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2018 Dr James LD Glockling Technical Director, Fire Protection Association and Director RISCAuthority 1/1/2018 Fires in Thatched Properties with Wood Burning Stoves
2018
Dr James LD Glockling
Technical Director, Fire Protection
Association and Director RISCAuthority
1/1/2018
Fires in Thatched Properties with Wood Burning Stoves
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Contents
Figures & Tables
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Sweeping residue
annulus – slow
build up restriction
Birds nest -
instantaneous
restriction
CONDUCTION
through liner
CONVECTION
through mortar
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CONDUCTION
through brickwork
CONDUCTION
through liner
CONDUCTION
through brickwork
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0 100 200 300 400 500 600 700 800 900
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1
2
3
4
5
6
7
8
9
10
Flu
e V
elo
city (
m/s
)
Stove Temperature (degC)
Outside ToC
-50C
-20C
-10C
0C
+10C
+20C
+50C
Stove temperature vs. Flue gas velocity
(Flue diameter = 150mm : Flue height = 10m)
Decreasing Outdoor
Temperature
0 100 200 300 400 500 600 700 800 900
0
1
2
3
4
5
6
7
8
9
10
Flu
e V
elo
city (
m/s
)
Stove Temperature (degC)
Flue height
1m
2m
3m
4m
5m
6m
7m
8m
9m
10m
11m
12m
13m
14m
15m
Stove temperature vs. Flue gas velocity
(Flue diameter = 150mm : Outside temperature = 10o
C)
Increasing Flue Height
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Air-wash controlled
air inlet
Over-fuel controlled
air inlet
Under-fuel
controlled air inlet
(for coal burning
only)
Air-wash controlled
air inlet
Over-fuel controlled
air inlet
Under-fuel
uncontrolled air inlet
(ash pan door open)
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o
o
o
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o
o
o
o
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o
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o
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o
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o
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0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
100
200
300
400
500
600
700
800
900
1000
Ga
s T
em
pe
ratu
re (
C)
Time (S)
Ambient
Fire box
Fire box temperature
0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
100
200
300
400
500
600
700
800
Gas T
em
pera
ture
(C
)
Time (S)
0m
1m
2m
3m
4m
5m
6m
Flue gas temperatures
0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
50
100
150
200
250
300
350
400
450
500
Ga
s T
em
pe
ratu
re (
C)
Time (S)
0m
1m
2m
3m
4m
5m
6m
Flue wall temperatures
0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
50
100
150
200
250
300
Ga
s T
em
pe
ratu
re (
C)
Time (S)
0.5m
1.0m
1.5m
Plume gas temperatures
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0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Gas v
elo
city (
m/s
)
Time (S)
High
Low
Flue gas Velocity
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o
o
o
o
o
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o
o
o
o
o
o
0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
2
4
6
8
10
12
14
16
18
20
22
Concentr
ation (
%)
Time (S)
O2
CO
Oxygen & Carbon Dioxide Concentrations
0 240 480 720 960 1200 1440 1680 1920 2160 2400
07-10-2014
Refuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only All ventilation
closedRefuel and
vent on ash
tray
Poke
Ash tray closed
Vent by air
wash only
Test 003 - Normal operation with refuelling and poking
0 240 480 720 960 1200 1440 1680 1920 2160 2400
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
CO
Co
nce
ntr
atio
n (
pp
m)
Time (S)
Carbon Monoxide
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Sparks
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Chimney brickwork
Flue liner
Hot
fire
gases
Liner to brick air gap
Thatch insulation
mimic
Temperature
measurement points
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0 30 60 90 120 150 180 210 240 270 300 330 360 390
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100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
CONDUCTION INVESTIGATION
4 hour aggressive ventilation of perfectly lined (Flexi) chimney
Tem
pera
ture
(C
)
Time after ignition (mins)
Fire box
All following measurements on horizontal
at 6m with chimney insulated to simulate
thatch
Gas in flue
Flue liner external surface
Gas between flue and brickwork
Inside brick surface
Exterior brick surface (Insulated)
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0 30 60 90 120 150 180 210 240 270 300 330 360 390
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100
200
300
400
500
600
700
800
900
1000
CONDUCTION INVESTIGATION
4 hour aggresive ventilation of SPLIT Flexi lined chimney
Te
mp
era
ture
(C
)
Time after ignition (mins)
Fire box
All following measurements on horizontal
at 6m with chimney insulated to simulate
thatch
Gas in flue
Flue liner external surface
Gas between flue and brickwork
Inside brick surface
Exterior brick surface (Insulated)
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0 30 60 90 120 150 180 210 240 270 300 330 360 390
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50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
CONDUCTION INVESTIGATION
4 hour aggressive ventilation of unlined chimney
Te
mp
era
ture
(C
)
Time after ignition (mins)
Fire box
All following measurements on horizontal
at 6m with chimney insulated to simulate
thatch
Gas in flue
Interior brick surface
Gas in flue midway 1
Gas in flue midway 2
Exterior brick surface (Insulated)
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0 30 60 90 120 150 180 210 240 270 300 330 360 390
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
CONDUCTION INVESTIGATION
4 hour normal ventilation of unlined chimney & 50% blockage
Tem
pera
ture
(C
)
Time after ignition (mins)
Fire box
All following measurements on horizontal
at 6m with chimney insulated to simulate
thatch
Gas in flue
Interior brick surface
Gas in flue midway 1
Gas in flue midway 2
Exterior brick surface (Insulated)
0 10 20 30 40 50 60 70 80 90 100
0
20
40
60
80
100
120
140
Flue Gas (oC)
Internal Brick (oC)
External Brick (oC)
Woodburning stove - 4 days continuous 'normal' operation - lined flue
Te
mp
era
ture
(C
)
Time from ignition (hours)
0 10 20 30 40 50 60 70 80 90 100
0
20
40
60
80
100
120
140
Woodburning stove - 4 days continuous 'normal' operation - unlined flue
Tem
pe
ratu
re (
C)
Time from ignition (hours)
Flue gas (oC)
Internal brick (oC)
External brick (oC)
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250C
175C
80C
300C
Time
Model
Time
200C
Actual
Flow
Real-life vs. modelling Severity
difference
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0 15 30 45 60 75 90 105 120 135 150 165 180
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200
300
400
500
600
700
800
Unrestricted flue 1/4 open1/2 open
Ga
p t
em
pe
ratu
re (
C)
Time (mins)
Slot gas temperature
Fire box temperature
CONVECTION - Mortar failure 120mm Slot - Normal Stove operation
3/4 open
0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
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100
200
300
400
500
600
700
800
900
1000
Unrestricted flueUnrestricted flue 1/4 open1/2 open
Gap t
em
pera
ture
(C
)
Time (mins)
Slot gas temperature
Fire box temperature
CONVECTION - Mortar failure 120mm Slot - Aggressive Stove operation
3/4 open
0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240
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100
200
300
400
500
600
700
800
900
1000
3/4 open (Ignition attempt)Unrestricted flue 1/4 open1/2 open
Gap t
em
pera
ture
(C
)
Time (mins)
Brick gap temperature
Fire box temperature
CONVECTION - Brick failure - Normal Stove operation
3/4 open
0 15 30 45 60 75 90 105 120 135 150 165 180 195 210
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100
200
300
400
500
600
700
800
900
1000
1100
Unrestricted flue 1/4 open1/2 open
Gap t
em
pera
ture
(C
)
Time (mins)
Brick gap temperature
Fire box temperature
CONVECTION - Brick failure - Aggressive Stove operation
3/4 open
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