TA3211-10 Bahan Peledak & Safety Blasting.pdf

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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TA3211-10 Bahan Peledak & Safety Blasting.pdf