Hot Surface Ignition
SCHUYLER NICHOLS
Special Topics (Fire Dynamics)
Dr. Peter Disimile
Spring 2013
1
Basic Things to Know
Hot Surface Ignition - The ignition of a material as the result of
heat liberation due to an exothermic oxidation reaction from a hot
surface, while an external ignition source such as a spark or
flame is completely absent.
Auto-ignition Temperature (AIT) – The minimum temperature
required to initiate or cause self-sustained combustion
(exothermic reaction) independent of an external ignition source.
Minimum Ignition Temperature (MIT) – The minimum
temperature required to initiate or cause self-sustained
combustion resulting solely from a hot surface.
2
Controlled Sources of Hot Surface Ignition
Glow Plug on a Gas Furnace
Diesel Engine Glow Plug
Gas Stove Glow Plug
3
Non-Controlled Sources of Hot Surface Ignition
Fluid
Hot brakes + leaking brake fluid = New Car Payment
Dust
Hot Conveyer Belt Bearing + Sugar Dust = No Sweets for you.
Imperial Sugar Factory, 2008
Port Wentworth, Georgia
Gas
Space Heater + Natural Gas Leak = Homeless
4
Main Obstacles

Despite being a well know problem, Hot surface ignition has received
little fundamental research to help understand the ignition mechanism.
Most materials (fluids, powders, etc.) have only received superficial
treatment in literature.
Example: American Petroleum Institute recommends a general rule of
thumb that a hot surface ignition in open air should not be
assumed unless the surface temperature is about 200°C
greater than the accepted auto-ignition temperature.

Hot Surface Ignition is probabilistic in nature and cannot be defined
by a single ignition temperature. In other words, ignition temperature
is defined by several factors:
1.) Surface Properties
* material
* geometry
* size
* roughness
2.) Enviornmental Factors
* air temperature
* airflow
* humidity
3.) Physical Properties
* chemical composition
* flash point
* volatility
4.) Other Possible Factors
* exposure time
* etc.
5
Determining Auto-Ignition Temperature

The auto-ignition temperature of a number of materials (mostly flammable liquids) is reported in a
large number of literature and have mainly been obtained using standardized tests such as ASTM
E 659 for Chemical Liquids, ASTM G72 for Plastics, etc.
Example:
Apparatus used to measure auto-ignition temperature of liquid chemicals as defined by ASTM E 659
 Uniformly heated 500 ml glass flask
 Flask contains air at a pre-determined
temperature
 Approximately 100ml of fluid is inserted into the
flask
 The Fuel/Air mixture is observed for 10 minutes,
or until auto-ignition occurs.
Since auto-ignition is dependent on the mole
fraction of a liquid, the ASTM E 659 standard calls
for a series of tests in which the volume of liquid
injected into the flask is varied until auto-ignition
is finally observed.
Auto-Ignition Video: http://www.youtube.com/watch?v=yG0rP3D_0-s
6
Determining Auto-Ignition Temperature continued…
 Auto-Ignition Equation
The time it takes for a material to reach its auto-ignition temperature
a heat flux 𝒒′′ is given by:
𝒕𝒊𝒈 =
𝝅
𝟒
(𝒌𝝆𝒄)
𝑻𝒊𝒈 when exposed to
𝑻𝒊𝒈 −𝑻𝒐 𝟐
𝒒′′
where : 𝒌 = 𝒕𝒉𝒆𝒓𝒎𝒂𝒍 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒊𝒗𝒊𝒕𝒚
𝒌𝒈
𝝆 = 𝒅𝒆𝒏𝒔𝒊𝒕𝒚 𝒎𝟑
𝒄 = 𝒔𝒑𝒆𝒄𝒊𝒇𝒊𝒄 𝒉𝒆𝒂𝒕
𝑱
𝒌𝒈∗𝑲
𝑻𝒐 = 𝑰𝒏𝒊𝒕𝒊𝒂𝒍 𝑻𝒆𝒎𝒑𝒆𝒓𝒂𝒕𝒖𝒓𝒆 𝐊
𝑾
𝒒′′ = 𝒉𝒆𝒂𝒕 𝒇𝒍𝒖𝒙 𝒎𝟐 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐭 𝐭𝐨 𝐭𝐡𝐞 𝐦𝐚𝐭𝐞𝐫𝐢𝐚𝐥
 Auto-Ignition temperatures vary widely in the available literature, with most
stating that the given auto-ignition temperatures should only be used as
estimates.
