ANFO non tolerate water and moisture is a problem at moment to make blasting, however, in some mines thats the only one explosive available. which could be the limit of moisture to evite energy losses in blasting ? Please add any reference. Thanks all.
ANFO is most widely used explosive in the world, because blasters find it very user friendly and its it is very attractive to the mine management due to its lower cost.Its biggest disadvantage is the lack of water resistance, because it is hygroscopic in nature. The energy losses due to moisture depend upon the % moisture as well as the time of exposure.There is no established critical limit for moisture content. The most common precautions against the deterioration of ANFO by water are:
(I) Blowing the holes with compressed air before charging (ii) Loading ANFO in plastic liners.
Number of products have been developed to make ANFO water resistant. But these new additives increase the cost of those products and take away its major advantage of lowest cost.
An other important factor is the diameter of the borehole and the strength of the initiators (boosters).
Technically speaking it has performs best at zero-moisture level. However, the quantitative critical limits have not been defined. Apart from the precautions narrated to you by Prof. Singh, the sleeping time of ANFO inside the hole should be minimized. Even though the blast hole may apparently appear dry, there may be immeasurable moisture in-situ.
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