Explosives

What is an explosive? Explosive is a solid or liquid substance or a mixture of substances which on application of suitable stimulus is converted in a very short time interval into other more stable substances, largely or entirely gaseous with the development of heat and high pressure

Classification of Explosives LOW EXPLOSIVES Deflagrate rather than detonate, Low reaction velocity, no water resistance, highly flammable, very sensitive, 2,000-5,000 FPS EG, black powder BLASTING AGENTS Combination of oxidizer and fuel, cannot be detonated by just blasting cap. HIGH EXPLOSIVES Can be detonated by blasting cap DYNAMITES Composed of nitro glycerin & filler material WATER GELS, SURRIES & EMULSIONS Can be classed as high explosives or blasting agent, depending on its cap sensitivity & chemical composition mixture of oxidizers, fuels and sensitizers which contain 5-40% water. Available in a wide range of densities, commonly packed in polyethylene tubing excellent water resistance. STRAIGHT DYNAMITES weight strength is equivalent % of nitro glycerin. AMONIA DYNAMITES Ammonia nitrate substituted BULK MIXED COMPOUNDS Ammonium Nitrate and fuel oil mixed on the job by the consumer; very economical, good fumes if mixed properly; no water resistance. GELATIN DYNAMITES Combination of nitroglycerine & nitrocellulose. PRE-MIXED NCN Nitocarbonitrate mixtures prepared by manufacturer, light density, no water resistance. STRAIGHT GELATIN SPECIAL GELATIN TWO COMPONENT Each individual component is non explosive can be shipped by any means. SEMI GELATIN

Velocity of Detonation 2000 to 7000 m/s Pressure >1800 GPa Temperature 3000o K to 4000o K

Pressure in a blast hole can exceed 10 GPa (100,000 atm) sufficient to shatter the rock near the hole, and also generate a stress wave that travels outward at a velocity of 3000 to 7000m/sec.

Explosive Classification Initiation Explosives Low Explosives. High Explosives. Blasting Agents

Initiating Explosives Initiating explosives are used in small quantities to initiate detonation in larger and less sensitive high explosives. They are supplied in copper or aluminum tubes to form detonators, or are used in detonating cord.

Low Explosives Blasting or black powder. Used for dimension stone work, will heave the stone rather than fracture it. Splitting products. Usually are of plastic construction and have blasting powder in them. May be fired by a fuse head inserted like a primer in a rifle cartridge.

High Explosives NG-EXPLOSIVES SOME SLURRY SOME EMULSIONS SPECIAL PRODUCTS

Blasting Agents ANFO SOME SLURRY SPECIAL PRODUCTS

Significant Developments In Commercial Explosives YEAR DEVELOPMENT 13th Century Mention of saltpeter and other blasting powders in Arabian and Chinese writings 1242 Black powder formula by Bacon 1846 Sobrero discovered nitroglycerine 1861 Alfred Nobel sets up nitroglycerine plant 1866-75 Dynamite and Blasting gelatine commercially manufactured 1880's Permissible Dynamites investigated 1950's Ammonium Nitrate and combustibles as dry powders (ANFO) 1957 Watergel (Ammonium Nitrate, TNT and Aluminum powder) 1964 Emulsions (Emulsified Ammonium Nitrate and Nitric Acid) 1969-74 Watergel (Mono Methyl amine Nitrate, or Hexamine Nitrate or Aluminum powder) 1979-82 Heavy ANFO (Up to 50% Emulsion and ANFO)

Nitroglycerine Explosives Nitroglycerine (NG), a major component of The dynamites, when in pure form, is relatively unsafe and sensitive to impact. Straight dynamites contain 20 - 60% nitroglycerine. They have poor fume characteristics. Ammonia dynamites have largely replaced straight dynamites. Gelatines contain liquid nitroglycerine with nitrocellulose supplied as cartridges or "sticks". Nitroglycerine C3 H5 (ONO2) 3 NOW DISCONTIUED IN USAGE

AMMONIUM NITRATE FUELOIL (ANFO) and Other Blasting Agents Ammonium nitrate (AN), mixed with fuel oil (FO) in the ratio of 94.5:5.5 by weight. NH4N03+CH2→3N2+7H20+C02+967 kcal/kg ANFO is the least expensive explosive available. When correctly used, ANFO performs as well as dynamites and is much safer. However, it absorbs water hence, it cannot be employed in wet conditions. Density is low.

Mixing ANFO When mixing ANFO the following sign must be displayed: DANGER EXPLOSIVES NO SMOKING OR FLAME No source of flame or spark must be brought within 10 metres of the operation. If any ANFO is left over, then it must be stored in a Licensed Magazine. It be placed in a sealed, leak proof, non metallic container. This container be labelled, “EXPLOSIVES MIXTURE”. This ANFO will be used as soon as practicable.

Cartridge Explosives NG EXPLOSIVES ? SLURRY ? ANFO ?

Slurries Ammonium Nitrate (AN) slurries and emulsions have been developed for blasting in watery conditions. AN with sensitiser, combustible material and thickener + 20% Water produced as slurries, gels and emulsions. Much higher pressure Waterproof Higher VOD Denser Can be pumped. Costs are higher than ANFO

Slurries Composition OXIDISERS FUELS SENSITIZERS Such as AN, SN or CN FUELS OIL SENSITIZERS Chemical - Organic Amines, Perchlorate Salts, Small Particles of AL Physical - Entrapped Air Bubbles

BULK MIX TRUCKS OR ANFO TRUCKS Mix and deliver AN/FO/AI Powder Bulk Loading System For Explosives ADVANTAGES Packaging Cost Saved Loading rates much faster Better Coupling Rigid quality specifications variable SUITABILITY Normally suited for large operations. Shared services for smaller operations. Schedule to be arranged and also size of shot to be tailored to suit capacity of trucks. Increased coupling allows larger charge per hole but may cause vibrations at times. BULK MIX TRUCKS OR ANFO TRUCKS Mix and deliver AN/FO/AI Powder

Bulk Trucks Bulk Trucks (Site Mix Trucks) Raw materials for making explosives like AN, SN solutions from support plant, are carried in trucks and explosive mixed at site. Pump Trucks for delivery of plant-mixed slurry or emulsion.

Bulk Explosives ANFO in dry hole application, low cost and easy mixing but has low density and unsuitable in wet holes

Special Application Explosives Special explosives are needed for controlled blasting, underwater blasting, and blasting of high temperature rock. PIPE CHARGES LOW ENERGY EXPLOSIVES PRODUCT WITH VARIABLE ENERGY

Cast Primers These are made from a mixture of PETN and TNT. Are used to initiate bulk explosives. Have a very high VOD. They have a high density of 1.5 and readily sink in water.

INITATED BY SHOCK TUBE AND DETONATOR, DETONATING CORD CAST BOOSTERS PRIMERS MIXTURES OF PETN AND TNT, HIGH DENSITY 1.6 g/cc TO 1.7 g/cc Detonation velocity 7000m/s INITATED BY SHOCK TUBE AND DETONATOR, DETONATING CORD RELIABLY INITIATE BULK Their high strength, high density and very high velocity of detonation (7000 m / s) make them suitable for priming ANFO mixtures and slurries. An additional advantage is their lower sensitivity to shock, friction and impact. explosives.

Medical Aspects Now a days more consideration given to medical aspects Less toxic gases Non-headache producing explosives For opencast workings not much problem For underground workings carbon monoxide, oxides of nitrogen and fumes are kept within acceptable limits Some explosives cause skin irritation and eczema