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Mine Development PPT 7

This document discusses misfires that can occur during blasting and their causes. It notes that official regulations should be followed for treating misfires and they should only be handled by experienced personnel. Misfires with safety fuse initiation can be caused by faulty cutting, loose crimping, or using non-waterproof fuse in wet conditions. Misfires with electric firing can result from faulty connections, detonators left unconnected, damaged wires, inadequate current, or too many detonators. Misfires with detonating fuse can be due to incorrect limiting methods, crossovers, delays that are too long, or improper sequencing. Misfires with exploders are often caused by faulty or inadequate exploders, defective generators, poor contact

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110 views7 pages

Mine Development PPT 7

This document discusses misfires that can occur during blasting and their causes. It notes that official regulations should be followed for treating misfires and they should only be handled by experienced personnel. Misfires with safety fuse initiation can be caused by faulty cutting, loose crimping, or using non-waterproof fuse in wet conditions. Misfires with electric firing can result from faulty connections, detonators left unconnected, damaged wires, inadequate current, or too many detonators. Misfires with detonating fuse can be due to incorrect limiting methods, crossovers, delays that are too long, or improper sequencing. Misfires with exploders are often caused by faulty or inadequate exploders, defective generators, poor contact

Uploaded by

shivam rai
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Faculty Name – Prof.

Satya Prakash
Program – B.Tech IV (MIN)
Batch – 2018-22
Course – Mine Development
MISFIRES IN BLASTING
• There are many circumstances under which a
misfire can occur and there are official
regulations covering the treatment of misfires.
These should be strictly adhered to and nothing
in this chapter should be construed as altering or
amending such regulations. All misfires should be
treated with greatest care and all operations
dealing with them should be entrusted only to
experienced conscientious and careful men.
• No person should be allowed to approach a
misfire until either it has exploded or a sage
period has elapsed. This period should be at least
30 minutes with safety use initiation and at least
5 minutes with electric shot firing.
1. Misfires with Safety Fuse Initiation : In safety fuse
firing faulty cutting of safety fuse, loose crimping,
use of non-waterproof fuse in watery conditions
can lead to misfires.
2. Misfires with Electric Shot Firing : In electric shot
firing faulty connections, detonators left-off
unconnected, lead wires becoming bare during
stemming internally shot-circuited cable / damage
in the insulation, inadequate firing current due to
failure of the exploder toreach the rated output or
the number of detonators being greater that that
can be fired by the exploder, current leakage and
other factors can cause misfires.
3. Misfires with Detonating Fuse :
While firing with detonating fuse incorrect
method of limiting the detonating fuse, loop
cross-over, approach of a different branch of
detonating fuse, improper joints and branch-
line failure, use of detonators with too long a
delay interval, wrong sequencing of shots and
improper handling / use if delay detonator-
relays could lead to cut-offs of detonating fuse.
4. Misfire with Exploders :
A large number of misfires are generally caused
by the use of faulty exploders and use of wrong
type of exploder for a given purpose;
Maintenance of exploders is very essential to
obtain the output. Following are the causes of
misfires with exploders :
a) Inadequate exploder capacity
b) Faulty exploder-defective generator/conductor
c) Poor contact in rotating crank type exploders
d) Exhausted cells
e) Faulty indicator
CONCLUSION
• Wherever possible, it is safer to fire the
explosives using a fresh primer than to
attempt to dislodge it and recover the
cartridges from the debris. However, before
deciding on the repriming of the explosives,
consideration should be given to the
possibility of excessive cracks in rocks, which
may occur because of the relief of the burden
of the misfired hole, by adjacent shots.
THANK YOU

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