Demolition Procedures Flashcards
Describe a non-electric firing system?
One in which an explosive charge is prepared for detonation by means of a non-electric blasting cap.
Describe Safety Fuse and Time Fuse?
It consists of a black powder core tightly wrapped with several layers of fiber and waterproofing material, can be any color.
What does a non-electric firing system consist of?
Non-electric blasting cap, the safety fuse and the igniter.
What must be combined with a non-electric firing system if more than one charge must be detonated simultaneously?
Detonation Cord.
What is the average burn rate of Safety/Time Fuse?
30-45 Seconds per foot.
How is the burn rate of Safety/Time Fuse determined?
A test burn must be conducted, particularly if used underwater.
In arctic conditions what can happen to Safety/Time Fuse?
It can become brittle and will crack easily.
What are the proper methods for preparation of Safety/Time Fuse?
- When cutting hold both ends so they don’t drop to the ground
- Cut off and dispose of six inches from the free end of the roll and tie a knot in the other end.
- Always cut the fuse smoothly and squarely, a jagged or rough cut can cause a misfire
What is the process to determine the burn rate of Safety/Time Fuse?
Cut and test burn three feet to determine the burn rate. (converting to inches and seconds)
How much Safety/Time Fuse is needed for a shot?
Adequate length determined by how long the person detonating the charge to reach a safe distance while walking at a normal pace or a minimum of 6 feet, whichever is greater.
What is the formula for calculating Safety/Time Fuse?
SST(in seconds) / BR = Whole number + decimal x 12 rounded up to the nearest 1/4 inch
What must always be done when calculating Safety/Time Fuse burn?
Round up when performing calculations.
What is sensitizing detonation cord?
Crimping a non-electric cap onto detonation cord.
What is the process for sensitizing detonation cord?
- Maintain positive control of the blasting cap an and keep it pointed away from personnel.
- Inspect blasting cap for foreign material and perform hand bump to remove.
- Use proper crimping procedures
What should you never do when sensitizing detonation cord or time fuse?
-Never force time fuse or set cord into a blasting cap
To avoid detonation where must you crimp blasting caps?
- 1/8 to 1/4 inch form the open end of the cap
What are proper crimping procedures?
- Hold cord/fuse up at arms length and seat into cap
- Hold cap against fuse/cord with fingers
- Form a marriage crimp
- Turn blasting cap downrange, finger over end, crimp fully
- Inspect crimp
- If good remove finger and keep downrange
What should you never do with your head during the crimping procedure?
Turn your head to the side or down as this negates eye protection
What are the procedures for inserting a blasting cap into a charge?
- Go to one knee
- Insert the cap
- Secure it to the charge so it won’t be pulled out
- Weight down the fuse at two points to prevent curling (don not use rocks or the items that will add fragmentation)
- Give a warning before the detonation
Why do you want to weigh down fuse/det cord?
If it curls back onto itself it could shorten the burn time, stop the burn time or coil onto heat sensitive items or explosives.
Describe how to give a warning before detonation?
- Have hearing protection off so you can hear anyone in the area.
- Yell “Fire in the Hole” 3 times (Once downrange and once to each side).
- After the warning wait a short amount of time, so people in the area have time to react.
How long must you wait before investigating a non-electric misfire?
60 minutes plus burn time.
When practical how should you deal with non-electric misfires?
- Insert a new fused blasting cap into the charge, only if it can be done without disturbing the old blasting cap.
- As an alternate place a new primed charge close enough to the original to ensure detonation of both.
- When necessary a misfired cap can be removed and a new used cap inserted.
What are the advantages of a non-electric firing system?
- Minimum amount of equipment required.
- Not subject to premature detonation due to static or stray current.