Installation Manual

Electrical & Electronic Application And Installation Manual
Production Release Version 1.0
Page 14
2.2.3 Selective Catalytic Reduction (SCR) Technologies
The SCR system supplied by Perkins with each Tier 4 Final engine family
differs depending on the selected product. In principle however the 1204F
and 1206F DEF systems are made up of the same core components as listed
below;
• DEF Tank and Header Unit. The Header controls feed of DEF out to
the DEF pump and houses temperature and level sensors. Unit also
provides mechanism for tank thaw to be achieved during engine
running.
• Coolant Valve. Controls the flow of engine coolant out to the DEF
header to aid DEF thaw.
• DEF Heated Lines. Required to supply DEF to and from the DEF
pump and from the DEF pump out to the DEF injector. Each line has a
heated element electrical connection to ensure DEF flowing through
the lines is kept form freezing.
• Dosing Control Unit. The SCR system DCU controller is required to
provide localised control of the aftertreatment DEF system and manage
the system communication between the SCR system and the engine
ECM.
• DEF Pump Unit. The DEF pump unit is required to draw DEF from the
tank and provide pressurised fluid to the DEF injector. The DEF pump
is also responsible for purging the system of DEF during engine
shutdown.
• DEF Injector. The DEF injector is responsible for dispersing DEF into
the engine exhaust Post DOC / DPF to provide DEF storage across the
SCR catalyst.
• SCR (Selective Catalytic Reduction) Catalyst. Used to store DEF
(Urea) across a catalyst material so that when engine exhaust gas is
passed over it NOx gas is removed.