The pour point of a

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

is the

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

below which the liquid loses its flow characteristics. It is defined as the minimum temperature in which the oil has the ability to pour down from a beaker. In

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

a high pour point is generally associated with a high

paraffin Paraffin may refer to: Substances * Paraffin wax, a white or colorless soft solid (also in liquid form) that is used as a lubricant and for other applications * Liquid paraffin (drug), a very highly refined mineral oil used in cosmetics and for med ...

content, typically found in crude deriving from a larger proportion of plant material. That type of crude oil is mainly derived from a

kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. It consists of a variety of organic materials, including dead plants, algae, and other microorganisms, that have been compressed and heated by geological processes. All the kero ...

Type III.

Measuring the pour point of petroleum products

Manual method

ASTM D97, Standard Test Method for Pour Point of Crude Oils. The specimen is cooled inside a cooling bath to allow the formation of

paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting poi ...

crystals. At about above the expected pour point, and for every subsequent , the test jar is removed and tilted to check for surface movement. When the specimen does not flow when tilted, the jar is held horizontally for 5 seconds. If it does not flow, 3 °C is added to the corresponding temperature and the result is the pour point temperature. It is also useful to note that failure to flow at the pour point may also be due to the effect of viscosity or the previous thermal history of the specimen. Therefore, the pour point may give a misleading view of the handling properties of the oil. Additional fluidity tests may also be undertaken. An approximate range of pour point can be observed from the specimen's upper and lower pour point.

Automatic method

ASTM D5949, Standard Test Method for Pour Point of Petroleum Products (Automatic Pressure Pulsing Method) is an alternative to the manual test procedure. It uses automatic apparatus and yields pour point results in a format similar to the manual method (ASTM D97) when reporting at a 3 °C. The D5949 test method determines the pour point in a shorter period of time than manual method D97. Less operator time is required to run the test using this automatic method. Additionally, no external chiller bath or refrigeration unit is needed. D5949 is capable of determining pour point within a temperature range of . Results can be reported at or 3 °C testing intervals. This test method has better repeatability and reproducibility than manual method D97. Under ASTM D5949, the test sample is heated and then cooled by a Peltier device at a rate of 1.5±0.1 °C/min. At either 1 °C or 3 °C intervals, a pressurized pulse of compressed gas is imparted onto the surface of the sample. Multiple optical detectors continuously monitor the sample for movement. The lowest temperature at which movement is detected on the sample surface is determined to be the pour point.

Measuring the pour point of crude oils

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 happens because wax crystals form less readily when it has been heated within the past 24 hours and contributes to the lower pour point. The upper pour point is measured by pouring the test sample directly into a test jar. The sample is then cooled and inspected for pour point as per the usual pour point method. The method usually gives higher pour point because the thermal history has not been cancelled by a prolonged thermal treatment. The lower pour point is measured by first pouring the sample into a stainless steel

pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...

. The vessel is then screwed tight and heated to above in an oil bath. 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 A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...

. The sample is then cooled and then inspected for pour point as per the usual pour point method.

References

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External links

Some background knowledge about pour point and different measuring methods ''(manufacturer of pour point tester)''
* USF
Pour Point and Product Fluidity
of Various Class A Foams
Phase Technology
Manufacturer of ASTM D5949 automatic pour point analyzers Chemical properties Threshold temperatures