Significance of Demulsibility Tests: In many
applications, oil is exposed to contamination by
water condensed from the atmosphere. With
turbine oils, exposure is even more severe,
since the oil tends to come in contact with
Water promotes the rusting of ferrous parts and
accelerates oxidation of the oil. For effective
removal of the water, the oil must have good
Steam cylinder oils that serve in closed systems
require good emulsibillty for the opposite rea-
son: to facilitate removal of oil from the
condensate, so that oil is kept out of the boiler.
Hydraulic fluids, motor oils, gear oils, diesel
engine oils, insulating oils, and many similar
petroleum products must resist emulsification.
Oil and water must separate rapidly and thor-
Either of the ASTM methods is suitable for eval-
uating the demulsification properties both of
inhibited and uninhibited oils. However, corre-
lation with field performance is difficult. There
are many cases where the circulating oil is op-
erating satisfactorily in the field, but falls the
demulsibility test in the laboratory. Hence, it
must be recognized that these laboratory test
results should be used in conjunction with other
facts in evaluating an oil's suitability for contin-
DROPPING POINT OF GREASE
ASTM D 566 and ASTM D 2265
It is often desirable to know the temperature at
which a particular lubricating grease becomes
so hot as to lose its plastic consistency. Being a
mixture of lubricating oil and thickener, grease
has no distinct melting point in the way that
homogeneous crystalline substances do. At
some elevated temperature, however, the ordi-
nary grease becomes sufficiently fluid to drip.
This temperature is called the dropping point
and can be determined by the ASTM Method D
566--"Dropping Point of lubricating Grease" and
ASTM Method D 2265--"Dropping Point of
Lubricating Grease of Wide Temperature
Apparatus: Chromium-plated brass grease cup-
-with small orifice at bottom.
Test tube--designed to hold grease cup about
3/4" above bottom.
2 Thermometers--one for grease cup, one for
the heat source.
Source of heat--oil bath - ASTM D 566; Alumi-
num Block oven - ASTM D 2265.
ASTM D 566--The grease cup Is filled with the
grease to be tested and then placed In the test
tube with the thermometer and stopper inserted.
The test tube is then submerged in the oil bath.
The bath temperature is Increased until a drop
of material (grease or oil) falls from the orifice at
the bottom of the cup. The thermometer
readings for the oil bath and the grease are
recorded at this instant. The average of the two
temperatures is reported as the dropping point
of the grease.
ASTM D 2265--This test is the same as ASTM
D 566 except that this method provides for
heating with an aluminum block oven. The oven
makes it possible to measure dropping points up
to 625° F, higher than was possible with the oil
(FIST 2-4 11/90)