Explosives - Sensitivity, Testing and Performance

Question 1

How is the friction sensitivity of an explosive tested using the torpedo method?

Answer 1

• A “torpedo” is launched at the expolosive at an angle of 60 degrees.
• This impacts the explosive placed on the anvil leading to a mixture of friction and impact.
• The drop height is changed until 10 consecutive drops do not lead to detonation.

Question 2

What is the Rotary Friction Test?

Answer 2

• Negates any impact effects
• Explosive sample is initiated by a rough discus spun against it.
• Value for the Figure of Friction can be calculated through comparison with a standard value of RDX.
• The lower the value of the Figure of Friction, the more sensitive the explosive is.

Question 3

How is the impact sensitivity of an explosive standardised?

Answer 3

The impact sensitivity is standardised through the figure of insensitiveness.

F_i is the figure of insensitiveness = Drop height of explosive / Drop height of RDX standard

This value changes with the formulation of the explosive.

Question 4

How is static sensitivity of an explosive measured?

Answer 4

• 4J of energy is induced into the explosive.
• If an event occurs, reduce the amount of energy until no event occurs.
• If no event in 10 repetitions, then the explosive is not static sensitive.
• The human static on finger is about 0.02 J, and therefore if it is not sensitive to 2x this amount then the explosive is safe.

Question 5

How is heat sensitivity of an explosive measured?

Answer 5

• Heat the explosive gradually until an ‘explosive event’ occurs.
• Record the temperature for ignition to occur.
• Repeat 10 times.

T of I < 150 ^oC means the explosive has a short shelf life and is generally not used.

Question 6

How is the explosive performance of an explosive determined?

Answer 6

• The explosive performance of an explosive is determined using a ballistic mortar.
• The explosive detonates and the swing of the ballistic mortar is measured.
• This is then compared with a standard explosive.