Explosibility, partial test

The extent of detonation of an explosive, that is, partial detonation or complete detonation is concluded on the basis of mechanical effects hole cutting in a steel plate, dent depth in a witness steel block or compression of a copper cylinder, produced as a result of detonation of explosive under test. There are several variants of the gap test which have been the subject of investigation by several researchers described in the literature [74—77]. 

An alternative method for ascertaining the end of the reaction, which does not involve the removal of the cover, is to conduct the exit gas through an empty wash bottle (to eict as a trap in case of sucking back ) and then collect a sample in a test-tube over water. If an inflammable gas (hydrogen) is absent, the reaction may be considered complete. Under no circumstances should the reaction be stopped until all the sodium has completely reacted too early arrest of the reaction may result in the product containing sodium hydride, which appears to be partially responsible for the explosive properties of the impure substance ... 

Projectile Sensitivity. Andreev Belyaev (Ref 32, p 473) showed that PA packed in wooden crates detonates if impacted by a 4g projectile moving at greater than 40Qm/sec. In the rifle bullet sensitivity test 0% explosions, 60% partials and 40% combustions were observed for PA (Ref 48)... 

In the No. 2 break test the explosive is fired almost unconfined. Under these conditions weak coal mining explosives detonate only partially and the probability of ignition of the gas mixture is reduced. Measurement of... 

Equally severe in practice is the requirement of the break 2 test. To pass this test the explosive must have a low power when fired in an unconfined condition. The actual power has not been quantitatively measured, but is probably in the region of 15% blasting gelatine. To achieve such a result, it is necessary deliberately to design the explosive in such a way that only partial reaction occurs in the unstemmed condition. Such partial reaction can be achieved by either of two ways. 

On occasion a partial detonation may take place, resulting in large visible quantities of explosive being left at the scene in this event collection and subsequent identification of samples is relatively straightforward. However most explosions only leave invisible residues of unconsumed explosive at the scene. The first problem then is to find the right place from which to take samples. Of course, it wiU be necessary to have a stock of sampling and packaging materials available, which have been quality assured to ensure they are free from any possible traces of explosive so that the validity of any subsequent tests can be established. 

A method which might ensure safety in the recovery system is based on a partial or total replacement of the air within the pipelines by a gas containing no oxygen that does not form explosive mixtures with alcohol-ether, e.g. by nitrogen or carbon dioxide from exhaust gases. This method, however, proved too expensive, and was not carried beyond small scale tests. 

Brisance, by the following methods a) Lead Cylinder Compression Test, 54% of that of TNT b) 200 g Sand Test, only partial explosion takes place (Ref 122a) c) Kast Formula (Max Potential Work), 17,000 for complete and 5,800 for incomplete decomposition as compared with 86,000 for TNT (Ref 56) d) Fragmentation of 40 mm shell (average charge 44.5 g at d 1.0) - 16 fragments for AN coated with wax vs 66 fragments for TNT... 

Sensitivity. 1) B.D. Pollock R.F. Gentner, Impact Sensitivity of Wetted Primary Explosives as Determined by the Ball Drop Test , PATR 4311 (1972) [Table 8 lists the impact sensy data found by these workers on unconfined dry and w-wet Pb Azide. Addnly, they found that w completely desensitized Pb Styphnate and Tetracene and that all fully-wetted unconfined primary expls were less sensitive to impact than when dry, but that partially wet (w-soaked but no excess of w present) confined initiating expls are more sensitive to impact than when fully dried... 

Friction test in unglazed porcelain mortar. RDX in 0.03 g samples rubbed in a mortar produced partial deflagration, while PETN under the same conditions detonated completely (Ref 22, 341) Gases formed on explosion. It was formerly assumed (Avogadro) that RDX decompd on expln as follows ... 

The data treatment is different for the small gap test the variable initiator test The explosive materials evaluated in the small gap test are ignited and combusted easily by an open flame. Some materials in the closed space underwent deflagration to detonation. In the small gap test it seems to be dangerous when the exothermal decomposition occurs partially and complete explosion is incomplete. In the small gap test we must assume that a dangerous reaction has occurred when smoke or a flame is seen without explosive reaction. 

---