flammability characteristics of vapours and gases
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Bulletin
627
BuREu
OF MiNS
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND
VAPORS
By Michael
G. Zabetacis
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Bulletin 627
BUREAU
OF
MINES
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND
VAPORS
By
Michael G. Zabetakis
0
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CONTENTS
Page
Flammability characteristics-Continued
Pape
Abstract
--------------------------------------
Aromatic hydrocarbons- Continued
Introduction----------------------------------
I Limits in
other atmospheres---------------- 60
Definitions
and theory
-------------------------
2 Autoignition
------------------------------ 62
Limits
of
flammability ----------------------- 2 Burning
rate
-----------------------------
62
Ignition
------------------------------------
3 Alicyclic hydrocarbons---------------------- 63
Formation
of
flammiable
mixtures --------------
4
Limits
in
air
----------------------------- 63
Presentation
of data ----------------------
-----
9 Limits in other atmospheres ---------------- 64
Deflagration and
detonation
processes..-----------
15
Alcohols-----------------------------------
65
Deflagration ------------------------------- 15 Limits in air ----------------------------- 65
Detonation
--------------------------------
16 Limits in
other
atmospheres ----------------
66
Blast pressore ------------------------------ 16 Autoignition ------------------------------ 67
Preventive
measures
--------------------------
18
Burning
rate ------------------------------
68
Inerting
------------------------------------ 1
Ethers -------------------------------------
69
Flame
arrestors and relief diaphragms--------
18 Limits in
air
------------------------------ 69
Flammability characteristics ------- ------------ 20 Limits in other atmospheres ----------- -- ----
69
Paraffin
hydrocarbons ------------------------ 20
Autoignition
----
------------------------- 70
Limits
in
air-----------------------------
20
Esters-------------------------------------
70
Limits in
other atmospheres
---------------- 27
Aldehydes and
ketones ---------------------- 73
Autoignition
-----------------------------
32
Sulfur compounds
--------------------------- 74
Burning rate ----------------------------- 42 Fuels and fuel blends
-----------------------
74
Unsaturated
hydrocarbons
------------------- 47
aimmonia
and related compounds
----------
74
Limits
in air---------------------------- 47
Boron
hydrides----------------------------
82
Limits
in
other
atmospheres -----------------
50
Gasolines,
diesel
and
jet fuels --------------- 82
Autoignition
-----------------------------
50 Hydrogen -------------------------------
89
Burning
rate
------------------------------
51 Hydraulic fluids and engin) , oils
-------------- 95
Stability--------------------------- -- ---- 51 Miscellaneous
------------------------------
97
Acetylenic
hydrocarbons-------
-------------
653
Acknowledgments--------------------------
---
106
Limits in
air------------------------------
3 Bibliography
-------------------
--------------
107
Limits
in other attmospheres
------- --------- 55
Autoignition
------------------------------
0
Appendix
A.
Siirnmary
limits
of flammability-
114
Burni~ng rate -----------------------------
56 pnix.-oihoticom ston---17
Stability-- - -
----------------------------
57
Appendix C.
-11eat
contents
of
gases -----------
118
Aromictic hydrocarbons.---------------------
59
Appendix 1).
-Definitions
of
principal
symbols- 119
Limrits in air -------------------------- 59
Subject index--------------------------------120
ILLUSTRATONS
Fig.
Page
1. Ignitibility
curve and limits of
flammiability
for methane-air mixtures
at
atmosphieric pressure and 26* C-
2
2. FfI~tv
of
tempe-rature onl limits
of flinniatdlity of a conmbustibile
vapor in
air at
a
constant
initial pins-
'i. ini
d ilay
I
aforv
ignition
of
N PN
ini
air
at
1 000)1a ig
in
the
tem
pira ture
range from 1 10* to
21
0* C,
.
5
,.1
Logar i ni of time delay bewfore ign itijon of NJi
N
in
air at 1,0001 psig iinitial
pressur----------------
---- 6
..
Simiplified
nixer-----------------------------------------
------------------
------
7
6.
Comnposition of gas
in
chamlber 2, figure 5
(instantaneous muixing)-
- -
----------------------
------- 7
7,
Coiiiposition
of gas
in chambher
2,
figure
5 (delayed
mixing) -----------------------------------------
7
..
Variation in, lower limits oft
tlaininatilitv
of
various
comibustibles in
air
Ps a function
of
droplet
diameter 7
FVnn
i
n
ahi lit 3 di agrain for the systveiIin
i(t
Ii
ate-oxy
g(il-nit
rogetYi
atI
at
I
nospli e
pressure and
26' C
-
10.FlanmiiaI
ilitY (i
5grin
for
the
syst
iiii iii(-ithaoi'(-oxy'geni- nitrogeni
at at n osph eric pressure and~ 2110 C f
i. F;
icrt
of
iuiitia
en per
t uri on
liit s of flai
iiiability
of it
coin hust
ii
d vapor- iii rt-a
ir
syst
lii itt
atmnos-
lpheric
pr(-&ur--
-- -- -----------
I------- --------------
------------------
--
----
- - -----
12.
Ictrict oif
initial pressure on liimits
of' flaiinahility of
JP-4
in air at 26' C ------------
-1
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Iv CONTENTrS
13.
Effect
of temperature and
pressure on
limits
of
flammability of a combustible vapor
lin
a specified
oxident -----------------------------------------------------------------------------------
12
14.
Flammability
diagram
for
the system
gasoline
vapor-water vapor-air at
700 F
and at
2120
F anid atinlos-
pherio pressure-----------------------------------
--------- -I-----------
-------
13
15. Pressure
produced by Ignition
of
a
9,6
volumec-percent
mietbanie-air mixture in a
9-liter
cylinld(r ------
15
16. D~etonation velocity
I,
V';
9tatic
pressure, 11,; and reflected
pressure,
I',,
dleveloped
b)'Y
detonation
waveating
through
byxd ogen-oxygen
mixtures in
at
cylindrical
tube at atmzosphieric
pressure
and X0 F a9-a I --------- --- --- --- --- -- -- -- --- --- --- -- --- --- --- -- -
16
17.
Pressure variation
following ignition of
a flanimiable
mixtu re
ini unp)rotected
arid
prot;ect
ei
eiielosures~
18
18. P~ressure
produced by
Ignition of
at flamninal
le mixture in a
vonted
oven .--
-- -- -------------
it9
19.
Effect
of molecular
weight
onl
lower
limits
or
flammnability of paraffin
hydrocarbons
at
250
C
-----------
20
20. Effect
of
temperature
onl lower
limit
of
flainniability of mnethane in
Peir
tit
atmniperic
presilr-------22
21. Effect of temperature
onl lower limits
of
flamnmability of it0
pairaffin hydrocarbons init
r
ait
atmlospheric
pressure. .
. - -
- - - -------
- - --------
2:3
22.
Effect
of
temperature
on
lower
limits
of flamnnialnility of 10 parailin
liydi
darhoiis init;, ti
a
i
)nopl-rie
pressure
by wveight-----------------
-------- -----------------------------
24
23. Effect of temperature
on L,1/
2
,,-
ratio
of
paraffin hydrocarbons
lin
tir tit
atinoplicric
pressure --.
25
24.
Effect of
temperature onl
(71 7/U.s-
aitio of
liaril hydrocarbons ini
air
at atmnospheric
pressure
in the
absence
of cool
flames-----------------------------------------------------------
26
25.
Effect
of pressure on limits of flammnability of pentane,
hexane, and
hept
aite tin
air
ait 260
(C------------- 26
26.
Effect of pressure
on limits of flammnability of natural
gas in
air
tit
280
C-----------------------------
27
27. Effect of
pressure
onl
lower
temperature
limits Of flammiability
of pent'ane, blexance, beptanle.
and octanle
litair
------------------------------
------------------------------------------
_ ----
---
28
28.
Limits
of
flammability
of
various methane-inert
gas-mnir
mixtures
ait
250
C
and
attmiospheric
pressure_.-
29
29.
Limits of
flamnmability
of
ethano-carbon
dioxide-air
anni
cthaine-nitrogen-air mixtures
ait
250
C and
atmospheric pressure------------------------------------------------------------------------
30
30. Limits
of flammability of propane-carboni
ioxitie-air
and
propaoc-nitrogen-air
mixtures at 25'
C and
atmospheric pressuire-------------------------------------31
31. Limits
of flammabilityofbtn-rbndoiearadbt
1
-nton-rmiuest25Cad
atmospheric
pressure
-----------------------------------------------------------------------
32
32. Limits
of flammability
of
various
n-pentane-inert gas-air
nmixtu- i at
250 C and atmospheric
pressure-
33
33. Limits of flammability
of various
n-hexane-inert gas-air
mixtur
-s
ait
250
C
anid
atmospheric
pressure-
34
34. Limits of flammability
of n-heptane-water
vapor-air mixtures
at 1000
and
2000
C and atmospheric
pressure ---------- f------------------------------------------------------------------------
35
3.Approxiate
limits offlammability of
higher paraffin hydrocarbons
(C.11
2
,+
2
,
n2 5) in carbon dioxide-
air
and nitrogen-air
mixtures
at
250 C and atmospheric pressuire----------------------------------
36
36.
Effect
of pressure upon limits of flammability of natural
gats-nitrogen-air
mixtures at 260 C ------------ 37
37.
Effect of
pressure onl limits
of
flammability
of
ethane-carbon dioxide-air mixtures at 260 C ------------ 38
38.
Effect
of
pressure on limits of
flammability
of ethane-nitrogen-air
mixtures
at
260 C----------------- 39
39. Effect
of pressure
onl
limits of flammiability
of
propane-carbon flioxide-air
mixtures--------------------40
40. Effect of pressure onl
limits
of flammiability of
propanie-nitrogen-air mixtures --------------------------
41
41.
Effect of
pressure on
minimum
oxygen requirements for flame
propagation
through natural
gas-nlitrogen-
air, ethane-nitrogen-air,
and
propanie-nitrogen-air
mixtures
at 260 C
------------------------------
42
42.
Low-temperature
limit
of
flammiability of
decane-air, dodecane-air, anid mecan-dodecane-air
mixtures-
43. Minimum
autoignition temperatures
of paraffin
hydrocarbons in air ats
at function of average carbon
chain
length-------------------------------------------------------------------------------
44
44. Burning velocities
of
miethane-,
ethane-,
propane-, and n-hceptane vapor-air
mixtures
at
atmospheric
pressure
and room temperature - ---------------------------------------------------------
4
45.
Burning velocities
of
methane-, ethanne-,
and propane-oxygen mixtures
ait atmospheric pressure
and room
temperature
--------
----------------------------------------------------------------------
46
46.
Variation in horning v'elocity
of stoichiometric
methane-aiir and
propane-air mixtures
with
pressuii:
at
260 C---------------------------------------------------------
------------------
--------
47
47.
Variation in burning velocity of
stoichiornetric methane- andl
ethyl
cne-oxygen mixtures
with
presstire
4
a
t
26 '
C - - - - - - -
- - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - 4
48.
Effect of temperature on
burning
velocities
of four paraffin hydrocarbons
in
air
at atmospheric
pressure-
49
49. Detoiation
velocities
of
mnethane-air
mixtures
ait
atmospheric pressure------------------------------
49
50. D)etonation
velocities of
methane-,
ethane-, propane-, butane-,
and hexane-oxygen
mixtures at
atmos-
pheric pressure --------------------------------
------------------------------------------
4
51. D~etonation
velocities
of
n-heptatne
vapor
in
WFNA (white funming nitric
acid) -nitrogen gas
mixtures at
atmospheric
pressure
arnd
4000
K ----------------------------------------------------------
50)
52. Relation between
liquid-burning rate. (large-pool diameter) and ratio
of net heat
of
combustion
to
sensible
heat of
vapo rization----------------------------------------------------------------- 50
53.
Effect
of
temperature
on lower limit of flammnability
of ethylene in
air at
atmospheric
pressure..-----50
54.
Limits
of flammability
of ethylene-carbon (lioxide-air
and ethylene-nitrogeni-air
mixtures
at atmospheric
pressure
andl
26'
0
C---------------------------------------------------------------
5
55.
Limits
of flammability
of propylene-carboni
dioxide-air and
propylene-nitrogen-air
mixtures at
atmos-
phieric
ressure and
26'
C-------- ------------ ----------------------------------------------
51
.56.
Limits
of
flainmability of
inobutylerie-carbori
dioxide-air
and isobutylene-nitrogenl-air
mlixtures
lit
5
a
tmnlosp
ieric
pressurremandl26'
C
--------------------------------------------------------------
52
57 . Limits
of
flammnability of isobuitylene-water
vapor-oxygen
inixtures at
I
5)O
C and atmospheric pressumre- 53
58.
Limits of
flaminmibility of
bmtene-
I-carbon dioxide-air 1111d bUteme-
I-nitrogen-air
mixtures ait atniospl(briC
pressure and
26* ---
--------------- ----------------------------------------------------
54
59. Limits
of
flammnability
of 3 miethyl butemie-l-carbom
dioxide-,dr
and 3 miethyl-buiteie-
I-nitrogeni-air
mixtures
at
atmospheric pressure
and
260 C--------------------------------------------------- 54
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CONTrENTrS
V
Fig.
Prg
60). ,imyits of flatnmabilit
y of butudlenc-ccirbon
dioxide-cur
find
btitadlene-nitrogon-air mixtures at atmos-
phteric
pressure and 260 C-
-- -- - -- - - - - - - - - - - - - - - - - - - - - -
55
61.
Effect
of
tube
dliame'ter
onl
initial pressure requirements
for
propagation
of
dleflagration
aind
detonation
through
acetylene gas
--------------------- ---------
_--------
62.
Range
of flammiable
mixtures
for me(tbylatctylene-propcii(liene-propylenie system at
120'
C find at
50
find 100psig-- - ----------------------------------------------
------- --------------
------
63.
Quenched
limitsi of flammiability of acetylene-carbon dioxide-air and acetylene-nitrogen-air
mixtures
at atmosp~heric pressure find 2t1 C
otinced in at 2-inch tube-------------------------------------
58
64.
Mini
ccci
autoigi
iio
temperatures
of
aceetylene-air aind
acctylcne-oxygcn
mixtures at atmospheric
and elevated pressures-----------------------------------------------------------------------
58
65. Burning velocity of
acetylene-air
mixtures ait
atmospheric pressure and
room temperature -------------- 59
66. Maximumn
LID
ratio required
for
transition
of
at
defl
agration to
a
detonation fin acetylene vapor
at
600
F
and
froto
10
to 70 psia
--------------
----------------------------------------------------- 59
#17.
Ficcal-to-initial pressure ratios4 developed
by acetylene with (letonatijn initiation at
various
points
aloncgcatube---------------------------------------------------------------------
- -
60
68. Limits of
fihinicriability
of benzver-niethyl
bromide-air mixtures at
25'
C and
benizene-carbon
dioxide-air
aind
henzene-nitrogen-air
mnixtures at 250 aind 15(0' C aind atmospheric
pressure
-----------------
_ -
61
69. Lilits Of flammablttiility
Of ll
2
()
2
-C
6
lI
4
.(Cl13)h-ll
2
O ait 1540
C
aind
1 atmosphere pressure
----------------
62
70. Limits of flammnability
of 90-weight-perceet llY0
2
-C
6
11
4
.(
Clf
3
)
2
-lCOOiI at
154V
C and 1
atmosphere
pressure-.----------------------------------------------------------------------------------
63
71.
Nliniinuin autoignition
temperatures
of aroinatic hydrocarbons in air
as
a function
of
correlation
paramieter L --------- ----------------------------------------------- 64
72. Limits
of flammllInabili
ty of cyclopropan-cacrhon dioxide-air,
cyclopropane-nitrogen-air, and cyclopropane-
heliumn-air
miixtures
ait
250
C
aind
atmospheric pressure
------------------------------------------
65
73.
Limits
of
flammi
ability
of cyclopropatne-hiutni-oxygen aind cyclopropane-nitrous
oxide-oxygen mixtures
ait
25' C
and atmospheric pressure
------------------------------------------ ------------------ 66
74.
Limits
of flaninability
of cyclopropitne,-he(liumt-niitrotus
oxide mixtures
at
250
C
and atmospheric pressure- 66
75. Limits
of
flammability of methyl
alcohiol-carbon
dioxide-air
and methyl
alcohol-nitrogen-air mixtures at
25'
C and atmospheric pressure -------------------------------------------------- ------------ 66
76. Limits of
Flammability of methyl alcohol-water
vapor-air
mixtures at
1000,
2000, and
4000 C
and
alnospheric
pressure-----------------------------------------------------------------------
67
77. Limits Of
flammability
of
ethy)
alcohiol-carbon
dioxide-air and ethyl alcohol-nitrogen-air mixtures at
251
C and atmospheric pressure
-------------------------------------------------------------
68
78. Limits
of
flatmmnability of ethyl alcohiol-wt, vapor-air mixtumres at 1000 C and atmospheric pressure- 68
79).
Limits of flammnability
of
terf-bcctyl alcohol-water
vapor-air mixtures
at
1500
C
and atmospheric pressure- 68
80. Limits of flanmmability of terl-butyl alcohiol-carbon dioxide-oxygen mixtures at 1500 C and atmospheric
pressure --------------------------------------------------------- ------------------------- 68
81.
Limits
of
flammability
of 2-ethiylbtantol-niitrogeni-oxygeni
mixtures at 1500 C and atmospheric pressure- 69
82.
Limits
of
flamniability of dimethyl
ether-carbon dioxide-air aind dimethyl ether-nitrogen-air mixtures at
25' C anid atmnospheric presstire-------
------------------------------------------------------
69
83. Limits of
flammability
of dilethyl
ether-carbon dioxide-air aind diethyl ether-nitrogen-air
mixtures
at
250
Cafidatilloqpheric pr'ssccre-------- ------------------------------------------------------ - -69
84. Limits of flamnability of diethyl
ether-helium-oxygen
aind
diethyl ether-nitrous oxide-oxygen mixtures
ait 25' Canid atmospheric pressuire.-------- ---------------------------------------------------
70
S5. Limits
of
flammability
of
diethvl ether-nitrous
oxide-heliumn
mixtures
ait 25' C
and atmospheric pressure-
70
80i.
Limlits
of
flammnabilit
y of mnet hcyl
formcvite-cccrbon dioxide,-air aind
miethyl formate-iiitrogen-air mixtures- 71
87. Limits of taimicabilit
y
of
isobut'vi
forinate-ecarbon dioxide-air aind
isobutyl
formate-n1itrogen
-air
mixtures- 72
88. Limlits
of
flitInfilbilit
y of
flet
hI' acetate-carboci dioxide-air aind
methyl
aetate-nitrogvci-air
mnixtumres--
72
89). Effu-ct, of
temperature onl lower limits
of
flamomability
of
MEK-tolumene
mixtures in air itt atmosp~heric
4
essiirc'-------------
---- ----------------------------------------------------------------
73
90.
