MT20 : EXPLOSIVE AND ACCESSORIES

Explosive And Accessories Used In Mines

Introduction

Explosive is a reactive substance which is mixed of different composition which reacts the instanentous and large amount of gases produced. Dynamite was the first explosive and this explosive was invented by Swedish chemist and engineer Alfred Nobel in 1867. Dynamite is an explosive which is made of nitroglycerin (NG), sorbents (such as powdered shells or clay) and stabilizers.

Note: In India, all aspects of explosive licensing, manufacture, transport and storage are under the Petroleum and Explosives Safety Organization (PESO) while its use in U/G coal mines is allowed by the Directorate General of Mines Safety (DGMS).

Types/Classifications of Explosive

Permitted Explosive

Permitted explosive are those explosive whigh, is permitted by DGMS Chief Inspector. These explosive are used in underground coal mines due to the degree of gassiness and methane gas is found in mines. Example: P1, P2, P3, P4 and P5 type of explosive. PS type of explosive is used in Solid Blasting in Bord & Pillar method in Underground coal mines Powergel PS01 is a water resistant P5 Type of permitted explosive. P2 and P4 type of explosive are not manufactured in India and not used in gassy coal mines

Non-Permitted Explosive

Non-permitted explosive is manufactured by Indian company and which is not permitted by DGMS. These explosive are used in metal mine and open cast coal mine and quarries.

Low Explosive/Deflagrating explosives

Those explosive which strength is low, it less effect on hard surface or rock. Gunpowder is the example of low explosive. The main composition of Gunpowder explosive is carbon (15%), sulphur (10%) and potassium nitrate (75%) (KNO3). Its VOD is low as compared to high explosive. Potassium nitrate is also known as Saltpeter.

High Explosive/Detonating explosives

Those explosives which strength and VOD are high. These types of explosive are used in soft to hard type of rock. Example: Ammonium Nitrate Fuel Oil (ANFO: AN: 94% and FO: 06%). Liquid Oxygen Explosive (LOX, not used in any mine, Regulation 183. CMR 2017). Site Mixed Slurry based explosive (SMS) and Nitro Glycerin (NG) based explosive are high explosive.

Purpose of Explosive

It is used in open cast mines, Quarries and Underground mines to break the rock/minerals/ore deposits which are suitable for excavator performance.

Properties of Explosive

The different properties of explosive are:

1. Velocity of Detonation (VOD): VOD is the speed at which detonation wave travels through the media. VOD depends on the explosive type. VOD is test by Dautriche Test/Method. Average VOD of explosive varies from 2500 m/sec to 5800 m/s.

VOD ∝ strength of rock

2. Density: The density of an explosive is its mass per unit volume, usually expressed as kilograms per cubic metre (kg/m³) or grams per cubic centimetre (g/cm³). Density is an important property when explosive is seleted for rock strength. The density of most common mining explosives is varies from 0.9 kg/m³ to 1.3 kg/m³.

3. Water Resistance: An explosive's water resistance is a measure of its ability to withstand exposure to water without deteriorating or losing sensitivity. Sensitivity is the ease with which an explosive detonates. In dry work, water resistance is of no consequence.

4. Energy/Strength: In explosive materials, strength is the main parameter determining the ability of the explosive to move the surrounding material. Strength depends upon the rock physic mechanical properties. Energy content of explosive is normally expressed in calories per gram or kcal. per kg of explosive.

Bulk strength = Weight strength x Density

5 Sensitivity: It may be Can-sensitivity.and Booster sensitivity > MINING T20: 5. Sensitivity: It may be Cap-sensitivity and Booster sensitivity.

6. Fume characteristics: An explosive after blasting should generate minimum amount of toxic gases such as carbon monoxide, oxide of nitrogen etc.

7. Borehole pressure and critical diameter: It is an important parameter, which measures the breaking and displacement property of an explosive.

8. Safety in handling and storage qualities

9. Temperature resistance

Booster

It is a package of explosive having high strength (energy) and high VOD used to improve the initiation.

Primer

It is a package of explosive, used to initiate booster-sensitive products and contains a) a detonator or b) detonating cord to which a detonator is attached to initiate it. 

Note: Booster and Primer are cap-sensitive.