Experimental Study on Burning Characteristics of the Large-Scale Transformer Oil Pool Fire with Different Extinguishing Methods

In this study, a 100 m² steel tank was used to simulate transformer oil fires, with an aim of investigating the burning characteristics of a large-scale pool fire. To recover a real thermal state of transformer oil in operation, a heating system was employed to raise the initial fuel temperature. In total, three fire-extinguishing tests were performed using two delivery methods, i.e., a hand-held fire water branch (FWB) and fire water monitor (FWM) to understand their performance in fighting large-scale pool fires. The extinguishing activities using the FWB method were conducted by four trained firefighters, and the FWM was operated by a trained firefighter. Also, a sequence of bench-scale tests was conducted to investigate the impact of initial fuel temperature on the mass burning rate of transformer oil pool fires. This part is a supplement to the large-scale tests. The results demonstrated that the temperatures adjacent to the tank border were reduced as the vertical height increased. The growth rate of the flame height was enhanced in the development stage when the initial fuel temperature was pre-heated to a higher value. Meanwhile, it was found that the burning rate of transformer oil pool fire occurred a slight increase with the initial fuel temperature was grown according to the bench-scale data, while the impact of initial temperature was limited within the tested temperature range. In addition, it was shown that the FWB and FWM were both effective for fighting a large-scale transformer oil pool fire. However, their efficiency was influenced significantly by the concentration of the extinguishing agents and the application density of delivery. In contrast, the FWM might be a good choice when considering the safety of firefighters, because its delivery range is greater and extinguishing time is shorter as compared to the FWB. Here, it shall be noted that the FWM has also its flipsides. Sometimes, the application of a single FWM is not well to extinguish the corner fire or other fire types, in such cases, the FWM strategy should be to use two or more fire trucks in order to cover the whole accident pool.