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.
What are the disadvantages of a non-electric firing system?
- No control after system has been initiated.
- Misfire requires a 60 minute wait time (plus burn time).
Describe shock tube?
A small diameter, laminated plastic tube with an inside coating of 1/10th grain per foot of aluminized HMX.
What is the speed of the detonation wave of shock tube?
6500 fps
What will cause a failure in shock tube?
moisture
How can you connect shock tube?
T-adapters, line adapters, or tape.
what colors are shock tube?
Military shock tube is OD, commercial varies.
How large is a typical roll of shock tube?
2500 feet
What is Primadet?
Shock tube with a blasting cap pre-crimped on the end.
What are the two types of Primadet?
- High strength caps for initiating explosive charges.
- Low strength caps for propagating shock waves to other shock tube or Primdets without having to splice and degrade the system.
What are the procedures for splicing shock tube?
- Cut and discard 4-6 feet off the ends.
- Hold the ends parallel to each other
- Make an overhand knot , leaving overhang for the splice.
- insert ends into the splicing tube at least 1/4 inch
What happens when you spice shock tube?
it degrades the system.
What must you cut shock tube with?
A sharp knife or special cutter.
What precautions should be taken when cutting shock tube?
- Do not allow it to touch the ground where it may absorb moisture.
- Ensure both ends are cut cleanly and squarely.
Why should you not hold detonating shock tube?
While the explosion is usually contained within the tubing, burns can occur if the shock tube is held.
What are the special procedures for using shock tube for demolitions?
- Cut and discard approximately 4-6 feet of shock tube.
- When in a controlled environment, shock tube should be rolled out from the demolition area to the safe area.
How long should you wait before investigating shock tube misfires?
30 minutes.
What are the procedures for dealing with a shock tube misfire?
- If the igniter fails to fire, reset and attempt again, if it fails again try a new one.
- If the shock tube blew out, discard 4-6 feet and try again.
What should you do when using shock tube and the igniter functions but the charge does not go off?
- Cut 4-6 feet off the end to test for powder.
- Cut a 1 foot section off the end and check for powder.
- If powder is present the shock tube did not function, if powder is not present then the shock tube functioned and the detonator failed.
- Wait 30 minutes before going downrange to check components.
- Check shock tube for damage and check damaged areas for powder before replacing charge or splicing damaged area.
What are the advantages of the shock tube firing system?
- A minimum amount of equipment is required.
- Not subject to premature detonation due to static or stray current.
- Compete control of the initiation.
What are the disadvantages of the shock tube firing system?
- Misfire requires 30 minute wait time.
- Expended tubing needs to be collected and disposed of properly.
Describe an electric firing system?
An electric firing system is one in which electricity is used to fire the primary initiating element.
How does an electric firing system work?
An electrical impulse travels through the firing wire and cap lead wires to fire an electric initiator.
What are the components of electric firing system?
- Electric blasting cap/Squib
- Firing wire
- Blasting machine
What is the preparation of the explosive charge by electric means called?
Electric priming
Do the procedures for using electric blasting caps with high explosives differ from using electric squibs with low explosives?
No.
Name some rules of dealing with electric firing systems?
- Do not wear static producing clothes like wool, silk or synthetics.
- Ground yourself prior to touching or passing blasting caps or primed charges.
Why does grounding help?
It dissipates build up static electricity and equalizes any potential.
How can you accomplish grounding?
Touching a grounded metal stake, grounding strap, a grounded pipe, or touching the ground.
What should be taken downrange to ensure safety when conducting electric firing system operations?
Galvanometer and the blasting machine.
When will firing wire be tested?
Ater being laid out.
What are the procedures for testing the firing wire continuity?
- Check continuity with circuit closed at the up-range end. Ensure their IS defection of the meter.
- Check continuity with the firing wire circuit open at the up-range end. Ensure NO deflection.
- Check continuity with circuit closed at the up-range end. Ensure their IS defection of the meter.
