On Group Misfiring in Series Circuit Electric Blasting

Abstract

In an electric blasting circuit where a large number of electric detonating caps are hooked up in a straight series, several instances have been reported in which a group of detonating caps situated in the vicinity of the middle part of the circuit were apt to misfire, and the cause of this kind of misfire has been ascribed to the leak of igniting current. Every misfire will ultimately be traceable to the lack of the amount of electric power given to the detonating cap, while in this paper, to account for one of the factors leading to the cause of such misfire, the time required for the progressing current wave to arrive at the middle part of the circuit and also the gradual decay of the intensity of current during the transition are investigated. Consequently, the intensity-time curves of igniting current and the amount of accumulated heat energy for detonating caps placed at the middle part and both ends in the circuit were studied and discussed under several feasible circuit conditions, and next, it was suggested that both the higher and the lower limits of the intensity of igniting current should be considered in order to reduce the possibility of misfire in such situations.