Perkins 1206A-E70TTA Operation And Maintenance Manual page 46

46
Operation Section
Radiator Restrictions
The Water Temperature Regulator and
Insulated Heater Lines
The engine is equipped with a water temperature
regulator. When the engine coolant is below the
correct operating temperature, jacket water circulates
through the engine cylinder block and into the engine
cylinder head. The coolant then returns to the
cylinder block via an internal passage that bypasses
the valve of the coolant temperature regulator. This
return ensures that coolant flows around the engine
under cold operating conditions. The water
temperature regulator begins to open when the
engine jacket water has reached the correct
minimum operating temperature. As the jacket water
coolant temperature rises above the minimum
operating temperature, the water temperature
regulator opens further allowing more coolant
through the radiator to dissipate excess heat.
The progressive opening of the water temperature
regulator operates the progressive closing of the
bypass passage between the cylinder block and
head. This action ensures maximum coolant flow to
the radiator to achieve maximum heat dissipation.
Note: Do not restrict the air flow. Restriction of the air
flow can damage the fuel system. Perkins
discourages the use of all air flow restriction devices
such as radiator shutters. Restriction of the air flow
can result in the following: high exhaust
temperatures, power loss, excessive fan usage, and
reduction in fuel economy.
A cab heater is beneficial in very cold weather. The
feed from the engine and the return lines from the
cab should be insulated to reduce heat loss to the
outside air.
Radiator Restrictions
Perkins discourages the use of airflow restriction
devices that are mounted in front of radiators. Airflow
restriction can cause the following conditions:
• High exhaust temperatures
• Power loss
• Excessive fan usage
• Reduction in fuel economy
Reducing air flow over components will also affect
under hood temperatures. Reducing air flow can
increase surface temperatures and could affect
component reliability.
If an airflow restriction device must be used, the
device should have a permanent opening directly in
line with the fan hub. The device must have a
minimum opening dimension of at least 770 cm
2
(120 in ).
A centered opening that is directly in line with the fan
hub is specified to prevent an interrupted airflow on
the fan blades. Interrupted airflow on the fan blades
could cause a fan failure.
Perkins recommends a warning device for the inlet
manifold temperature and/or the installation of an
inlet air temperature gauge. The warning device for
the inlet manifold temperature should be set at 75 °C
(167 °F). The inlet manifold air temperature should
not exceed 75 °C (167 °F). Temperatures that
exceed this limit can cause power loss and potential
engine damage.
Fuel and the Effect from Cold
Weather
Note: Only use grades of fuel that are recommended
by Perkins. Refer to this Operation and Maintenance
Manual, "Fluid Recommendations".
Properties of the diesel fuel can have a significant
effect on the engine cold start capability. It is critical
that the low temperature properties of diesel fuel are
acceptable for the minimum ambient temperature the
engine is expected to see in the operation.
Following properties are used to define fuels low
temperature capability:
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• Cloud point
• Pour point
• Cold Filter Plugging Point (CFPP)
The cloud point of the fuel is the temperature at
which waxes naturally found in the diesel fuel begin
to form crystals. The cloud point of the fuel must be
below lowest ambient temperature to prevent filters
from plugging.
Cold Filter Plugging Point is a temperature at which a
particular fuel will pass through a standardized
filtration device. This CFPP gives an estimate of the
lower operability temperature of fuel
Pour point is the last temperature before the fuel flow
stops and waxing of the fuel will start.
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