English to Dutch Tech/Engineering Petroleum Eng/Sci

Just as part of a list: flashing the hydrocarbon feed with steam at high temperature.

Is this just an evaporation of the more volatile parts of the feed by means of the steam, or is the feed really lit, thereby evaporating these same lighter fractions (I cannot imagine this latter possibility, because the contents of the feed would then be lost). Or is flashing just an expression to indicate the evaporation of the lighter fractions?

Help from an expert would be very welcome.