EXPLOSION MITIGATION IN OFFSHORE MODULES BY GENERAL AREA DELUGE

An investigation has been conducted into the influence of water sprays on gas explosions. Proprietary high and medium velocity nozzles have been used in two test rig geometries representative of offshore module s: one closed on all sides except for a small vent; the other with a c ompletely open side. Measurements have been made of the droplet sizes and water content in the spray from individual nozzles. Field-scale ex plosion experiments investigated the influence of the number of obstac les, the number of nozzles, their supply pressure and the addition of a foaming agent to the water. In the experiment with one side open, th e sprays substantially reduced the overpressures, with the beneficial effect being greater for larger numbers of nozzles, higher nozzle supp ly pressures, and the more uniform spray distribution created by the m edium velocity compared to the high velocity nozzle. In the more confi ned geometry the peak overpressure was always increased above that whi ch would have been produced had the sprays not been activated. A theor etical analysis indicates that for explosion suppression to occur the flame acceleration must be above some minimum threshold. The potential benefits of mitigation using water sprays warrants a more thorough va lidation of the proposed criterion for deciding when mitigation will o ccur.