R. Meyer J. Köhler A. Homburg Explosives

51 Cap Sensitivity
and initiated. No change in the condition of the plate or denting with or
without fissure is classed as non-detonation. A circular hole indicates
detonation.
Table 2. Cap test results.
Composition Loading
Density
Test Result:
Detonation
g/cm 3
ANFO, porous prills 0.79–0.93 none
AN cryst. with
TNT and fuels 0.82–1.07 always +
AN cryst. with
TNT, DNT and fuels 0.82–1.07 always +
AN cryst. with
DNT and fuels (N.C.N.’s) 0.75–1.10 always +*)
AN porous prills
coated with DNT 0.82–0.84 none
AN cryst. with fuel 0.62–1.10 not at higher densities
AN cryst. with Al,
earth alkaline
nitrates, fuels and
water (slurries) 1.13–1.26 +
(also with TNT) 1.37–1.60 none
AN = ammonium nitrate
The results are unchanged when explosives are tested at increased
temperatures (30 °C). An exception to this are the AN prills coated
with DNT.
DNT diffuses into the pores, the explosive becomes more homogeneous
and therefore more sensitive. No change occurs when the
European test fuse is replaced by a No. 8 detonator (0.75 g Tetryl).
A similar test has been developed in the USA (according the deformation
of a lead block, using commercial caps with 0.4–0.45 g PETN). It
is advisable to classify according to test results and not, as was the
custom in the USA, by the classification of N.C.N. according to the
explosive composition. As indicated above, ANFO’s are not cap sensitive;
mixtures of finely ground ammonium nitrate containing only 2%
instead of 6% of oil or wax can, however, be cap sensitive.
* N.C.N.-explosives can be non-cap-sensitive at somewhat higher densities.