Deterioration in quality during storage

Deterioration in quality during storage

The chemical composition of explosives may change slightly after storage under humid and hot conditions. The explosive may become insensitive to detonation or unsafe to use if the change in chemical composition is excessive. At the mines no laboratory tests are carried out to decide the extent of deterioration, but visual examination is the only guide. When the wrapper of a gelatinous nitro-glycerine explosive is removed carefully an explosive in a good state would permit the wrapper to come off cleanly from the cartridge and there would be no evidence of discoloration, incrustation,-softening or exudation of liquid in the explosive itself. A gelatinous explosive slightly darkens during storage, particularly at the ends due to absorption of moisture from the air. Such discoloration is usually accompanied by softening and dampening of the explosives. The moisture absorbed by the explosive may cause a white incrustation of ammonium nitrate or sodium nitrate on a gelatinous explosive. A higher degree of deterioration is indicated by exudation of nitro-glycerine or aqueous solutions of sodium or ammonium nitrate and the cartridges becoming too plastic. Such explosive should not be used but destroyed.

Powdery nitro-glycerine explosives deteriorate much faster than the gelatinous quality as the former absorb moisture more readily. The deterioration is indicated by discoloration at the ends, softening and dampness. If there is any exudation of liquid the cartridges should be destroyed.

Ammonium nitrate explosives mixed with T.N.T cake and become solid due to absorption of moisture during storage. If the cartridges become so solid that they cannot break easily between the finger and the thumb, they should not be used but destroyed.

Slurry / water gel / emulsion explosives — Deterioration of slurry explosives is usually indicated by a breakdown of the gel into separate liquid and solid components. It may also appear as hardening of the explosive cartridge. Cartridges may also be swollen or distorted and salts in the composition may crystallise on the outside.

Detonators — Detonators showing signs of corrosion of the tubes are dangerous and must not be used; this applies particularly to plain detonators.

Detonating cords — Almost the only cause of deterioration or desensitization of detonating cords is moisture penetration into the explosive core. Prolonged exposure to sunlight may cause the plastic outer coating to become brittle.