SECTION 2 600H, 700HH, 750, 750H, 750HH, 825, 900H, 1050 USER MANUAL
61
2.23 ENGINE EXHAUST
AFTERTREATMENT,
FUNCTIONAL DESCRIPTION
Refer to Section 2.23. The Clean Emissions Module
(CEM) or aftertreatment serves as the means of
achieving the Tier IV emissions requirements set forth
by the EPA/ EU (69 FR 38957-39273, 29 Jun 2004) to
be phased in from 2008-2015. The module itself
consists of a Diesel Particulate Filter (DPF), Muffler,
Exhaust Outlet, DOC/Inlet Cap, Absolute pressure
sensor, CEM Connector to ECM, Combustion Air
Valve, Exhaust inlet, Outlet cap, and a Caterpillar RS
head. The basic function of the aftertreatment is to
remove soot and other solid particulates from the
exhaust via the DPF. The level of soot is monitored by
the engine and, when needed, the system will
automatically regenerate the DPF by raising the
temperature in the DPF through active combustion and
reducing the soot to ash. This system allows the unit to
keep the particulate concentrations of the exhaust at
levels that comply with EPA/EU regulations.
Regeneration can be engaged by two methods:
1. Regeneration Switch (manual force/ inhibition)
2. ECU controlled (automatically managed)
Instead of expelling exhaust gases to the atmosphere as
typical exhaust systems do, exhaust exits the engine
turbocharger and enters the inlet of the CEM, where the
level of soot loading in the DPF is measured by the
pressure differential across the DPF. This information in
conjunction with engine speed is used to determine if
conditions are correct to initiate an automatic
regeneration cycle. During regeneration the CAT RS
module adds diesel fuel and air from the turbocharger to
burn the exhaust fumes and reduce the accumulated
soot to ash. The table in Figure 4-1 describes the
reaction of the system at various stages of the soot
loading profile. For detailed CEM component information
please see the Engine Operator's Manual
Figure 2-7: Exhaust System
1. MUFFLER/SPARK ARRESTOR
2. CEM MODULE
3. EXHAUST PIPE
4. CEM FAN
A1. FUEL LINE IN
A2. COOLANT IN
A3. COOLANT OUT
A4. FROM ENGINE TURBOCHARGER
.
WARNING
Regenerated exhaust gases can reach temperatures of up to
1400ºF. DO NOT come into direct contact with these gases.
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