AN-FO explosives

In the U.S.A. in 1956 a new class of rock explosives was tried for the use in opencast mines, based on a patent taken out by Lee and Akre [88]. They are low cost explosives composed of ammonium nitrate and an inexpensive fuel such as carbon black. Rapid development took place in 1957-58 and their use was extended to certain underground operations. Fuel oil was next used as a combustible ingredient (AN-FO) explosives. 

AN-FO explosives are usually made in the mine ( do-it-yourself explosives) thus saving the cost of explosives transport. 

As mentioned before, preparation of AN-FO explosives is usually carried out where they are to be used. The methods are described later in the chapter on the manufacture of mining explosives. 

AN-FO explosives are approximately twice as cheap as the usual ammonium nitrate rock explosives and three times cheaper than dynamites. 

A modified type of AN-FO explosive has been suggested in the U.S.A., made by mixing ammonium nitrate with nitromethane (ca. 5%)which is itself explosive. They have a higher rate of detonation than AN-FO (e.g. 3900 m/sec). However, they have not been widely used because of their higher price. 

The following are figures on the use of AN-FO explosives in the U.S.A. in 1979 and 1980 over 1300 and nearly 1400 million pounds respectively. Their use was mainly in quarrying, non-metal mining and construction work (10). 

An International Symposium on Mining Research took place in 1961 (60) and was partly dedicated to AN—FO explosives. Hino and Yokogawa (61) described the action of sur/actants on the detonation ability of ammonium nitrate and its mixtures with coal tar in proportions 93.3/6.2- The addition of 0.55 of surfactant increased the detonation ability of the mixtures. Particularly effective were sodium dinaphthylmethane disulphonate, sodium laurylsulphon-ale and sodium dodecylbenzene sulphonate. 

Figure 11. Hanging-wall blast vibration attenuation. AN-FO explosive population 100 kg charge, located in blastholes 2.5 m from hanging-wall contact...

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