 Causes of variation in auto-ignition temperatures include altitude, humidity,
amount of time required for ignition, partial pressure of oxygen, etc.
7
Hot Surface Ignition
of Selected Fluids
Most problematic type of hot surface ignition within
the aviation and automotive industries
8
Experimental Setup [6]
 48 cm x 38 cm x 4.8mm, 304 stainless steel plate, surrounded on three sides by draft shields.
 Plate was covered with a 2.5 cm thick refractory insulation, with a 15.9 cm x 10.8 cm section in the center removed.
 Electric heater consisted of a nichrome wire heating element which was powered by a 0-240 volts A.C. variac.
 Single drops of fluid from a 2 mL pipette were dropped onto the center of the plate from a height of 25 cm.
 Seven type K thermocouples were welded to the plate to characterize spatial temperature variations
* One T/C welded near the center of the plate
* Four T/C’s welded at 2.5 cm and 5.1 cm on either side in the x-direction.
* Two T/C’s welded at 2.5 cm on either side in the y-direction.
 Plate temperatures at the seven locations were monitored using a data logger sampling at 4 samples/minute.
9
Experimental Setup [6] continued…
 After each test, the plate temperature and ignition result were recorded.
 The time between any two consecutive tests was at least 15 seconds.
 To remove any residue from the surface, it was sanded with a 200 grit sand paper before testing each
fluid.
 Since ignition on a freshly sanded surface was observed to be more difficult, several pre-test ignitions
were achieved before collecting the data set.
 Since ignition is probabilistic near the ignition threshold, 200 ignition tests were conducted with each
fluid such that logistic regression and goodness of fit statistical tests could be performed.
 In total, over 2500 ignition tests were conducted.
10
Results [6]
Due to the issue of overlap of the data from ignition and non-ignition cases, a single minimum ignition
temperature from the hot surface is impossible to come by. Instead, a logistic regression curve fit of the
data was used to help determine the Ignition Probability for each fluid over a range of temperatures.
𝑰𝒈𝒏𝒊𝒕𝒊𝒐𝒏 𝑷𝒓𝒐𝒃𝒂𝒃𝒊𝒍𝒊𝒕𝒚 = 𝑬 𝒀 =
𝒆𝒙𝒑 𝒃𝒐 + 𝒃𝟏 𝑻
𝟏 + 𝒆𝒙𝒑 𝒃𝒐 + 𝒃𝟏 𝑻
where 𝒃𝒐 and 𝒃𝟏 are the logistic regression coefficients and 𝑻 is the temperature.
Example:
11
Results [6]
continued…
12
Comparisons
Summary of Research Involving Hot Surface Ignition of Aviation and Automotive Liquids
Fluids
Number of Tests
Performed
Reference
Test Surface
Material
Surrounding Enclosure
Air Flow (m/s)
Liquid Injection
Strasser [14]
Horizontal Rods: 2.5-10 cm diameter, 30-61 cm length;
Plate: 9 x 30 cm, horizontal and 22.5°
Not Specified
20 cm tube
0- 2
Stream
Myronuk [13]
Horizontal 7.6 x 99 cm tube with fins
Stainless Steel
None
0.8 - 50
Stream, Spray
Parts [12]
Horizontal rod 7.6 x 30 cm
Stainless Steel
None
Stream, Spray
Johnson [11]
Bleed air duct on a section of an F-16 engine
Inconel
0- 6
Stream, Spray
Foose [10]
Segments of and engine bleed air duct
Inconel
0- 3
Stream, Spray
Severy [9]
Horizontal tube (size not specified)
Not Specified
None
Aircraft Engine Nacelle
Fire Simulator
Aircraft Engine Nacelle
Fire Simulator
Box
(details not specified)
MIL-H-5606, MIL-H-83282,
MIL-L-7808, JP8
MIL-H-5606, MIL-H-83282,
Jet A
MIL-H-5606, MIL-H-83282,
MIL-L-7808, JP8
MIL-H-5606, MIL-H-83282,
MIL-L-7808, JP8
MIL-H-5606, MIL-H-83282,
MIL-L-7808
None
Stream
Gasoline, Diesel
102
Arndt [8]
Catalytic converter (location not specified)
Not Specified
None
Not Specified
Spray
8 Automotive Fluids
38
API [7]
122 x 13 cm sheet metal
Stainless Steel
Not Specified
Not Specified
Not Specified
Not Specified
Colwell [6]
10.8 x 15.9 cm horizontal plate
Stainless Steel
None
None
Single Drop
Gasoline, Diesel
6 Aviation fluids,
8 Automotive Fluids
Not Specified
Not Specified
417
1096
943
2600
13
Comparisons
continued…
Comparison of Ignition Temperature Ranges for Various Aviation Fluids
 The temperature range associated with Colwell’s study corresponds to the 10% and 90% ignition probability
temperatures.
