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7/25/2019 TA3211-10 Bahan Peledak & Safety Blasting.pdf
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Explosives andBlasting Safety
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Safety is Based on Duty of Care
Employers are required to:
provide and maintain a working environment in which employees
are not exposed to hazards.
Employees are required to:
ensure their own safety and health at work
avoid adversely affecting the safety or health of any other person
through their actions or failure to act at work.
Failure to comply with the Duty of Care is an offence
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Legislation, Codes of Practice, Standards etc prescribe the requirements
for explosives and blasting safety.
Mines Act and Regulations in each State cover explosives use on
a mine site, ie Decree of Mine Minister 555.K/1995
Dangerous Goods Act in each state for transport regulation
(comply with each state through which the explosives are to be
transported) Australian Standards and Codes
Procedures laid down by mine management
Risk assessment processes for deciding whether a new method
or procedure is acceptable
Explosives Safety
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A comprehensive safety management system should include:
Corporate Safety Policy
Programs to give effect to the policyJSAs, Take 5!s, Hazard Assessment procedures etc
Work procedures flowing from the programs
SWPs, SOPs etc
Drill & Blast Safety programs will be guided by Corporate Safety
Policy in how they approach and manage safety
Safety Management Systems
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Definitions of Blasting Areas
Safety Zone
Blast SiteBlast Area
Safety Buffer
Region between Blast Area
and Safety Zone where
Flyrock is possible
Region designated by the
Blaster-in-Charge where
Flyrock is not expected
Region designated by the
Blaster-in-Charge where
flying material is expected
Region where boreholes
are loaded or in the process
of being loaded
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Blast area must be adequately barricaded and signed to preventunauthorised entry
No smoking in the vicinity of explosives (min 6m)
No activity or machinery that could be a potential ignition source isallowed within 6m of the loading
Until charging has started, explosives should remain separated from
detonatorsIf drilling while loading holes, sufficient separation distance must bemaintained at least one uncharged hole (i.e. 2 burdens min separation)
Primers should be made immediately prior to usePrimers shall not be dropped freely to the bottom of the hole
No undue force (excessive forces) is to be used to insert the detonator into theprimer
Blast Pattern Safety
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The final pre-blast inspection by the shot firer in charge should ensure
that:
The tie-in is consistent with the design initiation sequence All components have been properly connected with no omissions
(oversight)
Initiation of the blast is to be connected at the correct point
No damage has occurred to any of the system components
No excess products remain on the blast pattern
Excess charging or inadequate burdens must be noted
Pre-Blast Inspection
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Blasting signs erected to notify mine staff the time and location of blast
Blast guards must be adequately informed of their duties andresponsibilities
Blast clearance plan to safely guard the blast area and all access pointsto be completed and circulated well before the blast
All clearance control points to comply with the minimum safety distance
Different methods used to notify employees of an impending blast (siren,flashing lights, radio warning, etc)
Consider the most likely direction of flyrock when establishing clearancedistances
Overcharged holes pose a risk of flyrock and excess charge mustbe removed or additional clearance distance allowed
All personnel and equipment to be removed to a safe distance from theblast and all areas checked prior to blasting
Blast Clearance
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Shotfirer should be familiar with blast clearance procedure and followthis procedure
Shotfirer is responsible for clearance of all equipment and personnel
from the blast area Clearly audible blast warning signal should be sounded for the set
period prior to firing
Blast is to be fired only after clearance is confirmed and approvalgranted by blast controller
Blast Clearance
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Respect Blast Signs and Barricades
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Check for hazardous conditions
such as overhanging walls,voids
and unstable ground
Shotfirer to check for signs ofmisfires
Post Blast Clearance
Allow adequate time for dust and fumes
to dissipate. The time required for this
wil l vary. Remember that many fumes
are invisible to the eye and that clear air
does not mean fumes are not present.
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Misfires may be recognised when
inspecting the muckpile immediately after
a blast by:
Unusual shape or Flat areas in themuckpile
Unfired surface initiation system
components on top of the muckpile
Unfired explosive on face
Misfires
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Handling of Misfires
Performed only by competent, experienced persons
Every misfire evaluated on individual basis
Specific explosives involved Circumstances
Location
Hazards resulting from event
Methods of handling misfires
In-place detonation (preferred)
Neutralize and/or remove & dispose
Removal of explosives with industrial vacuum (non-electric detonators only) Relieving/nearby charge (least preferred)
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Report misfire: Immediately report to supervisor in charge
Secure area
Post warning signs
Rope off area (adjust size according to hazard)
All clear signal should NOT be sounded
Guards remain in place during investigation
Allow suitable waiting period before detailed investigation
ANFO may be washed from the hole: Use copious quantities of water, preferably by using a water cannon type
spray
A fresh primer is then loaded and fired to detonate the original primer
Gassed emulsions may not wash out properly and refiring the booster may causea larger detonation that expected.
