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3.22 SELECTIVE CATALYTIC REDUCTION (SCR) -
MACHINES USING DIESEL EXHAUST FLUID (DEF)
Selective Catalytic Reduction (SCR) is an emissions control
used in diesel engines.
This system injects a liquid-reductant agent through a special
catalyst into the exhaust stream of a diesel engine. The reduc-
tant source is usually automotive-grade urea known as Diesel
Exhaust Fluid (DEF). DEF sets off a chemical reaction that con-
verts nitrogen oxides into nitrogen, water, and tiny amounts of
carbon dioxide (CO2), which is then expelled through the
engine exhaust pipe.
For peak operation, the SCR system must be cleaned using
one of two methods, Standstill Cleaning and Maintenance
Standstill Cleaning. Standstill Cleaning is any cleaning
requested by the engine outside of the regular maintenance
window (for example, if the system detects crystallization in
the DEF solution). Maintenance Standstill Cleaning is cleaning
requested by the engine on the maintenance interval.
SCR technology is designed to permit nitrogen oxide (NOx)
reduction reactions to take place in an oxidizing atmosphere.
It is called "selective" because it reduces levels of NOx using
ammonia as a reductant within a catalyst system. The chemi-
cal reaction is known as "reduction" where the DEF is the
reducing agent that reacts with NOx to convert the pollutants
into nitrogen, water and tiny amounts of CO2. The DEF can be
rapidly broken down to produce the oxidizing ammonia in the
exhaust stream. SCR technology alone can achieve NOx reduc-
tions up to 90 percent.
NOTE: The system will reset the maintenance interval back to 0
hours after Standstill or Maintenance Standstill cleaning
events are performed.
Standstill Cleaning
The following conditions must be met to perform Standstill
Cleaning.
• Machine must be stationary
• Engine must be idling
• Coolant temperature must be above 104° F (40° C)
• Diesel Exhaust Fluid (DEF) tank must not be frozen
• Machine in Ground Station mode
1. The Selective Catalytic Reduction Indica-
tor will flash when standstill cleaning is
required.
2. Move the machine to an area free of flammables and
personnel that could be exposed to hot exhaust. Launch
the cleaning process by pressing the SCR button on the
Ground Console for 3 seconds. The Indicator Gauge will
display the following screen.
3. The Main Cleaning process will begin and last for
approximately 30 to 60 minutes. The following screen
will show that the process has begun and includes a sta-
tus bar that indicates the progress of the cleaning pro-
cess.