reactive and explosive materials an introduction

Reactive and Explosive Materials

An Introduction


• What are explosive materials?

• Definitions

• Hazard Categories

• Reactivity

• Video

What are reactive and explosive materials?

• Any material capable of violent or explosive decomposition when subjected to shock, heat, friction, flame, static discharge, elevated temperature, or exposure to air or water.

• Resulting decomposition may produce a lethal shock front, extreme heat, flame or a gaseous atmosphere that may explode or ignite.

Reactive and explosive materials

• These materials may be reactive by nature or may become reactive due to age, exposure to air, to a contaminant, exhausted inhibitors, elevated temperatures, or separation of product while under bad storage conditions.

Reactive and explosive materials

• Any materials that fit this description, and whose condition is not known, should be considered extremely dangerous and should only be handled by qualified personnel who are properly equipped to do so.

• All these materials can be safely handled and disposed of if you maintain the proper attitude, respect, procedures and technical expertise.



• Definitions


• Reactivity

• Video

Definitions

• Decomposition: A breakdown of a substance into a group of different substances. In the case of highly reactive or explosive materials, large amounts of energy will be released

Definitions

• Explosion: A chemical reaction that generates high temperatures and large amounts of gas at a very fast rate. If under confinement, an explosion may produce a shock front and a missile hazard. This may be a rapid gas expansion (deflagration) in a confined area or a detonation.

Definitions

• Deflagration: A rapid or violent decomposition with flame and large amounts of heat. The speed of the decomposition (the reaction front as it moves through the material) is subsonic, i.e.: slower than ~1250 ft/sec. A characteristic of propellant explosives such as smokeless powder or a match.

Definitions

• Detonation: An extremely rapid and violent decomposition producing a lethal shock front, heat and flame. The speed of the decomposition is supersonic, i.e.: 1250 to 30,000 ft/sec. Picric acid, for example, detonates at 24,000 ft/sec or 16,344 mph!

Definitions

• Shock wave: A high pressure wave that radiates from the surface of an explosion that has detonated.

• Overpressure: The pressure, over atmospheric pressure, that is present at the leading end of a shock wave.

Over Pressure

• Example for 1 lbm of TNT• Distance Over Pressure Effect • 10 ft 5 psi lethal, wooden utility poles

snapped• 16 ft 3 psi structural damage, steel

framed buildings pulled from foundation

• 40 ft 1 psi windows break, partial demolition of houses

• 250 ft 0.1 psi some windows break

Definitions

• SADT: Self Accelerating Decomposition Temperature.

• MSST: Maximum Safe Storage Temperature

Definitions

• Compressed gas (DOT): Any substance having an absolute pressure exceeding 40 psi at 70°F, or, regardless of pressure at 70°F, having an absolute pressure exceeding 104 psi at 130°F, or any flammable liquid having a vapor pressure exceeding 40 psi at 100°F. Any compressed gas may have a high pressure hazard regardless of other hazards specific to the material, and must be protected against an uncontrolled release



• Definitions


• Reactivity

• Video

Hazard Categories

• Explosive A: A chemical compound capable of detonating when unconfined and subjected to shock or heat. The degree of sensitivity varies greatly. Some materials which deflagrate but do not detonate are also considered class A explosive by DOT. Black powder is one such example.

Hazard Categories

• Explosive B: A chemical compound that generally deflagrates rather than detonates. Examples are propellants and pyrotechnic powders.

Hazard Categories

• Explosive C: Any manufactured article that may contain a small quantity of a class A or B explosive. Examples are certain types of fireworks.

Hazard Categories

• Flammable Liquid: Any liquid material that will ignite easily and burn rapidly with a flash point below 100°F, and a vapor pressure not over 40 psia at 100°F.

Hazard Categories

• Pyrophoric Liquid: Any liquid material that will spontaneously ignite and burn rapidly when exposed to air that is below 130°F.

• Pyrophoric Solid: Any solid material that will spontaneously ignite and burn rapidly when exposed to air that is below 130°F

Hazard Categories

• Oxidizer, Solid or Liquid: Any solid or liquid material that spontaneously evolves oxygen either at room temperature or when under slight heat.

Hazard Categories

• Organic Peroxide, Solid or Liquid: Any solid or liquid organic compound containing the bivalent O-O in its structure. Such compounds release oxygen readily, are capable of violent or explosive decomposition, and are generally unstable at elevated temperatures.

Hazard Categories

• Flammable Solid: Any solid material that will ignite easily and burn rapidly.

• Flammable Solid DWW: Basically the same as a flammable solid, these materials, when in contact with water, will ignite, explode, or liberate a flammable gas that itself may ignite or explode

Hazard Categories

• Flammable Gas: Any gas that will ignite easily and burn rapidly. The flame and heat propagation rate is so great as to resemble an explosion, especially if confined.

• Non-Flammable Gas: Any gas that doesn’t meet the definition above. Although a gas may be nonflammable, it may be a strong oxidizer, very corrosive, or toxic. The high pressure in many cylinders is a hazard in itself



• Definitions


• Reactivity

• Video

Reactivity

• Initiating Stimuli:– Temperature, elevated above SADT– Air, exposure to air– Water, contact with water or moisture– Shock (heat, friction, static), exposure to high

temperatures, flame, grinding friction, or electrical discharge.

– Contamination, contact with an incompatible material

Reactivity

• Sensitizing Stimuli– Contamination, introduction of another material– Age, loss of desensitizer, inhibitor, or a slow, long-term

degradation– Elevated temperature, temperatures high enough to

cause degradation or separation of product– Light, initiates a slow or violent decomposition– Moisture, separation of a product– Freezing, separation of a product

Reactivity

• Degrees of Initiating Stimuli– Low sensitivity, must be subjected to a strong shock

or heat source to initiate decomposition– Moderate, any moderate stimuli found in normal

handling, transportation, or disposal.– High, a very sensitive or spontaneous material that,

for no “apparent” reason, will generate a gas, ignite, decompose violently, explode, or detonate. Usually the result of age, exposure, contamination, etc.

Reactivity

• Degree of Decomposition– Mild, ignition of a material that burns at a moderate

rate and may ignite adjacent materials.– Severe, ignition of a material that will decompose

with a rapid deflagration and may produce very high temperatures or large amounts of gas.

– Violent, ignition or initiation of a material that will detonate, produce a lethal shock and missile hazard.

Video

• Although filmed in 1988, the message is timeless: what precautions must be made when working with explosive and reactive chemicals.

reactive and explosive materials an introduction

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