Assessment of explosives

Some PBX formulations along with their density, VOD and compression strength are given in Table 3.4. Some important PBX formulations based on high explosives such as TATB, NTO and CL-20 which are used for specialized applications have already been described in Chapter 2. 

In conclusion, it is obvious that formulation research is of great importance and it will continue as long as improvements in performance, safety and cost are desired. 

An overview of the important characteristics of explosives is given in Chapter 1. With the advent of various modeling techniques, much information concerning any given explosive can be obtained by theoretically calculating its properties. This information is valuable but indicative as calculations predict performance, which an explosive may have under ideal conditions. In practise, such perfection is never achieved and it is a matter of practical importance to assess their properties experimentally under conditions more appropriate to their use. Such an assessment is usually made by a series of tests chosen to determine the performance of explosives under various conditions. While these tests are of considerable value, it must be remembered that no laboratory test or series of tests can predict precisely the performance of explosives which may be used for widely varying purposes. The ultimate test for all explosives is their performance in the field. 

The experimental assessment of the following properties, which are considered to be of utmost importance from the point of view of their application, are given in the following paragraphs. 

2) Sensitivity to heat, impact, friction, spark and shock. 

The power, or strength of an explosive, is one of the most iihportant properties of interest to the user. It is usually expressed in terms of power per unit weight, which is appropriate for comparing explosives used in charges measured by weight. It can alternatively be expressed as power per unit volume, which is appropriate for explosives which are used to fill boreholes of a given size. The relation between the two depends solely on the density, so that the one is readily calculated from the other. 

The ultimate test used by NEC for commercial explosives consists in carrying out small-scale blasting operations in a quarry. The maximum weight of rock adequately broken per 0-5 kg of the explosive is calculated and used to indicate the power of the explosive. The rock involved is of fairly average nature for the district and the results therefore form a useful general comparison of strengths. Such testing is tedious and expensive and carried out only as a final assessment. 

The maximum potential power of an explosive can be calculated, or it can be measured by techniques such as those developed by Cook. A typical method consists of firing the explosive under water and measuring the energy liberated in the various forms, such as shock wave in the water, the work of expansion of the gas bubble, etc. These figures have limited practical value as the methods of application of explosives are of low and variable efficiency. A more practical measurement of strength can be obtained by the measurement of cratering efficiency. This, again, demands considerable expense and also requires the availability of uniform rock. 

In the ballistic mortar test the explosive is well confined and develops 

The ballistic mortar and lead block tests use only small amounts of explosive and are not applicable to slurry explosives which are too insensitive to detonate properly under such conditions. For these explosives it is useful to fire larger amounts of several kg under water and measure the period of oscillation of the gas bubble produced. The longer the period the greater the energy of the gas bubble and this part of the total energy of the explosive has been found to correlate well with the blasting effect of the explosive. 

---

Chapter 6, 1 Assessment of Explosives", which includes Power or Strength (pp 65-8) Velocity of Detonation (69-72) Sensitiveness, to Friction and to Impact (72—6) Stability on Storage (76—8) Fume Test (78—9) and Miscellaneous Tests, such as for. Brisance and Speed of Gelatinization of NC (79—80). Chapter 7 Gallery Testing of Permitted Explosives (85—9)... 

MN) D.P. Lindstone, "The Assessment of Explosive Performance by Means of a Cartridge Case Deformation Test", Explosiv-stoffe 17(9), 193—201(1969). Abstracted in Expls Pyrots 3(8), 1970 [Two-gram charges are fired in brass small-arms cartridge cases (cal. 303) and results compared with a cartridge in which a 2-g "standard" was fired]... 

Assessment of Explosives 179 have little or no appreciable effect on explosives... 

This book is split into six well-defined chapters Salient Features of Explosives, Status of Explosives, Processing and Assessment of Explosives, Propellants, Pyrotechnics, and Explosive and Chemical Safety. Further, the book includes an exhaustive bibliography at the end of each chapter (total references cited are more than 1000). It also provides the status of HEMs reported mainly during the last 50 years, including their prospects for military applications in the light of their physical, chemical, thermal and explosive properties. The likely development areas for further research are also highlighted. Accidents, fires and explosions in the explosive and chemical industries may be eliminated or minimized if the safety measures described in this book are implemented. 

Robidoux PY et al., Ecotoxicological risk assessment of explosives contaminated sites, in Environmental Analysis of Contaminated Sites Toxicological Methods and Approaches, Sunahara GI et al., Eds., John Wiley and Sons, UK, 2002, 335. 

---