 All other temperature ranges that are given correspond to the lowest temperatures at which ignition did occur
and the highest temperatures at which ignition did not occur.
 Cases where only the lowest ignition temperature was reported are represented by a single data point.
14
Comparisons
continued…
Comparison of Ignition Temperature Ranges for Various Automotive Fluids
15
Observations
 For each fluid the temperature range necessary to achieve ignition is
generally consistent, although the ranges themselves are generally
substantial.
 The range tends to be largest for hydraulic and lubricating oils, but
smaller for various fuels.
 The temperature increase from the auto-ignition temperature to the
minimum ignition temperature tends to be smaller for most of the oils
than for the fuels.
 In general, the minimum ignition temperatures do not seem to be
related to the auto-ignition temperatures, therefore the general rule of
thumb recommended by the American Petroleum Institute that a hot
surface ignition in open air is about 200°C greater than the auto-ignition
temperature is in poor agreement with the results.
 Most cases, with the exception of Colwell, were mainly interested in
obtaining the minimum ignition temperature, therefore not enough data
sets were obtained to perform a good statistical analysis that could
have helped mask the effect of large isolated variations in the data.
16
Conclusions
 Unlike the auto-ignition temperature, the minimum ignition
temperature is not a fundamental fluid property, and is strongly
coupled to numerous factors (i.e. surface texture, airflow, liquid
spray or stream, etc.)
 Due to said coupling, the temperature required for ignition can vary
widely.
 Hot surface ignition data cannot easily be extrapolated to different
conditions.
 The general rules of thumb based on the auto ignition temperature
can be very inaccurate.
17
Hot Surface Ignition
of Selected Dusts
Very problematic type of hot surface ignition within
many manufacturing industries
18
Background
 When the rate of heat release generated by the oxidation of combustible
materials exceeds the rate of heat loss, the temperature rises within the
system, consequently accelerating oxidation reactions, until self ignition
occurs.
 Industrial plants, storages, silos, hoppers, driers, mixing plants, etc, are
common places that this phenomena can occur, and can often lead to
impressive and hazardous physical manifestations, such as dust explosions.
 Since 1999, the ATEX (Explosive Atmosphere) regulations require employers
to carry out hazard identifications, risk assessments, and to take prevention
measures regarding the explosion of gas, vapors, and dusts.
 The European directive 1999/92/EC especially requires the following actions
concerning the production or the storage of combustible dusts:
* The avoidance of the formation of explosive atmosphere
(clouds or dust layers)
* The avoidance of igniting an explosive atmosphere.
* A reduction of the damages for a potential explosion on
workers
Hot Surface Ignition of Dust Video: http://www.youtube.com/watch?v=Jg7mLSG-Yws
19
Background continued…

Due to a high number of industrial dust fires that occurred from the industrial
revolution all the way up through the 1960’s, the MIT of dust layers for particular dusts
was introduced to specify safe surface temperatures or maximum permissible surface
temperatures (MPST).

The MIT at which dust ignites is typically determined by hot plate testing according to
EN 50281-2-1 (European Standards), IEC 61241-2-1 (International Electrotechnical
Commission), and ASTM E2021 (American Society for Testing and Materials).

Experiments to determine the MIT of dust layers can be costly and very hard to carry
out when considering all the factors that the dust layers may experience in actual
industry conditions.

To try and avoid the high cost and complexity of carrying out physical experiments to
determine MIT, many industries have resorted to creating mathematical models to
simulate self ignition. These mathematical models allow for multiple factors to be
considered all at once that would be very difficult or require lengthy preparation to set
up in a physical experiment.
