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Determination of the initiation strength of commercial detonators using an adjustable-sensitivity liquid explosive.

Bajpayee-TS; Hay-JE
Proceedings of the 18th Annual Symposium on Explosives and Blasting Research, Orlando, Florida, January 22-23, 1992, 1992 Jan 22; :167-180
A test procedure is being developed to determine the initiating strength of commercial detonators. Various tests of detonator strength are in use, but many of them do not correlate well with each other, and so far, there is little evidence that any of them correlates well with the ability of detonators to initiate detonation in an explosive. Therefore, researchers decided to attempt a measurement of the ability of detonators to initiate detonation. To this end, an explosive mixture of adjustable sensitivity was developed. This mixture was nitromethane sensitized with ethylene diamine; the sensitivity was "fine-tuned" by the addition of nitropropane. Most of the tests were done with military J-2, commercial No. 6 copper-shell, and commercial No. 8 aluminum-shell detonators. Early results with detonators immersed in the explosive showed marked discrepancies with other strength test results and with expectations based on presumed strength of detonators. This prompted further investigation of directional effects in the initiation of explosives by detonators. For these additional tests, detonators were fired (1) immersed in the test explosive, oriented axially, (2) with the tip of the detonator just touching the surface of the explosive, and (3) immersed in the explosive transversely so that the tip of the detonator extended out of the explosive. Markedly different results were obtained in these three configurations, indicating that the directional effects are important. This explains why different detonator strength tests do not correlate well with each other. Some tests, such as the sand-bomb and the underwater test, measure the total energy output, while others such as the side-on plate-dent test and the nail test measure the energy in the axial direction, and still others such as the lead-block test measure the energy in the radial direction. These results show the importance of conducting the test in the manner in which the detonator is actually intended to be used.
Explosives; Detonators; Safety-research; Explosives-industry; Explosive-hazards
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
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Proceedings of the 18th Annual Symposium on Explosives and Blasting Research