Pour point

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The pour point ( English "pour" for "pour" in the sense of "pour") is referred to in DIN 51597 (now replaced by: DIN EN 23015: 1994-05, DIN ISO 3015: 1982-10, DIN ISO 3016: 1982- 10) for a liquid product - mostly oil - the temperature at which it just flows when it cools down . The pour point describes the temperature at which the previously liquid product solidifies. The procedure that defines the procedure is certified according to ISO 3016 .

Methods

Different cooling baths are used for the measurement, each set 3 ° C lower. The oil sample is poured into a glass vessel and cooled in the baths. As soon as the sample has reached the bath temperature, the vessel is removed and tilted horizontally. If the oil is still flowing , the pour point has not yet been reached; the sample is cooled in the next colder bath until the sample no longer flows after it has been removed. The next-to-last used bath temperature is then given as the pour point, i.e. the last temperature at which the sample was still liquid. Pour point and pour point are thus 3 to 6 ° C apart (see also:, however, it should be taken into account that this reference refers to a different (DIN) procedure. This reference also clearly describes the demarcation between pour point and pour point).

In the petrochemical sector, the slightly different ASTM standard D97 (for petroleum products) or D5853 (for crude oils) is often used . Here, too, the sample is cooled and, in the case of integer multiples of 3 ° C, the flow behavior of the sample is checked by tilting the measuring vessel. If the sample no longer flows, the pour point has been reached. The last temperature step at which flow behavior was still to be observed is given as the pour point.

A more precise specification is achieved by using the ASTM D5985 standard. The measuring vessel with the sample is set in slow rotation (approx. 0.1 min −1 ). A flexibly mounted measuring head is immersed in the sample and, when the pour point is reached, is moved away from its position by the sudden increase in viscosity; the resulting tilting movement triggers a sensor. This method provides an indication of the pour point accurate to approx. 0.1 ° C. The standard-compliant pour point according to ASTM / DIN / ISO can also be obtained by rounding to the next higher degree divisible by 3.

Applications

The pour point is still specified in ISO 8217: 2005 , which is valid for heavy fuel oil and marine diesel oil, but is no longer used in all other current specifications of the most important mineral oil products such as jet , diesel or heating oil EL .

Definition of terms

Pour point and pour point are often used synonymously - even in technical descriptions - but this is incorrect because the pour point is referred to in accordance with DIN 51583 . The term freezing point should also not be used in connection with pour point and pour point, as this defines the transition between liquid and crystalline phase and represents a change in the state of aggregation . Petrochemical products usually solidify in an amorphous phase ( glass ).

Individual evidence

  1. ↑ DIN 51597 - 1972-01 - Beuth.de. Retrieved September 21, 2018 .
  2. ↑ Horst-Walter Grollius: Basic Hydraulics, ISBN 978-3-446-41596-6 , Hanser technical book publishing; fourth updated edition (June 5, 2008) online

See also