Example:
* Dust composition
* Dust Deposition Configuration
* Surface Material
* Heating Conditions
* Airflow
* etc.
20
Experimental Setup [18]
 Magnesium powder layers were conducted with four different particle sizes: 6, 47, 104, and 173 mm
 Dust Container was a stainless steel ring, 45 mm diameter and 30 mm high, position on the center of a stainless steel plate.
 Five bare thermocouples with a bead size of 0.5 mm O/D were placed throughout the dust layer.
 Thermocouples were positioned at 6, 12, 18 and 24 mm in height from the hot surface for experiments estimating effective dust layer
thermal conductivity, and at 3, 6, 15, and 24 mm in height for other ignition tests.
 After thermocouple positioning, surface temperature of the plate was set using a ND8000 temperature controller.
 Once the plate temperature was stable, the ring was gently filled with Mg powder equilibrated to ambient temperature.
 Dust layer temperatures were measured and recorded by a DT9805 temperature recording device.
 All tests were done in a quiescent environment with ambient temperature at 300 K.
 Tests were run until either the layer temperature reached equilibrium for no less than 60 minutes, or a clear thermal runaway was
observed.
 Inherent uncertainty of the test apparatus was within acceptable limits given a testing resolution of 5 K in layer ignition temperature.
 Fresh magnesium powders were used for each test.
21
Mathematical Model [18]
Equation for Temperature Distribution
 In the Case of the deposited on a flat plate, the dust layer is considered to have infinite thickness L.
 Due to the relatively slow oxidation process leading to ignition, it is assumed that oxygen diffusion
from the face exposed to the atmosphere was sufficiently fast that the reaction was not oxygen
diffusion limited.
 Diffusion resistance for the oxidizing agent was neglected.
 A heterogeneous reaction at magnesium particle surfaces is also assumed.
 A one-dimensional non-equilibrium heat conduction equation for the dust layer is written as:
𝝆𝒃 𝒄
𝝏𝑻
𝝏𝒕
=𝒌
𝝏𝟐
𝝏𝒙𝟐
+ 𝑨∆𝑯𝑹 𝝆𝒃 𝒆𝒙𝒑
−𝑬
𝑹𝑻
(Eqn. 1)
where: k = thermal conductivity of a dust layer (W m-1 K-1)
T = temperature (K)
rb = packing density (kg m-3)
c = specific heat of the dust (J kg-1 K-1)
DHR = heat of reaction (J kg-1)
A = Arrhenius pre-exponential factor (s-1)
E = activation energy (J mol-1)
R = universal gas constant
 To stay in line with the experimental ignition procedure, the powder inside the ring is equilibrated to
ambient room temperature of:
T = Ta = 300K, at time t = 0.
(Eqn. 2)
22
Mathematical Model [18]
continued…
Equation for Temperature Distribution
 Boundary Conditions:
At the cool surface of the dust layer:
𝒅𝒕
𝒙 = 𝑳 ∶ −𝒌 𝒅𝒙 = 𝒉 𝑻𝒔 − 𝑻𝒂 = 𝒉𝒄 𝑻𝒔 − 𝑻𝒂 + 𝜺𝝈(𝑻𝒔 𝟒 − 𝑻𝒂 𝟒 )
(Eqn. 3)
At the hot-plate surface:
𝒙 = 𝟎 ∶ 𝑻 = 𝑻𝒑
(Eqn. 4)
where: h = hc+ hr is the total heat transfer coefficient (W m-2 K-1) accounting for the convective (hc)
and radiant (hr) heat transfer coefficients.