ICetof teiperattire
on
lower
limits of
flammability
of TIIF..toluiene
mixtures in air at
atmospheric
pressur -------
------------------
-----
----------------------------------------------------
74
91. Effect
of
liquid
composition on lower
finciti
of
flammability
of
MIEK-tolice mixtures in air
at 300 alid
20010 C------------------------ ---------------------------------------------------------- 75
02.
Effec I of liquid composition onl
lower
limits
of
flammability of TIIF-toluene
mixtures in
air
at 30* and
2001
C..----------
-----------
--------------------
-------------- -----------------------
--- 76
9:3.
Limits
of
fliamomcilbili~y of
acetomie-carboci
dioxide-air and
acetone-iiitrogeni-air
mixtures
----------------
77
94.
Limiits
of flamumnalilit
v
of mocthtil Othyl ktocie (NI
EK)-chilorobromomecthlace
(CBM)-air,
MIEK-carbon
dioxide-air acnd NI F'IK-ctitrog(.ci-itir'tiixtiires
at 250 C aid atmospheric
p~ressure --------------------
79
95. Limcit
s of
launiibilit
y
of
carboci
distilfide-etirbon dioxide-air,
ccarbon
dioxide-nitrogen-air
mixtures cit
25 '
C andi
cit
cmslieric
pressure, aid carboni discilfide-water
vapor-air
ait 1000 C
and atmospheric pressure.
79
96. Limits of fl Icucictability
of
liydropemi sclfidvearboci
dioxide-air
mixtures ait
250 C amid
atmnosp~heric
pressuir---------------------
-------------------------------------
-------- 79
97.
Licoits
of
flit titcatdlit
Nof ethiyl
moerecptaci-F'-12-air aid ethyl
mercaptaic-F-22-air mixtures ait atmos.
phiiric
priesurvandul27'
C_----_------
---- -------------
----
--
- -
71)
98. 1
m
its
of
fil
c
cI)
hlil y
of
ium nioc
iii,
U
I)
N
l
NI
NI
,
anicd
hydrazice
cit
at
mosphieric
pressure
icc
satcurated
acid ieur-saurited
vapor-dir
inixtcri--------------------------------0
91)I.
Flu
iinnable
mcix
tiure
cocinpositioc s of
It razici -hept ccc-air cit 1250 C acid approximcatel y
atmospheric
,pressutre
_--_
_
. --.
-
-
-- -
-
- - -
-
- -
- -
-
- -
- -
-- -
-
- -
- -
81
100.
'N tiniiui Spout anieous
igncition
tcinpurat ores
of
liquid
hydrazine,
MINI1,
and U
I)
I I
at
sil incit ial
ucciprauo of
250
C ici
cocctact wit"
N02)*-air mcixtucrus cit 740(10 mt
in
Hg
as a funct
ion of
No,*
coiiecctratioc------------------1--------------------
----
-------------- 82
101 . N
lci iciucci
spoict t olis
ign
it ioc
t
ciiipi rcto ris
of
l
quiiid
hcydcraz
inc
at
various initial tecI puwrat
ores ill
NO
2
*-air
mixtures
at
740 1
1t)
mmi
fig as
at function of NOJ,*
coccntration
--------------------- 1
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V1
CONTENTS
rig.
P84e
102. Minimum
spontaneous ignition
tomperatures of
liquid
MMH
at
various
initial
temperatures in NO,*-
air
mixtures at
740
± 10 mm Hg
as
a function
of
NO?*concentration
--------------------------.
84
103. Minimum spontaneous ignition
temperatures
of
liquid UI)MH at
various initial temperatures
in
NO,*-air
mixtures
at 740 ± 10 mm
Hg
as a
function
of
NO,* concentration
..--------------------
85
104.
Minimum
spontaneous
ignition
teirperatures
of 0.05
cc
of
liquid UDMH
in
tle-OrNO,*
atmospheres
at 1 atmosphere for various He/Os
ratios--
-----
----------------------------------------- 80
105,
Minimum spontaneous ignition temperatures of
0.05
cc
of
liquid UDMH
in
NO,e-air
mixtures at
15
and
45
pas
as
a function
of
NO,* concentratioc
.......
87
106.
Minimum
spontaneous
Ignition
temperatures of vaporized
UDMH-air
mixtures
in contact
with 100
pet NO,* at
250 C and
740±
10
mm Hg
as a tunetion of UDMH concentration
in
air
-------------
87
107. Limits of
flammability of diborane-ethane-air
mixtures at laboratory
temperatures and
300 mm Hg
initial pressure
------------------------------------------------------------------------------- 88
108. ASTM distillation curves for,
A
aviation
gasoline, grade 100/130;
B, aviation gasoline, grade 115/145;
C
aviation jet fuel, grade
JP-I; D, aviation jet fuel,
grade JP--3; and,
B,
aviation jet
fuel,
grade
JP-4
.....................................
...................................
88
109.
Limits
of
flammability
of aviation gasoline, grades 115/145 vapor-carbon
dioxide-air vad
115/145
vapor-nitrogen-air, at
270
C and atmospheric
pressure -----------------------------------------
88
110. Limits
of
flammability
of
JP-4
vapor-carbon
dioxide-air and JP-4 vapor-nitrogen-air mixtures at 270 C
and
atmospheric presure ---------------------------------------------------------------
-
88
Ill.
Limits
of
flprnmabi9t"
nf
hydrogen-carbon dioxide-air
and
hydrogen-nitrogen-air mixtures at
250
C
and atmospheric pressure -----------.-----------.-------------------------------------
89
112. Limits of
flammability
of IHrNO-NjO at approximately 280 C and I atmosphuee ------------------ A
113.
Limits
of
flammability
of
HrNO-air
at
approximately
280
C and I atmosphere--------------------
91
114.
Limits of
flammability
of
Hi-NO-air
at
approximately 280
C and
I
atmosphere -----.................
92
115. Rate of vaporisation of liquid hydrogen from paraffin in a 2.8-inch l)ewar
flask:
Initial
liquid
depth-
6.7
inches
------------------------------------------.-----------------------------------
93
116.
Theoretical liquid
regression
rates
following
spillage
of liquid hydrogen
onto,
A, an
average
soil; B,
moist
sandy soil;
and
C, dry sandy soil --------------------------.--------------------------------
93
117. Theoretical
decrease in liquid hydrogen
level following spillage onto, A,
dry sandy soil; B, moist
sandy
soil; and C, an average soil
---------------------------------------------------------------- 94
118.
Extent of flammable mixtures and height
of
v(sible
cloud
formed
after rapid
s illage of 3
liters
of liquid
hydrogen
on a dry macadam surface
in a quiescent air atmosphere
at 15'C
--------------------- 94
119.
Motion picture sequence
of visible clouds and
flames resulting
fron, rapid
spi~lage
of 7.8 liters
of liquid
hydrogen
on a gravel surface
at 180 C ------------------------------------------------------
95
120. Maximum
flame
height
and width produced by ignition
of
vapor-air
mixtures formed
by sudden spil-
lage
of
2.8 to 89 liters
of liquid
hydrogen --------- ---------------------------------------
96
121.
Burning
rates
of
liquid hydrogen and
of liquid
methane at
the
boiling points in
6-inch-Pyrex
Dewar
flaks ---------------------------------------------------------------------------
96
122. Variation
in
minimum
autoignition temperature with
pressure
of commercial phosphate
ester and
mineral
oil lubricantd
in
air
in
r 450-cc-stainless steel
bomb ----------------------------------
98
123. Logarithm
of
initial pressure-AIT ratio
of
seven
fluids in
air for various reciprocal temperatures ------ 99
124.
Variation
in
TnT,
of
air with
V,/Vf
and with
Pf/P,
in
an
adiabatic compression process
------------- 10 0
125.
Variation
in
air
temperature
with P,/Pj in
an adiabatic compression process
for
five
initial air
tem-
peratures -----------------------------------------------------------------------
101
126.
Limits
of
flammability
of
carbon
monoxide-carbon dioxide-air
and carbon monoxide-nitrogen-air
mixtures
at atmospheric
pressure
and
26
C ---------------------------------------------
102
127.
Lower limits of
flammability of NPN vapor-air
mixtures
over
the
pressure range
from
0
to
1,000 psig
at 750 1250 1500 and 1700
C
-------------------------------------------------------------- 102
128. Flammable
NPN
vapor-air mixtures
formed
over the pressure
range from 0 to
1,000 psig
at
500
and
1250 C--------------------------.---------------------.--------------------------------
103
129. Variation
of
explosion pressure
following spontaneous ignition with
NPN
concentration-
-----.. -- 104
130.
Minimum
spontaneous ignition and decomposition
temperatures
of
n-propyl
nitrate in air
as
a
func-
tion of pressure -------------------------------------------------------------------------
104
131.
Flammability
of
trichloroethylene-air
mixtures --------------------------------------------
105
TABLES
Page
1.
Conditions of failure
of
peak overpressure-sensitive
elements -------------------------------------
17
2. Properties of paraffin hydrocarbons
----
-.----------
---.-------.------------.------------------
21
3. Upper
flammability
limits of methane-air mixtures
at 15 psig _... ...-------------------------
24
4.
Lower
temperature
limits
and
autoignition
temperatures
of
paraffin hydrocarbons
at
atmospheric
pressure
-----------------.---------------------------
--------------------------------
25
5. Limits
of
flammability
of
methane in chlorine-
.
...............----------------------------
27
6.
Limits of flammability
of ethane
in
chlorine-
---.--------- -----------------------------------
28
7.
Properties
of
unsaturated
hydrocarbons
....
..---------------------------------------------------
8
8. Limits
of
flammability
of
unsaturated
hydrocarbons
at
atmospheric pressure
and room temperature,
in
volume-percent
combustible
vapor
-----------.-------------------------------------------- 52
9. Minimum autoignition
temperatures of unsaturated hydrocarbons at
atmospheric pressure
----------...
52
10. Heats
of formation
of
unsaturated hydrocarbons
at 250 C
----------------------------------------
53
II. Properties of
selected aromatic
hydrocarbons
---------------------------------------------------
60
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CONT
7N'rS
VIU
Pageo
12.
Prop ,rties
of aelected
alicyclic
hydrocarbons
-------------------------------------------------------
64
13.
Properties
of
selected simple alcohols ----------------------------------------------------------
67
14. Propertie
of selected
ethers ---------------------.------------------------------------------------
70
15.
Properties of
selected esters ---------------------------------------------------------------
- --
71
16.
Properties of selected
aldehydes and ketones ----------------------------------------------------
73
17.
Properties of selected
sulfur compounds
-------------------------------------------------------
74
18. Properties of
selected
fuels
and
fuel
blends------------------------------------------------------
77
19. Limits
of flammability
of ammonia
at room
temperature
and
near atmospheric
pressure---------------
78
20. Autoignition
temperature
values
of
various fuels
in air at
I
atmosphere ----------------------------
88
21. Limits of
flammability of
hydrogen in various
oxidants
at
250
C
and
atmospheric
pressure
.------------
89
A-I.
Summary of
limits of
flammability,
lower
temperature
limits, and minimum
autoignition
temperatures
of
individual
gases and
vapors
in
air
at
atmospheric preuure
--------------------------------
114
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FLAMMABILITY
CHARACTERISTICS
OF COM-
BUSTIBLE
GASES
AND
VAPORS
Acu
I
A Zxketakiqi
A bstract
3IS is a
summiary of the available limit of flammiability,
autoignition,
and burning-rate
(lata
for
more
than
200
combustible
gases
ancd
vapors
in air and other
oxidants, its well as of
empirical rules
and
graphs
that
c'an be used to predict
similar dta
for
thousands
of other
combustibles unider
a variety
of
environmental
conditions.
Specific
data
are presented on the
paraffinic, unsaturated, aromatic, arid
alivNycl ic
hydrocarbons,
alcohols,
ethers,
aldehydes, ketones,
and
sulfur vomnpoundls,
and"
an
assortment
of
fuels, fuel
blends, hydraulic
fluids,
engine
oils, and miscellaneous
combustible
gases and
vapors.
Introduction
Prevention of
unwanted fires
andl gas4
explosion
disasters
requirei
a
knowledge
of
flamimability
chlaracteristics (limits of flamnimabdity, ignition
Mrequirements,
and
burning
rates)
of
pertinent
combustible
gases
and
vapors
lky to be
enicountered
under
various
conditions oif use
(or
misuse).
Available
data maly not always
be adequate for use
in at particular
application
since
they
mnay have
been
obtained at, tt lower
temperature and pressure than is encountered
in practice.
For example, tile quantity of
air
that
is required to
diecrease
the
comlbustible
vapor
concentration to at safe level
in
in.
particular proem"; Carried
out
at 200
'Cj should be
based
onl
flammiability
data obtained at
this
temperature.
When
these are
not, available,
suitable approximations
can be made to
permit a
realistic evaluation
of
the hazards
associated
with the process
b)eing
considered;
such
approxiniat ions can
serve
as the
basis
for dezsi;7;tng suitable safety devices
for
the protection of
personnel and equipment.
Tile purpose of this
bulletin
is to present
a general review
of the subject
of flammability,
and
to supply
select
expe-rimiental
data
and
empirical rules on
the flainiabillty characteristices
of
various
famiilies
of combustible gases arid
vapors
iii air
and
other oxidizing atmospheres. It contains what,
are believed
to be the latest
and molst
reliable
dlata
for
more than
200 combustibles
of
interest to
those
concerned
with
the prevention of
dishstrous
gas explosions.
In addition,
the
emipirical rules
and graphs presenlted
here can
be
used to
preti ict
similar
data
for other com bustiles tunder
a variety of
conditions.
This b~ulletin
sup
plemients
Bureau bulletins
(40)
andh other pub~lications
(158).
Basic
knowledge
of
coimihust
ion is
(desirable for I- thorough understanding
of
thie
material,
which can be found
in numierous publications (69, 19.9, eoe).
Therefore,
only
t
hose
aspects requiiredl
for anl
understanding, of
flammability
are considered here;
even
these
are considered
from
a
fairly
elemnentary
viewpoint.
lhrii
hernlst. project coordinator, Otxi ~
Explosi
wilves
Reeh center, numeu of Mines.
Pittsburgh,
Na
itldntumbers
in parenthes reer
to
Items In the bibiloi phy at
toand of titl
report
Work
onmanumoript
oompleted
May 19N.
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2
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND
VAPORS
DEFINITIONS
AND
THEORY
LUMil1S
OF
FLAMM
AIIT
I
'
'
I
I
combustible
gas-air
mixture can
be burned
ILimits
of
__
over
a wile
range
of
concentiations-when
F
f lammability
either subjected to elevated
temperatures
or
exposed to
a
catalytic surface
at ordinary E
4-
temperatures. However,
homogeneoug corn-
>:
bustible
gas-air mixtures
are flammable,
that,
is,
I.,g2
blit
they
can
propagate
flame
freelyv
within
a
W 2-
r
lmt
- ~
Z
X
limnlted
range
of
compositionts.
F~or
examplke, W
trace
amounts
of
methane in air
can be
readily
X
oxidized on
a
heated surfaee,
but a flame
wi
propagate
from
an
ignition source
at
amirbient
.8
tmetures
and
pressures
only
if
the sur-
n
.6
ronigmixture
contains at
least
5
but
less A
than
15 volume-percent
methane.
The
more
X--
dilute mixture
is
known
as
the
lower
limit,
or
combustible-lean,
limit, mixture;
the more .
concentrated mixture
is
known
as
the
upper
2
4
6
8
10
12-
14
16
18
limit, or
combustible-rich
limit,
mixture.
In
METHANE,
volume-percent
practice, thle
limits of
flammability
of at
par-
ticular
system
of
gases aire affected
by
the
Fiouau
.-
Ignitihility
Curve and
Limits of Fiamn-
temperature,
pressure, direction
offan
rp-
inability
for
Methane-Air
Mixtures
at
Atmospheric
gation,
gravitational
field
strength,
and
sur-
Prsuead2'C
roundings. The
limits are obtained experi-
mentally
by
determining
thle
limiting mixture
ignition of
meothane-air
mixtures
(75).
For
compositions
between
flammable
and
nion-
example, at
0.2-millijoule
(mij) spark
is inade-
flammable
mixtures
(244). That is,
quate to
ignite
even a
stoichiometric mixture
at
atmospheric
pressure
and
260 C;
a 1-mj
spark
LT.
11[C,+C~1, 1)
can
ignite
mixtures containing
between 6
and
and
11.5
volume-percent
methane,
etc.
Such
limit-
UTT.p=
1/2[(,,+ C1.],
(2)
mixture
compositions
that
depend on
the
igni-
tion source
strength
may be d~efined ats
limits of
where
L,.P and
U
7
.P are the
lower andl
uppe.r ignitibiity
or
more
simply
ignitibility
limits;
limits of
flmmability,
respectively,
at
at
speci-
th'ey
are thus
indicative
ot the ignitin'g
ability
fled
temperature
and
pressure,
C,,,
and
C,
are
of
the energy
source.
Limit
mixtures
that
tire
the greatest
and
least concentrations
of
fuel
in essentially
independent
of
the
ignition
source
oxidant
that
are
nonflammnable,
and
('if
and
strength and that
give
a
measure
of
the ability
(?gf
are
the
least and greatest
concentrations
of of
at
flamie
to
propagate
iaay from
the
ignition
fiiel
in
oxidant that
aire flamimable.
Tile
rate
source
mnay
be
defined ats
lim'its
of flammability.
at which
a
flamie propagates
through it
flamn-
Considerably greater
spark energies
aire
required
mable mixture
depends
on at number
of
factors,
to
establish
limits
of
flammability
than tire
including
temperature,
pressure, amnd
mnixture
required
for limits
of ignitibility
(218);
further,
composition.
It
is
at
minimui
ait thle limits
of more
energy is usually
required
to
establish tile
flunmnuabifity
and at
maximumi at
near' stoichio-
upper limit
thani
is requiredl
to
establish thle
metric
mixtures
(130).
lower
limit.
n
general,
when
the sour-ce
The
Bureau of Mlines
has
adop)ted at
st andaird
strength
is adlequate,
mixtures
just, outside
the-
apparatus for
limit
-of-flammiability
doeteininail-
range
of flammnable
comp1ositionls
Yield
flaime
tions
(40).
Originally
designed
for
use
ait
caps
when
ignitedl.
These
flaiiie
caps prop~agate
atmospheric
pre'ssu~re
and
roo~m
t
emplera
ture,
on
Iv
at short,
(listaunce
fromn
the ignitioni
source
it, wats
later
mnodified
for use t.t rediuced
preg-
illit uniifor
in
iixture. The
reason
for
t his
;tire,
1wIcloa
mgasar-a
gl
il
a
e
seenii i
figure 2 which shows
(,he
effec't of
tile
hase,
of
thme 2-inch, glass,
flaine-propagation
temp~erature oil
limits
of
flaimmnlability
at
at
tube.
