Investigating the danger of fires and explosions when spraying flammable liquids and when mixing these mechanically with water, taking into account in particular flammable solvents with flash points above 55 °C.

Status:

completed 12/1994

Aims:

It is intended for halogenated hydrocarbons to be replaced by more environmentally friendly but flammable hydrocarbons. These are above all solvents with flash points above 55 °C which must be heated, diluted with water and sprayed in order to compensate for their poorer application characteristics. It remains unclear how the solvents are to be assessed from a technical safety point of view as vaporised droplets and when mixed with water. Goal: creating evaluation criteria in accordance with practice to assess the danger of fire/explosion. With these assessment criteria and substance ratings safe operating conditions can be determined for all the substances and plants concerned.

Activities/Methods:

Determining the situation with regard to demand and selecting the test substances; experimental examinations (spray and ignition tests) in a closed and an open plant

Results:

Only water concentrations over 76 % by volume make the spray jets inert; ignition energy increases in relation to water free spray jets only with water concentrations over 65 % by volume. Explosions in spray jets, however, as a rule run slower and with lower maximum pressure than explosions of steam-air-mixtures. The actual danger of explosions requires the exclusion of sources of ignition (electrical sparks, hot surfaces, mechanical sparks); only where the water concentration is over 80 % can protective measures against explosion be dispensed with.

Publications:

Förster, H. et al.: PTB Bericht W-62. Wirtschaftsverlag NW, Bremerhaven

Hirsch, W. et al.: Brand- und Explosionsgefahren beim Versprühen von flüssigen Kohlenwasserstoffen mit hohen Flammpunkt in industriellen Anlagen. PTB-Mitteilungen 108 (1998) Nr. 6, S. 442-447

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