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.

Project No. FFFF 0076


completed 12/1994


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.


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


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.


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

Last Update:



Financed by:
  • Hauptverband der gewerblichen Berufsgenossenschaften (HVBG)
Research institution(s):
  • Physikalisch Technische Bundesanstalt (PTB)
  • Braunschweig

-cross sectoral-

Type of hazard:

dangerous substances


Brand- und Explosionsschutz, Gefährdungsbeurteilung, Lösungsmittel

Description, key words:

Danger of explosion with regard to ignition of solutions of up to 65 % water unchanged, over 76 % none, explosion pressure less, safety measures against explosions recommended for solutions of up to 80 % water