Pour Point and Cloud Point
Pour points are determined initially by heat-treating the petroleum specimen above
its expected pour point and then by cooling the specimen in controlled stages until
the pour point is observed. The pour point is the temperature of the material at
which it ceases to flow.
ASTM D97
The apparatus used to determine pour point (and cloud point) consists of a cylindrical glass jar with a flat bottom and a cork stopper at its top. A thermometer is
inserted through the cork stopper so that the bulb is immersed up to 3 mm of the
capillary in the specimen. The sample is inserted into the jar up to a prescribed
level. The apparatus is shown in the following Fig. 3 and is self-explanatory.
The sample is first heated as follows:
Material with an estimated pour point above 33
C – heat to a temperature of
expected pour point plus 9
C but at least 45
C in a bath controlled to at least 48
C.
Material with an expected pour point of below 33
C – heat to at least 45
C and
cool to 15
C in a bath controlled at 6
C.
THERMOMETER
CORK
44.2 - 45.8 ID.
30 - 32.4 ID.
33.2 - 34.8 OD.
25 MAX.
6
5
115 - 125
115
COOLANT LEVEL
JACKET
TEST JAR
FILL LEVEL
CASKET
COOLING BATH
DISK
NOTE 1- Dimensions are in millimetres (not to scale).
Fig. 3 Apparatus for pour point tests
666
D.S.J. Jones