Safe Handling of Explosives: Key Definitions and Classifications

Posted on Aug 25, 2024 in Technology

Safe Handling of Explosives:

Definition: – Industrial explosives are mixtures of fuel and oxidizer that, when properly initiated, result in a chemical reaction producing an expansion and increased temperature at a very high speed.

General Characteristics of Explosives:

  • Explosive Power: – The absolute power in a unit of weight and volume.
  • Power-Breaker: – The ability to break rock.
  • Detonation Velocity: – The speed of transmission of the blast.
  • Density: – The concentration of explosive in a given volume.
  • Water Resistance: – The stability of the component without wrapping.
  • Smoke: – Levels of CO, CO2, and NO during the explosion.
  • Sensitivity: – The amount of energy required to initiate detonation.
  • Chemical Stability: – The ability to remain chemically unaltered over time.

Classification of Explosives:

  • Dynamite: – A mixture of nitroglycerin and nitrocellulose. High power and detonation velocity. Water-resistant. Used for underwater blasting.
  • Dusty: – A mixture of nitroglycerin with other products. Granular consistency. Lower power and detonation velocity. Limited by the diameter of the wrapping. Used for underground blasting.
  • ANFO: – A mixture of ammonium nitrate and fuel oil (usually diesel). Requires good initiation for proper detonation. Powdery consistency. Poor water resistance.
  • Hydrogels: – Composed of non-explosive components. High power and excellent water resistance. High safety for transportation.
  • Emulsion Explosives: – Dispersions of immiscible liquids. Composed of a majority oxidant (nitrate solution) and oily fuel (waxes and oils). Sensitive wrapping. Bulk-loaded into large trucks or pumped from boreholes.
  • Heavy ANFO: – A mixture of emulsion and ANFO. Water-resistant and pumpable with high detonation velocity.

Explosive Security: – The mining explosives market mainly involves coal.

Firedamp: – A gas produced by wood carbonization, predominantly methane.

Classification of Firedamp:

  • 1st Category: No mine gas.
  • 2nd Category: Weak presence of flammable gases.
  • 3rd Category: Abundant amounts of flammable gases.
  • 4th Category: Large amounts of flammable gases, with violent release of large quantities of rock.

Powder Mine: – Not explosive itself, but deflagrating with low detonation velocity (< 500 m/s). Produces gas to break rock through gas expansion. Sensitive to touch and flame. Used to start ornamental rocks.

Parameters for Assessment:

  • Type, location, and work to be performed.
  • Diameter of holes.
  • Type of rock being blasted.
  • Presence of water.
  • Security of the explosive.
  • Toxicity of gases after the explosion.

Initiation Systems:

  • Electric Detonator:
    • Description: Electrical part includes cables, igniter or match, explosive strength, and paste.
    • Delay: Cap of controlled ignition explosive paste.
    • Explosive: Primary charge and base charge.
  • Characteristics:
    • Power: Its equivalence with PETN (0 to 8).
    • Electrical: The resistance bridge or connection wires which is the sum total of the previous two.

Intensity of the Current: – Minimum intensity required for initiation of detonation.

Current Security: – Maximum intensity across the stream that does not cause ignition of the match for 5 minutes.

Sensitivity of Detonators: – Measured in (Mw or Ohms).

Classification of Detonators:

  • By Function:
    • AL Capsules: Commonly used.
    • Cu Capsules: Used in flammable environments.
    • Seismic: Used in high hydrostatic pressure for long periods.
  • By Electrical Sensitivity:
    • Sensitive (S): Used in areas with static electricity risk; security current is 0.18 A, ignition is 1.2 A. The wire is red.
    • Insensitive (I): Used in areas with low static electricity risk; security current is 0.45 A, ignition is 2.5 A. The wire is pink.
    • Highly Sensitive (AL): Used where there is a high risk of static electricity; security current is 4 A, ignition is 25 A. The wire is green.

For Time Detonation:

  • Instant: No time delay; the wire is white.
  • Microretardo: From 20 ms; series of 1 to 15; the wire is white.
  • From 30 ms: Series of 1 to 18; the wire is yellow.
  • Delay of 500 ms: Set of 12 points; the wire is blue.

Non-Electric Detonators:

  • No electric.
  • Safety fuse.
  • Detonating cord.

Electric Connection:

  • The bombing begins with electric detonators.
  • It is a bait cartridge.
  • Types of Connections:
    • Series.
    • Parallel.
    • Mixed.
  • Bait Cartridge:
    • A cartridge inserted into the hole that hosts the detonator.
    • Initiation is performed before loading.
    • The bottom of the detonator must be directed towards the explosive.

Forms of Priming:

  • Hole in Priming of Funds:
    • Blasting is done indoors.
    • The trigger is completely inside the cartridge.
    • During filling, keep pulling the strings of the detonator.
    • Do not attack the bait cartridge.
  • Priming in Head:
    • Done in open-pit mining.
    • The first hole is filled.
    • Chubby carefully, but never on the cartridge primer.

Connection Types:

  • Connection in Series:
    • Detonators are connected one after another.
    • Turn the cable first and last line of the wheel.
    • Lines must be shorted until the final check.
    • Total circuit resistance is tested with a special ohmmeter.
    • RT = Rl + (Rd x n).
  • Parallel Connection:
    • Detonator wires are joined in two lines.
    • Requires special permission.
    • Widely used in underwater blasting.
    • RT = RL + (RD / No).
  • Mixed Connections:
    • Used for bombing with a large number of holes.
    • Special permission is required.

Checks Prior to Firing:

  • Line of Fire: Check the continuity of the firing line at one end.
  • Circuit Package:
    • Disconnect detonators and fly lines.
    • Check RT to coincide with the theoretical calculated resistance.
    • If not, check for line failure; R may be too high due to failure in joints or detonators, or too low indicating a short circuit.
    • Disconnect half the circuit and test.

Bugs: Does Not Detonate All Drills.

Explosive Malfunction:

  • Revisions to testers.
  • Explosives appropriate for each paste.

Current Leakage:

  • Tap into wet holes.
  • Shorts in lines.

Mix Different Detonators:

  • Break cable detonator.
  • Firing line too long or too many detonators.
  • Shot by battery or AC; special authorization is required.

Accidents By:

  • Connecting the exploder too soon.
  • Checking power.
  • Strange electricity.

Precautions:

  • The spark should be connected just before the blast.
  • Equipment should be reviewed periodically for testing.

Electricity Strange:

  • Thunderstorm: There are risks even at -200 m deep, and less than 500 m from the mouth.
  • Static Electricity: Wear antistatic footwear and clothing, and use insensitive detonators.
  • Electric Networks: Use insensitive detonators.
  • Radio Stations: Be cautious.

Current Gabbana: – Produced in underwater blasting.