John Visser - Johen Consulting

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

17-Oct-16Dust Explosions Conference 2


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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


Secret Life of Dust, Hannah Holmes

17-Oct-16Dust Explosions ConferenceNASA Photo 5


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



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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



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


0

10

20

30

40

50

60

70

80

90

100

Avera

ge E

mis

sion

(m

g/m

3)


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


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


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


Consequence = f(Density, Duration, Frequency): Convert to a value 1, 2, 3 or 4

Simple calculation: C = (CD + D + F)/3


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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17-Oct-16John H Visser 18





• 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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As short as possible

As direct as possible

Holcim chart


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


Those responsible for poor maintenance

Informa



Business

John Visser - Johen Consulting