Flash detonator

Detonators are used to detonate high explosives. Stab detonators are initiated by sharp firing pins and are used in explosive trains of different types of fuses. Flash detonators are initiated by flames produced by safety fuses, primers, or delay elements. A special type of flash detonator ignited by the flame of a safety fuse is called a blasting cap. Detonators are primarily composed of three types of explosives including sinoxid mixtures, lead azide-based mixtures, and mercury fulminate-based mixtures. 

The construction of flash type detonators is similar to other detonators. Each flash type detonator consists of a metal capsule contg a chge of expls. The capsule, which is usually of A1 (on account of presence of LA as an expl ingredient in US Army and Navy flash detonators) may be closed with paper or thin A1 disk, as indicated in Fig... 

The compn of some foreign flash detonators used during WWII was, accdg to analyses made at PicArsn (Refs 8 12a), different from those used in USA. Following is a copy of Table 4-1 given in Ref 23, p 4-3... 

Table 4-1. Explosive Charges Used in Foreign Flash Detonators...

Fig 21 for stab detonators M18, M24 M44 and for flash detonator M17 are used. In these cuts, the lower(base) charge can be Tetryl, RDX or PETN, the intermediate charge is LA and the upper (top) charge is a priming composition... 

Fig 5-44 (Flame initiated 0.10-second flash detonator) 5-60, Fig 5-45 (Stab initiated 0.02-second delay detonator) Chapter 6, pp 6-1 to 6-11, Characteristics of Leads"... 

Output tests for detonator type components are generally based on an attempt to measure the brisance or the peak pressure of the shock wave. The common tests for detonators are practically all applicable to each of the three main varieties, namely stab, electric and flash detonators. Following are brief descriptions of output test for detonators and primers ... 

Nitroethanol prepared by the formaldehyde-nitromethane method should not be distilled without use of diphenyl ether as a heat-dispersing agent. The residue, consisting of di- and tricondensation products of formaldehyde with nitromethane, when hot and concentrated, and particularly when the vacuum is broken and air is let in on the hot distillation residue, is very likely to undergo a flash detonation, or at least a fume-off which may proceed with explosive violence. Use of diphenyl ether is a wise safety precaution in the distillation of 2-nitroethanol made by other methods as well. 

The delay detonator (Figure lb) uses lead azide as the output charge and converts and augments the heat fiom a gasless delay column to a detonation. The small amount of azide used in this example would require the use of a relay or flash detonator as the next element if the sequence is to terminate in the detonation of a secondary explosive. Otherwise the output from the 20 mg of lead azide is adequate only to ignite a sensitive pyrotechnic or another lead azide charge. 

Figure 2, Lead azide in flash detonators and relays [1] (a) relay (b) detonator.

A typical flash detonator and relay are shown in Figure 2. These are designed to be initiated by a flame and produce a detonation output pulse. The input faces are either bare lead azide or have a thin paper covering to allow the flame to reach the azide. Again the rapid buildup in lead azide from heat to detonation is the important process involved. 

Detonators (Figure 1.2) are used to detonate high explosives. They are classified according to their external initiation mechanism into stab and flash detonators. Stab detonators are initiated by a sharp firing pin and used in the explosive train of different types of fuses, viiile flash detonators are initiated by flame produced by a safety fose, primer, delay elements, etc. 

Determination of the Sensitivity of Flash Detonators to Open Flame... 

Flash detonators, which are initiated a flame (e.g., safety fuse flame), should to be tested to the action of the open flame. 

Devices used for the determination of the flash detonator s sensitivity to the open flame may be of different design. The basic difference refers to the flame source used for the initiation of flash detonators. The flame may be originated... 

A typical device for the determination of the flash detonator sensitivity to the flame of the black powder ignition charge is presented in Figure 2.34. 

Figure 2.35. Test arrangement for the determinati

By changing the distance between the flame source and the flash detonator, one can establish the maximum distance at which 100% of initiations of the detonator occur. The number of consecutive trials for the same distance may vary from at least 6 up to 50. 

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