Drilling/Blasting Forum/Detonating Cord Downlines Cause Energy Losses

摘要

Since the early 20th century, detonating cord (DC) has been used as an initiation system. Detonating cord is composed of a fiber-wound plastic tube, which is filled with PETN explosive. It fires at 18-23K ft/sec depending on the type of cord. Today there are many different types of initiation systems available. For electric initiation systems there are electric caps, electric sequential timers, electronic delays, and magnedet systems. For non-electric systems there are many different shock-tube systems and Detaline available. No need exists for using detonating cord downlines in blastholes unless you intentionally want to reduce the energy from the main charge. DC is supplied in many different sizes. Loads vary from 2.4-400 grains/ft. It is relatively insensitive to accidental initiation from normal shock or friction and is normally unaffected by stray electric currents or lightning. DC has been used in initiation systems for years in mines and quarries and on surface coal-mining operations. It is not uncommon to see DC being used from the surface trunk-line down the blasthole to the primer. This is commonly called the "downline." What ordinarily is not discussed, however, is the effect of the detonating cord downline on the blasting agents. It has been known for at least 30 years that if the detonating cord is too large for the size of hole, the blasting agent (such as Anfo) may be ignited by DC and burn as the detonation is progressing down the blasthole. As the downline detonates, the Anfo burns and releases only a fraction of its potential energy.