Dust Explosions Conference Brisbane 2017
John Visser Johen Consulting
17-Oct-16Dust Explosions Conference
Some interesting dusty stuff
Assessing a dusty problem
Examples Truck dump station
Ducting and off takes
Spontaneous combustion
Happy to take questions as you think of them
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Tonnages from
Space rains down 36,500 t annually
Deserts 1 vs. 3 Bt annually
Salt flecks 3.5 Bt annually
Trees/plants 1 Bt annually
Sulphur
Plankton/volcanoes/swamps 20-30 Mt annually
Fossil fuels 90-100 Mt annually
Human skin cells: 50 Million produced daily700,000 inhaled daily
17-Oct-16Dust Explosions Conference
Secret Life of Dust, Hannah Holmes
17-Oct-16Dust Explosions ConferenceNASA Photo 5
17-Oct-16Dust Explosions Conference
Aerosols
Tobacco smoke
Fog/mist/rain
Viruses
Bacteria
Pollens
Plant spores
Thermally generated dust & fume
Foundry sand
Cement dust
Carbon black
Wood dust
Human hair
Talcum powder
Respirable dust
Inhalable dust
Mine dust
0.001 0.01 0.1 1 10 100 1000Microns
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Inhalable
0 to 150µ
Thoracic
10 to 30µ
Respirable
0 to 10µ
Alveoli Typically 200µ when inflated
17-Oct-16Dust Explosions Conference
17-Oct-16Dust Explosions Conference
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4 Observations and optionally 1 Measurement
of dust events for each source
Observe: Duration
Observe: Frequency Consequence
Observe/Measure: Density
Observe: Exposure Likelihood
Consequence Risk ranking
Likelihood
17-Oct-16Dust Explosions Conference
17-Oct-16Dust Explosions Conference
Measurement: Typically a TSI 8520 DustTrak monitor:
Requires a competent scientist
0
20
40
60
80
100
120
140
160
180
07:45:07 07:46:34 07:48:00 07:49:26 07:50:53 07:52:19 07:53:46 07:55:12 07:56:38
Grizzly data mg/m^3
Allowable limit
17-Oct-16Dust Explosions Conference
0
10
20
30
40
50
60
70
80
90
100
Avera
ge E
mis
sion
(m
g/m
3)
17-Oct-16Dust Explosions Conference
Consequence
Likelihood minor medium serious major
almost certain Moderate High Critical Critical
likely Moderate High High Critical
possible Low Moderate High Critical
unlikely Low Low Moderate High
Risk Level
Risk
Rating
Critical 4
High 3
Moderate 2
Low 1
Cloud density Exposure
1Nothing 1Rarely
2Mild: objects easily seen 2Multiple events a month
3
High: outline of objects very
little detail 3Multiple events a week
4
Extreme: outline of objects, no
details can be seen 4Multiple events a day
17-Oct-16Dust Explosions Conference
Event Duration Event Frequency
1< 1 min 1Once a shift
21 to 5 min 2several times per shift
35 to 60 min 3every 10 minutes
4> 1 hour 4Continuous
Item Dust source locations Exposure Cloud density Duration Frequency
1 Crusher dump pocket 1 2 2 3
2 Primary crusher vault 2 1 3 4
3 Primary stockpile 1 4 3 3
4 Secondary crusher house 3 4 3 2
5 Screen house 2 4 4 2
6 Conveyor transfer station 1 3 3 1
7 Stockyard stackers 1 3 4 3
8 Train load out 2 1 2 3
17-Oct-16Dust Explosions Conference
Likelihood = Exposure = number of events in a time frame: Read straight off the Risk matrix
ConsequenceLikelihood
Item Dust source locationsCloud density
CD
Duration
D
Frequency
F
Consequence
C1 Crusher dump pocket 2 2 3 2
2 Primary crusher vault 1 3 4 3
3 Primary stockpile 4 3 3 3
4 Secondary crusher house 4 3 2 3
5 Screen house 4 4 3 4
6 Conveyor transfer station 3 3 1 2
7 Stockyard stackers 3 4 3 3
8 Train load out 1 2 3 2
17-Oct-16Dust Explosions Conference
Consequence = f(Density, Duration, Frequency): Convert to a value 1, 2, 3 or 4
Simple calculation: C = (CD + D + F)/3
17-Oct-16Dust Explosions Conference
ItemDust source
locationsConsequence Likelihood Risk
Value Rating Value Rating
1 Crusher dump pocket 2 Medium 1 Unlikely Low
2 Primary crusher vault 3 Serious 2 Possible High
3 Primary stockpile 3 Serious 1 Unlikely Moderate
4Secondary crusher
house 3 Serious 3 Likely High
5 Screen house 4 Major 2 Possible Critical
6Conveyor transfer
station 3 Serious 1 Unlikely Low
7 Stockyard stackers 3 Serious 1 Unlikely Moderate
8 Train load out 2 Medium 2 Possible Moderate
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• Dust generation is linked to incident velocity
• No dust generation below threshold velocity
• Dust Barrier up-wind of source diverts wind flow and reduces wind velocity
• Dust barrier down-wind collects the dust
• Barrier effectivenessWidth & height
Wind
Office blocks, etc
Berm
RoM pad
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17-Oct-16Dust Explosions Conference
17-Oct-16Dust Explosions Conference
As short as possible
As direct as possible
Holcim chart
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Typical shape
Preferred shape
Efficiency losses
Bin side offtake
As large as possible
Conveyor offtake hood
Minimise sharp corners
Typical shape
Efficiency losses
Preferred shape
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Furnace Baghouses
Build up in the hoppers underneath the bags
Size distribution of the dust P80~25µ
Dry conditions
Carbon present
17-Oct-16Dust Explosions Conference
Those responsible for poor maintenance
Informa
17-Oct-16Dust Explosions Conference
17-Oct-16Dust Explosions Conference
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