Ts = top surface temperature (K)
Tp = hot plate temperature (K)
s= Stefan-Bolzmann constant
e = emissivity of layer surface
23
Mathematical Model [18]
continued…
Equation for Temperature Distribution
𝒙
 Using 𝝃 = 𝑳 , 𝛉 =
𝑬
𝑹𝑻𝒑 𝟐
𝒕
𝑻, 𝝉 = 𝑳𝟐 𝝆𝒃 𝒄 equations 1 – 4 are re-written in non-dimensional form:
𝝏𝜽
𝝆𝒃 𝒄𝑳𝟐
𝝏𝒕
=𝒌
𝝉 = 𝟎, 𝜽 =
𝝃 = 𝟏, −𝒌
𝝏𝝃𝟐
𝑬
𝑹𝑻𝒑 𝟐
𝝏𝜽
𝝏𝝃
𝝃 = 𝟎, 𝜽 =
𝝏𝟐 𝜽
+
𝑬𝑳𝟐
𝑹𝑻𝒑 𝟐
𝑻𝒂
𝑨𝚫𝑯𝑹 𝝆𝒃 𝒆𝒙𝒑
𝑹𝑻𝒑
𝟐
𝜽
(Eqn. 5)
(Eqn. 6)
= 𝒉𝑳 𝜽 − 𝜽𝑨 + 𝑳𝜺𝝈
𝑬
− 𝑬 𝑹𝑻𝒑
𝑹𝑻𝒑 𝟐
𝑬
𝟑
𝜽𝟒 − 𝜽𝑨 𝟒
(Eqn. 7)
(Eqn. 8)
24
Mathematical Model [18]
continued…
Solving Non-Dimensional Equations
 The discretization of non-dimensional equations was carried out using the finite volume method.
 The arrangement of grid point and the associated control volume is shown in the following figure:
 Temperature at the bottom of the and top surfaces of dust layers is denoted by 𝜽𝟏 and 𝜽 𝑵
 The total number N of grid points in the thickness dimension was set to 100 (i.e. 𝚫𝝃 = 𝟏 𝟏𝟎𝟎) for
numerical simulations, which means the mesh size was about 0.3 mm in height.
 Solving the non-dimensional equations 5 – 8 was done using a stepwise timing method beginning
with the initial temperature distribution (Eqn. 8).
 Given the grid point value of 𝜽𝟎 𝒊 at time 𝝉, the typical time step task was to find the values of 𝜽𝟏 𝒊 at
𝝉 + 𝚫𝝉
25
Mathematical Model [18]
continued…
Solving Non-Dimensional Equations
 The corresponding discretization equations of equations 5 – 8 were derived in a fully implicit scheme as:
𝚫𝝃
𝚫𝒌
+ 𝚫𝝃
𝚫𝒕
𝒌
𝒌
𝝉 = 𝟎 , 𝜽𝒊 =
𝚫𝝃
𝚫𝝉
𝒌
+ 𝒉𝑳 + 𝚫𝝃 + 𝑳𝜺𝝈
𝑹𝑻𝟐 𝒑
𝑬
𝚫𝝃
𝜽𝒊 = 𝚫𝝃 𝜽𝒊+𝟏 + 𝚫𝝃 𝜽𝒊−𝟏 + 𝚫𝒕 𝜽𝟎 𝒊 +
𝟑
𝒌
𝑬
𝑹𝑻𝟐 𝒑
− 𝑬 𝑹𝑻𝒑
𝑬𝑳𝟐 𝚫𝑹 𝝆𝒃 𝚫𝝃
𝒆𝒙𝒑
𝟐
𝑹𝑻 𝒑
𝜽𝟎 𝒊
𝟐
, (𝐢 = 𝟐, 𝟑, . . . 𝐍 − 𝟏)
𝑻𝒂 , 𝒊 = 𝟐, 𝟑, … 𝑵
𝚫𝝃
𝜽𝟑 𝑵 𝜽𝑵 = 𝚫𝝃 𝜽𝑵−𝟏 + 𝚫𝝉 𝜽𝟎 𝑵 + 𝒉𝑳𝜽𝑨 + 𝑳𝜺𝝈
𝜽𝟏 =
𝑬
𝑹𝑻𝒑
(Eqn. 9)
(Eqn. 10)
𝑹𝑻𝟐 𝒑
𝑬
𝟑
𝜽𝟒 𝑨 +
𝑬𝑳𝟐 𝑨𝚫𝑯𝑹 𝝆𝒃 𝚫𝝃
𝑹𝑻𝟐 𝒑
𝒆𝒙𝒑
− 𝑬 𝑹𝑻𝒑
𝜽𝟎 𝑵
𝟐
(Eqn. 11)
(Eqn. 12)
26
Mathematical Model [18]
continued…
Solving Non-Dimensional Equations
 For interior points 𝒊 = 𝟐 𝒕𝒐 𝒊 = 𝑵 , equation 9 was rewritten in the following form as:
𝒂𝒊 𝜽𝒊 = 𝒂𝒊+𝟏 𝜽𝒊+𝟏 + 𝒂𝒊−𝟏 𝜽𝒊−𝟏 + 𝒃𝒊
(Eqn. 13)
where,
𝒂𝒊+𝟏 = 𝒂𝒊−𝟏 =
𝒂𝒊 =
𝒃𝒊 =
𝚫𝝃
𝚫𝝉
𝜽
𝟎
𝒊
+
𝚫𝝃
𝚫𝝉
+
𝒌
𝚫𝝃
𝟐𝒌
(Eqn. 15)
𝚫𝝃
𝑬𝑳𝟐 𝑨 𝚫𝑯𝑹 𝝆𝒃 𝚫𝝃
𝑹𝑻𝟐 𝒑
(Eqn. 14)
𝒆𝒙𝒑
− 𝑬 𝑹𝑻𝒑
𝟐
𝜽𝟎 𝒊
(Eqn. 16)
 For the boundary point 𝒊 = 𝟏:
𝜽𝟏 =
𝑬
𝑹𝑻𝒑
