Cetane numbers more than 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.
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 to lubricate the
fuel system in both cold temperatures and 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 cSt 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 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
the heat output from a given injected volume of fuel.
This parameter is quoted in the following kg/m3 at
15 °C (59 °F).
Perkins recommends a value of density of 841 kg/m3
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.
LSD fuel with less than 0.05 percent (≤ 500 ppm (mg/
kg)) sulfur is recommended for use in these engine
models.
ULSD less than 0.0015% (≤15 PPM (mg/Kg)) sulphur
is acceptable to use in these engine models. The
lubricity of these fuels must not exceed wear scar
diameter of 0.46 mm (0.01811 inch) as per “ISO
12156-1”. Refer to “Lubricity” for more information.
Fuels with sulphur content higher than 0.05 percent
(500 PPM) can be used where allowed by legislation.
Fuel with a high sulfur content can cause engine
wear. High sulfur fuel will have a negative impact on
emissions of particulates. High sulfur fuel can be
used if the local emissions legislation will allow the
use. High sulfur fuel can be used in countries that do
not regulate emissions.
When only high sulfur fuels are available, use a high
alkaline lubricating oil, or reduce the oil change
interval. Refer to Operation and Maintenance
Manual, “Fluid Recommendations (Lubricant
Information)” for information on sulfur in fuel.
Lubricity
Lubricity is the capability of the fuel to prevent pump
wear. The lubricity of the fluid describes the ability of
the fluid to reduce the friction between surfaces that
are under load. This ability reduces the damage that
is caused by friction. Fuel injection systems rely on
the lubricating properties of the fuel. Until fuel sulfur
limits were mandated, the lubricity of the fuel was
believed to be a function of fuel viscosity.
The lubricity has particular significance to the current
low viscosity fuel, low sulfur fuel, and low aromatic
fossil fuel. These fuels are made to meet stringent
exhaust emissions.
The lubricity of these fuels must not exceed wear
scar diameter of 0.46 mm (0.01811 inch). The fuel
lubricity test must be performed on an HFRR,
operated at 60 °C (140 °F). Refer to “ISO 12156-1”.
NOTICE
The fuels system has been qualified with fuel having
lubricity up to 0.46 mm (0.01811 inch) wear scar di-
ameter as tested by “ISO 12156-1”. Fuel with higher
wear scar diameter than 0.46 mm (0.01811 inch) will
lead to reduced service life and premature failure of
the fuel system.
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