Do not attempt to forcibly remove explosives from holes.
Dealing with Misfires
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Disposing of the misfire by re-firing the hole:
For a surface initiation system, if the downline(s) is in good condition
and easily accessed, connect a new detonator and refire according
to procedures Where downline is inaccessible or damaged, the stemming should
be removed from the hole (with a compressed air/water jet through a
non-ferrous pipe), a fresh primer inserted into the explosive and the
hole refired
NB: Refiring misfires creates a significantly greater risk of flyrock and
noise than a standard blast!
Dealing with Misfires
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It is critical that the underlying cause of misfires be determinedwherever possible to prevent a recurrence
Misfire records should document the state of the misfire at time of
discovery
Immediate cause and method of disposal should form part of therecord
Failed product, if recovered should be returned to the explosivessupplier for detailed examination
Details of the full investigation and conclusions are required tocomplete the record
Regular reviews of misfire records will provide a guide to trends inmisfire causes
Misfire Investigations
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In the case of misfires, prevention is always
better than cure
All steps in the charge-up process must be
correctly and diligently carried out All checks of the pattern tie-in must be
completed without rushing prior to blasting
Post blast clearances must be thorough
and complete If a blast is known to have misfired, no
person is to re-enter the area until a
prescribed time period has elapsed
This period differs from state to state and
is different for different initiation systems
Misfires on top of that
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Flyrock
Flyrock is the undesirable throw
of rock or debris from a blast
area and is the leading cause of
fatalities and equipment damagefrom blasting
Extra margins of safety must be
allowed when working with
explosives.
Dont get complacent (too
righteous).Expect flyrock to
occur and protect yourself and
others accordingly.
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What Causes Flyrock?
In adequate burden Excess charge
Inaccurate drilling
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What Causes Flyrock? Contd
Loose material against face
Mud seams and
cavities
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Controls
Good design is the primary way to avoid flyrock
problems avoid over/under confinement
Adverse geology is always a risk and must be
considered
Do not alter blast designs without careful consideration
of the effects - including flyrock
Measure to manage
Any blast observers must have adequate protection -
and a light vehicle cab is not it!
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Why are fumes a problem?
Health & Safety
Regulatory responsibilities and public relations
Commercial impact
Principal gases that constitute the reddish brown BlastFumes are the various oxides of nitrogen:
Dinitrogen Oxide - N2O
Nitrous Oxide NO
Nitrogen Dioxide NO2These are collectively known as NOx (pronounced nox)
Blast Fumes
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The gases resulting from detonating an oxygen balanced explosive are
principally carbon dioxide, nitrogen and steam:
3NH4NO3 + (CH2)n 3N2 + 7H20 + CO2
Small amounts of CO, NO, NO2 and NH3 may also be produced (depends onconfinement, mixing etc)
In perfect conditions the oxygen balance determines the ratio of products:
over-fuelled (oxygen negative) favours increased CO2 and CO under-fuelled (oxygen positive) favours Nox
NO is colourless. NO2 is red brown
heavier than O2, and the other constituents of air
It does not disperse quickly
Basic Chemistry
One of the most insidious gases. Inflammation of the lungs may cause only slight
pain or pass unnoticed, but the resulting edema several days later may cause
death. 100 ppm is dangerous for even a short exposure. 200 ppm may be fatal.
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Appropriate explosive selection
Loading procedures (bottom loading, sleeves, sleep time etc.)
Priming increased primer size to increase energy in detonation front
Increased relief (reduce burden or increase delay timing)
Eliminate explosive induced dessensitisation and premature detonation
Blast design
Blast size
Hole diameter (larger holes provide better detonation
characteristics)
Hole depth (effects density of gassed Emulsion Blends)
Fumes Minimisation Strategies
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When you see this
You leave the Blast Pattern Immediately!
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Toulouse AN Plant Explosion 30 deaths
More than 2000 injured
442 other companies
damaged 3000 ha severely damaged
15 Billion Euros cost
Crater 50m dia, 40m deep
Explosives Safety
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