(Eqn. 17)
27
Mathematical Model [18]
continued…
Solving Non-Dimensional Equations
 For the boundary point 𝒊 = 𝑵:
𝒂𝒏+𝟏 = 𝟎
𝒂𝒏−𝟏 =
𝒂𝑵 =
𝒃𝑵 =
𝚫𝝃
𝚫𝝉
𝟎
𝜽
𝑵
𝚫𝝃
𝚫𝝉
+ 𝒉𝑳 +
+ 𝒉𝑳𝜽𝑨 + 𝑳𝜺𝝈
𝒌
𝚫𝝃
𝑹𝑻𝟐 𝒑
𝑬
(Eqn. 18)
𝒌
(Eqn.19)
𝚫𝝃
+ 𝑳𝜺𝝈
𝟑
𝟒
𝜽
𝑨
+
𝑹𝑻𝟐 𝒑
𝑬
𝟑
𝜽𝟑 𝑵
𝑬𝑳𝟐 𝑨𝚫𝑯𝑹 𝝆𝒃 𝚫𝝃
𝑹𝑻𝟐 𝒑
(Eqn. 20)
𝒆𝒙𝒑
− 𝑬 𝑹𝑻𝟐 𝒑
𝜽𝟎 𝑵
𝟐
(Eqn. 21)
28
Mathematical Model [18]
continued…
Solving Non-Dimensional Equations

Local temperatures in the discretization equations were calculated using a Tri-Diagonal
Matrix Algorithm.

Computation convergence at all grid points was considered to occur at a grid in the
successive iterative step when the maximum temperature difference 𝜽𝟏 𝒊 − 𝜽𝟎 𝒊 𝒎𝒂𝒙 was
<0.001

A variable time step was needed to compute the detailed temperature distribution beyond
the time of thermal runaway, so the following scheme was used to automatically adjust the
time step along with nodal temperature changes on the grid occurring during computations:
𝚫𝝉 =

𝟏
𝜽𝟏 𝒊 −𝜽𝟎 𝒊 𝒎𝒂𝒙
(Eqn. 22)
The initial time step in the computation was set to 5 sec.
29
Mathematical Model [18]
continued…
Estimation of Input Parameters

Effective thermal conductivity (k) in equation 1 would influence the temperature
distribution inside the dust layer, so some testing was initially carried out to determine the
parameters at a lower hot plate temperature.

The remaining input parameters were obtained from literature references.
30
Results [18]
Temperature Change Inside Magnesium Powder Layers in Contact with the Heated Plate
 The temperature of the heated plate was set at 710 K and the Magnesium particle size used was 6 mm.
 The dotted curves correspond to the data simulation model, whereas the solid curves correspond to the data
from the experiment.
 The sharp incline at the end of each curved indicates when ignition occurs.
31
Results [18]
continued…
Temperature Change Inside Magnesium Powder Layers in Contact with the Heated Plate
 The layer thickness that was used was 6 mm.
 The plate temperature was initially set at 710 K, but was then increased each time a larger particle size was
being used in order to achieve ignition, with 763 K being the highest plate temperature when the 173 mm particle
size was being tested.
