Explosives initiating devices

Detonator—A somewhat more general term than blasting cap (q.v.) for an explosive initiating device, which in turn is initiated by a primer (q.v.) or other forms of heat input. 

System safety often utilizes redundancy as a safety design feature or mechanism to enhance safety. The probability of two items failing is much smaller than for a single item, thus reducing the potential risk. It should be noted, however, that sometimes redundancy for reliability actually can increase the safety risk. For example, two explosive initiator devices might be used in a system design to make initiation more reliable however, now the probability of inadvertent initiation becomes twice as likely. 

Initiating device Another term for primary explosive. 

Explosives are generally detonated with the assistance of initiating devices (initiators) that are activated by external stimulation sources (friction, spark, or flame), and may include (1) primers, (2) detonators, (3) electric detonators, (4) safety fuses, and (5) detonating cord. 

H. Kast (104-07) Determination of Sensitivity to Friction (Medicion de la sensibili-dad al rozamiento) (107) Determination of Sensitivity to Initiation by Detonation (110-12) Determination of Sensitivity to Initiation by Influence (112-13) Determination of Power of Explosives using Trauzl Test (113-17), Small Lead Block Test (117), Quinan Apparatus (118), Guttmann Apparatus (118-19), Ballistic Pendulum (119-20), Mortar (Mortero probeta) (120-21) Determination of Efficiency of Initiating Devices by Lead Plate Test (121-23), Nail Test (123), Sand Test (124) and Acoustic Tests (124) Determination of Characteristics of Flames Produced on Explosion (125-29)... 

Nuclear explosives release their energy much more rapidly than chemical explosives typically the time in the case of nuclear explosives or devices, is less than lps and that for a chemical explosive is in the range of microseconds. Thus, a nuclear explosive produces a sharper shock wave and as a result, it is somewhat more effective in shattering rocks and somewhat less effective as an earthmover. In terms of physical dimensions, the nuclear charge is much more compact than the chemical explosives leading to a much higher initial energy-density and con-... 

Primary explosives (also known as primary high explosives) differ from secondary explosives in that they undergo a very rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive explosives. Primary explosives will detonate when they are subjected to heat or shock. On detonation the molecules in the explosive dissociate and produce a tremendous amount of heat and/or shock. This will in turn initiate a second, more stable explosive. For these reasons, they are used in initiating devices. The reaction scheme for the decomposition of the primary explosive lead azide is given in Reaction 2.2. 

Lead and silver azides are widely used as initiating, or primary explosives because they can be readily detonated by heat, impact, or friction. As such, these materials, particularly lead azide, arc used in blasting caps, percussion caps, and delay initiating devices. The function of the azides is similar to that of mercury fulminate or silver fulminate. 

Fig. 1. Quam blast utilising high explosives initiated with electrical delay devices l millisecond delay electric blasting caps)...

In this section we will examine the phenomenon of initiation of explosives. Starting with the extant theories, we will see how all methods of initiation are basically thermal in nature. We will then examine the common types of initiating devices and see how the various modes of initiation and the theories that explain them are applied to both design and performance analysis of these devices. We will also examine the interplay of electrical initiator design and electrical firing circuits. 

Once initiating devices are connected to a cord or fuse they become assemblies, hence blasting cap assembly and detonator assembly. Detonating relays are assemblies of detonators connected in such a way that multiple charges are fired in parallel or sequentially as one explosive initiates another. 

Fuzes, a term often used synonymously with fuse, are devices which initiate high explosives (detonating fuze) or low explosives (igniting fuze) in projectile ammunition or pyrotechnics after launch, or which activate the main charge of a mine, bomb, or other nonprojectile ammunition. In addition to an explosive, fuzes incorporate some kind of mechanical or electronic initiation device ... 

In the introduction to this book, I stated that there are four basic method.s of initiating or starting explosive decomposition. Because wh are interested primarily in detonation, the preferred method for initiation i.s through a. shock wave that is of sufficient velocity to cause our explosive charge to undergo detonation. Thus our interpretation of sensitivity is "the relative amount of shock energy required to cause an explosive to detonate. For basic applications, the source of the detonation shock wave is a standard blasting-cap-type initiation device. 

There is a vast array of energetic materiald that falls mder the sensitivity classification of primary explosives. When the complexity and extent of primer explosives are multiplied by all the different ways manufacturers use initiation devices, the subject becomes extremely voluminous. Rather than cover all these materials and their applications, we noil concentrate on only those most commonly used in the construction of such initiation systems as blasting caps and primers. Figure 13 contains some of the physical attributes of common primary explosives. 

The initiation of high explosives in practice is performed by initiating devices, or initiators. The term initiation here denotes bringing an explosive into the state of deflagration or detonation. 

The determination of the initiating strength or priming ability of primary explosives is very important for the correct solution of tasks related to the service application of the primary explosives in initial devices, explosive trains, etc. 

---