T i
riodifiCat io1
iintr0otlueVi' I
ihCullt r
('on1sUta inlitil
pressurem.
As
the
temperat
tire
that wats not
inmiiediatelY apparenlt,
as
thle is increased, t he
lower
limit
delec(ases
and1(ile
spark
energ v
was
lill alwalys
adiequate for uise
ill upper limiit
jecretses, Thus, since at localized
hliit-of 'I*
mniiv(etmiutos
F'i'ure
energy
somirc(.
elevates'
the
ternpermit
tire
of
illmusita , tihle
effit oif
miixtur'e conmpositionl
on nlemimby
gases,
even at nonflaniiale mixture
vall
hle
electrical spark
energy reqjuiremlenits
fora
propaigate
llaiiie at
shorit
distance
fromin
lhe
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DiEFINIT'IONS AND THEORY 3
Saturated vapr-
limits of
flammability
has
been questioned.
aurmxtur
Upper
After
a thorough study,
Linnett
and
Simpson
z
limit
concluded that
while
fundamental
limits
ma y
exist
there
is
no
experimental evidence
to
indicate
that
such
limits
have
been measured
Auto-
(18).
In
a
more
recent
publication,
Mullins
i
t
Fignition
reached
the
same
conclusion
(154).
Accord-
Mist
Flammable
ingly,
the
limits
of flammability
obtained
in
an
apparatus of
suitable
sise and
with
a satis-
'
9factory
ignition
source should
not
be
termed
8
fundamental
or
absolute
limits until
the exist-
ence of such
limits
has been established.
A
limit
However,
as
long as experimentally
determined
limits are obtained under conditions similar to
those found
in
practice,
they
may
be used to
I I
AlT
design
installations
that
are
safe
and
to
assess
r
u
AIT
potential
gas-explosion
hazards.
TEMPERATURE-
Industrially,
heterogeneous
single-phase
(gas)
Fiouis
2.--Effect of Temperature
on Limits
of and multi-phase (gas, liquid,
and
solid). flaa.
Flammability
of
a
Combustible Vapor
in
Air at a mable
mixtures
are probably even
more impor-
Constant Initial Pressure.
tant
than homogeneous
gas
mixtures.
Un-
fortunately,
our
knowledge
of
such mixtures
source.
That is,
a nonflammable
mixture
(for
is
rather limited.
It
is
important to
recognire,
example,
com
)osition-temperature
point
A, however, that heterogeneous
mixtures can
fig. 2)
may
become
flammable
for
a time, if
its
ignite
at
concentrations
that would
normally
temperature
is elevated
sufficiently (composi-
be nonflammable
if
the
mixture were
homoge-
tion-temperature
point B).
neous. For example,
I
liter of
methane
can
Flammable
mixtures considered
in figure
2 form a flammable
mixture
with air
near
the
top
fall
in one
of three regions.
The
first isleft of
of
a
100-liter
container,
although
a nonflam-
the saturated
vapor-air
mixtures
curve,
in the
mable
(1.0
volume-percent)
mixture would
region
labeled
"Mist".
Such
mixtures consist,
result
if
complete
mixing
occurred
at
room
of droplets
suspended
in
a
vapor-air
mixture;
temperature.
This is
an importa:t
concept,
they are discussed
in
greater
detail
in
the
section since
layering
can
occur
with any
combustible
on formation
of flammable
mixtures.
The
second
gas
or
vapor
in
both
stationary
and
flowing
lies along the
curve
for
saturated
vapor-air
mixtures.
Roberts,
Pursall and
Sellers
(176-
mixtures; the
last
and
most
common
region lies
180) have
presented
an excelent
series
of review
to the
right of this
curve.
Compositions
in the
articles on
the
layering and dispersion
of
second
and
third
regions
make up
the
saturated
methane
in coal
mines.
and
unsaturated
flammable
mixtures
of
a The
subject of flammable
sprays, mists,
and
combustible-oxidant
system
at a specified
foams
is well-documented
(5, 18,
£,
£7, 76 ,
pressure.
£05, 215,
£45). Again, where
such
hetero-
In
practice, complications
may
arise when
geneous
mixtures
exist,
flame propagation
can
flame propagation
and flammability
limit
deter-
occur
at
so-called average
concentrations
well
minations are
made
in
small
tubes.
Since
heat
below
the lower
limit
of
flammability
(86);
is transferred
to
the tube
walis from
the
flame thus,
the term
"average"
may be meaningless
front
by radiation,
conduction,
and
convection,
when
used
to define
mixture composition
in
a flame
may
be
quenched
by the
surrounding
heterogeneous
systems.
walls. Accordingly,
limit determinations
must
be made
in apparatus of such
a size
that.
wall
IGNrON
quenching
is
minimized.
A
2-inch-ID
vertical
tube is
suitable
for use
with the paraffin
Lewis and
von
Elbe (130). Mullins
(153,154)
hydrocarbons
(methane,
ethane,
etc.) at
at-
and
Belles and
Swett
(156)
have prepareA
mospheric
pressure
and
room temperature.
excellent
reviews
of the processes
associated
lowever,
such
a tube
is neither
satisfactory
with
spark-ignition
and
spontaneous-ignition
under these conditions
for memny
halogenated
of a
flammable
mixture.
In
general, many
and
other compounds
nor
for paraffin
hydro-
flammable
mixtures
can
be ignited
by
sparks
carbons
at. very
low
temperatures
and
pressures
having
a relatively
small energy
content (1 to
(1,97,
2, /N).
100
mj)
but a large
power
density
(greater
Because
of the many difficulties
associated
than
1 megawatt/cm).
However,
when
the
with
choosing
suitable
apparatus,
it
is
not
source
energy is
diffuse,
as
in a
sheet
discharge,
surprising
to find
that
the
very
existence
of the
even
the
total
energy
requirements
for ignition
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4
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
OASES AND
VAPORS
may be
extremely
large
(79,
82,
85, IeS, 181,
1950
C; another
equation
must be
used for
28).
There
is still
much
to
be learned
in
this
data
at
higher
temperatures.
The solid
lines
field,
however,
since electrical
discharges
are
in figure 4
define an
8
C'
band
that
includes
not
normally
as
well
defined
in
practice as
the experimental
points
in the
temperature
they are
in the
laboratory.
range
from
1700 to
1950 C.
When
a
flammable
mixture
is
heated to
an
elevated
temperature,
a reaction
is
initiated that
FORMATION
OF FLAMMABLE
may
proceed
with
sufficient
rapidity
to ignite
MIXTUES
the mixture.
The
time that elapses
between
the
instant
the
mixture temperature
is
raised and
In practice,
heterogeneous
mixtures
are
that
in
which
a flame
appears
is
loosely
called always
formed
when
two
gases or
vapors are
the time
lag or
time
delay before
ignition.
In
first'brought
together.
Before
discussing
the
general,
this time
delay decreases
as the
tem-
formation
of
such
mixtures
in detail,
a
simpli-
perature
increases.
According
to Semenov
fled
mixer
such
as
that
shown
in
figure
5
will
be
(193), these
quantities are
related
by
the
considered briefly.
This
mixer
consists
of
expression
chambers
I and
2 containing
gases
A and
B,
0.22E
respectively;
chamber 2,
which contains a
log
r=---+B,
(3)
stirrer,
is separated
from
chamber
1
and
piston
3 by
a partition
with a small
hole, H.
At time
where
T
is
the
time
delay
before
ignition
in
te,
a
force
F
applied
to piston
3
drives
gas A
seconds; E
is an
apparent activation
energy for
into
chamber
2
at
a constant
rate.
If
gas A
the rate
controing
reaction
in calories
per is
distributed
instantaneously
throughout
cham-
mole;
T is the absolute
temperature,
expressed
ber
2
as
soon
as it
asses through
H,
a
coupo-
in
degrees,
Kelvin;
and
B is
a
constant.
Two
sition
diagram
such as
a
given in figure
6
types
of
ignition temperature
data are
found in
results;
the (uniform)
piston motion starts
at
urrent literature.
In the
first,
the
effect
of
t.
and
stops
at t,.
However,
if a
time
interval
temperature
on
time delay
is considered
for
de-
At
is required
to
distribute
a
samll volume
from
lays of less than
1
second (127,
158).
Such
data
chamber
1 throughout
chamber 2,
then
at
any
are
applicable to
systems
in
which the contact
instant
between
t. and t,
+ At, a variety
of
time
between
the heated
surface
and a flowing
mixture
compositions
exists
in chamber
2.
flammable
mixture
is
very
short;
they are
not
This
situation
is represented
schematically
in
satisfactory
when
the contact
time
is
indefinite.
figure 7.
The interval
of time during
which
Frt
hefactr
e
n
(3)contatti
e
sf
de
i
se
heterogeneous
gas mixtures
would
exist in
the
Further,second
case
is
determined
in
part by
the
rate
it gives
only
the time
delay
for a range
of
tem-
at
which gas
A is added
to chamber
2,
by
the
peratures
at
which
autoignition
occurs;
if
the
size
of the two
chambers,
and
by
the efficiency
temperature
is reduced
sufficiently,
ignition
does
of the
tirrer.
not
occur.
From the
standpoint
of
safety,
it
of
the stirrer.
is
the
lowest
temperature
at
which
ignition
can
In
practice,
flammable
mixtures
may
form
occur
that is
of interest.
This
is called
the
either
by accident,
or
design.
When they
are
minimum
spontaneous-ignition,
or autoignition,
formed
by
accident,
it
is
usually
desirable
to
temperature
(AIT)
and is
determined
in
a uni-
reduce
the combustible
coicentration
quickly
formly heated
apparatus
that
is
sufficiently
nona
b mirr
n
erta n
con-
large
to minimize
wall
quenching
effects (194,
nonflammable
mixtures.
Under
certain
con-
287).
Figures 3
and
4 illustrate typical
auto-
ditions,
it
may be
possible
to
increase the con-
ignition-temperature
data.
In figure
3 the
bustible
concentration
so
as
to produce
a
nonflammable
mixture.
Such
procedures
are
minimum
autoignition-temperature
or
AIT
discussed
in greater
detail in
the following
value
for n-propyl
nitrate
is
1700
C at
an section.
initial
pressure
of
1,000
psig
(243).
Data
in
Fectinb
this figure
may be
used
to construct
a log T
Flammable
mixtures are
encountered
in
I
production
of many
chemicals
and
in certain
versus
, plot such
as
that
in figure
4.
Such
physical
operations.
These
include
gasfreeing
ic tank
containing
a combustible
gas
(232),
graphs
illustrate
the applicability
of
equation
drying
plastic-wire
coating,
and
recovering
(3)
to
autoignition temperature
data.
The solvent
fromt
solvent-air mixture.
When
equation
of the
broken
line
in
figure
4 is
layering
can
occur,
as
in drying
operations,
it
is not enough
to add
air at
such
a rate that
the
log
12.3 10
25
(
verall mixture
composition
is
below the
lower
ogr
-25T.
(4)
limit of
flammability
(assuming
that uniform
mixtures
result).
Special
precautions must,
be
In 'his
specific
case,
equation
(4) is applicable
taken
to
assure
the rapid
formation
of non-
only
in the temperature
range from
1700
to flammable
mixtures
(235).
When
a batch
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DEFINITIONS
AND
THEORY5
4o
1*
1
I
I
i
360
Sample
A
vol, cc
y 0.50
32
0.75
320-
1.00
X
1.50
0
1.75
C
0
2.00
28
0
2.25
A
2.50
v 2.75
Q
240
-
A
300
0-
0
325
0
w
2000
m.
Region
of
160-
au
toignition
0
120I
w
80--
K
JAT
I
1
%
150
160
170
180
190
200
210
220
TEMPERATURE,
OC
FIOURE
3.-Time
l)elay
Before
Ignition
of
NPN
in
Air
at
1,000 Psig
it,
he Temperature
Range
From
1500
to 2100
C.
(1-33
apparatus;
type-347,
stainless
steel
test chamber.)
rocess
is
involved,
an added
precaution
must
tures
that
are
initially
above
the
upper
limit
of
Ce taken;
a constituent
at
a
partial
pressure
flammability
may
become
flammable.
A
simi-
near
its
vapor
pressure
value
may
condense
lar
effect
must
be
considered
when
mixtures
are
when
it
is momentarily
compressed
by
addition
sampled
with
equipment
that
is cooler
than
of
other
gases or
vapors.
Accordingly,
mix-
the original
sample;
if
vapor condenses
in
the
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6
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE GASES
AND VAPORS
TEMPERATURE,
OC
210
200
190
I80
170
600
1
|
AWT
400
V
°
l:I/
Co
'0200-
0
80- Region of
--
outoignition
w 60
°_
0
tL
co
40-
°/o
U020
A
I- 20
A
10 0
8-
EI
IIII0
2.05
2.10
2.15
2.20
2.2
2.0
RECIPROCAL
TEMPERATURE,
15r.
Fzouits
4,-Logarithm
of Time Delay Before Ignition of
NPN
in Air at 1,000 Paig Initial Pressure.
(Data from figure 3.)
sampling
line, the
test sample will
not yield
mists and
sprays (particle sizes below
10 mi-
accurate
data. A
flammable
mixture
sampled crons)
the combustible concentration
at
the
in this manner may appear to be nonflammable
lower fimit is about the
same
as
that
in uniform
and thus create a hazardous
situation (236).
vapor-air mixtures (17,
18,
22, £4, 76, 245).
A
flammable mixture can
also form at tern-
However,
a.
the
droplet diameter
increases,
the
peratures below the flash point
of
the
liquid lower
limit appears
to
decrease.
In
studying
combustible either
if
the
latter
i6
sprayed into this
problem,
Burgoyne
found
that
coarse
drop-
the air, or if mist or foam forms. With fine lets tend to fail towards the flame front
in an
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DEFINITIONS
AND
THEORY
7
Chamber I
Chamber 2
100oo-
- fl3
Gas AGs8
Figure
5.-Simplified
mixer.
1
100
FIGURE
5.-Simplified
Mixer.
ELAPSED
TIME
Z~
10
-
FIGURE
7.-Compo
ition of
Gas in
Chamber
2, Figure
5
(Delayed Mixing).
16
of fine
droplets
and
vapors
(24).
With
sprays,
1
0E
the
motion of the droplets
also
affects
the
limit
0
composition,
so that the resultant
behavior
is
rather complex.
The
effect of mist
and
spray
Qi
5
7
droplet
size
on
the
apparent
lower
limit
isillus-
S trated
in
figure 8.
Kerosine vapor
and
mist
0 0-
100
0
data
were
obtained
by Zabetakis and Rosen
10
If
2045);
tetralin
mist
data,
by
Burgoyne
an d
ELAPSED
TIME
Cohen
(24);
kerosine
spray
data,
by
Anson
(5); and
the
methylene
bistearamide
data,
by
FIGURE
6.-Composition
of Gas
in
Chamber
2, Figure
Browning,
Tyler,
and Krall
(18).
5
(Instantaneous
Mixing).
Flammable
mist-vapor-air
mixtures
may
occur
as
the
foam
on
a
flammable
liquid
col-
upward propagating
flame, and
as
a result the
lapses.
Thus,
when ignited,
many
foams can
concentration at
the
flame front actually
ap- propagate
flame.
Bartkowiak,
Lambiris,
and
proaches
the
value found in
lower
limit
mixtures
Zabetaki
found that
the pressure
rise
AP pro-
100
-0.07
----
Stoichiometric
B
L
80
-
mixture
(decane-air)
£17
-
.06
Kerosine
spray
0 0
-.
05.aZ
U
60 Kerosine
vapor
E
and mist
.
-. 04
E
0
0
00
.- Methylene
Z bistearamide spray
20.0
o
-
retaln
is
-Tetralin
mist
.01
8
0
20 40
60
80
100
120 140
160
DROP'.ET
DIAMETER,
miictonv
FiouRJF 8.-Variatioi
i" Lower
Limits
of FlanitabilIity
of Various
Combustibles
in
Air
m~ Function of
D~roplIet
Aiame£ter.
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8
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND
VAPORS
duced
in
an enclosure by the complete
combus-
enriched
air at
reduced pressures
(215).
Air
tion
of
a layer of foam
of
thickness
A,
is proper-
can
become
oxygen-enriched
as
the
pressure is
tional to
h,
and inversely
proportional
to
hA
reduced, because oxygen
is
more soluble
than
the height
of the
air
space
above the
liquid
nitrogen
in most
liquids (83).
Thus
the pres-
before foaming
(7).
That is
ence
of foams
on
combustible
liquids
are a po-
tential
explosion
hazard.
A flammable
foam can also
form
on
nonflam-
ha
mable liquid if the
foam
is
generated
bi
a
flam-
unable gas
mixture
instead of
air. urgoyne
Pressures
in excess
of 30
psi
were
produced
by and
Steel, who
studied
this problem,
found
that
the ignition
of foams in small
containers,
the
flammability
of methane-air
mixtures
in
Thomas
found
that an
additional
hazard water-base
foanis was
affected
by both the wet-
could
arise
from
production
of foams by
oxygen- ness
of
the
foam and
the
bubble
size
(28).
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PRESENTATION OF
DATA
Limit-of-flammability
data
that
have been
With either
type of
presentation, addition
of
obtained
at
a specified
temperature and pressure methane,
oxygen,
or
nitrogen to
a
particular
with
a
particular combustible-oxidant-inert
mixture results
in formation
of a
series
of mix-
system
may be
presented
on either a
triangular
tures
that
fall along the
line between
the com-
or
a rectangular
plot.
For example,
figure
9
position point
(for
example,
Mi in figures
9
and
shows a
triangular
flammability
diagram
for
10)
and
the vertices
of the
bounding triangle.
the
system
methane-oxygen-nitrogen.
This For
example,
addition of
methane
(+CH,) to
method
of presentation
is
frequently
used
mixture M1
yields initially
all mixture
corn-
because
all
mixture
components
are included
positions
between
Mi
and C (100
pct
CH
4
).
in
the diagram. However,
as the sum
of
all After a
homogeneous
mixture
is produced,
a
mixture compositions
at,
any point on the
tri- new
mixture composition
point, such
as
M2,
is
angular plot
is constant
(100 pct)
the
diagram obtained.
Similarly,
if oxygen is added
(+02)
can be
simplified by use of
a
rectangular
plot to the
mixture represented
by point
Mi, all
(24.).
For
example,
the flammable
area
of compositions
between
M1
and 0
(100
pct O)
figure 9
may be
presented as
illustrated
in are obtained
initially;
if nitrogen is added,
all
figure
10. As noted,
the oxygen
concentration
compositions
between
MI
and
N (100
pct
N
2
)
at any
point
is
obtained
by subtracting
the
are obtained
initially.
