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Dust Testing for DSEAR Compliance
www.explosiontesting.co.uk Dust explosion testing for Industry
Reported UK incidents by Industry
0
20
40
60
80
100
120
140
123 36 95 41
Fire - no injury Fire - injury Explosion - noinjury
Explosion - withinjury
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Source: HSE over a 10 year periodSource: HSE over a 10 year period
injury injury
2
UK Explosions by industry
69Paper/wood
43
3Dyes/pigments10
Plastic/resins
24Pulverised fuel
27Pharmaceutical
25Animal feed
Food products
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Source: HSE 10 year periodSource: HSE 10 year period
55Metals
21Other
26Grain/cereals
What is an explosion?
Unconfined explosion
Gas/air mix
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10m/sec
3
Confined Explosion
COLD
HOT
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10m/sec330m/sec
Explosion Pressure Curve
PRES
SUR
EPR
ESSU
RE PPmaxmax
dp/dt
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TIMETIME
Normal pressureNormal pressure
4
What explodes?
• Flammable gases– E.g. natural gas, hydrogen
Flammable liquids (as vapours)• Flammable liquids (as vapours)– E.g. petrol, toluene
• Combustible dusts– E.g. coal, flour, sewage sludge
• Liquid mists– E.g. cooking oil, engine oil
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oxygenparticle size
Conditions for a dust explosion
oxygenpa t c e s e<200 micron
d t
ignition
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dustconcentration>30gm-3
combustibledust
5
Primary explosion
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Secondary explosion
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6
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7
Housekeeping
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Standard tests - Classification
Determines whether the dust explodes or not
Group A (explosible)Group B (non-explosible)
Hot coil ignition, 10kV electric spark, 800oC hot surface & pressure rise in test vessel
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8
Standard tests – Minimum Ignition Temperature
Lowest temperature of a hot surface which will cause a dust cloud to ignite and propagate flame.
The test apparatus and method follow BS EN 50281-2-1:1999.
For dryers or similar equipment
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For dryers or similar equipment.
Standard tests – Layer Ignition Temperature
Lowest temperature at which a l f d t f ifilayer of dust of specific thickness (usually 5mm) ignites on a heated surface.
The test apparatus and method follow BS EN 50281-2-1:1999.
Specify appropriate temperature rating for electrical equipment
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rating for electrical equipment.
9
Standard tests – Minimum Explosible Concentration
Determines the lowest concentration of a dust that willconcentration of a dust that will allow combustion.
The test follows BS EN 14034-3:2006.
May be used as an explosion prevention method in areas where the concentration of the
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where the concentration of the dust can be reliably controlled.
Standard tests – Minimum Ignition Energy
Test measures the ease of ignition of a dust cloud by electrical and electrostaticelectrical and electrostatic discharges.
Follows BS EN 13821:2002.
Determines whether special precautions are necessary to prevent electrostatic discharge
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discharge.
10
Standard tests – Limiting Oxygen Concentration
Determines the minimum concentration of oxygen into which a dust cloud is dispersed that will sustain flame propagation.
Follows BS EN 14034-4:2004.
The test is required if inerting is the basis of safety
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Different results for different inertants eg Steam, Nitrogen, Carbon Dioxide.
Standard tests – Explosible Indices (Kst & Pmax)
Test measures the maximum explosion pressure and rate ofexplosion pressure and rate of pressure rise.
The test follows BS EN 14034-1:2004 & BS EN 14034-2:2006 .
Pmax & Kst value is used to design explosion protection systems –venting & suppression.
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venting & suppression.
11
Standard tests – Self-Heating
Ascertain the risk from self-heating leading to spontaneous combustion
Ramped Aerated Cell Test on WDF Granules
600
Screening testIsothermal basket test to BS EN
15188:2007.Finite element analysis software
is used to computer model the self-heating process.
0
100
200
300
400
500
0 5 10 15 20 25
Time (hours)
Tem
pera
ture
(°C
)
Oven temperature
Sample temperature
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Example explosibility data
Mean particle size (micron)
Maximum explosion pressure
Kst (bar m/s)
St Class
(micron) pressure (bar)
Aluminium 10 11.8 455 3Calcium 23 6.8 119 1Expoxy powder 32 6.9 125 1Lycopdium 27 6.5 135 1Polyester 30 6.1 85 1Polyethylene 14 5.9 134 1Soya bean meal 70 5.7 26 1Tinuvin 320 22 6.8 244 2
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Wheat 22 6.1 65 1Zinc 17 4.7 35 1
12
Explosion Classification
Dust Explosion Class
Kst (bar m/sec)Characteristics
St 0 0 No explosionSt 1 >0 <200 Weak explosionSt 2 >200 <300 Strong explosionSt 3 >300 Very strong explosion
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Generic vs actual test data
• Example (sugar)Kst 138 bar m/sec & Pmax 8 5 bar• Kst = 138 bar m/sec & Pmax = 8.5 bar
• Kst = 11 bar m/sec & Pmax = 3.9 bar• Kst = 205 bar m/sec & Pmax = 9.1 bar
Relying on data … get it writing!
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y g g g
13
Data required for DSEAR/ATEX compliance
LOC (inerting)LOC (inerting)
Pmax Kst (venting, suppression or containment)
MIT (dryers etc)
LIT (electrical or mechanical equipment)
MIE (all plant)
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Screening test (self-heating materials)
Questions?
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