Fire Safety Science Digital Archive

This study was carried out to obtain data on the performance characteristics of two powders (sodium bicarbonate [SB] and monoammonium phosphate [MAP]) and water as explosion suppression agents, and to understand the effects of geometric variables on suppression system performance. Tests were carried out in a 2.5-m' test vessel with 10% (by volume) methane/air mixtures, both under initially quiescent and turbulent conditions. Tests with the two powder agents (SB and MAP) at a concentration of 1200 g/m3 resulted in similarly successful suppression of quiescent mixtures, with small increases in final overpressures as the detection/system trigger pressure was increased (from 0.07 to 0.55 barg [I to 8 psig]). Successful suppressions were also obtained with turbulent mixtures, although with greater overpressures than for quiescent mixtures. Water at ambient temperature (approximately 20°C) was not successful at suppressing the explosion, even when carbon dioxide was added to the charge. In tests where the suppression failed, the pressure inside the vessel reached the value corresponding to fully unvented conditions. Heated water (at or above 230°C [446°F]) performed reasonably well as a suppression agent, both in quiescent and turbulent tests, for trigger pressures up to 055 barg (8 psig). The introduction of the superheated water into the vessel, however, contributed about 0.83 barg (12 psig) to the total pressure increase.