Aim: This paper presents the operation of an active dust explosion (HRD, high rate discharge) suppression system in a confined space.
Project and methods: The study involved tests of the developed fire protection system for suppressing dust explosions. The work was carried out under the project entitled “Innovative explosion protection technologies, including for highly protected facilities” No. DOBR-BIO4/052/13073/2013 at the Scientific and Research Centre for Fire Protection in Józefów. A test station designed and constructed to meet the prerequisites of the PN-EN 14034 series of standards was designed for testing. The test equipment consisted of a closed roughly spherical chamber with a volume of 1 m3, an ignition system, a system producing a dust-air atmosphere, and a pressure change detection system. Inside the sphere, a dust-air mixture of a certain concentration was obtained in a reproducible manner. The station was armed with a dust explosion suppression system consisting of: 5 dm3 fire extinguisher tank containing pressurized fire-extinguishing powder, a diffusing nozzle, an explosion detection system. The operation of the extinguishing system is based on the early detection of changes in the explosion pressure of the dust-air mixture, the processing of the signal, and the release of the extinguishing agent inside the apparatus in order to interrupt the explosion process at the earliest possible stage of its development.
Results: On the basis of the conducted experiments, it can be concluded that the HRD system effectively interrupts explosive combustion for dust with a Kst ≤ 100 bar · m/s. For the examined potato starch dust, the system significantly reduced the explosion pressure to an acceptable value. The system is also characterised by a short reaction time, and the discharge of the extinguishing powder takes place in less than 100 ms, which is a satisfactory value.
Conclusions: The tests were carried out for potato starch and lycopodium. The phenomenon of explosive combustion occurring in the mixture of lycopodium and air is characterised by greater dynamics, compared to starch. This difference allowed to identify the limitation of extinguishing dust explosions in small cubic capacity areas. In addition, research identified issues related to the source of ignition in the form of pyrotechnical heads, the use of which requires the setting of a high-pressure threshold activating the HRD system. This results in a delayed system reaction in the event of ignition of high Kst dust mixtures.
Keywords: HRD, explosion suppression system, dust explosion
Type of article: original scientific article