PREVOST H 2018 Series Operator'S Manual Download

Page: 120 / 258

5-6 OTHER FEATURES

PA1628 H3-41, H3-45 Operator’s Manual

CAUTION

If an active regeneration is stopped
repeatedly, the vehicle may need to be
taken to a service facility. The service
facility will use a service tool to manually
initiate the regeneration. Moreover, the
interruption of active regeneration should
not be considered as a normal practice.
Some components of the aftertreatment
system might be damaged in the long term.

SELECTIVE CATALYTIC REDUCTION UNIT

Selective Catalytic Reduction (SCR) is a
technology that uses Diesel Exhaust Fluid (DEF)
and a catalytic converter to reduce nitrogen
oxides (NOx) emissions.

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, it is important that
electrical connectors to be connected or well
encapsulated, 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):



If urea solution comes into contact with the
skin, rinse with plenty of water and remove
contaminated clothing.



If urea solution comes into contact with the
eyes rinse for several minutes and call for
medical help if necessary.



If inhaled breathe fresh air and call for
medical help if necessary.



Do not allow the DEF solution to come into
contact with other chemicals.



The DEF solution is not flammable. If the DEF
solution is exposed to high temperatures, it
breaks down into ammonia and carbon
dioxide.



The DEF solution is highly corrosive to certain
metals, including copper and aluminum.



If the DEF solution is spilled onto the vehicle,
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.