If
more
than one gas
is
methane
and
nitrogen
concentrations
at
the
added to
M1
or example,
methane
and oxy-
point
of
interest
from
100
as follows: gen,
the
resultant
composition
point
may
be
Pet
02=100 pet-pct
CH
4
-pct N
2
.
(6) obtained
by
considering
that the mixing
process
00
+
+CH
4
06
io
MI
02
J
4
M3~
+N
Air
/ -
Flammable
0
S mixtures
//
/O7
Min 02
r1gz::aticol
/N
0'
100
90 so
70 60
50
40 30 2
0 i0 0
0
OXYGEN,
volume-percent
FIGURE
9.--Flammability
Diagram
for
the
Syatem Methane-Oxygen-Nitrogen
at Atmospherilo
Pressure
and
200 C.
9
______
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10
FLAMLABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND VAPORS
100
-
L
0
2
-100%-%
CH
4
-
N
2
80-
C
160
02
+CH
E
-N
-N
1
N2
zA
I
40 6
44-
/4
Fla mmaoble
20-
mixtures-
Lriticl
C/NL
MiN
0
20
40
60 Aso 100
NITROGEN,
volurne-percent
Fioulz 10.-Flammability Diagram for
the System Methano-Oxygen- Nitrogen at Atmospheric P ressure and
W6 C.
(Data from fig.
9).
occurs in two
steps. First,,
the methane
is
added
composition
point (for
example, M1 n figures
9
and
to Mi and
the
gases
are
mixed thoroughly
to
10) shifts
away from
the vertices
C,
0,
and N
give
M2. Oxygen
is then added
to Af2 with
along
tile extensions to
the lines
MI-C, Mi
mixing
to give a new (flammable)
mixture,
M3. -O
and
Mi
-N,
indicated
in
figures
9
and 10
If the methane
and oxygen were
added
to a by
the minus signs. The
final
composition
is
fixed volume
at constant
pressure, some
of M
1
determined
by
the percentage
of
each
component,
and then of M2
would escape
and mix
with the
removed from
the initial mixture.
surrounding
atmosphere.
In
many
instances
Mixtures with
constant oxygen-to-nitrogen
this is an important
consideration
because
the
ratio
(as in
air),
are obtained
in
figures 9 and 10
resulting mixtures
may be
flammable.
For by joining
the apex,
C, with
the
appropriate
example,
even
if an
inert gas
is
added to
a mixture
composition along
the baselne,
ON.
constant-volume
tank
filled
with
methane,
Thus,
the
Air line,
CA,
(fig. 10)
is
formed
by
flamnmable
mixtures
(-an form outside
the
tank
joining
C
with the
mixture
A (21 percent
0
as the
displaced
methane escapes
into the +79 percent
N2).
Using
this latter point,
A,
atmosphere.
If
the
inethant,
is
not dissipated
one
can readily
determine the
mixture
cornposi-
quickly, a dangerous
situation
1
can
arise.
tions
that are formed
when
mixture
M1
is
When
a mixttire compoment
is
removed by displaced
from
an enclosure and
mixed with
air.
condensation
or
absorption,
the corresponding
Initially, all
mixture
compositions between
Af
I
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ie
PRESENTATION
OF
DATA
11
and A
would
form.
Since these
would
pass
%oir
100
%
combustible
vapor-%
nert
through
the
flammable
mixture
zone,
a hazard-
r
ous
condition would
be
created. Similarly,
if
pure
combustible
CH,
were
dumped
into
the
atmosphere
(air)
all mixtures
between C and
A
would form. These would
include
the flam-
mable mixtures
along CA
so
that a
hazardous
condition
would again
be
created,
unless
the
c)mbustible
were
dissipated
quickly.
Mixtures
with
constant
oxidant
content
are
obtained
by constructing
straight
lines parallel
to zero oxidant
line- such
mixtures
also
have
a
i
constant
combustible-plus-inert
content.
One
particular
constant
oxidant
line
is of
special
importance-the
minimum
constant
oxidant
line
that
is
tangent
to
the
flammability
diagram
or, in
some cases,
the
one that
passes
through
the
extreme
upper-limit-of-flammability
value.
This
line
gives
the
minimum
oxidant
(air,
INERT,
volume-Percent
oxygen,
chlorine,
etc.) concentration
needed
to
FIouRm
ll.-Effect
of
Initial
Temperature
on Limit.
support combustion
of
a
particular
combustible
of
Flammability
of a Combustible Vapor-Inert-Air
at
a specified
temperature
and pressure.
In
System at Atmospheric
Pressure.
figures 9 and
10,
the
tangent
line gives the
9
-
minimuin
oxygen
value
(Min
01, 12
volume-
%
ir 100
%
%
J
P4
vapor
percent)
required
for
flame
propagation
through
8
V
methane-oxygen-nitrogen
mixtures
at 260
C
1E
and
1 atmosphere.
.
7
Another
important
construction
line
is that
which
gives
the
maximum
nonflammable
com-
0
bustible-to-inert
ratio (critical
C/N). Mixtures
*
along
and
below
this
line
form
nonflammable
2
mixtures
upon
addition
of oxidant.
The
critical
/
Flammable
C/N
ratio
is
the
slope
of
the
tangent
line from
mixtures
the origin (Figs.
9
and
10), 100 percent
oxidant,
4-
to the lean
side of
the
flammable
mixtures
a
curve.
The
reciprocal
of this
slope
gives the
> 3
minimum
ratio
of inert-to-combustible
at
which
.r
nonflammable mixtures
form
upon addition
of a
2
-
oxidant.
It is of
interest
in
fire extinguishing.
-
An
increase
in
temperature
or
pressure
iL
usually
widens
the
flammable
range
of a
particular
combustible-oxidant
system.
The
I
effect
of
temperature
is
shown
in
figure
11;
0
200
400
600
800
two flammable
areas,
T, and
T,, are
defined for
a combustible-inert-oxidant
system
at constant
INITIAL
PRESSURE,
mm Hg
presure.
The
effect of temperature
on the
Frouaz
12.-Effect
of Initial
Presure
on Limita
of
limi ts
of
flammability
of
a combustible
in
a
Flammability
of JP-4
(Jet Fuel
Vapor)
in Air
at
specified
oxidant
was
previously
shown
in
269
C.
figure
2. This
type of graph
is
especially
useful since
it gives
the
vapor
pressure
of the
downward
propagation
of flame
is
used.
Since
combustible,
the
lower and
upper
temperature
T,
is
the intersection
of the
lower-limit
and
limits
of
flammability
(T,
and Tv),
the
Ham-
vapor-pressure
curves,
a relationship
can
be
mable
region
for
a range
of ten
eratures,
and
developed
between
Tl,,
or the
flash
point,
and
the
autoignition
temperature
(AlT).
Nearly
the
constants
defining
the vapor
pressure
of a
20 of
these graphs
were
presented
by
Van
combustible
liquid.
An excellent
summary
of
Dolah and
coworkers
for
a
group
of
corn-
such relationships
has
been presented
by
M
ullins
bustibles
used
in
flight
vehicles
(218).
for
simple
fuels and
fuel
blends
(154).
The
lower
temperature
limit,
TL,
is
essentially
At constant
temperature,
the
flammable
the flash point
of
a combustible
in
which up-
range
of
a combustible
in
a specified
oxidant
can
ward
propagation
of
flame
is use
4
; in
general,
it
be represented
as
in figure
12.
Here
the
flam-
is somewhat
lower than the
flash point,
in
which mable
range
of
JP-4 vapor-air
mixturm
is given
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12
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND
VAPORS
rL1
-~
I
_ p
S
--
--
-
_IT
2
Pvapor
hp
Fiouns 13.-Effect
of
Temperature
and Pressure
on Limits of
Flammability
of
a Combustible
Vapor
in a
Specified
Oxidant.
as
a function
of
pressure (241). A more
The flammable range
is the
same as that
de-
generalized
flammability diagram of
a particular
picted
in
figure
2. At constant temperature
combustible-oxidant
system
can be
presented (for example,
T), the flammable
range
is
in
a three
dimensional plot of
temperature, pres-
bounded by
the lower limit
curve LIPLI
and the
sure,
and
combustible
content-as
illustrated
upper
limit curve
U
1
Pc,;
the
broken
curve
in figure
13 (244). Here,
composition
is
given PLIPUI represents
the low
pressure (quenched)
as the ratio
of
partial
pressure
of
the combustible
limit.
The flammable
range is
the
same
as
vapor,
VAPOR, to
the total pressure
P. For
any that depicted
in figure
12. A similar
range is
value
of P,
the
limitis
of flammabiity ar given
defined
at temperatures T,,
T3, and T# which
as
a function of the
temperature.
For example,
are
less
than T,.
However, at
T3 and
T, the
at
I
atmosphere
(P= 1),
the
flammable
range is
upper
limit curves intersect
the
vapor pressure
bounded by
the lower limit
curve
L4LL",
and curves, so that,
no upper
limits
are
found
above
the upper
limit curve UU2;
all mixtures
along U.
and U,.
In other words,
all compositions
the
vapor pressure
curve
L4U,'
U
are
flammable.
along U.U.
and U.L4
are flamuable. The
curve
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PRESENTATION OF DATA 13
28
-T
A
24
X
air
=100
-
gasoline
vapor
-
%water vapor
20
C
4
Nonflammablemmixture
B
10 20 30
40
50 60
70 80 90
100
WATER
VAPOR,
volumtu-percent
70
100 120
140 150 160
]70 180
190
200
210 212-
I
I I I I
.. I
=
I I
IL
CORRESPONDING
AIR-SATURAT ON
TEMPERATURE.
"F.
Fionw 14.- Flammability
Diagram
for the
System Gasoline
Vapor-Water
Vapor-Air at
700 F
(2i
°
C) and at
2120 F (iO0
°
C) and At
:u
spheric
Pressure.
L
4
'LUJ UZU
defines the
range
of limit mixtures
percent-water-vapor
point. If
water vapor
is
which
are saturated
with fuel vapor.
Further, removed
by
condensation or absorbtion,
the
since L
4
is the saturated
lower
limit mixture at~
composition
point
will
move
along the
extension
one
atmosphere,
TW
s
the flash point,
to the line
drawn
from A
to the 100-percent-
Some of the
points considered in
this and
the water-vapor
point. The same applies
to
the
prex
ious
,ectioni
are illustrated
in figure 14
other components,
air
and gasoline,
as
indicated
(A73).
This
is the
flammability diagram
for earlier.
.Moreover,
if more than
one component
the
system gasoline
v-apor-wWterr vapor-air
at
is
involved,
the final
composition
point can
be
700 F(2 10
()
and 2120F
(100
°C) and atnos- found
by considering
the effect of each
cor-
pheric
pres.ure. The
air saturation
tempera-
ponent separately.
po
ture, that
is,
the
temperature at which
saturated
Figure 14
is of
special
interest since
it can
be
air contains the quantity
of
water given
on
the
used to
evaluate the
hazards
associated with
a
water vapor
axis, is t1lsncluded.
For
precise gas-freeing
operation.
For example, mixture
work, a
much larger graph
or an enlargement
represents
a
saturated
gasoline vapor-air-
of
the
region from
0
to 8
percent gasoline
vapor
water
vapor
mixture
at
700
F.
A
more volatile
and from
0 to 30 percent
water
vapor
ould
gasoline
than the
one
used
here would
give
a
be
used.
However,
figure 14 is adequate here.
saturated
mixture
with
more
gasoline
vapor
If
water
vapor is added
to a particular
mixture and
less air
in a
closed
tank, a
less volatile
A,
all
mixture
compositions
between t
nd gasoline would
give less gasoline
vapor and
pure
water
vapor
will form
as noted (if the
more air. In any
event,
if a continuous
supply
temperature
is at
least 2120
F),
and
the
corn-
of air saturated
with
water vapor is
added to
a
position
point will shift
towards
the
100- tank
containing
mixture A,
all
compositions
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14
FLAMMABILIT1 CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND
VAPORS
between
A
and B (air
plus
water vapor) will be
between points along
AE
and B.
Again, as
formed until all
the
gasoline
vapor
is
flushed the water
vapor in these
mixtures
condens
i
from the tank, and
mixturv
B
alone remains.
outside the tank, the
composition
of
the
result-
If
steam
is
used to
flush
mixture
A
from
the
ant
mixtures
will
shift
away
from
the
100-
tank, all compositions
between A
and
C
will
percent-water-vapor
point,
C.
The mixture in
form
until all the gasoline
vapor has
beer the
tank
will remain at
E unless air is used
to
flushed from
the tank and only steam
remains
flush
the tank,
in
which case
mixture
composi-
(at 2120
F
or higher).
If
the tank
is permitted
tons
between
E
and B will
form. Again,
if
to cool,
the steam will condense
and air will be
the water vapor within
the tank
condenses,
the
drawn
into the tank giving
mixtures along mixture
composition
will shift away from C.
C-B. At
700
F, only
air
plus a small
amount
In
any
event, at
this temperature (175
°
F),
the
of water
vapor will remain.
If
hot
water
and
water
vapor
at
1750 F
are
addition
of
air
to mixture
E will
lead to
forma-
used
to flush mixture
A from
the
tank,
the
tion of
flammable
mixtures.
Thus, mixture
A
mixture
composition
can
only
shift along AC
to
cannot
be
flushed from
a tank
without
form
ing
E.
Mixtures
between
A
andE that are flushed flammable
mixtures,
anless steam
or some
other
from
the tank mix
with air
to
give
mixtures
inert vapor or gas is
used.
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DEFLAGRATION
AND DETONATION
PROCESSES
Once
a flammable mixture
is
ignited,
the weight,
of
the
burned
gases,
and T
is
the
final
resulting flame, if not extinguished,
will either (16,
',mttic)
temperature
of the
products. With
attach itself to the ignition source
or propagate
otle
1 eCloisurem, or with
noncentral ignition,
tra)m
it. If it propagates from the
source, the the
flame
front is disturbed by the
walls before
propagation rate
will be either
subsonic
(de-
,orihuntion is completed,
so that calculated
ilagration)
or supersonic
(detonation)
relative
pressure
cannot be
expected
to approximate
to the
unburned
gas.
If
it
is subsonic, the pres-
actual pressure. Even
with
spherical
enclosures,
sure
will equalize
at
the
speed of sound through-
the flame front is
not actually spherical, so
that
out
the
enclosure
in
which combustion
is taking the
walls
tend
to disturb
the
flame before corn-
place
so that the
pressure drop
across
the flame
hustion
is complete
(118,
130).
A graph
of the
(reaction) front will
be
relatively small. If the
pressure developed
by
the combustion
of a
rate
is
supersonic,
the
rate
of
pressure equaliza- stoichiometric
methane-air mixture (central
tion will be less than the
propagation rate
and
ignition)
in a
19.7 cm
diameter, 9-liter
cylinder
,hire
will be
an
appreciable pressure
drop
across is given
in
figure 15. The
calculated pressure
the flame front.
Moreover, with most con-
for
a 9-liter sphere
is included for comparison;
butible-air mixtures,
at
ordinary
temperatures, K
in
equation
(7)
was evaluated from the
the
ratio of the
peak-to-initial pressure
within
experimental curve at
70
milliseconds.
The
the enclosure
will
seldom
exceed
about
8:1
in calculated
curve follows the
experimental
curve
the
former,
but
may be more than
40:1
in
the
closely
about 75 milliseconds,
when the
latter
latter case.
The pressure buildup
is
especially curve has
a
break.
This suggests that the
great
when detonation
follows
a
large
pressure flame
front
was
affected
by tbe
cylinder
walls
rise
due
to
deflagration.
The distance
required
in
such a way that the
rate of pressure
rise
for a deflagration
to transit to a detonation
decreased,
and
the
experimental
curve fell
below
depends on
the
flammable
mixture, temperature,
the calculated curve.
Further,
since the
com-
pessure, the
enclosure, and the ignition
source.
bustion
gases were
being cooled, the maximum
ith
a sufficiently powerful ignition
sourbe,
detonation
may
occur immediately
upon igni-
00
tion, even in
the
open.
However, the ignition
energy
required
to
initiate
a
detonation
is
Calculated
I
usually many orders of magnitude greater
than (9-liter sphre)--, 11
that
required
to initiate a deflagration (3, 249). 80 I
Experimental
DEFLAGRATION
t
(9-liter
cylinder)
Where
a
deflagration
occurs
in
a
spherical
L
60
enclosuire of volume V with central
ignition,
the ci)
approximate
pressure
rise AP at aLv
instant t &
itter
ignition is given by the
expressions:
W
c/n40-
APA7
_]P=
(7)
Wu)
and
0.
1 = A- _.'-
(I)
20
where
K is a constant.
S. is
the
burning
velocity,
', is the initial pressure, 1'm is the maximum
[
pressure, '1
is
the initial
temperlture,
it, is the
0
40 80
120 160
number of
inoles
of gas
in
the initial
mixture, ELAPSED
TIME, milliseconds
n,
is the
nU'nl)er of
moles
of
gas in
the hurned
gases, Al7
is
the average
molecular weight of the Fiuar 15.---Pr(wssure
Produced by Ignition of a 9.6
olum(",Percent
Methane-Air Mixture
in
H 9-Liter
initial
mixture, -Ifb
is the average
molecular Cylinder (E-xperimental).
15
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16 FLAMMABILITY CHARAC*TERISTICS OF
COMBUSTIBLE
GASES
AND VAPORS
pressure fell below the calculated value. The Wolfson and Dunn have developed generalized
minimum
elapsed
time
(in milliseconds) re- charts
that
simplify
the operations
involved
in
quired to reach the maximum
pressure
appears obtaining the
pressure
ratio as well as the den-
to
be
about
75
iV
for
the
paraffin
hydrocarbons
sity
and temperature/molecular
weight
ratios
and
fuel blends
such
as gasoline;
V is
the across
the detonation
wave
and
the energy
volume
in cubic
feet in
this case.
release
in the detonation
wave.
Many
investigators have
measured
and
cal-
culated detonation
and reflected pressures
DETONATION
resulting
from
detonation
waves
(54
57,
204).
Figure
16 from the
data of
Stoner
and Bleakney
Wolfson and Dunn (52, 230) have
expressed
(204) gives
the detonation velocity, the
static
the pressure
ratio P2/P
1
across a
detonation
or
detonation pressure,
and the reflected pres-
front as sure developed
by
a detonation wave propa-
P
2
I
gating through
hydrogen-oxy
en mixtures at
(,,M,
2
+ 1),
(9)
atmospheric
pressure
and
180
C.
where
%,s
the specific heat ratio of the burned BLAST
PRESSURE
gases, y
is
the specific
heat
ratio
of the initial
mixture, and £ is the Mach ntunber of the
diretatond
wv
ithe
respct
tomber
the
The
pressures
produced
by
a deflagration
or
detonation
wave
with
respect
to
the initial
a detonation
are
often
sufficient
to
demolish
an
mixture.
M,
is
given in
terms
of
the tempera-
enclosure
(reactor,
building,
etc.).
