(Table 8, contd)
(4)
The values of the fuel viscosity are the values as the fuel is delivered to the fuel injection pumps. Fuel should also meet the minimum viscos-
ity requirement and the fuel should meet the maximum viscosity requirements at 40°C (104°F) of either the “ASTM D445” test method or the
“ISO 3104” test method. If a fuel with a low viscosity is used, cooling of the fuel may be required to maintain “1.4 cSt”or greater viscosity at
the fuel injection pump. Fuels with a high viscosity might require fuel heaters in order to lower the viscosity to “1.4 cSt” at the fuel injection
pump.
(5)
Follow the test conditions and procedures for gasoline (motor).
(6)
Refer to the lubricity section within this Fuel Recommendation Section.
Engines that are manufactured by Perkins are
certified with the fuel that is prescribed by the
appropriate regulatory agency. Engines that are
manufactured by Perkins are certified with the fuel
that is prescribed by the European Certification.
Perkins does not certify diesel engines on any other
fuel.
Note: The owner and the operator of the engine has
responsibility of using the fuel that is prescribed by
the EPA and other appropriate regulatory agencies.
NOTICE
Operating with fuels that do not meet the Perkins rec-
ommendations can cause the following effects: Start-
ing difficulty, reduced fuel filter service life, poor
combustion, deposits in the fuel injectors, signifi-
cantly reduce service life of the fuel system, deposits
in the combustion chamber and reduced service life
of the engine.
Diesel Fuel Characteristics
Cetane Number
Fuel that has a high cetane number will give a shorter
ignition delay. A high cetane number will produce a
better ignition quality. Cetane numbers are derived
for fuels against proportions of cetane and
heptamethylnonane in the standard CFR engine.
Refer to “ISO 5165” for the test method.
Cetane numbers in excess of 45 are normally
expected from current diesel fuel. However, a cetane
number of 40 may be experienced in some territories.
The United States of America is one of the territories
that can have a low cetane value. A minimum cetane
value of 40 is required during average starting
conditions. A fuel with higher cetane number is
recommended for operations at high altitudes or in
cold-weather operations.
Fuel with a low cetane number can be the root cause
of problems during a cold start.
Viscosity
Viscosity is the property of a liquid of offering
resistance to shear or flow. Viscosity decreases with
increasing temperature. This decrease in viscosity
follows a logarithmic relationship for normal fossil
fuel. The common reference is to kinematic viscosity.
Kinematic viscosity is the quotient of the dynamic
viscosity that is divided by the density. The
determination of kinematic viscosity is normally by
readings from gravity flow viscometers at standard
temperatures. Refer to “ISO 3104” for the test
method.
The viscosity of the fuel is significant because fuel
serves as a lubricant for the fuel system components.
Fuel must have sufficient viscosity in order to
lubricate the fuel system in both extremely cold
temperatures and extremely hot temperatures. If the
kinematic viscosity of the fuel is lower than “1.4 cSt”
at the fuel injection pump, damage to the fuel
injection pump can occur. This damage can be
excessive scuffing and seizure. Low viscosity may
lead to difficult hot restarting, stalling, and loss of
performance. High viscosity may result in seizure of
the pump.
Perkins recommends kinematic viscosities of 1.4 and
4.5 mm2/sec that is delivered to the fuel injection
pump. If a fuel with a low viscosity is used, cooling of
the fuel may be required to maintain 1.4 cSt or
greater viscosity at the fuel injection pump. Fuels with
a high viscosity might require fuel heaters in order to
lower the viscosity to 4.5 cSt at the fuel injection
pump.
Density
Density is the mass of the fuel per unit volume at a
specific temperature. This parameter has a direct
influence on engine performance and a direct
influence on emissions. This influence determines
from a heat output given injected volume of fuel. This
parameter is quoted in the following kg/m
3
at 15 °C
(59 °F).
Perkins recommends a density of 841 kg/m
3
in order
to obtain the correct power output. Lighter fuels are
acceptable but these fuels will not produce the rated
power.
58
SEBU8731-04
Maintenance Section
Fuel Specification
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