32
Other Results
Material
Heated Surface Partical Size (mm)
Dust Fromation
Dust Depth (mm) Ignition Temperature (°C)
Ignition Criteria
Time Until Ignition (minutes)
Cork
Steel Plate
< 0.065
Conical Heap
25
260
Smoldering
not specified
Cork
Steel Plate
0.43
Conical Heap
25
280
Smoldering
not specified
Cork
Steel Plate
3.8
Conical Heap
25
320
Smoldering
not specified
Cork
Steel Plate
3.8
Conical Heap
50
260
Smoldering
not specified
Mixed Wood Sawdust
Steel Plate
1.4
Conical Heap
25
270
Smoldering
51
Mixed Wood Sawdust
Steel Plate
1.4
Conical Heap
50
240
Smoldering
216
Mixed Wood Sawdust
Steel Plate
1.4
Conical Heap
75
230
Smoldering
420
Mixed Wood Sawdust
Steel Plate
1.4
Conical Heap
100
230
Smoldering
450
Mixed Wood Sawdust
Steel Plate
1.4
Conical Heap
125
220
828
Potato Powder
Metal Plate
not specified
Packed in Metal Ring
5
300
not specified
Potato Powder
Metal Plate
not specified
Packed in Metal Ring
12.5
280
Smoldering
Visible glowing, or flaming, or a temperature of
450°C is reached, or a temperature rise of 250 K
above the heated plate is measured
-
Potato Powder
Metal Plate
not specified
Packed in Metal Ring
15
270
-
not specified
Cacao Powder
Metal Plate
not specified
Packed in Metal Ring
5
270
-
not specified
Cacao Powder
Metal Plate
not specified
Packed in Metal Ring
12.5
260
-
not specified
Cacao Powder
Metal Plate
not specified
Packed in Metal Ring
15
240
-
not specified
Wood and Flax Dust
Metal Plate
not specified
Packed in Metal Ring
5
340
-
not specified
Wood and Flax Dust
Metal Plate
not specified
Packed in Metal Ring
12.5
320
-
not specified
Wood and Flax Dust
Metal Plate
not specified
Packed in Metal Ring
15
300
-
not specified
Activated Carbon Dust
Metal Plate
not specified
Packed in Metal Ring
5
> 450
-
not specified
Activated Carbon Dust
Metal Plate
not specified
Packed in Metal Ring
12.5
> 450
-
not specified
not specified
not specified
Activated Carbon Dust
Metal Plate
not specified
Packed in Metal Ring
15
> 450
-
Wheat Dust
Metal Plate
not specified
Packed in Metal Ring
5
> 450
-
not specified
Wheat Dust
Metal Plate
not specified
Packed in Metal Ring
12.5
390
-
not specified
Wheat Dust
Metal Plate
not specified
Packed in Metal Ring
15
290
-
not specified
33
Observations
 No mater the material or the experiment setup, all data tends to show
the same trend in regards to the relationship between the layer
thickness and the MIT, as well as the particle size and MIT.
 All simulation models were dependent to some degree on data from
actual experiments in order to set initial and boundary conditions.
 Although the curves from simulation seemed to generally follow the
same trend as the curves from the experimental data.
 The MIT temperature generally seems to be considerably higher for
inorganic materials such as metal dusts versus organic materials such
as wood or wheat dusts.
34
Conclusions
 No matter the material, all experimental data, as well as simulation
data proves that there is a direct relation between the thickness of
the dust layer and the MIT. The thicker the dust layer, the lower the
MIT will be.
 Much like the previous relation, the experimental and simulation data
proves that there is also a direct relation between the particle size
and the MIT. The larger the particle size, the higher the MIT will be.
 Although the data from experiment vs. simulation follows the same
general trend, the discrepancies between the two would still be large
enough to cause concern if an industry was wanting to use
simulation data to set their safety standards.
 The resulting experiments and simulations failed to take into
account the many other factors that could easily influence MIT, such
as different surface textures, airflow, humidity, cracks in the layers,
etc. Until all factors can be taken into account, most industries are
going to be left having to enforce very large safety factors that in the
long run could end up hurting productivity.
35
Hot Surface Ignition
of Selected Gases
An all around general hazard
36
SORRY!!!!
Great opportunity for some personal research.
