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ERZ Studies. > 11---Friday---Explosives---updated 2nd Feb 2016 > Flashcards

11---Friday---Explosives---updated 2nd Feb 2016 Flashcards

1
Q

Explain what is Powder factor?

A

Powder factor = weight of the explosive in kg to the m3 of ground

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2
Q

What is the Powder factor for Coal and Stone?

A
  • Coal PF should be around 0.6kg (0.5 to 0.7)
  • Stone PF can be up to 0.8kg (0.7 to 1.0)
  • Sandstone (1.0 to 1.3)
  • Hard rock conglomerate (1.0 to 1.3)
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3
Q

How long is each Plug of Senatel.

A
  • Each plug is approximately 300mm in length and weighs 400 grams
  • Notes in the explosives shot firing scenario detail 375 grams although indicates 400 grams
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4
Q

If the hole is greater than 1.8 metres then how much explosive per hole?

A
  • Hole depth of greater than 1.8 metres a maximum of 1400 grams per hole.
  • Number of holes 12,000 / 1400 = 8.5 holes for instance
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5
Q

What are the stemming requirements for coal?

A
  • Stemming requirements for coal stem at least 3 plugs of clay,
  • Old rule of thumb 1/3 stemming to 2/3rds powder
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6
Q

What is the current firing capacity?

A
  • Firing capacity The current has been set at 1.5 amps
  • Voltage = Current x resistance
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7
Q

What is the Circuit resistance for 2.3 ohms per detonator 8.4 ohms for the firing cable For 10 detonators?

A
  • Circuit resistance 2.3 ohms per detonator 8.4 ohms for the firing cable For 10 detonators
  • 2.3 x 10 = 23 23 + 8.4 = 31.4 ohms
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8
Q

List the Shot firing equipment that a shot firer will have to fire a shot?

A
  • Shot firing equipment
  • Exploder
  • Key of the exploder with the shotfirer
  • Ohms meter
  • Firing cable
  • Crack detector
  • Stemming stick
  • Sharp stick to piece the powergel
  • Plastic knife
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9
Q

Circuit resistance is 2.3 ohms per detonator 8.4 ohms for the firing cable For 10 detonators 2.3 x 10 = 23 23 + 8.4 = 31.4 ohms What is the volts required to fire the shot?

A
  • 1.5 x 31.4 = 47.1 volts required to fire the charge
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10
Q

If the hole is less than 1.8 metres then how much explosive per hole?

A
  • Hole depth less than 1.8 metres a maximum of 800 grams per hole.
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11
Q

What are the stemming requirements for Stone?

A
  • Stemming requirements for stone stem the entire hole.
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12
Q

What must the site senior executive ensure with respect to explosives used at the mine?

A
  • Authorised explosives
  • The site senior executive must ensure explosives used at the mine are authorised by the chief inspector for the Explosives Act 1999 as suitable for use in an underground mine.
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13
Q

list 8 items a container must be for tansporting and storing explosives underground?

The underground mine manager must ensure explosives are not transported, or stored, underground unless the explosives are enclosed in a container complying with this section.

A
  • Transporting and storing explosives underground The container must be— conspicuously labelled with the word ‘EXPLOSIVES’ printed in red on a white background; and designed and constructed
  • to minimise damage from impact
  • to prevent the following— friction sparks
  • the build-up and retention of static electricity
  • the explosives spilling
  • for containers for detonators or detonator sensitive explosives lined with timber or other shock absorbing material
  • locked; and used only for transporting or storing explosives underground.
  • The container must not contain more than 1 type of explosive.
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14
Q

Temporarily storing explosives underground list the 6 requirements?

A

Temporarily storing explosives underground The underground explosive storage must be

  • in a NERZ
  • in a location that minimises the risk of the explosives suffering an impact or being buried burnt
  • free of rubbish, particularly rubbish of a flammable nature
  • clearly marked by a flashing red light, or other warning device, as an underground explosive storage
  • have fire fighting facilities situated on the intake air side close to the storage.
  • Material other than explosives and explosive containers must not be stored in the storage.
  • A container of detonators must be stored separately, by at least 10m, from a container of other explosive in the storage.
  • The underground mine manager must keep a record of the number and location of underground explosive storages at the mine.
  • The underground mine manager must ensure that when the job is finished, or if it is delayed for more than 48 hours, all unused explosives for the job are returned immediately and stored in surface magazines.
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15
Q

The site senior executive must ensure a vehicle used to transport explosives at the mine has appropriate facilities list Two?