As
noted,
a
tures T and molecular weights
W
of the initial
deflagration
can produce
pressure
rises in excess
and
final mixtures by the expression: of
8:1,
and
pressure
rises
of 40:1
(reflected
pressure) can accompany
a
detonation.
As
(
1
M'+l)'
(ya±)TW (10)
ordinary
structures can be demolished by
pres-
"n
1
'
7
Y2T,W
2
sure
differentials
of
2
or
3
psi,
it is
not surprising
3,500 50
P (
theoretical)
45
40
/ 35
30
2,500
25 E
E Ps
(experimental)0
-20
15
2,000
10
5
1,500
I 1 1 I I I 0
20
30
40
50
60
70
80
90
H
2
, volume -
percent
FIoUsZ 1.Detonation
Velocity,
V; Static Presure P.;
and Reflected Pressure,
P,,
Developed by a Detonation
Wave
Propagating Through
Hydrogen-Oxygen
Miziures
in
a
Cylindrical TuIbe
at
Atmospheric Pressure and
180 C.
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DEFLAGRATION
AND DETONATION PROCESSES 17
that
even
reinforced concrete structures
have
must be
taken to
protect
the
personnel
and
been
completely
demolished by
explosions
of equipment
from blast
and missiles.
Browne,
near-limit,
flammable
mixtures.
Hileman, and
Weger
(16) have
reviewed
the
Jacobs and
coworkers
have
studied the
dam- design
criteria
for
suitable barricades.
Other
age potential of
detonation
waves
in
great detail
authors
have
considered the design of suitable
(91,
170). They have
considered
the principlcs laboratories and
structures to prevent frag-
involved in
rupturing of
pipes
and vessels
by ment
damage
to surrounding
ar-9,s
(44,
174,
detonations and
the
relevance
of engineering
203, 20).
and
metallurgical
data to
explosions.
More
recently,
Randall
and Ginsburg
(171) have
in- TABLE
1.-Conditions
of failure of peak
over-
vestigated
bursting of tubular specimens
at pressure-sensitive
dements
(217)
ordinary and
reduced temperatures. They
found
that the detonation pressure
required to
Approx-
burst such
specimens
was, in general,
slightly
iniate
higher
than the
corresponding
static-bursting
incident
pressure.
Ductility
of
the
test
specimen
ap-
Structural
element
Failure
blast
peared
to
have
little
effect on the bursting
pressure
pressure,
but
ductility increased
the strength
(psi)
of pipes
containing
notches or other
stress
raisers.
Glass
windows,
large
Usually
shattering,
0.
5-1.0
When
a
detonation
causes
an
enclosure to
and
small. occasional
frame
fail,
a shock
wave
may propagate outward
at a failure.
rate determined
by
characteristics
of
the Corrugated
Asbestos Sh ittering. 1.0-2. 0
medium
through
which it
is transmitted,
and
Aidiug.
the available
energy. hi
the shock
velocity,
,
Corrigattd
steel
or Conneclion
failure, 1.0-2. 0
aluninumrr
panel-
followed
by
buck-
is known,
the resulting overpressure,
(P-P,),
ing. Iih
I
is given
by the expression
(20.1)
Wood
siding
panels,
Usually failure
oc- 1.0-2.
0
standard house curs
at main
con-
construction. nections,
allowing
PP~l~
(11)a whole panel to
be
blown
in.
Concrete
or cinder-
Shattering
of the
2.
0-3.0
where,
is
the ratio
of specific
heats, and
a is
the
block
wall panels,
wall.
velocity of sound
in the medium through
which
8
or
12 inches
the
shock
wave passes. The approximate thick (not rein-
damage
potential
can
be
assessed
from
the
data
forced).
Brick wall panel,
8 Shearing and
flexure 7.
0-8.0
in
table 1 (217).
or
12
irches
thick
failures.
In conducting experiments
in
which
blast (not
reinforced).
pressures
may
be
generated,
special
precautions
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PREVENTIVE
MEASURES
INERTING1
In principle,
a gas explosion hazard
can be
eliminated by removing
either
all flammable
mixtures or
all
ignition sources
(23, 240).
Unprotected
However this is
not
always practical,
as
many
industrial
operations require the vresence of
flammable
mixtures, and actual
or potential
ignition
sources.
Accordingly
special
pre- C
cautions
must be taken to minimize the damage
that
would result if
an
accidental
ignition were
Co
to
occur.
One
such
precaution
involves
the
W
use of explosive
actuators
which
attempt
to
a.
add
inert, material
at
such a
rate that
an
Protected
explosive reaction is
quenohi
d
before structural
damage occurs
(70, 72).
Figure 17 shows how
the pressure varies with and without such
protection.
In
the latter
case,
the
pressure ti
rise
is approximately
a cubic
function of
time,
ELAPSED
TIME
as noted earlier.
In
the former
case, inert
is
FIGURE 1-Pressure Variation Following
Ignition of
added when the
pressure or the rate of pressure a Flammable Mixture in Unprotected
and
Protected
rise
exceeds
a
predetermined
value.
This Enclosures.
occurs at the time t, in figure 17 when
the
explosive actuators function to add
the
inert.
As noted, the pressure increases momentarily where
k
is
the thermal conductivity
of
the
gas;
aboe the value
found in the unprotected m is the mesh width; T is the mean bulk
tern-
case and
then
falls rapidly as the combustion
perature of the flame gases through
the
arrestor;
reaction is
quenched by
the
inert.
T.
is
the initial
temperature of the arrestor;
Q
is
the heat
lost
by
unit area
of flame; x, is
the
FLAME ARRESTORS
AND RELIEF
thickness
of
the
flame
propagating
at
the burn-
DIAPHRAGMS
ing velocity,
S; d
is the diameter of
an
aperture;
A is
the
area
of
a hole in unit area of the
Inert atmospheres must
be used
when
not arrestor
face;
and t is the arrestor thickness.
even a small
explosive
reaction
can
be tolerated. Equations
(12) and (13) can be
used to
However, when the ignition of
a
flammable
determine the mesh width or aperture diam-
mixture
would
create
little hazard
if
the burning eter needed
to stop a flame having a
particulur
mixture were vented, flame arrestors and relief approach
velocity.
In practice, application of
diaphragms
could be used effectively.
The
these equations assumes a knowledge
of
the
design
of such systems is determined
by the
flame
speed
in
the system
of
interest. Some
size and strength of the confining vessels, ducts,
useful data
have
been made available by
etc.
Palmer and Rasbash and Rogowski (172,
173),
In recent
studies of the
efficiency of wire
as well as by
Jost
(118) and Lewis and
von
Elbe
gauze
and perforated block
arrestors
(161, 162),
(130).
almer found the velocity of approach
of the Tube
bundles
also
may
be used in
place
of
flame to be
the major factor
in
determining
wire scraens. SC3tt found that these permit
whether
flame
passed through an
arrestor. For
increased
aperture
diametera for a given ap-
these two
types of arrestors,
lie found the proach velocity
(192).
critical
approach
velocity
to
be In practice,
it
may
be desirable to install
pressure relief
vents
tu imit damage
to
duct
S1.75k(2-T.),
systems
where
flime
may
propafate.
Rasbash
0
1,(12)
and Rogowski (173) found
that
with propane-
and
and
pentane-air
mixtures,
the
maximum
pres-
andT sure PM (pounds per square inch) developed
in
V9 6kA (T-T°), (3 an open-ended duct, having
a
cross section
of
dQ/13)
1
ft-
is:
18
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p
PREVENTIVE
MEASURES
19
L L
and it is
thus
proportional
to
K.
For
small
PM--O.7
,and6<
<48,
(14)
values
of K
it, was
found
that
where
is
the
ratio
of
duct
length
to
diameter.
PS=K.
D
As with
ducts,
larger
pressures
wvr6
obtained
However,
the
presence
of
an
obstacle
(bend,
whea
obstructions
were
placed
in
the oven.
constriction,
etc.)
in the
path of escaping
gases
increased
the
pressure
due to
resistance
to
fluid flow
by the
obstacle.
Location
of
a
relief
vent
near
the ignition
source decreased
P
2
the
maximum
pressure
as
well
as
the
flame
speed.
For values
of
K
(cross-section
area
4
of
duct/area
of vent)
greater
than
1, these
I
authors
found
O.8K<P,
_i.8K,
(15)
P
L
0W
where
2_5K<32,
and
6
<5T__.30.
To
keep the
c
pressure
at
a
minimum
either
many
small
vents
or
a
continuous
slot was
recommended
rather
than
a
few
large
vents.
In
addition,
vents
should
be
located
at
positions where
ignition is likely
to occur and
should open
ELAPSED TIME-
before
the
flame
has traveled
more
than 2
feet.
When
possible,
relief vents
should
be
used
F
iouE
18--Pressure
Produced
by
Ignition
of
a
with
flame
arrestors.
The
vents
tend
not
only
Fiammable
Mixture
in a Vented
Oven.
to
reduce
the pressure
within
a system
following
ignition
but
also
to reduce
the
flame
speed,
In designing
explosion
reliefs
for ovens,
Sim-
thus
making
all
arrestors
more
effective.
Un-
monds
ubbage
pointcd
out
that
(1) the
fortunately,
in certain
large
applications
(for
reliefs
should
be
c,.astrueted
in such
a
way
that
example,
drying
ovens),
it is difficult
to use
they
do not
form
dangerous
missiles
if
an
explo-
flame
arrestors
effectively.
In
such
cases,
sion
occurs;
(2) the
weight
of
the
relief must
bc
greater
reliance
minst
Ie
placed
on
the
proper
small
so that
it, opens
before
the
pressure
builds
fue
,tioningf
relief
vents.
Siesmonds
and
up
to a dangerous
level:
(3)
the areas
and
posi-
Cubbage
(42,
43,
195)
have
investigated
the
tions
of
relief
openings
must
be
such
that
the
design of
affective
vents
for
industrial
ovens,
explosion
pressure
is not
excessive;
(4) sufficient
They found
two peaks
in the
pressure
re-ords
free
space
must
be
utilized
around
the
oven
to
obtained
during
the
vnting
of cubical
ovens
pterrmit
satisfactory
operation
of
the relief
and
(fig.
18). The
first peak,
Pi;
the oven volume,
minimize
risk
of
burns
to
personnel;
and
(5)
I"; the
factor,
K;
and
the
weight
per unit
oven
doors should
be
fastened
securely
so
that
area
(lb/ft)
of relief,
w,
were
related
as follows
they
do not
open in
the
event
of an explosion.
for
-t
25
percent
town
gas
-air
mixture:
Burgoyne
and Wilson
have presented
the
results
of
an experimental study
of pentane
vapor-air
explosions
in
vessels
of 60-
and 200-
More
generally,
cubic-foot
volume
(30).
They
found
the
rates
of
pressure
rise
greater
than
could
be
predicted
Po(O.3Kw+0.4),
(17) from
laminar burning
velocity data,
so
that the
effect of
a
relief
area
in lowering
the
peak
where
S,
is the
burning
velocity
of
the mixture
pressure
was
less
than
expected.
All experi-
tit the
oven
temperature.
ments
were
conducted
at an
initial
pressure
of
The first,
pressure
pulse
was ascribed
to
the
I atmosphere.
Vent
data
for use
at
higher
release and mIotion
o tAe
relief
vent
following
initial press,.res
are
summarized
in
an article
igniton;
the
sec('ond
pulse,
to (ontitue(d
jurn-
by Block
(10);
a code for
designing
pressure
ing at an
inrcased
rate. 'Phe
secord
pulse
relief
systems
has been
proposed
in
this
article.
represents
thip
pressure
drop
across
the
vent,
Other
authors
have
considered
the effects
of
temperature
and
characteristics
of the flare-
, Town US
epetmane;
proxalnely
52 theyroon
17 ICt
cprtn
mable
mixture
on
vent
requirements
(14, 35,
,OWnogien,
IS
pet i ,thane; the
,Uali
; i
o" nr
8ydrc4u5I
46ns,
pet1
Otrot~i
mmpet ca~on
ioaiieS pt; nd
o~en
8
5 46 134
14.,8
2
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FLAMMABILITY
CHARACTERISTICS
The
flammability
data (limits of
flamma-
bustible
vapor per liter of
air
at standard con-
bility,
flash point, ignition
temperature and
ditions,
that
is,
00 C and
760
mm
Hg (0.045
to
burning velocity)
of the various
chemical
farn-
0.050 oz combustible
vapor per
cubic foot
of
ilies exhibit
many
similarities. Accordingly,
air)
(247). This
is illustrated
in
figure
19
in
the
data presented
here
are
grouped
under
the which
some
lower
limits
of flammability
are
various commercially
important
families,
blends,
plotted against
molecular weight;
except
for
and miscellaneous
combustibles.
methane, ethane,
and
propane all
limit values
fall
in a
band
between
concentrations
of approx-
PARAFFIN
HYDROCARBONS
imately 45 and
50
mg/r.
(C.H
The following expression
may
be
used to
R
2
)
convert
from
a
lower
lirrit
L in
volume-percent
Limits
in
Air
of
vapor in the vapor-air
mixture
to one
in
Lower and
upper limits
of
flammability
at
milligrams
of
combustible,
per
liter
of air at
250
C
(or
at
the
temperature
noted)
and 1
standard
conditions:
atmosphere
(L
25
and U25) for
many members
of
lmg\
L (vol
pct)
the
paraffin
hydrocarbon
series
are
given
in
L
(mg)
0
L(volpct)
table
2, together with the
molecular weight, M,
1 1
vapor
specific
gravity, sp
gr, stoichiometrict[
volmg
composition
in
air,
C.,
(appendix B) and heat
of combustion,
AH, (188).
At
room
tempera-
specific volume
being
volume of combustible
ture and
atmospheric or reduced
pressure,
the
vapor per milligram
of combustible.
At
stand-
lower
limits of
flammability
of
most of
this
ard conditions
(00 C
and
760
mm
Hg) this is
series
fall in the range from
45 to
50 mg com-
about 22.414/1,OOOM, where
M is the molecular
6
5 X
i50mg/I
.4
L
45
mg/I
0
2240-
0
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FLAMMABILITY CHARACTERISTICS
21
TABLE 2.-Properties
of parafinhydrocarbons
Lower limit i air Upper
limit in
air
Net
AH.
Pr
I.n
(W a
U
N
Ur
Combustible
Formula M (A -1) (n
pr
ol
Rf (Vol g)
R
p(ot)
,
pot)
(
(vol
pot) /
)(vol
ef t)vl)
Ref.
Methane
...............
CH,-----------
16.04 0.65
9.48 191.8
5.0 0. 3 8 40 1.0 1.6
126 (40)
Ethane
---------------
CaH .----------
30.07 1.04
8.65
341.3 3.0 .53
1 4
12.4
2.2
190
4,
Propane .................
CsH .---------
44.09
1.52
4.02
488. 5 2.A .52 42
(116)
9.6
2.4
210
(41
n-Butane...----.------
C
4
H0--------- 88,12
2.01
3.12
635.4 1.8 .58 48 (11) 84
2.7
240
41
n-Pentane
------------ C all
- - - - - - - - - -
72.15
2. 49
2.55
782.0
1.4 .85 4 J40 7.8 3 1 270
40)
n-Hexane .............
.
-----
-
..........
88.17 2.96 2.16
928.9
1.2
.56
47 (546
7. 4
8.4
810 401
n-Heptane ................
C,Ha
...........
10020
3.46
1.87 107.8
1.05
. W
47 (546 6.7 8.6 820
n-Octane
----.---------- Call, --------- 114.23
3.94
1.65 1222.8 .96 .58 49 (56
..........
-
.................
n-No,,ane
----------.---
Cll,
.---------
1. 28 443
147 169.7 . .6 48 ,146)
....
9.(546)
n-Decane -- _----------- Colin
--------- 142.28
4.91
1.33 1516.6 '.75
.6
48
(4) '5.6 4.2 880.
n-Undecane -----------
--- -.......... 1 .30 5.40 1.22
1663.6 .68
.6 8 (4 __
n-Dodecane ....... C-
..----_---- 170.33
5.88
1.12
1810.5 .60
.84 46 (4
- -
n-Tridecane------Ciallsa,.........184.36
6.37
1.04 1957.4
.85 .3
40
(').........................-----
n-Tetradecane ............
Cills
0
. . . . . . .
..
..
198.38
7.8 97
2104.3 b.
.62 44 )
n.1'entadecane--------- C::la............212
41 7:33 90
2231.
.4 5.1
40 1(------
n-llexadecane----------C 11
- - - - - - - - -
22644
7 82
85 2398.
51
44 (I
1
-43'
C.
4Calculated
value
extrapolated to 25" C at Explosives
Re. Center,
Uj.53
C.
Federal
Bureau
of Mlnes.
t-86
C.
weight
of
the combustible.
Since L (vol pct)
Combining this
equation
with equation (21),
of
most members
of this series is much
less
than we
have
100 percent, the lower limit can be
expressed L
2
o(mg/1)
-48 mg/i, (27)
as
(for
paraffin
hydrocarbons,
except
methane,
L -0.45ML (vol
pet). (20) ethane,
and propane.
Substitution
of
this
value
into
equation
(20)
gives
At any
specified temperature, the ratio of 107
the lower limit to the amount
of combustible L 2 o l O t (28)
needed for
complete combustion, C,,,
also is
approximately constant.
This
was
first
noted
by
Jones (95)
and later
by Lloyd (138),
who
The
following
expression
may
be used to
found
that
for paraffin
hydrocarbons at
about
convert
a lower limit
value
in
volume-percent
250
C,
to
a fuel-air
(weight)
ratio:
L
21
. ru0.55C,,.
(21)
L (Vol pet)
For
the
complete
combustion
of
the
paraffin
L(F
.96/A)0_0-L
(vol
pt)j
hydrocarbons, we have:
The
reciprocal
expression
gives
the
air-fuel
CaH
2
.+
2
+
(1.5n +
0.5)O--*nCO
2
+
(n-+
1)H
2
0,
(weight)
ratio:
so
that
in air
(22).
7NF-- --
(30)
50
*
00
-~* (30
100
vo
(Al
LL
(vol
pct)
j
C,=I+4.73(.5n 0.5
vo
pet,
(23)
1+4.773(1.5n+0.5) pAs
noted, the
lower limits
given
in figure 19
were determined
at room temperature
and
at-
where
4.773 is the
reciprocal
of 0.2095,
the
mospheric or
reduced
pressure. Lower limits
molar concentration of oxygen
in
dry
air.
The vary
with temperature as shown for methane
in
values of
C,,
(appendix B) are
included in
table
figure 20. The limit values
obtained with up-
2. By
weight these
become
ward
propagation of
flame
(R1) fall fairly close
to a
straight
line
that
passes through the
lower
1,000[12.01n+
1.008(2n±2))
ing
limit value
at
250 C and the flame temperature
(
22.414X4.773(1.5n±0.5)
1- (24)
(12250
C).