- Twist the free ends of the wires together at both ends with a minimum of three twists to shunt the wires.
What are the procedures for testing the electric blasting cap?
-Turn wire at base of cap several times around index finger to allow 1-3 inches of operation from the base of the cap and the hand.
-Keep cap pointed downrange
-Uncoil cap wires completely
-Place the cap under a sandbag
-Extend the cap leg wires completely
-Kneel and turn your back to the caps
remove the factory shunt and touch each lead to galvanometer. Ensure their IS a deflection.
-If no needle deflection, check the galvanometer for correct function.
-If cap is the problem, properly dispose of and start over with a new cap.
How far should electric blasting caps be away from explosives before testing continuity?
25 feet downwind.
After electric blasting caps are tested, what should be done?
- Shunt the leg wires or attach them to the firing wire.
- Ensure each connection is insulated with non-static producing tape.
If two or more electric caps are utilized, how should they be connected?
In parallel or series.
If connecting electric caps in a series circuit, what must be done?
Check with the galvanometer before connecting to the firing wire.
What is the last thing done in a demolition using electric blasting caps?
The charge is primed only after all other steps are taken.
After electric priming of a charge is complete, what is done next?
- Retreat to a safe area.
- Check continuity of the entire system.
- Operate blasting machine several times prior to connecting it to the firing wire.
- Warnings are given.
- Attach blasting machine and initiate.
How long do you wait before investigating a misfire on an electric firing system?
30 minutes from the last attempt to fire.
What are the steps to deal with an electric firing system misfire?
- Make several attempts to fire.
- Check wiring connections at blasting machine.
- Try again with another blasting machine.
- Disconnect blasting machine and re-shunt firing wire.
- Test firing circuit for breaks and short circuits, correct any found.
- Remove blasting cap from charge, then remove from firing wire and shunt leg wires.
- Properly dispose of blasting caps.
- Perform procedures for new cap and prime charge.
What are the advantages of an electric firing system?
- Positive control over the detonation
- Misfires require a 30 minute wait time.
What are the disadvantages of an electric firing system?
- Specialized equipment needed.
- Subject to premature detonation due to outside sources, such as static, electro-magnetic radiation, or stray currents.
Where is the use of detonating cord especially useful?
Multiple shots, underwater and underground because the blasting cap can remain above the surface.
What type of cap must be used to fire detonation cord?
Electric or non-electric.
What could happen if the cover on detonation cord is damaged?
It can misfire.
How must detonation cord be laid out?
As straight as possible but not stretched taut. It must be straightened to avoid intersections that can cause a misfire.
What type of lines must be used for detonation cord underwater?
A double main line and double branch lines.
When using detonation cord underwater what precautions should be taken?
- The cord should be initiated from the dry end.
- The free end should be waterproofed.
- Tape used should be coated with a sealing compound.
What are the two types of detonating cord lines?
- The main line
- Ring main line
What is a main line for detonating cord?
A single line running one length
What is a ring main line?
A continuous loop of debt cord initiated from the juncture of the two ends. It uses two detonation waves that meet at the middle point.
What is a branch line?
Lines of det cord run off a main or ring main line. Used to connect explosive charges.
What must you ensure with branch lines?
That they only touch one another or the main line at the connections. If not the passing detonation wave can cut the det cord.
Why must you keep sharp turns and kinks out of detonation cord?
Misfire is probable when detonating cord turns 90 degrees or sharper.
Name the types of connections for detonation cord?
- Tape
- Square knot
- Modified Girth Hitch
How many branch lines can connect to a main or ring main line at any one point?
One and never at a splice in the main line.
How do you tape detonation cord together?
- Overlap the ends by 18 inches minimum total (six inch minimum overlap taped with six inch overlap beyond the taped center)
- Branch lines taped a minimum 6 inches with 6 inch pigtail
How do you use a square knot to join detonation cord?
Tie a square knot with the two det cord ends and leave an extra 6 inches beyond the knot and taped down.
