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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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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5.2 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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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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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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8. Cloud and Pour Points Test