This
is
in
accordance with
the
or
White criterion that
the flame
temperature is
14.03n+2.02
1
g.
constant
at'
the
lower
limit
(RO2).
The
data
(,9.34
1 l
_.n+0.5
J 1
(25)
obtained by
White with
downward propagation
of
flame fall
along a line parallel to
the line
Thus,
through the
limit values
obtained with upward
C,,-87 mg/l,
n>4. (26) propagation. Taking
the value
1,300'
C as
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22
FLAMMABILITY CHARACTERISTICS
OF COMBUSTIBLE GASES
AND
VAPORS
air
100%-% methane
5-
Flammable
mixtures
--
Vapor
pressure
4
curve
Downward propagation
of
flame
E
r
AIT
z
qc
Upward
propagation of flame
1 -
-200
0 200 400 600 800
1,000
1,200 1,400
TEMPERATURE,
°
C
Fiouim 20.-Effect
of Temperature
on Lower
Limit
of
Flammability of
Methane
in Air at
Atmospheric
Pressure.
the approximate
flame
temperature for the plot of L,/L
2
5
.
against the temperature
(fig.
23 ,
paraffin hydrocarbon
series
(5), and using
the solid
line).
lower limit
values at
room
temperature
in table
These
data are also correlated
fairly well with
2, the
limits
of
the
first 10 paraffin
hydrocar-
the
modified
Burgess-Wheeler Law
suggested
bons are represented
as in
figures 21
and 22. by Zabetakis,
Lambiris,
and Scott (.42):
Figure
21 ives
the
lower
limits
in
volume-per-07
cent and figure 22 in
milligrams
per liter.
By
0"75 (t-25'),
(33)
weight, the lower
limits of most
members
of
this series
again
fall
in a fairly
narrow
band
("higher hydrocarbons"
region). Individual
where t is the temperature in
'C
and AM, is
the
adiabatic flame temperatures
can be determined net
heat
of combustion in
kilocalories
per mole.
for
lower
limit
mixtures
using the
data in table Then,
2 and
appendix
C (55).
L,
=
0.75
The straight
lines of figures
21 and
22
are
L
2
- So- (t-25).
(34)
iven
by:
L
2
o t
L
Substituting
the
value
1,040
for
L
2
5
.AH,
ob-
Li
2&
-
(t-25
), (31)
tained
by Spakowski (R01),
we have
1,3000--250)
or
L
L,-
1-0.000784(t-25*). (32)
L
2
*-- 1-0.000721(t-250), (35)
which
is also
given
in
figure
23 for
a
limited
They
are described
in more general terms
by a
temperature
range with the
broken line.
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FLAMMABILITY
CHARACTERISTICS
23
6
f I
% air
=
100 - combustible
5
Flammable mixtures
-
4
MetPrpn
C,
9.
0> Ethane
AIT
L" 3 -
j
Propane
DButane
CD )
22-
AIT-
Pentane
Hexane. -'" .
1
Heptane
Octane
,,
Deane
AIT
-200
0
200
400
600
800
1,000
1,200
1,400
TEMPERATURE, C
FIGURE
21.-Effect
of
Temperature
on Lower
Limits
of Flammabilty
of
10 Paraffin
Hydrocarbons
in
Air
at
Atmospheric
Pressure.
Only
the lower
limit
at
250
C and
atmospheric
flames
(87,
88), the
upper
limit also
increases
pressure
is
needed
to use
figure 23.
For exam-
linearly
with
temperature.
The
effect
of
pie, assuming
a
constant
flame
temperature,
the
temperature
appears
to
be
fairly
well
correlated
ratio
L
tL
3
.
at 6000
C
is
0.55.
The
calculated
by the
modified
Burgess-Wheeler
law:
lower
limit
of
methane
at
6000
C therefore
is
5.0X0.55,
or 2.75 volume-percent.
The same
0.75
value
can
be obtained
directly
from figure
21.
U-
+
y-
(t-25
0
).
(36)
From
the
modified
Burgess-Wheeler
Law
curve,
L/L
25
.=0.585
at
6000
C, so
that
L4o.=2.92
If
we
assume
that the heat
release
at
the
upper
volume-percent.
limit
is equal
to
that at
the lower
limit,
th n
Limit-of-flammability
measurements
are corn-
plicated
by surface
and
vapor-phase
reactions
that
occur
at
temperatures
above
the
auto-
U
= 0
0
(
)
ignition
temperature.
For example,
Burgoyne
-
1+0.000721(t-25). (37)
and
Hirsch
(25)
have
shown
that
methane'air
mixtures
containing
up
to
5
percent
methane
A
plot
of
Ui
Un. against
temperature
fig.
24)
burn
readily
at
1,000
C.
E'xperinments
were was
used
to
corn are
recent
experimental
values
conducted
with
mixtures
containing
as
lit
le as
of Rolingson
and
coworkers
(18.e)
for
methane-
0.5
percent
methane;
figure
20
predicts
that
a
air
mixtures
at
15 psig
with those
predicted
bY
flame would
not propagate through
such a
the
modified Burgess-Wheeler law. The expen-r
mixture,
mental
and calculated
upper
limits
are
givenx
in
Flammability
experiments
at
elevated
ten-
table
3
together
with
tlie
difference
U,,-
peratures
indicate
that
in
the
absence
of
cool
U..r,
In each
case,
the
difference
is
iess
than
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24
FLAMMABILITY CHARACTERISTICS
OF
COMBUSTIBLE
aASES AND VAPORS
60
50
Higher
hydro-
carbons
Propane
40-
Ethane
0 Methane
I3O
20-
I
10
-200
0
200
400 600 800 1,000 1,200
1,400
TEMPERATURE,
°
C
Fouau
22.-Effect
of Temperature
on Lower Limits of Flammability
of 10 Paraffin Hydrocarbons
in Air
at
Atmospheric Pressure by
Weight.
4 percent of
the experimental value,
which
is
point. The
lower
temperature
limits
of
paraffin
approximately within
the
limit
of
experimental
hydrocarbon
at
atmospheric pressure
are given
error. Earlier
experiments
of
White (222)
at
in table 4.
temperatures
to 4000
C,
with
downward
flame
propagation,
also are
represented
quite ade-
TABLE
3.-Upper
lammability
limits, U,
of
quately
by
equation
(37). For example,
White
methane-air
mixtures
at 15
psig
found that
the upper limit
of pentane
in
air
(downward
propagation)
increased
linearly
from
4.50
volume-percent
at
about 170
C to
5.35
Temperature U,.p,,
(vol
U.,1.
(vol Uo.I -Uo.
.
volume-percent at 300' C. The ratio of
5.35: (C) perceLt) percent)
(vol percent)
4.50
is 1.17,
which compares
quite
well
with
UW./U&.
=l.20
obtained from
figure
24.
25 ----------
15.5
15.5 0
Given
the vapor
pressure curve
and
the
lower
100
-------- 16.
3
16. 4
.1
limit
of
flammability,
the low
"
temperature
200 --------
17.0
17. 5
.5
limit
or approximate
lash point
of a
combustible
30.
17.
9 18.
6
.7
can
be calculated
from
either equation
(32)
or
(35)
(.018).
Approximate
flash
points were
(J8I.
obtained
previously, using
only
the
vapor
pressure curve and the
lower
linit
at
ordinary
Moderate
changes
in pressure
do
not
ordi-
or elevated temperatures
(1,54).
The values
narily
affect
the
limits
of flammability
of
the
obtained
with
this
procedure are
somewhat
paraffins
in
air,
as
shown in
figure
25 for
pen-
low
because
the lower
limit at any temperature
tane, hexane,
and
heptane
in
air
(241) in a
above the
flash
point is less than at
the flash range
from
75 to
760 mm Hg.
The
lower limits
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FLAMMABILITY
CHARACTERISTICS
25
TABLE 4.-Lower
temperature limits
and
autoignltion emperatures
oJ
paraffln
hAdrocarbonw at
atmospheric pressure
Autoignition temperature
Lower temperature
limit
In air
In
air
In oxygen
C oF Ref.
C 0
F
Ref. o C F
Ref.
Methane
----------------- 187 -305
(1)
537
999 (158) -------- ...........
Ethane
------------------ 130 -202
(1)
515 959 (937) 506
943
(94)
Propane ----------------- -102 -152 (1)
466 871
(158) ----................
n-Butane
------------------
72
-96 (1)
405 761 (2,17) 283 542 (191)
Isobutane-----------------81 -114 (1)
462
864 (158)
319 606
94)
n-Pentane- ----.--------
-48
-54
(1)
258 496 (194) 258 496 (144)
n-Hexane ----------------- 26 -15
(159)
223 433
194) 225 437
94)
n-Heptane --------------- 4 25
(169)
223 433 (237) 209 408 (94)
n-Octane
----------------
13
56 (159) 220 428 (*37) 208 406 (191)
n-Nonane
---------------- 31 88 (159)
206 403 (2,37) - - --------
n-Decane ----------------
46
115 (159) 208 406 (237)
202
396
(94)
n-l)odecane--------------
74 165 (159) 204 399 (237)
........................
n-1(exadecane
-------------
126
259
(1)
205
401
(237)
.........................
Caculated
value.
1.2
7 7 p 7
I
N2
.8 N
Modified Burgess-Wheeler Low
" .6 -N
.4
.4 -
Constant flame
temperature
.2
01 1
-200
0
200
400 600
800
1,000
1,200 1,400
TEMPERATURE, -C
Fiounz
23.-Effect
of
Temperature on
L,/LNo Ratio
of Paraffin Hydrocarbons
in
Air at Atmospheric Pressure.
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26
FLAMMABILITY
CHARACTERISTICS
OF' COMBUSTIBLE
GASES AND
VAPORS
1.4
Neither
expression
is applicable when
cool
flames are
obtained.
Substitution
of equation
(21) for
Lw. into equation
(39)
gives
1.3
U.=4.8
(40)
The limits
of
flammability
of natural
ga s
1.2
-
(85-95
pct methane
and 15-5
pct
ethane)
have been
determined
over
an
extended pres-
sure
range by Jones
and coworkers
(78,
105).
They
are given
in
figure
26 for
pressures
from
1 to
680
atmnos
heres
(10,000 psig).
An
analysis
of these
Sata shows
tile
limits
vary
linearly
with
the
logarithm
of the
initial
1% ,
pressure. That is,
1
0
100 200 300 400 300
TEMPERATURE,'C
L
(vol pet) =4.9-0.71
log
I'
(atm),
(41)
Fioum
24.-Effect of Temperature
on
U,/U.
Ratio
and
of
Paraffin
Hydrocarbons
in
Air
at
Atmospheric
Pressure
in
the
Absence of
Cool
Flames.
U (vol
pet) =14.1 +20.4
log
P (atm),
(42)
coincide,
but
the
upper
limits,
by
weight,
with
a standard
error
of estimate
of
0.53 vol
increase
with
increasing
molecular
weight.
pet
for
L
and 1.51 vol pet,
for
U.
Be volume,
at
atmospheric
pressure
and
250 Although
the limits
of
flammability
are
not
C, Spakowski
(201) found
that the
upper
and
taffected significantly
by
moderate changes
in
lower
limits
were related
by the
exprcs~sion:
pressure,
the
temperature
limits are
pressure
dependent. As
the total
pressure
is lowered,
U
26
. =-7.1L5'.
(38) the
partial
pressure
of the combustible
must
also
be lowered to
maintain a
constant
corn-
However,
the data
presented
here are
correlated
bustible
concentration.
The effect
of pressure
more
precisely
by a somewhat
simpler
expres-
on
the lower
temperature
limit of the
normal
sion:
paraffins
pentane,
hexane,
heptane,
and octane
U
2
6.=6.5 421n.
(39) in
air,
for
pressures from
0.2 to 2 atmospheres,
400
~Heptane
z
0
300
z
Hexane
Uj.
Pentane
0
200
0-,",
Flammable
mixtures
W
W
= 10 0
o0
0
100
200 300
400
500
600
700 800
INITIAL
PRESSURE,
mm Hg
FIuu'aE
25.-Effect of
Presure
on Limits
of Flammability
of
Pentare,
Ilexane,
and lieptane
in Air at
26' C.
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FLAMMABILITY
CHARACTERISTICS
27
60
air
= 100%-%
natural gas
50
C
®
40
E
.2
Flammable
mixtures
9 30
20
z
10
0
100 200 300 400
500 600
700
800
INITIAL PRESSURE,
atmospheres
FJGuRE
26-Effect
of Pressure
on
Limits
of
Flammability of Natural Gas
in
Air
at 280
C.
is
shown
in
figure 27.
'[ire
tepn
erature limits
TABLE
5.-Limits
of
flammability of
methane
in
were
calculated
from
the L,,. values,
the vapor
chcrine
pressure
curves,
and
the data
of figure
23.
(volume-pecnt)
Limits
in Other
Atmospheres
Temperature,
0 C
Prevmre,
Limits
Liim its
of fla aininbility
of
soine
paraffin
y- p
sig L5_100
drocarbots
hav-e been
determined in oxygen,
25 100 200
c h lo in e
, a
n
d ox
id
e s
o f n itr o
g en
, .'we
ll 'a
s in
. . . .. .
m ixtures of air
id various
inerts.
The
l
wer
fLowr
5.63
0.6
li ,its ill
o x
y g
e n a l ( in
a w id e v a r
ie y o f t
[. U p p
e
r --- 70 6
6 -. - 0.-
Ox g
n-imtrogen iixtures
are
essentially the
100 ... . .
.-ower- ------
.
---
2.4
6
sliw
its those
ill
air at
the smniiie temperatire
tUppcr
-
"-
2 76 77
an d p
re
s
s
u
re (fig .
1
0
) . L m i -o
i-I ttlan. a
b
ilit
y 20 0 .. .
. .-
L
o w r
. ..
..--
-
- - - - - -- - - -
Iileasurements
by Bartkowirik
and
Zabetaki.;
pjwr
73
72
75
for mrthiane
aii
eliaic
iii
clilrinte
at
1,
7.8,
-
wid 4.6 atio spheres, riuiiiiig
from
2
5 to 200
°
i
re ,
iniliarized
in
tab
vs
5
ad
6(
(S).
atiiiosphere
with
wich
tie
combustible
is
('oard ad
,
oles (,;0)
have Iresiit
vd lixed.
''hie
cimrrposit
ion
of i
poitnt oi such
a
gi allhicall
v
e liimi
f
fla
inahbilit vof the first diagrani,
exc
pt
one that
represents
only
conl-
six
INVIIiii* s of
lie
paralnfihi
series in
air con-
bustible a)d
air,
cannot be
read
directly.
tainig various ii
ts, based mi a
repivse
nita-
list
ad, one
mnust determinie he
co miposition
tion
foiund
useful ill
som 111i1iig
applitations of
the atillosphere,
add the combustible
con-
aid
treating inert gas or
vapor as part oif
the tent,
and then compute
the total mixture coin-
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28
FLAMMAL4ITY
C1-L.IACTERISTICS OF
COMBUST'IBLE
GASES
AND VAPORS
40
-
Unfortunately,
the methane-methyl
bromide-
air
data
were obtained
in a
17-inch
tube.
Although
satsfactory
for methane
and other
hydrocarbons,,
th.3
tube
is
apparently
not
satisfactory
for miany of
the halogenated
ydro
20-
carbons.
Thus
a
recent
industrial
explosion
0~n.
involvitig
methvi
b~romide
prompted
Hill to
Octane
reconsider the f
i-immabiity of methyl bromide
itL
air (84), He
found that methyl
bromide
wa s
not
,nly
iiammable
in air but
that,
it formed
:3
flananable
mixtures 4t
1
atmosphere wits
a
wider
variety
of eoncentrations
than
Jones had
Heptanereportad (96).
This would
sug,-e&,
that,
there
is no
justification
for the
assumption
that
Jones'
flammabii
r
data
for
methyl
bromide
were
influenced bsy
the presence of mercury
0Hexanepressure
aire
included
in
figure
'8
amid are
used
to form
the approximate,
brokeon, flammability
curves for
the
methane-methyl
bromide-air
system.
-40-
Data
of
Moran.
and Bertschy for pentane-
prnoropropane-air,
pentane-sulfur
hexafluo-
Pentan
~
rie-air
and peintane-perfiuoromethiane-air
mix-
ture
aeicuded
in
figure
32 (147).
Data
by
-60
IBurgoyne
and
Williams-Leir
for hexane-methyl
-60
- 71
1bromnide-air
and hexane-Freon-12
I (F-12;
0.2 0.4 0.6
1 2 CF
2
Cl
2
)-air mixtures
have
been included in
PRESSURE,
atmospheres
figure 33.
These data
were
all obtained
in
1'%-inch-diameter
tubes.
An
investigation
of
FIGURE
27.-Effect of Pressure on Lower
Temperature flamm~biity
of hexane-methyl
bromide-air
Limits of
Flammability
of
Pentane, Ilexane, lleptane,
mixtures in a 4-inch tube
indicated that an in-
and ctan
in
r.crease
in
tube size
(from
17
%-inclies
to 4-inches-
ID) resulted
in a
narrowing
of the
flammable
TABLE
6.-Limits
of flammability
of
ethane
in range;
the
uipper
limit
decreased
from
7.5 to
ch.,o
ine
5.7 volume-percent.
n-hexane
vapor
in
air
while
the
lower
linmit
remained
constant.
The
(volume-percent) amount of methyl
bromide required for
extinc-
tion decreased
from
7.05
volume-percent
in the
Prsur,
Liis
Temperature,
C13a'-inch
tube
to
ti.0
volume-percent
in
the
4-
Pssure
Liis____
inch
tube.
However,
again
this is
not
in
line
25
100
200
with
the results
obtained
by
Hill
with
meth
vI
______ ____bromide-air
mixtures
(84).
Accordingly,
winkl
the data
obtained
in approximately
2-inch
tubes
9------------
{9wer--
6. 1 2.
5
2.5
'
eue
ocnsc
iue3,the
Hill data,
Lppe---
58 58
- - - -
100
---------
JLowr--
3.5
1
0
1
0 obtained
in
*t
larger
apparatus,
tire also
used
to
Ulpper_
__ 63
75
82
form
the approximate,
broken,
flammability
200
---------
Lower.------------- -------
-----------
curves
for
the
hiexane-inethyl
bromide-air
~Upper~.
-
(6 73
76 system.
______________________________
--
The
limits
of flammability
diagrams
for
the
systemi
n-hieptane-w.ater
vapor-air
tit 100'
and
position.
This
'oas been
done for
methane
2000 C (fig. 34)
show the
effects
of temperature
through hexane
(figs.
28-33).
C onmpositionis on
it systemi
that, pro~iuces
both
nornial anid
aire
determined directly
fromi
the
abscissas
(inert Cool
flu~nes
at
atm~osphieric
pressure
(192).
