Abstract: In order to solve the problem of frequent accidents with serious consequences involving oil gas pipe tanks at their old age, this paper was aimed at developing an inert gas protection and sealing technology. A method for oxygen concentration classification of inerting system, an oxygen concentration safety margin setting principle and a LOC test method were proposed. The influences of CO₂ and N₂ on explosion limits of liquefied petroleum gas(LPG) and LOC were studied theoretically and experimentally. The restraining mechanism was analyzed. Warning thresholds were set. The results indicate that there is a positive correlation between the maximum explosion pressure arrival time and the volume fraction of CO₂ or N₂, the ratio of the time delayed to that undelayed could reach 7 depending on the fraction, that the mechanisms of explosion suppression of the two inert agents are different, which is mainly reflected in ternary collision reaction, that when the volume fraction of CO₂ is 22% or that of N₂ is 32%, LPG is completely in a state of inertia, and that the early warning valve values could be set according to the experimental results for LPG inerting system on-line monitoring and oxygen concentration monitoring.

Key words: explosive gases, explosion limit, limit oxygen concentration(LOC), monitoring and warning, inert explosion-proof