PREVOST H3-45 2023 Operator's Manual page 138

5-6 Other Features
SCR is an exhaust aftertreatment system that
injects small amount of DEF into the exhaust gas
between the DPF and the selective reduction
catalytic converter. DEF turns to ammonia and
carbon dioxide when heated. The exhaust stream
then passes over a catalyst, the ammonia reacts
with the NOx to form nitrogen and water vapor.
The basic elements of the SCR system consist of
a 15.9 gallons (60 liters) DEF tank complete with
pump, lines and heating system, a dosing
injector, a catalytic converter and the control and
monitoring system.
Diesel Exhaust Fluid (DEF)
When handling DEF solution, keep electrical
connectors properly connected or well capped,
otherwise there is a risk that the DEF will cause
oxidation that cannot be removed. Water or
compressed air will not help, since DEF quickly
oxidizes certain metals. If a disconnected
connector comes into contact with the DEF
solution, it must be replaced immediately to
prevent the DEF solution from creeping further
into the copper wiring, which takes place at a
speed of about 2.4 in (60 mm) per hour.
CAUTION
Diesel Exhaust Fluid (DEF) is a nontoxic
aqueous solution of urea (32.5%) and ultra-
pure water (67.5%). Urea is a compound of
nitrogen that turns to ammonia when heated.
The fluid is non flammable, and is not
dangerous when handled as recommended.
However, it is highly corrosive to certain metals,
especially copper and brass.
When detaching hoses and components, do
not spill DEF on disconnected or unsealed
connectors. If DEF is spilled on a disconnected
or unsealed connector, the connector must be
removed immediately and replaced.
Things to know about spilt diesel exhaust fluid
(DEF):
DEF freezing and expansion
DEF will begin to crystallize and freeze at 12°f
(- 11°c). DEF expands by approximately 7%
when frozen. During freezing weather, do not
store a DEF container on the coach unless it is
designed to allow for expansion.
Make sure the DEF container is not completely
full. DEF expansion may split an inappropriate
container, causing a spill and corrosion as a
result.
DEF spilt onto hot components will quickly
vaporize. Turn your face away!
PA-1652 Operator's Manual H3-45 Coach
If urea solution comes into contact with the
l
skin, rinse with plenty of water and remove
contaminated clothing.
If urea solution comes into contact with the
l
eyes rinse for several minutes and call for
medical help if necessary.
If inhaled breathe fresh air and call for
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medical help if necessary.
Do not allow the DEF solution to come into
l
contact with other chemicals.
The DEF solution is not flammable. If the
l
DEF solution is
temperatures, it breaks down into ammonia
and carbon dioxide.
The DEF solution is highly corrosive to
l
certain metals, including
aluminum.
If the DEF solution is spilled onto the vehicle,
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wipe off the excess and rinse with water.
Spilled DEF solution can form concentrated
white crystals on the vehicle. Rinse off these
crystals with water.
CAUTION
WARNING
exposed to high
copper and