Point flash

A Liquid, in oneself and from a Physical point of view purely , is not Inflammable. It is the mixture of the vapors liquid in the Air which can form a flammable gas mixture.

The point flash is thus defined as the lowest Température to which the liquid considered provides sufficient vapors to form, for the ambient air, a gas mixture which ignites under the effect of a calorific energy source such as a pilot flame, but not sufficiently so that the Combustion discusses itself (for this, it is necessary to reach the Flash point). If the ignition does not require a pilot flame, one speaks then about spontaneous combustion.

The flash point is an oil concept and the first apparatuses which make it possible to define a flash point were described in oil standards. It is thus necessary always to specify the apparatus which was used when one gives a value of flash point. The value depends not only on the apparatus but also on the good sight of the operator who must detect the beginning of ignition.

Measure

There exist two types of flash point: the flash point COC (open cup) and the PMCC (closed cup).

The flash point in closed cup is measured using an apparatus known as of Pensky-Martens (Closed Cup: reason of the PMCC). A semi-automatic apparatus of this type consists of a cup which one can fill of the liquid (in general a Hydrocarbure) which one wishes to know the flash point. One closes again then the cup. The lid is provided with a thermometer whose end is located at the top of the liquid in the vapors. The apparatus has a heating which makes it possible to raise the temperature degree per degree. Each time the temperature reaches a higher degree, a flame is plunged in the vapors. If there is ignition, it is that the flash point is reached, in the contrary case equipment continues to increase the temperature of the liquid.

Estimate

Sources:
  • L. Catoire and Al, Journal off Physical and Chemical Reference Dated, vol. 35, N°1, pp. 9-14 (2006)
  • L. Catoire and Al, Journal off Physical and Chemical Reference Dated, vol. 33, N°4, pp. 1083-1111 (2004)

Vocabulary

A substance is all the more flammable (thus dangerous) that its flash point is low.

The European regulation differentiates the liquids in:

  • Extremely flammable - point flash lower than 0°C AND Not of boiling < 35°C (Example: point flash of the Gasoline < -40°C);
  • Easily flammable - point flash lower than 21°C and not of boiling superior than 35 °C. (Example: point flash of the Methanol = 11°C; Acetone = -18°C ); Note the negative flash point for acetone, which must are easily flammable classification only at its boiling point of 56 °C.
  • Flammable - point flash ranging between 21 and 55°C (Example: point flash of the White Spirit (= +35°C).
A liquid whose flash point is higher than 55°C is regarded as fuel (Example Gasoil or Diesel whose flash point is higher than +55°C);

For the Canadian regulation (SIMDUT), flammable means that the matter ignites easily at normal temperatures (in lower part of 37,8°C or 100°F). The combustible materials must they be heated at temperatures with the top of 37,8°C (100°F) before igniting. Beyond 93,3°C (200°F), the matter is not characterized any more like fuel.

See too

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