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8/13/2019 8. Cloud and Pour Points Test
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8. CLOUD AND POURPOINTS TEST
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1. AIM
To determine the Cloud point and pour point of
the given sample.
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2. REQUIREMENTS
Cloud and pour point apparatus, Thermometer, Ice
crystals.
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3. DEFINITIONS
The cloud point of a fluid is the temperature at
which dissolved solids are no longer completely
soluble, precipitating as a second phase giving the
fluid a cloudy appearance. This term is relevant toseveral applications with different consequences.
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3. DEFINITIONS (CONT..)
Also, the pour point can be defined as the lowest
temperature expressed in multiples of 3C at
which the oil is observed to flow when cooled and
examined under prescribed conditions.
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4. THEORY
Cloud point and pour point are indicators of the
lowest temperature of utility for petroleum
products. Cloud Point gives a rough idea of
temperature above which the oil can be safelyhandled without any fear of congealing or filter
clogging. The sample is periodically examined
while it is being cooled in the cloud and pour point
apparatus.
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4. THEORY (CONT..)
The highest temperature at which haziness is
observed (cloud point), or the lowest temperature
at which the oil ceased to flow is observed (pour
point), is reported as the test result.
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4. THEORY (CONT..)
The cold filter plugging point test is used to
determine the extent to which diesel fuel or gas oil
will flow, even though the temperature is below
that at which wax crystals normally appear, i.e.cloud point.
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4. THEORY (CONT..)
Pour point is a well established test to estimate
the temperature at which a sample of oil becomes
sufficiently solid to prevent its movement by
pumping. The pour point indicates the waxy natureof the oils.
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4. THEORY (CONT..)
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4. THEORY (CONT..)
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5. PROCEDURE
5.1 Measuring cloud point of petroleum product:
The test oil is required to be transparent in layers
40mm in thickness (in accordance with ASTM
D2500). The crystals of the sample typically firstform at the lower circumferential wall with the
appearance of a whitish or milky cloud. The cloud
point is the temperature at which these crystals
first appear.
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5. PROCEDURE (CONT..)
The test sample is first poured into a test jar to a
level approximately half full. A cork carrying the
test thermometer is used to close the jar. The
thermometer bulb is positioned to rest at thebottom of the jar. The entire test subject is then
placed in a constant temperature cooling bath on
top of a gasket to prevent excessive cooling.
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5. PROCEDURE (CONT..)
At every 1C, the sample is taken out and
inspected for cloud then quickly replaced.
Successively lower temperature cooling baths may
be used depending on the cloud point. Lowertemperature cooling bath must have temperature
stability not less than 1.5 K for this test.
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5. PROCEDURE (CONT..)
5.2 Measuring pour point of petroleum product:
Two pour points can be derived which can give an
approximate temperature window depending on
its thermal history. Within this temperature range,the sample may appear liquid or solid. This
peculiarity happens because sample crystals form
more readily when it has been heated within the
past 24hrs and contributes to the lower pour
point.
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5. PROCEDURE (CONT..)
The upper pour point is measured by pouring
the test sample directly into a test jar. The sample
is then cooled and then inspected for pour point as
per the usual pour point method. The lower pour point is measured by first
pouring the sample into a stainless steel pressure
vessel. The vessel is then screwed tight and heated
to above 100oC in an oil bath.
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5. PROCEDURE (CONT..)
After a specified time, the vessel is removed and
cooled for a short while. The sample is then
poured into a test jar and immediately closed with
a cork carrying the thermometer. The sample isthen cooled and then inspected for pour point as
per the usual pour point method
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6. RESULT19
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