EXPLOSIVES - PROF. NEHA PATNI

INTRODUCTION TO EXPLOSIVES

Explosives: Substance that undergoes decomposition or combustion with great

rapidity, evolving much heat and producing a large volume of gas.

The reaction products fill a much greater volume than that occupied by the original

material and exert an enormous pressure, which can be used for blasting and for

propelling.

“Explosive” means a reactive chemical substance or mixture, which when subjected

to thermal or mechanical shock, gets very rapidly oxidized exothermically into

products of greatly increased volume, with a sudden release of the stored

potential energy, in form of light, heat, sound and pressure.

DISARMAMENT

Disarmament is the act of reducing, limiting or abolishing weapons.

There are four key parts to it:

Reduction in quantity of military items

Formal meeting and agreement to achieve

Emphasis on weapons and tools

Body or group overseeing the process

Nuclear disarmament refers to both the act of reducing or eliminating nuclear weapons

and to the end state of a nuclear-free world in which; nuclear weapons are completely

eliminated.

Ultimately, the main purpose of disarmament is world peace and the survival of

mankind.

WEAPONS OF MASS DESTRUCTION (WMD)

A weapon of mass destruction (WMD or WoMD) is a nuclear, radiological, chemical,

biological or other weapon that can kill and bring significant harm to a large number of

humans or cause great damage to human-made structures (e.g. buildings), natural structures

(e.g. mountains), or the biosphere.

Weapon of mass destruction can be defined as:

I. Any destructive device;

II. Any weapon that is designed or intended to cause death or serious bodily injury through the release,

dissemination, or impact of toxic or poisonous chemicals, or their precursors;

III. Any weapon involving a biological agent, toxin, or vector

IV. Any weapon that is designed to release radiation or radioactivity at a level dangerous to human life;

Uncontrolled explosion Controlled explosion

In general, an explosive has four basic characteristics:

1. It is a chemical compound or mixture ignited by heat, shock, impact, friction, or a combination ofthese conditions;

2. Upon ignition, it decomposes rapidly in a detonation;

3. There is a rapid release of heat and large quantities of high-pressure gases that expand rapidlywith sufficient force to overcome confining forces; and

4. The energy released by the detonation of explosives produces four basic effects;

(a) rock fragmentation;

(b) rock displacement;

(c) ground vibration; and

(d) air blast.

Explosives should be cheap and stable under normal conditions. It should not be volatile andhygroscopic.

It must have at least one chemical bond that can be easily broken. This means its molecule should havelow energy of dissociation. Usually such molecules contain N-N, N-O, N-Cl and O-Cl bonds

CLASSIFICATION

1 . By sensitivity…..

Primary explosives

Secondary explosives

Tertiary explosives

2. By velocity…..

Low explosives

High explosives

Primary explosives are highly sensitive explosives which explode on receiving a slight stimulus such

as impact, friction, heat, static electricity, or electromagnetic radiation.

A relatively small amount of energy is required for initiation.

As a practical measure, primary explosives are sufficiently sensitive that they can be reliably

initiated with a blow from hammer.

Primary explosives are often used in detonators or to trigger larger charges of less sensitive

secondary explosives.

They are commonly used in blasting caps to translate a physical shock signal. In other situation

different signals such as electrical/physical shock, or in the case of laser detonation system, lights

are used to initiate an action i.e. an explosion.

A small quantity usually milligram is sufficient to initiate a larger charge of explosive that is usually

safer to handle.

Additionally, Nitrogen triiodide is a primary explosive that cannot be handled without detonation.

Uses: Primary explosives are often used in:

1. Detonators or to trigger larger charges of less sensitive secondary explosives.Example- tetracene.

2. Blasting caps and percussion caps to translate a physical shock signal. Example-diazodinitrophenol (DDNP).

3. Laser detonation systems to initiate an action, i.e., an explosion.

Examples of primary explosives are:

Acetone peroxide, Ammonium permanganate, Azo-clathrates, Diazodinitrophenol,Lead azide, Nitrogen trichloride, Nitrogen triiodide, Nitroglycerin, Silver azide,Silver acetylide, Sodium azide, Tetrazine, Tetraamine copper complexes, Tetrazoles,etc.