What method do you use to join a branch line to a main or ring main line?
Modified Girth Hitch
What angle should the branch line be form the main or ring main line?
Not less than 90 degrees or it may not detonate.
How tight must the modified girth hitch branch line be on the main or ring main line?
Tight to prevent slippage, but not tight enough to deform the detonation cord. Tape or twine can be used to prevent slippage.
How do you attach a blasting cap to detonation cord?
Double over a section of detonation cord to create a priming loop. Blasting caps should be placed on the top and bottom of the loop and taped in place.
What direction will blasting caps be pointed when attached to detonation cord?
In the direction of the detonation wave.
Why is it not recommended that plastic explosives be primed by wrapping them in detonation cord?
They will not properly detonate the explosive charge.
What is a half hitch used for?
Secure blasting cap leg wires to an explosive charge.
Name the common knots used in demolitions?
- Double overhand knot
- Hasty Whip
- Modified girth hitch
- Square knot
What is a double overhand knot used for?
To concentrate detonating cord to facilitate initiation of an explosive charge without the use of sensitized detonation cord.
What will making a smaller loop on a double overhand knot with detonation cord do?
The smaller the loop the more concentrated the detonation cord.
What is a hasty whip knot used for?
Can be used to initiate an explosive charge without a blasting cap.
How many wraps are used on a hasty whip knot?
Minimum 4 to ensure reliable initiation of the explosives.
What is lace priming?
Using crimpers to create a minimum of 4 holes through an explosive charge and lacing detonation cord through the holes and knotting the end or weaving back through the laces.
What type of explosives should not be lace primed?
Plastic explosives.
What are the procedures for misfires involving detonation cord and non-electric blasting caps?
- Allow 60 minutes to elapse
- Cut the detonating cord between the cap and charge
- Attach a new cap and fuse to the end of the detonating cord
- Initiate new fuse
What are the procedures for misfires involving detonation cord and shock tube?
- Perform appropriate shock tube misfire procedure
- Cut the detonating cord between the cap and charge
- Attach a new primadet to the end of the detonating cord
- Initiate new fuse
What are the procedures for misfires involving detonation cord and electric blasting caps?
- Perform procedures for electric misfires
- Connect a new blasting cap to the end of the detonating cord
- Return to safe area and check circuit continuity
- Reconnect firing wire ends to blasting machine and fire new cap
What are the procedures for misfires involving detonation cord failure?
- Attach a new blasting cap to the detonation cord and attempt to fire the charge again
- If it still fails to fire, carefully remove earth cover (if any) and re-prime charge with new cord
- Replace earth cover (if any) and fire new detonation cord
What are the procedures for misfires involving detonation cord and the charge fails to fire?
- If charge has not been buried and is still intact, place a new charge next to the failed charge (as close as possible to the failed charge without touching)
- If buried, carefully remove earth cover, place a new charge next to failed charge (as close as possible to the failed charge without touching)
- Fire new charge
Explain a dual firing system?
It consists of two completely independent electric or non-electric systems, or a combination of one electric and one non-electric system. Each system is capable of initiating the charge by itself.
Explain a dual priming system?
It consists of one electric firing wire with two electric blasting caps connected in parallel, or two non-electric systems placed into the same charge.
The proper priming of explosives will ensure what?
A reliable detonation and help prevent misfires.
What is priming dependent on?
The available explosives, initiation system used, and available materials.
What should you never do with a cap?
Force it into a cap well that is too small to admit it easily. Remove the cap and enlarge hole.
Describe end priming?
Using crimpers, create a hole in the end of the explosive charge large enough for the blasting cap to fit in without forcing it. If using TNT, use crimpers to break the priming well cover.
Describe side priming?
Using crimpers, create a hole in the side of the explosive charge large enough for the blasting cap to fit in without forcing it. Take care not to puncture through the opposite side and ensure there is enough explosive charge around the entire cap to create reliable detonation.
