TM 5-3895-383-24
Illustration 122
Cloud point of fuel mixtures
Generally, the most practical method that is used to prevent
problems that are caused by fuel cloud point at low
temperatures is the use fuel heaters. In most applications, fuel
heaters can be used at a lower cost than fuel mixtures.
Pour Point
The fuel's pour point is a temperature below the fuel's cloud
point. Fuel stops flowing below the pour point. The pour point
is the temperature which limits movement of the fuel with
pumps.
To measure the pour point the fuel temperature is lowered
below the cloud point in steps of 3C (5F) at a time. The
temperature is lowered until the fuel does not flow. The pour
point is the last temperature that is shown before the flow
stops. At the pour point, the wax has solidified out of the fuel.
This makes the fuel more solid than liquid. The pour point of
the fuel can be improved. This does not require the removal of
important elements. This process is the same process that is
used to improve the cloud point of a fuel.
A fuel's pour point should be at least 6C (10°F) below the
lowest
ambient
temperature
that
is
required
for
engine start-up and for engine operation. To operate the
engine in extremely cold weather, No. 1 fuel or No. 1-D fuel
may be necessary because of these fuels' lower pour points.
Modifying the Pour Point
You can lower the fuel's pour point by using additives. You
can also lower the pour point by mixing the fuel with a fuel that
has a lower pour point. See the topic "Cloud Point" for the
procedure. This procedure is not the best procedure to use.
The same table that was use for cloud point can be used for an
estimate of pour points. This is true only if the fuels do not
have additives which change the pour point.
Illustration 123
Cloud point of fuel mixtures
In order to calculate the amount of lighter fuel that is required
to be Mended with the heavier fuel, perform the following
steps:
1.
Obtain the specification for fuel cloud point of both fuels
from your fuel supplier.
2.
Locate the cloud point of the heavier fuel on the left side
of the table. Mark the point on the table.
Maintenance Section
Fuel Specifications
1-36