Lead Azide

Ammonium permanganate

Acetone peroxide

Nitroglycerine

Tetrazine

A secondary explosive is less sensitive than a primary explosive and require

substantially more energy to be initiated.

Because they are less sensitive they are usable in wide variety of applications and

are safer to handle and store.

Secondary explosives are used in larger quantities in an explosive train and are

usually initiated by a smaller quantity of a primary explosive.

Examples : TNT (trinitrotoluene), RDX

Tertiary explosives, also called blasting agents, are so insensitive to shock that they

cannot be reliably detonated by practical quantities of primary explosives and instead

require an intermediate explosive booster of secondary explosive.

These are primarily used in large scale mining and construction operations and in

terrorism.

Example : Ammonium nitrate/fuel oil(ANFO) ( 94 percent porous

prilled ammonium nitrate (NH4NO3), (AN) that acts as the oxidizing agent and

absorbent for the fuel — six percent Number 2 Fuel Oil (FO))

Ammonium nitrate prills used in ANFO 25-kilogram (55 lb) sacks containing ANFO

They are the compounds where the rate of decomposition proceeds through thematerial at a speed less than the speed of sound.

They simply burn and do not explode suddenly.

The decomposition is propagated by a flame front which travels much more slowlythrough the explosive material than a shock wave of high explosive.

Under normal conditions, low explosives undergo deflagration at rates that varyfrom a few centimeters per seconds to approximately 400m per second.

It is possible for them to deflagrate very quickly, producing an effect similar todetonation.

This can happen under higher pressure or temperature which usually occurs whenignited in a confined space.

Deflagrate: To burn or cause to burn with great heat and intense light.

A low explosive is usually a mixture of combustible substance and an oxidant that

decomposes rapidly ; however they burn more slowly than a high explosive which has

extremely fast burn rate.

Low explosives are normally employed as propellants. Gun powder and light pyrotechnics

such as flares and fireworks are also included in this group.

They are explosive material that detonate, meaning that the explosive shock front

passes through the material at a supersonic speed.

High explosives detonate with explosive velocity rates ranging from 3,000 – 9,000m

per second.

They are normally employed in mining, demolition and military application.

They can be divided into 2 explosives classes differentiated by sensitivity:

Primary and secondary explosive.

As “bursting chargers” for bombs, missile warheads, grenades and mines.

As “propellants” to fire bullets and artillery shells.

For social and useful work like digging earth, construction of tunnels and roads etc.

For Launching rockets and spacecrafts.

As “blasting chargers” in military or commercial demolition, for earth-moving and

demolition of bulidings and other structures.

Explosives are used in large quantity for destructive purpose by terrorists today.

PEACEFUL USES OF EXPLOSIVES

The major use of explosives has been in warfare.

- High explosives have been used in bombs, explosive shells, torpedoes, and missile warheads.

- Non-detonating explosives, e.g., gunpowder and the smokeless powders, have foundextensive use as propellants for bullets and artillery shells.

The detonating explosives is to break rocks in mining. One important explosive used inmining, called ANFO, is a mixture of ammonium nitrate and fuel oil.

In scientific research investigations.

Excavation: The nuclear explosive may be used for large-scale earth moving, e.g., diggingsea-level canals, stripping rock layers from deep mineral deposits, cutting highways andrailway passes through mountains creating harbours and lakes, and altering watersheds forbetter distribution of water resources.

The very fine industrial-type diamonds used for grinding and polishing are produced by thecarefully controlled action of explosives on carbon.

They should be treated with extreme care.

They should be handled only by experienced and properly instructed person.

They should be stored under the favorable conditions and positions sufficiently isolated fromany working furnace kilns.

The boundaries of the explosive store should be protected by fencing and watchman withproper “Caution Boards”.

Smoking or fire should be strictly prohibited within 50 m radius from the explosive store.

Jerks and drops of explosives should be prohibited.

All electrical fitting of the store should be properly insulated and only torch light should beallowed in case of power failure.

Different types of explosives should be stored separately.

They should not be handled during thunder storms.

Explosive store should be at safe distance from residences, railway tracks, highway and anypublic places.

THANK YOU.