Mack M359, Manual

Page: 208 / 332

EMISSION SOLUTION AND CONTROL
AFTERTREATMENT, MACK
Selective Catalytic
Reduction (SCR)
Selective Catalytic Reduction (SCR) is
an emissions-reduction aftertreatment
technology with the ability to deliver
near-zero emissions of nitrogen oxides
(NOx), a smog-causing pollutant, and
greenhouse gas.
SCR reduces NOx emissions to low
levels, and delivers excellent fuel
economy and reliability. The system
does not change the design of the basic
engine. Rather, SCR is an aftertreatment
system which converts NOx in the
exhaust stream into harmless gases.
The SCR works by injecting Diesel
Exhaust Fluid (DEF) into the exhaust.
DEF is a solution of ultra-pure water and
urea. DEF works with the heat of the
exhaust and a catalyst to convert NOx
into nitrogen and water vapor. Both
substances are harmless and natural
components. The result is cleaner air,
fuel efficiency, and a reliable emissions
control system.
1 Diesel Engine
2 Aftertreatment DEF Tank
3 Aftertreatment DEF Pump
4 Aftertreatment DEF Dosing Unit
5 Aftertreatment Diesel Particulate Filter (DPF)
6 Selective Catalytic Reduction (SCR) Catalyst
7 Aftertreatment DEF Tank Gauge
1 Diesel Engine
2 Combined Aftertreatment System (SCR and
DPF)
3 Aftertreatment DEF Dosing Unit
4 Aftertreatment DEF Pump
5 Aftertreatment DEF Tank
6 Aftertreatment DEF Tank Gauge
CAUTION
Do not put diesel fuel in the Aftertreatment
DEF tank. Diesel fuel, if sprayed into the
hot exhaust along with the DEF, could
ignite causing personal injury or damage
the exhaust system.
NOTE
The SCR is equipped with an insulation
blanket, this blanket is critical to the
performance of the Exhaust
Aftertreatment System (EATS).
If this blanket is compromised or
damaged the EATS system might not
perform as designed and you should take
the vehicle to an approved dealer for
inspection.
This information is for the 2 box
Aftertreatment System only.
CAUTION
When handling the blankets and or straps,
gloves should be worn to protect from
cuts and abrasions.
There are three different configurations
for the SCR catalysts, they are vertical,
horizontal and the one box EATS.
The SCR system is simple and effective,
with few components. It consists of an
Aftertreatment DEF tank positioned near
the standard diesel tank, plus an
198
X Publication_PC28