In-
conicent ration)
amnd orintes
(comnbust
ible
eonl- terestinigly
enough,
the
mininima
o
xygen
re-
centration-);
the
air in tany mixture is
thle
differ- quirernent
for flaine
propagation
(Mii
002 t
emice
between~ 100
percent and
the sum
of
inert
200-
C is thc
samie for the
(coo1
and
normnal
and
coinbuitible.
Data of
13urgoyne
amid
flame
regions
in this instance.
Further,
the
XWiIliainr-. Leir
for inethane-miethmyl
bromide
decrease
in zninimnuni
oxygen
requirements
(.MeBr)-air an~d
niethane-carbori tetrachlloride-
11 Trade
names
are
Used
for
leniificatiol (only; this
does
not imply
atir
mixtures
aire included
in figure
28
(29). endorseinent by
the
Bfureau
of
Wines.
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FLAMMABILITY
CHAP
ACTERISTICS
29
16
-1-
--
1
%air
=100%--% methane.-% inert
14
12
MeBr
U~10
CCI4
E
C02
Lj
Flammable
H0H
0
10
20
30
40
50
ADDED INERT,
volume-percent
FioUnt 28.
-Limits
of Flammability
of
Various
Methane-Irer,
'*ts.Air
Mixii rs
at
250
C
and
Atmospheric
Pressure.
(fromn 1:3.5±0.3
vourne-percent
tt
1000
C
to
extinction
(peak
values)
at 250
C
and
atmos-
12.8±0.3
volutre-pereent
kit,
200'
C) is wit'
in
pheric
pressure
tire about
28 and
42 volurne-
the range
predicted
by
the
miodified
Burgess-
percent,
respectively.
Ti.
7utio
of
these
values
Wheeler
law
(equation
35 and
fig. 231),
HIow-
is appro:,
,dtely inversel
y
proportional
to
the
ever, the
a~'iiable
data
ve14)'
o mear-r
ait ratio
of tfieii
nieat
capacities
at
the temnperature
present
to
permit at
realistic
evaluation
of
the
ait which
co .bustion
occurs.
Accordingly,
vaitidity of
this
latw,
genieralized
flammability
diagramns
of the
type
N'Spection
of
the liinit-of-flaniuability
curves
given
in
figure
35 can
be constructed
for
the
in
figures
28
to
33
reveals
that
c
cept
for
higher
Itydr
-arbons,
ignoring
Lhe presence
of
miethatn(
and
ethane,
Clio
miinium
amounts
Of
cool
flamies.
31uch
diagralms do
not appear to
carbon
dioxide
and
nitrogen
required
for
flame
be applicable
to
the
Maogenated
hydrocabons
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30
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND
VAPORS
14
%air
=100 -
ethane-%
inert
12
10-
-
E
Flammable
La
N2
z
6
4-
2-
0
10
20
30
40
50
ADDED
INERT,
volume-percent
FicUE
29.-Limits
of
Flammability
of
Ethane-Carbon
Dioxide-Air
and Ethane-Nitrogen-Air
Mixtures
at
25* C
and
Atmospheric
Pres8ire.
since these
materials
tend to
decompose
even
Similar
dtai
atre given
for ethane-carbon
in flames
of limnit-mixture
composition
and,
ats
dioxide-atir
(fig.
:37)
and
ethie-nitrogen-atir
noted,
may
themselves
propagate
flamne.
Cole-
(fig.
318)
(121),
andl for
propane-carbon
dlioxideC-
man
(37) hats
found
that
time
ratios
of the
peak
air (fig.
:19) and
propaine-nitrogen-air
(fig.
40)
values
of
a hialogenated
hydrocarbon
tire not
(122).
Miiii
oxygen
reqluiremuents
for
constant
but are
proportional
to the heats
of
flame
propagation
(inin
02)
through
natural
combustion
of
the combustibles
to which
the
gas-nitrogen-air,
ethane-nitrogen-alir,
and pro-
halogenated
ht'ydrocarbon
is
added.
Jpane-nitrogen-itir
att
atmospheric
and
elevated
Few
data
aire
available
for the
effects
of
pressures and
260
C
are
summarized
in figure
4
1.
pressure
on
the
limits
of flammability
of coin-
[he
inininmum
02
values
in
v'oluie-Vpi-rcent
b
ustible-inert-air
mixtures.
One
such
set
of are
related
to
pressure
ats
follows:
data
is sumnmairized
in figur
36,
which gives
the
limits
of flammability
of
natural gas
for
natural
gas:
(85
pct
nethane+15
pet ethane)
nitrogen-air
at
260 C and
0,
500,
1,000
and
2,000
psig
(106).
Miil.
02= 13.98-1.68
log P;,
(4:3)
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FLAMMABILITY
CHARACTERISTICS
31
10
air
=
100%-%
propane-%
inert
8
4,-
a)
)
6- Flammable
E
N2
mixtures
CL
0
0
2-
II
I I
0
10
20
30
40
50
ADDED
INERT,
volume-percent
FIouRE 30.-Limits
of Flammability
of Propane-Carbon
Dioxide-Air
and Propane-Nitrogen-Air
Mixtures at 250
C
and Atmospheric
Pressure.
for
ethane:
mixture
containing
80 volume-percent
methane,
15 volume-percent
ethane and 5
volume-percent
Min.
=12,60-.36
log
P;
and
(44) propane
has
a
lower
limit
in
air
at
250
C and
for
propane:
atmospheric
pressure
of:
Min.O=13.29-1.52
log
P;
(45)
100
v
where
I'
is the
initial
pressure
in
paia.
80
5
5
The lower
limit
of flammability
of
any
5.0+3.0
-
2.1
mixture
of
the paraffin
hydrocarbons
can
be
calculated
by
Le
Chatelier's
law (40,
12.9, 235): Liquid
mixtures can
be
treated
in the same way
if
tie relative escaping tendencies of the
various
300
",
components
are
known.
Since
the
paraffin
L
. _-
X-,
00
(46)
hydrocarbons
obey
Raoult's
law
(143),
the
I
I
partial
pressure
of
each
component
can
be
-
,
calculated
as
follows:
where
C, nd L, are
the
percentage
composition
p=paNj
(48)
and
lower
limit,
respectively,
of the
-tb om-
bustible
in the
mixture.
For example,
a
where p, s the
vapor
pressure
of
the i
'
com-
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32
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND VAPORS
10 - 1
%
air
=
100 -
butane-%
inert
8
6-
,N2
-.
E
Flammable
>
mixtures
z 4-
/Cst
C02
2-
SI
I
0
10
20
30
40
50
ADDED INERT,
volume-percent
FIGURE 31.-Limits
of Flammability
of Butane-Carbon
Dioxide-Air
and
Butane-Nitrogen-Air
Mixtures at
250
C
and Atmospheric
Pressure.
ponent in
the
blend,
po
is
the
vapor
pressure
Ashman
and
Biichler
(6),
and Kuchta,
Lam-
of
the
pure com ponent
and
N, is
its mole
biris,
and Zabetakis
(127). These
are not
fraction
in
the solution.
This
procedure
has
normally
used for
safety
purposes,
unless there
been used
to
calculate
the
lower
temperature
is some assurance
that
the contact
time of
limits
of
decane-dodecane
blends in air
(fig. 42). combustible
and
air is less
than
the
ignition
The vapor pressures
of
decane
and
dodecane
delay at
the temperature
of
the
hot
zone.
The
and the
calculated
low
temperature
limits
are
minimum
autoignition
temperature
(AIT)
is
given by
solid
lines
and four
experimental
usually
the quantity
of
interest
in
safety work,
values by
circles,
especially
when
combustible
and
air
can
remain
in contact
for an
indefinite
period.
Autoignition
Some
AIT
values for paraffin
hydrocarbons
in
air obtained by Setchkin in a 1-liter spherical
Two types
(,f
autoignition
data
are
obtained
Pyrex flask
(194) and
by Zabetakis,
Furno, and
depending
upon whether
the objective
is to
Jones in
a 200
cc
Pyrex
Erlenmeyer
flask
cause
or to
prevent
the ignition
of a
combustible
(237)
are given
in table
4. Interestingly
in
air. The first
type are usually
obtained at enough,
experiments
conducted
in
these and
high
temperatures,
where
the
ignition delay
is
other flasks generally
indicate
that flask
shape
relatively
short. Typical
of these are
the
data and
size
are
important
in determining
the
AIT.
of Mullins
(153), Brokaw
and Jackson
(15, 90),
The AIT data
obtained
in
the 200
ce flask
may
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FLAMMABILITY
CHARACTERISTICS
33
8
air
=100 -
n-pentane-%00
inert
7
6-
4-
0
3--N
z
L&J
0
10
20 30
40
50
ADDED
INERT, volume-percent
FIGURE
32.-Limits
of Flammability
of
Various n-Pentanc-Inert
Gas-Air
Mixtures at 250
C and Atmospheric
Pressure.
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34
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND VAPORS
8-11
air
= 1 0 0 % - %
n-hexane-%
inert
7
6
4-'
E
MeBr
zj
F-12
3-
C02
2N
117
0
10
20 30
40
50
ADDED INERT,
volume-percent
FIOURE
33.-Limits
of Flammability
of
Various n-I
Iexane-Iiiert
(ias-Air Mixtures
at
25 C
and Atmospheric
Pressure.
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FLAMMABILITY
CHARACTERISTICS
35
30
%air
=100 -
n-
heptane-%
water
25--
~20
E~c
\200'
C
Cool flame
z
5-
Normal
flame
1000 CCs
0
10
20
30
40
50
WATER
VAPOR,
volume-percent
FtouiE
34.-Limits
of
Flammability
of
n-llcptane-Water
Vnpor-Air
Mixtumres
at
1000
and
2000 C
and
Atmospheric
Pressu
re.
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36
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND VAPORS
4
F
I
1
1
%
air
=
100 -
combustible-%
inert
-,
E
.2_3
0
46
C
0
N2
Flammable
IJmixtures
Cst
0
C-,
L
0
10
20
30
40
50
ADDED
INERT, volume-percent
FIGuRE
35.-Approximate
Limits
of Flammability
of Higher
Paraffin
Hydrocarbons
(C.H
2
.+3,
n>5
n Carbon
Dioxide-Air
and Nitrogen-Air
Mixtures
at
230
C
and Atmospheric
Pressure.
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FLAMMABILITY
CH{ARACTERISTICS
37
%air =100%-% nitrogen-% natural
gas
56
1
4
w 4
2,000
psig
E
32 -100pi
U
500
psig
244
:D
Flammable
ZC
mixtures
Z 16-
Atm ospheric
8-
0
8 16 24
32
40
48 56
64
ADDED NITROGEN,
volume-percent
Fi' tiE 36.-Effect of Pressure on
Limits
of
Flammability
of Natural
Gans-Nitrogen-Air
Mixtures
at 260
C.
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38
FLAMMIABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND
VAPORS
56-
go air
=100% 0-% 0
ethane-%
00
O2
48-
40
900 psig
~32
R
500
psig
Ld
24-
250
psig
z
16-
8-
0
s 16 24
32
40
48
56
CARBON DIOXIDE,
volume-percent
IIG(LkL Ig.-L(1ect of
IPrcsiiri
oil
Ljimit-
of
Ihirnriinality of Ethancj-('nrbon Jioxio-Air Nhytire'. at 26' C
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FLAMMABILITY CH{ARACTERISTICS
39
561
0
ir
=100 7-10
ethane-%07
N
2
48
40
a)
900
psig
0
>24
z
w
16-
Atmospheric
8
0
8 16
24
32
40
48
56
ADDED
NITROGEN,
volume-percent
Fmumn.
3s".-
iI-rof I'russire
on
Limits of
FIaimability
of
Ethaict-Nitrogen-Air
Mixtures
at
26
'
C.
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40
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE GASES
AND
VAPORS
40
1
I
I
% air
=
100%-%
propane-%
C02
32
C
0)
9-24-
4)
E
>
200
psig
Ld
z
g
16-
100
psig
0
..,,,,,,.,.
At
mos phe ric
8
0
8 lb
24 32 40 48
CARBON DIOXIDE,
volume-percent
FIGuRE 39.-Effect of
Pressu.-c on Limits
of Flammability of Propane-Carbon
Dioxide-Air Mixtures.
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FLAMMABILITY CHARACTERISTICS 41
4U
[ I I I I
%
air
=
i00%-%
propane-%
N2
32-
24
d24
E
0
,/200
sig
L
S16 100 psig
0
,, I I I I I
0 8 16
24 32
40 48 56
ADDED NITROGEN, volume-percent
FIOURE 40.-Effect
of
Pressure on Limits
of Flammability
of
Propane-Nitrogen-Air Mixtures.
be
correlated with molecular
structure
by
length
as
abscissa
(fig.
43).
The
data
fall
into
p
lotting
them against the average
carbon
chain
two
regions-a
high-temperature region in
length defined as which the AIT is greater than 4000 Cand a
low temperature region in
which
the AIT
s
less
2 gjiN,
than
3000
C. These
regions
coincide
with
those
La~
(49)
of Mtilcahy
who
found
that oxidation
proceeds
Lay.-
4( -(4)) by one
of
two different mechanisms (162),
and
by Frank, Blackham, and
Swarts (60).
The
where g, is the number
of
possible
chains each
AIT
values of
combustibles in the first,
region
containing
N, carbon atoms and 31 is the
tIum-
are
normally
much more
sensitive
to the oxy-
her of methyl (--('113) groups. For example,
gen concentration of the oxidizing atmosphere
n-nonane and 2,2,3,3-tetraniethyl
pent e
each and to the spray injection pressure
than
are
the
have
9 carbon atoms, but
the former has 2 combustibles in the second
region.
Unfortu-
methyl
groups
and the
latter
ha 6.
The former nately, the available consistent
AIT data
about
has
only one
chain of 9 carbon
atoms
with
a
the effec's of oxygen
concentration and
in-
methyl group
on
each
eml, and the
latter
has
jection
pressure are too meager to permit a
LI maximnuni of
4
chains
with
:
carblon
at
oms,
8
detailed
comparison.
chains
witi 4
carbon
atoms,
and
3
chains with
5
The
physical processes
(206)
and
reactions
carbon at oms. Thus, n-nomanc has an average that lead to autoignition are
of
interest in any
chain length of
and 2,2,3,3-tei
ramnethvl detailed st uidy of
this ignition process.
Salooja
pentame has am average
of 3.9.
'The
more highly (18.J),
Terao (207),
Affens,
Johnson
and Carhart
branched
e combustible is, the higher its (1, 2), and others have studied the autoignition
ignition temperature
will
be.
.ininium auto-
of
various
hydrocarbons in an effort to deter-
ignition
temperatures of
20 paraflins were mine
the mechanisms
that lead to
the
ignition
plotted
as
ordinate against
the average
chain reaction.
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42
FLAMMABILITY CHARACTERISTICS OF COMBUSTIBLE GASES AND
VAPORS
4,000
2,000
1,000
800--
60 0
La 400-
1A
L
U'
200
-
U)
LiJ
in
0-
100
-
Natural
gas
80 Propane
0-
60-
40
Ethane
20-
10
I
6
8
10
12
14
OXYGEN, volume-percent
FIoURE
41.--Effect of Pressure on Minimum Oxygen Requirements for
Flame
Propagation Through
Natural Gas-
Nitrogen-Air, Ethane-Nitrogen-Air,
and
Propane.Nitrogen-Air Nlixtures
at 26'
C.
An
increase in pressure generally
decreases where T is the AIT at
in initial
pressure P, and
the
AlT
of
a .n If ustible in a
given
oxidant.
A and B are
constants. Accordingly,
the
& T
For
example,
the
AIT
of a nat
undl ga-; il
air
v'almes
obtained
at
atmospheric
pressure
should
decreased
front
530 (C at I atmosphere
to
240'
not
he
used
to
assess
ignition
hazards at high
(' at 610 atmospheres (9,000
psig) (7S). The pressures.
AIT's
of several hydrocarbons were
found to
obey
Semnenoiv's eq
uation
over
a
limited pressure
range
(248):
The burning velocities,
S.,
of
various hydro-
carbons
have
been measured
by
numerous
in-
P
A"
'
log
/
A
+B
(50)
vestigators
in air
and
other
oxidants
(68,
131).
At one atmosphere and
26'
C,
the
burning
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-P
FLAMMABILITY
CHARACXERISTIC13
43
TEMPERATURE,
0F
32 68
104
140 176
212 248
I
f I
t'O 101.32
CL
7_Flammable
1.05
6
E
E
E
Calculated,..
.79
_
W.,
.39
0
0-
Decane
.26
0
C
.5-
0 20 40
60
80
100 120
TEMPERATURE,
0C
FIGURE
42.-Low-Temperature
Limit of Flammability
of
Decane-Air, Dodecane-Air
and
Decane-Dodecane-Air
Mixtures
(Experimental
Points 0).
velocities
of paraffin hydrocarbons
in
air
range from
0.2 to
2 atmospheres
(fig. 47).
The effect
from
a few
centimeters
a
second
near the limits
of
temperature
is
more
consistent.
For
a
given
to about
45 cm/sec
near
the stoichiomietric
pressure
and
mixture composition,
an
increase
mixture
composition;
much higher
values
are
in temperature
raises
S..
In
general:
obtained
with paraffin
hydrocarbon-oxygen
miix-
tures. Figure
44
gives results
obtained by
(51)BT,
Gtibbs
and Calcote
for four
paraffin
hydrocar-
bon-air mixtures
at atmospheric
pressure
and
where
A
and
B
are
constants,
T is
the tempera-
roomi
iemperature
(68). The
datta are
ex- ture
and
n is; a constant
for a
particular
mixture
pressed
in t.?ris
of the
stoichio)letric
composi-
composition.
Dugger,
Heimel,
and
Weast
lion.
C,,;
burning
velocities aire
given
for the
(50,
51,
81) obtained
a value
of
2.0 for n for
composition
range
front
0.7
to
1.4 (',,.
These
some of
the paraffin
hydrocarbons
(fig.
48).
nut
hors hanve
presented1
similar
dtai for comn-
The
burning velocity
of the
stoichionietric
biistibles
ait
25'
and
100'
C.
Figure
45 gives
inethane-air
and
mietthane-oxygen
miixtures
given
results
ob~tained
by Singer, Giuner,
and Cook
in figures 44
and 45
(10 not,
agree
with the values
for
three paraffin
hydroearbon-oxygen
mnixt
ures
given
in
figures- 46
to 48
but, in each
catse,
the
ait at mospheric
p1
essure
and roolin
temperatuire
burning
velocity
data are internally
consistent.
'in thle range
from
0.3i
to 1 4 ( ,,
(198) .
Buirning
The
actualil flamle
speed
relative to
at fixed
x'elecities
range
front
t
low
of 125
('il/sec to
at
observer
maty
be much
greater than
S.
since
high
of 425
i/s&
; th~ese
vluies
aire coI sider-
the
burned
gases,
if not
vented,
will
expand
and
ably greater
thait those
obtainmed in
akir.