37
REFERENCES
1.) Davis, S.; Kelly, S.; Somandepalli, V., “Hot Surface Ignition of Performance Fuels”
Fire Technology, ISSN 0015-2684, 04/2010, Volume 46, Issue 2, pp. 363 - 374
2.) “Ignition Risk of Hydrocarbon Liquids and Vapors by Hot Surfaces in the Open Air”
API Recommended Practice 2216, Third Edition, December 2003
3.) Colwell, Jeff D., “Hot Surface Ignition”
Exponent Failure Analysis Associates
4.) Bowes, P.C. and Townshend, S.E., “Ignition of Combustible Dusts on Hot Surfaces”
British Journal of Applied Physics, ISSN 0508-3443, 03/1962, Volume 13, Issue 3, pp. 105 - 114
5.) Palmer, K.N. and Tonkin, P.S., “The Ignition of Dust Layers on a Hot Surface”
Combustion and Flame, ISSN 0010-2180, 1957, Volume 1, Issue 1, pp. 14 – 18
6.) Colwell, Jeff D. and Reza, Ali, “Hot Surface Ignition of Automotive and Aviation Fluids”
Fire Technology, ISSN 0015-2684, 04/2005, Volume 41, Issue 2, pp. 105 – 123
7.) API, “Ignition Risk of Hot Surfaces in Open Air,” API 2216, American Petroleum Institute,
Washington D.C., 1991.
8.) S.M. Arndt, D.C. Stevens, and M.W. Arndt, “The Motor Vehicle in the Post-Crash Environment,
An Understanding of Ignition Properties of Spilled Fuels,” SAE Paper No. 1999-01-0086, 1999.
9.) D.M. Severy, D.M. Blaisdell, and J.F. Kerkhoff, “Automotive Collision Fires,” in Proceedings
of Eighteenth STAPP Car Crash Conference, Society of Automotive Engineers, Warrendale,
PA, December 4–5, 1974, pp. 113–199.
10.) J.G. Foose, “F-16 Engine Nacelle Fire-Prevention Requirements Study,” General Dynamics
Report No. 16PR2771, 1983
11.) A.M. Johnson, A.J. Roth, and N.A. Moussa, “Hot Surface Ignition Tests of Aircraft Fluids,”
Report No. AFWAL-TR-88-2101, Wright-Patterson Air Force Base, OH, 1988.
12.) L. Parts, “Assessment of the Flammability of Aircraft Hydraulic Fluids,” Report No. AFAPLTR79-2055, Wright-Patterson Air Force Base, OH, 1979.
38
REFERENCES
continued…
13.) D.J. Myronuk, “Dynamic, Hot Surface Ignition of Aircraft Fuels and Hydraulic Fluids,” Report
No. AFAPL-TR-79-2095, Wright-Patterson Air Force Base, OH, 1980.
14.) A. Strasser, N.C. Waters, and J.M. Kuchta, “Ignition of Aircraft Fluids by Hot Surfaces Under
Dynamic Conditions,” Bureau of Mines PMSRC Report No. 4162, Report No. AFAPL-TR-7186, Wright-Patterson Air Force Base, OH, 1971.
15.) “Correlation between self-ignition of a dust layer on a hot surface and in baskets in an oven”
Journal of Hazardous Materials, ISSN 0304-3894, 11/2008, Volume 159, pp. 528 – 535
16.) Aristov, V. F; Barzykin, V. V; Krishenik, P. M; Rozenband, V. I, “Surface hot-Spot ignition of a layer of metal
powder in oxygen,” Combustion, Explosion, and Shock Waves, ISSN 0010-5082, 03/1985, Volume 21, Issue 2, pp. 131 – 137
17.) Miron, Y and Lazzara, CP, “Hot-surface ignition temperature of dust layers,”
Fire and Materials, ISSN 0308-0501, 1988, Volume 12, Issue 3, pp. 115 - 126
18.) Chunmiao, Yuan; Dezheng, Huang; Chang, Li; Gang, Li, “Ignition behavior of magnesium powder layers on a plate heated at
constant temperature,” Journal of hazardous materials, ISSN 0304-3894, 02/2013, Volume 246-247, p. 283
19.) Quintiere, James G, “Principles of Fire Behavior,”
Delmar Publishers, ISBN 9780827377325, 1998, xi, 258
20.) http://www.youtube.com/watch?v=yG0rP3D_0-s
21.) http://www.youtube.com/watch?v=Jg7mLSG-Yws
39
THANK YOU
40
QUESTIONS?
41