A
  • securing explosive containers to the vehicle
  • protecting the explosive containers against impact
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16
Q

Supervising and controlling shotfiring

The underground mine manager must ensure coal mining operations where shotfiring activities are taking place are directly supervised and controlled by a person holding What qualification?

A
  • a first or second class certificate of competency
  • a deputy’s certificate of competency.
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17
Q

Supervising person undertaking shotfiring training

An underground shotfirer must not, at any time, supervise the activities of more than How many Trainees?

A
  • 1 person who is undertaking shotfiring training.
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18
Q

Where explosives are prepared, charged or fired list the General requirements?

A
  • A general body concentration of methane of less than 0.5%
  • ventilation current capable of quickly diluting and removing any atmospheric contaminants released by the shot
  • its exposed surfaces within a radius of 20m from the location of the shot either (i) thoroughly saturated with water; or (ii) treated with stonedust so the deposited dust mixture comprises an incombustible coal dust concentration of at least 85%.
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19
Q

What should be switched off when explosives are being handled prepared charged or fired?

A
  • All radio transmitters installed at the mine
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20
Q

List the action to be taken if a shot misfires?

4 Items

A
  • Barricade each entrance to the place where the shot was fired
  • immediately report the misfire to any person about to work at the location of the misfire
  • if possible, remedy the misfired shot
  • prevent any work, other than work required to remedy the misfired shot, from being carried out in the vicinity of the shot
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21
Q

List the action to be taken if a shot misfires at the end of your shift?

A

At the end of the shift in which the misfire happened

  • prepare a written record of the location and details of the misfired shot and the action taken to remedy the shot
  • ensure a copy of the record is given to
  • the person in charge of the shift in which the misfire happened and at the start of the next shift—the person in charge of that shift.
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22
Q

What electrical equipment and circuits other than electrical equipment and circuits used for handling, preparing, charging and firing an explosive should be isolated?

A
  • The shotfirer must ensure the equipment and circuits are effectively isolated In the immediate vicinity
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23
Q

What is the maximum Limiting duration of the shot sequence first shot to last shot?

A
  • The shotfirer must ensure the time from firing the first detonator to firing the last detonator does not exceed 250ms.
24
Q

An underground mine must have a standard operating procedure for using explosives and explosive powered tools. The procedure must include provision for the following?

List 7 Things

A
  • transporting explosives underground
  • Storing explosives underground
  • selecting, handling, preparing, charging and firing explosives
  • using explosive powered tools
  • inspecting for flammable gas and combustible dust before a shot or explosive powered tool is fired
  • inspecting for flammable gas, airborne contaminants, blast damage and misfires after a shot is fired
  • establishing the location of (i) other workplaces likely to be affected by the shotfiring; and (ii) persons likely to be affected by a shot or explosive powered tool; necessary, evacuating them or preventing them from entering a dangerous place
  • preventing persons being affected by fumes from used explosives
  • protecting strata supports, ventilation control devices, equipment and other structures from blast damage
25
Q

Explosives generate at velocities of what speed?

A
  • 2000ms
26
Q

High explosives generate at what velocities?

A
  • 2000ms to 7500ms
27
Q

What are permitted explosives?

general statement required for answer.

A
  • They are emulsion based explosives that contain an ingredient to reduce the heat/flame generated during an explosion.
28
Q

What is the permitted explosive (Type Used) for use in an underground mine?

A

Senatel 3000

29
Q

What is the shelf life of explosives?

A
  • 12 months from the date of manufacture
30
Q

What is the manufacturers recommended firing currents?

A
  • 1.5 to 2.5 Amps
31
Q

Where on the detonator is the delay number?

A
  • A tag is on one of the lead wires
32
Q

What type of detonator is permitted to be used in underground coal mines?

Answer is not asking for classification.

A
  • Carrick short delay detonators
33
Q

How are Carrick short delay detonators identified?

A
  • They have a copper detonator shell all other detonators have a aluminuim shell
34
Q

How do we connect up the detonators?

