AEROSOL-POWDER METHOD OF EXPLOSIVE SUBSTANCES AND SOLID PROPELLANTS EXTINGUISHING

Method of water-foam extinguishing of explosive substances (ES) and solid propellants (SP) at the emergency ignition or fulmination is not efficient due to high persistence, which causes huge economical, ecological and human losses, especially at a large production facilities and army arsenals. Powder extinguishing method looks more promising, which besides cooling effect, just as water, has two additional fire suppression factors — inhibition of heterogeneous combustion reactions and homogeneous chemical interaction of powder decomposition fumes with active flame particles. This effect was confirmed experimentally but only on slow-burning butt ballistic cartridges. It was impossible to extinguish high-energy, mix SP and ES by standard powder fire extinguishers especially at their comprehensive burning. To solve the problem physical-chemical model of initial period was developed of mix propellants of standard composition: 60 % ammonium perchlorate (APC); 20 % binding agent (caoutchouc + + epoxy resin); 20 % Al. It was determined that at the moment of flash of the surface around APC particles (source of Î2) small caverns are formed in which combustible binding agent and Al burning is directed intensively deep into the propellant. Supply of fire extinguishing powder with dispersion of 50…300 m succeeds to cover and extinguish flat surfaces but small caverns near APC centers covered with big powder particles flame up even more intensively in closed volume which leads to pressure increase and powder clearing off extinguished propellant surfaces. Reliable extinguishing was achieved only with the use of aerosol powder mixture supplied with the rate of 200…250 m
s. Composition: 95 % standard fire extinguishing powder, 5 % fire extinguishing aerosol with dispersion of alkali metals salts 0.1…20 m. This composition has provided aerosol condensate intrusion into all caverns including on side and channel surfaces of samples of different SP. The developed method showed a hundred percent result of extinguishing on eight SP compositions of different types and 10 samples of packaged ammonal-200. Processes of manufacturing, storing and use of industrial and military explosive substances, and quick-burning solid propellants are rather well studied. At all stages of these substances handling there is a danger of their emergency fulmination or ignition. To prevent such situations automatic high-pressure water systems of BAPS type were used in the Soviet Union during ES and SP manufacturing and storing. At ES fulmination they could reduce damage of occurred fire, and at explosive substances and quick-burning solid propellants ignition in some case could extinguish them by strong water jets. The main disadvantage of BAPS was low operation speed at supply of large volume of water by pipes and sprayers and also threat of high-pressure water jets which could cut metal for articles equipped with ES and SP and especially service personnel. These systems also acquired negative reputation from economic point of view due to low reliability, complex mounting, maintenance especially at low temperatures. Due to the stated above water systems in the form of BAPS are very rarely used at present. They are replaced by simple drencher and sprinkler water units applied only as extinguishing means for package with highly explosive and flammable ES and SPitems at warm warehouses and deports. They can not extinguish quick-burning solid-propellant cartridges and charges themselves.