Significance of Results: Since both these tests
are held under static conditions, the results have
only limited significance with respect to service
performance. Many other factors such as time
exposed to high temperatures, changes from
high to low temperatures, evaporation resistance
and oxidation stability of the grease, frequency
of lubrication, and the design of the lubricated
mechanism are all influences that affect the
maximum usable temperature for the grease.
are held under static conditions, the results have
only limited significance with respect to service
performance. Many other factors such as time
exposed to high temperatures, changes from
high to low temperatures, evaporation resistance
and oxidation stability of the grease, frequency
of lubrication, and the design of the lubricated
mechanism are all influences that affect the
maximum usable temperature for the grease.
Though both dropping point and consistency are
related to temperature, the relationships follow
no consistent pattern. The fact that a grease
does not liquify at a particular temperature gives
related to temperature, the relationships follow
no consistent pattern. The fact that a grease
does not liquify at a particular temperature gives
no assurance that its consistency will be suitable
at that temperature. However, the dropping point
is useful in Identifying the grease as to type and
for establishing and maintaining bench marks
for quality control.
at that temperature. However, the dropping point
is useful in Identifying the grease as to type and
for establishing and maintaining bench marks
for quality control.
One of the weaknesses of either procedure is
that a drop of oil may separate and fall from the
grease cup at a temperature below that at which
the grease fluidizes. This would then give an
erroneous indication of the actual temperature at
which the grease becomes soft enough to flow
from the cup.
that a drop of oil may separate and fall from the
grease cup at a temperature below that at which
the grease fluidizes. This would then give an
erroneous indication of the actual temperature at
which the grease becomes soft enough to flow
from the cup.
FLASH AND FIRE POINTS-OPEN CUP
ASTM D 92
The flash point and the fire point of a petroleum
liquid are basically measurements of flammabil-
ity. The flash point is the minimum temperature
at which sufficient liquid is vaporized to create a
mixture of fuel and air that will burn if ignited. As
the name of the test implies, combustion at this
temperature is only of an instant's duration. The
fire point, however, runs somewhat higher. It is
the minimum temperature at which vapor is
generated at a rate sufficient to sustain combus-
tion. In either case, combustion is possible only
when the ratio of fuel vapor to air lies between
certain limits. A mixture that is too lean or too
rich will not burn.
liquid are basically measurements of flammabil-
ity. The flash point is the minimum temperature
at which sufficient liquid is vaporized to create a
mixture of fuel and air that will burn if ignited. As
the name of the test implies, combustion at this
temperature is only of an instant's duration. The
fire point, however, runs somewhat higher. It is
the minimum temperature at which vapor is
generated at a rate sufficient to sustain combus-
tion. In either case, combustion is possible only
when the ratio of fuel vapor to air lies between
certain limits. A mixture that is too lean or too
rich will not burn.
The practice of testing for flash and fire points
was originally applied to kerosene to indicate its
potentiality as a fire hazard. Since then, the
scope has been broadened to include lubricating
oils and other petroleum products. Though it has
become customary to report flash point (and
sometimes fire point) in lubricating oil data,
these properties are not as pertinent as they
might appear. Only in special instances does a
lubricating oil present any serious fire hazard.
Being closely related to the vaporization char-
acteristics of a petroleum product, however,
flash and fire points give a rough indication of
was originally applied to kerosene to indicate its
potentiality as a fire hazard. Since then, the
scope has been broadened to include lubricating
oils and other petroleum products. Though it has
become customary to report flash point (and
sometimes fire point) in lubricating oil data,
these properties are not as pertinent as they
might appear. Only in special instances does a
lubricating oil present any serious fire hazard.
Being closely related to the vaporization char-
acteristics of a petroleum product, however,
flash and fire points give a rough indication of
volatility and certain other properties.
The fire point of a conventional lubricating oil is
so closely associated with this flash points, that
is generally omitted from inspection data. For
the ordinary commercial products, the fire point
runs about 50° F above the flash point. Fire and
flash points are not to be confused, however,
with auto-ignition temperature, which Is an en-
tirely different matter. Auto-ignition deals, not so
much with volatility, as with the temperature
necessary to precipitate a chemical reaction,
combustion, without an external source of igni-
tion. Though a more volatile petroleum product
may be expected to have lower flash and fire
points than one that is less volatile, its ASTM
auto-ignition temperature is generally higher.
so closely associated with this flash points, that
is generally omitted from inspection data. For
the ordinary commercial products, the fire point
runs about 50° F above the flash point. Fire and
flash points are not to be confused, however,
with auto-ignition temperature, which Is an en-
tirely different matter. Auto-ignition deals, not so
much with volatility, as with the temperature
necessary to precipitate a chemical reaction,
combustion, without an external source of igni-
tion. Though a more volatile petroleum product
may be expected to have lower flash and fire
points than one that is less volatile, its ASTM
auto-ignition temperature is generally higher.
Apparatus: The oil sample is contained in a
precisely specified brass cup that rests on a
metal plate. Under the plate, a source of heat is
provided, and a thermometer in the cup indi-
cates the temperature of the sample. A small
gas igniting torch is used to test the air-vapor
mixture for flammability. Length of the fire-point
burning period is checked with a stop watch.
precisely specified brass cup that rests on a
metal plate. Under the plate, a source of heat is
provided, and a thermometer in the cup indi-
cates the temperature of the sample. A small
gas igniting torch is used to test the air-vapor
mixture for flammability. Length of the fire-point
burning period is checked with a stop watch.
A-3 (FIST 2-4 11/90)