A
  • In series
35
Q

A detonator has a damaged lead what do you do?

A
  • Mark the hole
  • tell the shot firer
  • tie the leads up
36
Q

Why are the lead wires twisted together when they are supplied?

A
  • So they are at the same potencial and will not set off with any stray volltages
37
Q

What labels are on a detonator (shot Firer/ exploder) and What does it say?

A
  • Instructions for use Remove key after firing
  • Capacity:- the maximum number of defined detonators or the maximum series circuit resistance
38
Q

What is the factor of safety for a circuit Tester?

list the output current of the tester

list the current to fire a detonator

A
  • factor of 6
  • 50ma supplied by the tester
  • 300ma have been known to fire a detonator
39
Q

What is the length of a shotfirers cable and resistance?

A
  • 100metres
  • 2 Ohms
40
Q

What is a tamping rod made of?

A
  • Non ferrous material
  • usually wood or in coal mines orange conduit with the ends plugged
41
Q

What else is a tamping rod used for?

A
  • Measure the length of the hole
  • To check the hole condition to make sure that the explosive will go to the end of the hole
42
Q

What is the powder factor for rock popping?

A
  • 50 to 100g ( 0.1KG per m3)
43
Q

How deep do we drill holes to pop rock?

A
  • 2/3rd way through
44
Q

Where multiple holes are used how do we fire these?

A
  • No delay all Together
45
Q

How do we know where to put holes, what is the rule?

A
  • Thickness of the rock or twice depth of the hole
46
Q

where do we try to drill holes when popping a rock?

A
  • Try to drill away from the goaf as this is the weakest point and we do not want hot gasses and blast energy towards the goaf
47
Q
  • Where a crack greater than 3mm is detected at the back of a blast hole what do you do?
A
  • Plug with stemming at the back of the hole to seal
48
Q

If gas is found to be comming from the hole what should you do?

A
  • Do not load the hole.
49
Q

How would you clean a blast hole?

A
  • you can use water or compressed air through a solid pipe
50
Q

Before the shot what happens to the empty explosive boxes and part filled explosive boxes?

who does this?

A
  • Returned to a secure explosive magazine. assistant shot firer?
51
Q

Explain the tie up procedure?

A
  • Connect up the detonators in series leave these shorted so they are at the same potencial
  • Run out the firing cable from the blast site ensure the end are twisted together and they have sufficient length to connect up when required to the detonators
52
Q

list the firing order?

A
  • Shot clean up
  • Tie up
  • Run out shotfiring cable
  • Notify all relevant persons of the shot i.e. control
  • Inspect the area
  • no road areas post sentries/blast guards no sentry in exhaust side of the gasses
  • shot firer will go to blast site connect to detonators.
  • inspect the blast area
  • when back at blast area he will check sentries
  • Shot firer will then check continuity
  • connect to exploder
  • fire the shot
  • wait 10 minutes
  • Inspect the area support contaminents etc
53
Q

list 3 misfires?

A
  • Shot does not go off after pressing the button
  • A charge is found in the blast pattern
  • A charge is found in the muck pile.
54
Q

Calculate the voltage required to fire the shot?

E.g. 50 detonators with a 5 meter leg wire connected in series.

Resistance of one detonator = 2 ohms

Resistance of 50 detonators = 50 ohms

Add Resistance of firing cable = 8 ohms

A

Voltage required for detonators is calculated by Ohms law which states:

Voltage = Current x Resistance

  • 50 detonators with a 5 meter leg wire connected in series.
  • Resistance of one detonator = 2 ohms
  • Resistance of 50 detonators = 50 ohms
  • Add Resistance of firing cable = 8 ohms

Current x resistance = voltage required

2 x50 = 100

100 + 8 = 108

2 (C) x 108 (R) = 216 (V)

55
Q

What is the current dilivered by a shot firers ohm tester?

Can you use an electricians test meter to test the circuit continuity for a round of detonators?

A

Circuit tester (ohm meter) – is used to test the resistance of a detonator circuit. It must be approved and deliver no more than 50 milli-amperes (0.05 amps) the circuit (300mA can initiate a fuse-head.

(Electrician ohm meters produce too much current)

YOU MUST NEVER USE ELECTRICIANS METERS

56
Q
A

ERZ Studies. (29 decks)

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