Perkins 1104D Operation And Maintenance Manual page 54

54
Maintenance Section
Fuel Specification
(Table 6, contd)
(5) 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 4.5 cSt at the fuel injection
pump.
(6) Follow the test conditions and procedures for gasoline (motor).
(7) The lubricity of a fuel is a concern with low sulfur and ultra low sulfur fuel. To determine the lubricity of the fuel, use the "ISO 12156-1 or ASTM
D6079 High Frequency Reciprocating Rig (HFRR)" test. If the lubricity of a fuel does not meet the minimum requirements, consult your fuel
supplier. Do not treat the fuel without consulting the fuel supplier. Some additives are not compatible. These additives can cause problems in
the fuel system.
NOTICE
Operating with fuels that do not meet the Perkins rec-
ommendations can cause the following effects: Start-
ing difficulty, poor combustion, deposits in the fuel
injectors, reduced service life of the fuel system, de-
posits in the combustion chamber and reduced serv-
ice life of the engine.
Diesel Fuel Characteristics
Perkins Recommendation
Cetane Number
Fuel that has a high cetane number will give a shorter
ignition delay. This 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 higher cetane value may be required for
operations at high altitudes or in cold weather
operations.
Fuel with a low cetane number can be the root cause
of problems during 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.
This 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.
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 determines the heat
output from a given injected volume of fuel. This is
generally quoted in the following kg/m at 15 °C
(59 °F).
Perkins recommends a value of density of 841 kg/m
in order to obtain the correct power output. Lighter
fuels are acceptable but these fuels will not produce
the rated power.
Sulfur
The level of sulfur is governed by emissions
legislations. Regional regulation, national regulations
or international regulations can require a fuel with a
specific sulfur limit. The sulfur content of the fuel and
the fuel quality must comply with all existing local
regulations for emissions.
SEBU8172-04