A
impart it
inot
ion
to~ thle
flamne zone.
If
detona-
chllge in
eithber
temperatuare
or
pre11suret will
t ion
occurs, thle
reacetioni
speed
increases
nmark-
ailter S,, for
at particulari
t
Pieor.exam ple,
edly.
For
example, figure
40
gives t hi
Kogarko
A~gnew aind (
iaifi
(3)
found
t
hat
an inicrease
in
data
oil velocities;
wit
li
which
at dot
onattiomi wave
Jpressure
caus~es S,,
of si
oichiioietri
n nlt
hane-air
piropagat es
t hroumgh various
miet hane-air
inix-
andl propatne-atir mixtuares
to~ decrease
in thle
t ares ait
atmnosphieric
pressure
iii a 310.5
CII-
pr.isim range
from
0.5 to 20 atimospheres
(fig.
diamieter
pipe
(12;5).
Similar
results hatve
been
46l))
S, of stoichioniet vie
nmetillne-uxygeii
mix-
obtained
b
y
(en:t
cim,
(C arlson,
and Hill
t low
tunes, however,
increasedi in the pressure
range
pressuires with
natural gas-air
mixtures (67).
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44
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND VAPORS
550
-CH
4
I
i
I
I
I
1
I
C
2
H
6
500-
C3
H
8
, o
---
-C-C
.-
.
9 C-C-C-C-C
6
96
m 400-
C-C-C-C.C
-
C-C-C-C
tC
C
-.
/~~-
z
6
n-C
4
H
1
0
1
z
350-
C
300-
z
n-C
5
H
12
C
n-C
2
/n-C10H22
250n
n-C
6
H
1 4
-
7.C H
1
8
n-CI
2
H
2 6
n-C16H34
n-CH
-
nC14H30
2001'
1
1
1
1
3
5
7
9
11
13
15
17
AVERAGE
CARBON
CHAIN
I ENGTH,
Lovg
FIGURE
43.-Minimum
Autoignition
I
rqnperaturc,
of Pi
"9flin Ifydrocart,
ijq ii
Air
as
a
Function
of Average
Carbon
Chin
oingth,
In each
case,
powerful
initiators
were
required
is
s,.
reait t'mt
pre.,
rq ,vaves
are
net
sent
ott
to obtain
a detonation
in relat,velv
large
ip'-.
ahea
of
the
:lctnati,,n
frwit
Thus,
pressure
Theenergyrequiremanausforignitioii
srere
ce,
detect
j- that
are
'sef
1 -1 e.\plosion
preven-
if oxygen
is
used
as
the oxidant
in
place
of air.
tion witi
loflagrati
i i'ovi
ire
useless with
Further,
the
detonation
velocity
incre
,s as
de 'fnatioj
the
oxygan
content of
the
atmosphere
in-
With
liqi
i fuels,,
t bthriiing
rote
depends
creased.
Detonation
velocities
,,tained
k
, r),rt
,i
tI
et P *r zktiol
,id
on
the
Morrison
for
methane,
ethane, propa;.i,
I,'itaie,
poI size
[3(;rges
Stia. er
itnd
("runer
(20)
and
hexane in
oxygen
are
given
in
Ifi
1
50 ,
.'0
siowi
that tho
liqu,
.. rcision
ate
'
Ls
(150);
similar data
obtained
by
Wayint,
tid
gi, by
Potter
are given
in
figure 51
for
n-hepLau.o-
v=v=( -e
,
(52)
nitrogen-white
fuming
nitric acid
. ipors
(219).
Of
principal
interest
ere is
the ii
gnitude
of wh.'r,
i
is
the vdue of
v _,l iargr
pour, IT
is
the
detonation
velocity;
even in air, ti
is
velocity
a
ca Aa.tt,
and
d is
the
pool
d;auetter
'iery
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FLAMMABILITY
CHARACTERISTICS
45
r-r-
.Ethane
40
-
,-/ /
n-Heptane-
.
\
Propane
E
30- /*'Methane
o/
20
10
0
_ I I
I
0.6
0.8 1.0
1.2 1.4
1.6
COMBUSTIBLE,
fraction of
stoichiometric
FIGuRE 44.--Burning
Velocities
of Miethane-,
Ethane-, Propane-,
and n-fleptane
Vapor-Air
Mixtures at
Atimos-
pheric
Pressure
and Room Temperature.
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46 FLAMMABIUTY CHARACTERISTICS
OF COMBUSTIBLE GASES AND VAPORS
5
0
0 - -
- T
I
I
I
I
1
I
450-
400
N" 350
E
0
300-
rpn
CD
z
250
200
150
100
1I
I
I
I
I
I
0
0.2
0.4 0.6 0.8
1.0
1.2
1.4 1.6
COMBUSTIBLE CONCENTRATION,
fraction of stoichiometric
J 'unIE 45.-Burning Velocitfi of N
ethane-,
E tha
,-,
niid
Propntrie-Oxygen Nfixtur..
tt
Atmo
t vhric
1Prvssurr
anOd
Room
"l'ipI
raturtv.
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mp
FLAMMABILITY
CHARACTERISTICS
47
_
50
- -T -
I I '
4o
-
E
30
Propane
020
zMethane-
106
10
0.2
0.4
0.6
1
2
4 6 10
20
40
PRESSURE,
atmospheres
FIGURE
46.-Variation
in
Burning Velocity
of Stoichiometric
Methane-Air
and Propane-Air
Mixtures
With
Pressure at
26"
C.
expressed
v_
as:
lower limits
of
flammabilit
of the
olefins
((Iv,) excluding
ethylene
fall in the
range
0 0076
(
net heat of
combustion,
AIh" from
46 to 48
ng combustible
vapor
per liter
- sensible heat
of vaporization,
Aif
of
air
(0.046 to
0.048 oz
combustible
vapor per
cubic
foot of air).
em/mai. (53)
The
effect
of
temperature
on
the
lower limit
Figure
52 gives a summary
of the r,, values
for
of flammability
of
ethvlene
in
air
at atmospieric
it
number
of
cojubustibles,
including
several
prsure.
assunilng
a
(onstant
limit flame
temperature,
is sh
own
by (he
curve labeled
p~araffin
hydlroarbos
(21). Of
special igiifi-
"U
pwird ropagation
of flane"
in
figure
53.
calce here
is tlat
Al J.All
is niearliv
cipnsti
t
1
ifirtunatlel,
ml
downward
Ilate
pro paga-
(about 100)
for
the
paraffin
liydrovarbons,
s
tion dt
art, available
over
an
extended
tern-
tliat their
linar
bitrnlinl[
rate,'
t
lre
. l
are
tir
l i per
ininrate
perat"ure
range
(2,22);
these are
included
in
figure
53. As
in the
case
of similar
data
ob-
tained
with inellane, tliese define a
straight
UNSATURATED
HYDROCARBONS
line
parilhl
tip t
ll'
(',,istant
flame
t:emipera-
,,,
)ur,
pward
pro
I
pagation
of
flari)'"
line.Again,
the nodifiel Burgess-Wiheler
law,
equation (33), give., a
variation
in lower
limit
Limits
in Air
with temperature
that
Is
('lose tip t
iot given
I)y
The iniecilar
weight,
.pecific gravity, iiid
t
he
( 'ntnt flauin
temiperature
line. so
that
1the.-
properties
of
tile
3I"rmlr'aimouin,
cosid- either u hel eI lit temllp)erat Uires
below tile
ered here ire
inluded
in' table
7.
At
roonm
AlT
(of
ethylere
(-|ttf)'
('. .I*,:,The
"
,
)as
tile
peniperat
ure
and atmospheric
pressure,
tit
lilnit Hlati'
te nperatniras
of
ohclins
are no
t
toot
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FLAM3ABILITY
CHARACTERISTICS
49
200
I
KEY
0
Methane
*
Propane
150-
o n
-eptane
A
iso-octane
0
100o
>
0A
z
S -,
0
+ 0.000342
r
2
z
a=50-0
ca
0
200
300
400
500
600
700
800
TEMPERATURE,
aK
FGuRz. 48.-Effect
of
Temperature
on Burning Velocities
of Four Paraffin Hydrocarbons in Air at Atmospheric
Pressure.
,000
-
3.000
1,500 0 2.500
01
00
EE
L
1,000
-
:
2,000
z
0
o
z
o
I
500-
-i
9
1,00
z
KEY
0A
Hexane
c1
1,000-
A
Butane
-
6
8
10 12 14
03 Propane
METHANE,
votume-percent
*
Ethane
0
Methane
F'ww
rip; 49
--
letoratiolt
Velocjtis of ),ttiume-kir 500
Mixtres at
Atiospheric I'ressuire. (Initintor:
50
70
0
10 20 30
40
grams
of
armitol exlloive.
Pipe diiietcr 30.5 er.)
COMBUSTIBLE,
volume percent
different
froin those
of p[araflili
hNI(II'(W1L1)orIs,
)etoyjti
Vejociiies of
\letrharl-,
he generalized
pralph fir
IL,,'L (fig.
23) (an 14- Ethanet*-, l'rolpar
e-,
Butane-,
ald Ilexrie-()xgr'l
used for these
un
iaturated
hydfocalbOmls.
Nlixture-
at
.itmospheric PtI.-.i.ure.
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50
FLAMMABILITY CIIARAC'rERISr01CS
OF COMBUSTIBLE
GASER AND)
VAPORIS
".001-
T
II
I
V 3
-Downward
proplagationl
9,400of
flame
E
2
Modified Burge'ss heeler Law
*WFNA
0
z~aUpward propagation
ui
2.000
- Constant flame temperature- of
flame
WFNA
N2
z(Mole
fraction N12
0.5)
i
0_
t~1,500--
0 ?l'0
400
600
800
1,000 i1200
oTEMPERATURE,
C
FIGURE 53.-Effect of
Temperature
on
Lower
Limit
of
1,000Flammability
of
Ethylene
in
Air
at Atmospheric
lOOC
I I
Pressure.
0
5
10
15
20
40
------
n-HEPTANE,
mole-percent
%air
=100 -
ethylene-%
inert
FIGURE
51.-Detonation Velocities
of
n-Heptane
Vapor-
in
WFNA
(White
Fuming
Nitric Acid)-Nitrogen
Gas
Mixtures
at
Atmospheric
P'ressure
and
400'
K.
30
1.42
1.0z
S.8 C41-11
0 10
20 30
40
50
\1
C61
1-O
ADDED INERT,
volume-percent
4
LNG
.6 - C 1-
0
-0 -Cg
6
,,
FIGURE
54.-Limits of Flamm~bility,
ef
-Hthylenie-
Carbon
1)ioxide-Air
anid Ethylene-Nitrogen-Air
Mixtures
at Atmnospheric
Pressure
and
26 C.
.4 UDMHO
-i
(100, 1101,
103), (figs.
154-60).
The
first two
figures
are modifications
of the limit-of-
.2 CT
flainniability
diagramns
given
in (.40);
the
third
C
C
0
is
essentilly
the
same
ITs
that
viven
in
the
earlier
Cf130H
Publication
hut include.,
the
experimental
points.
The
oither
curves
were
constructed1
0
50'
100 150
200
250
300 Irom
originail,
unpublished data
obtained
t
He
/N
Hthe
Explosives
Res.
Center, Federal
Bureau
of
Mines.
Firo;i 52-Relation
Between
Litrnid-Butrning Rate
Other liniit-of-flarnm-ability
determinations
(LarV
-
Pool Diameter)
and
Rtatio of Net
Heat
of
have been made in
oxygen
and
nitrous
oxide.
Comb -ltion to
Sensible
Heat
of Vaporization.
These
data are included in table
8
(40,
100,1007).
Limiis in
Other Atmospheres
Autoignition
Th~e limits
of flammability (if ethylene,
propy-
There
have
been few determinations
of
AIT's
lene,
isobutylene,
but
ene-
I, :3
methyl
butene-1I,
of the unsat
orated
liyplrocarbonus in air or
other
and butadienie in
various inert-air atniosphleres
oxidants;
the available data 9./j,
116,
191)
are
hii've
been determined
by
Jones and coworkers summarized in table 9.
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FLAMMABILITY
CHARACTERISTIC435
12
-1-
%air
= 1 00 % - %
propylene-%
Inert
10
-
E
Flammable
>6
mixtures
LAS
N
2
W
-j
a>,
IctCO
2
.42
2-
0
10
20
30
40
50
ADDED
INERT,
volume-percent
FI"ouRE
55-Lrnits
of Flammability
of
Propylene-Carbon
IDioxide-Air
and
Propylene-Nitrogen.
Air
Mixe
Ca t
Atmospheric
Pressure
and 26'
C.
itla
fill?-ina
rliiz,
110
'
I
tk
'-f
9i
.
lbustib
e,;
have
positive
heUL,
of
formiation,
The
burning
velocity
of
ethylene
has
been
AJI,
(table
10)
iunri
Would
therefore
it~erat-a
(leterinined
in air,
oxygen),
and
o)xygen-nitrogen
heat
if (iecomiposed
to
thle
elements
carbon
and
atmiospheres
by
numerous
investi
gators
(8,
7,
hydrogen.
Even
miore
heat
would
be
liber-
P/,
O'S,
131).
In
generatl,
it is
higher
than
the
ateol
if
gases
with
it negative
heat
of
for-
b
rning
velocities
of
the
paraffin
hydrocurbons nation
-~
or
example,
inetane-form
froin thleunder
the
samne
comiditionls
(fig.
47).
Simmnilar
elenments. In
practice,
at
mixture
of
products
results
tire
to Ibe
expectedl
for
other
unisaturatedl
results
ulpon
decoinposition
of
such
conibusti-
hydrocarbonis,
although
thie
available
datat
are
bles.
F~or
examlple,
at propagating
decompo-
rather
mneager.
sition
reaction
can
be
initiated
-ill
pure
ethylene
Stability
in
at 2-inch-iD
tube
at
230
C
an
dlpressures
as
low
as
750
psig,
using
2
gramso
guncottoll.
Many
unmsaturated
hydrocarbon
vapors
can
A reaction
can
lbe
initiated
at 2
1 'C
and
pro;;-
propagate
flame
in
the
absence
of air
at,
elevatedl
sures
ats low
as
975
psig
with
I grain
of
temperatures
and
pressures;
that
is,
they
have
guncotton.
'IFie
decomuposition
products
are
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52
FLAMMAB.LI'Y
CHARACTEREISTICS OF
COMBUSTIBLE
GASES AND VAPORS
80
.4-
N2
-
02
C02
Ljd
Flammable
Uj
mixtures
4-
0
10
20
ZG
40
50
ADDED
INERT, volume-percent
FIGURE 56.--Imits
of Flammability
of Iobutylfne-Carbon
Dioxide-Air
and
Irobutylen
-Nitrogon-Afr Mixturre at
Amosphcrio Prewure
and 26*
C.
TABLE 8.---Limit qfflammability
of unsaturate']
TAimL
0.-M.finimum
autoignition
temperatures
hydrocarbons
at atmospheric
pre
sure
and room
oj
unsaturated
hydrocarbons at
atmospheric
temperature,
in
2olume-percent combustible
prtssure
vapor
.......
Autoignition
temperature
In ai: In
oxygen In
nitrous
- .................
oxide Combustible In W'r In oaygen
ombustibleI
..
.
0
~
~
0
0
f
'C
F
Ref.
L
1
UIL
IU L
IU oC
0
F
Ref. -
°FRf
Ethylere
------- 2.
7 36 2. 9 80
1.9
40 Ethylene
---------
490
914 (116) 485
9
(116)
Fropylene
---- 2. 0 11 2.
1 53
1.4
29
Propylene
------- 458
156 (9) 423 793
(1)
Butene-i_-.-----
1.6 10 1.7
i
8 -----
.. Butene-l
--------
394
723 (I)
310
590 (1)
Butene-2-
-----
1.7
9.7
1.71 55
i
'3261Butene5
(1
)
1,2J•utadiene
418
784
(19
33
"
5
(
91)
I
Figures
oompiled by
Explosives es.
anter, Federal Bureau
ox
prinarily carbon, methane,
and hydrogen:
Mte.
approximately
30 Kcal are reieased per
iwole
of
ethylene decmposed.
Propylene yielded
si
i- Propadiene
and buiadiene also
decompose
lar
products followig explosive
decimposition
readily
under
the action of
powerful
igijitors.
during
compression
to 4,860 atmospheres
(34). Propadiene vapor
has beon decomposed
in a
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FLAMMAI3ILITY
CHARiACTERIBTICS
53
60
oxygen
100 -
isobutylene
-
water
vapor
50
2~Min 02
(1)40
16%
E
-5
030
a-
Flammable
m~ixtures
w
0
CC)
024060
80
100
WATER
VAPOR,
volume-percent
FIGURE
57.-Limits
of Flammability
of
Isobutylene-Water
Vapor-Oxygen
Mixture
at
150*
C
and
Atmosperie
Pressure.
~-,,wh
;1be
at 120'
C
an('
0 psig
using
a
ACETEN
ihl~hQCARBONS
piatir'umn
wire
ignitor.
Decomposition
of
buta-
(
R
diene
in
an
industrial
accidJent
resulted
in
a
itpopcorn"
polymer;
the
reaction
was
a
pparently
Af
initiated
by an
unstable peroxide
(.4).Lnt
i
i
TAHLE
lO.-Heats
ol formation
(Kcal/miole)
of
Acetylene
forms flammuble
mixtures
in
air
unsaturated
hydrocarbons
at
25'
C.
at atmospheric
pressure
and
250
C,
in a range
Combustible:
all/
from
2.5
to
100
volume-percent
acety'lene.
Acetylene
-----------------------------
~
4.
Quenched
and
apparatus
limited
upper
limits
Propadvne
-_-----------_--
45.
9
have
been obtained
in
1-,
and 2-,
and
3-inch-
1-3,
laetadjene.-
- ---------------
4,3
diameter
tubes
(40),
but pure
acetylene
can
1-,
thyene-----------------
----------
6.
propagate
flame
at
atmospheric
pressure
in
Propylene
--------------------------
---
~ 4.
tubes
with
diameters
of at
least
5
inches.
1-Butce
-----------------------------.
3
Sargent
has
summarized
availablo
data
on
I
Refs. (114,18P),
initial
pressure
requirements
for deflagration
and
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54
FLAMMABIITY
CHARACTERISTICS OF COMBUSTIBLE
GASES AND
VAPORS
10( 1 1 1
detonation
through acetylene
in
horizontal
air 100%-%
butene-I-%
Iner, tubes
of about .02
to 6 inches ID at
600 F. (89,
185). His curves
are
given
in figure 61, which
8 also
includes an
experimental point from
the
data of Jones and coworkers obtained
in a
.vertical
2-inch-diameter tube.
The
existence
N2
of
this
point,
at
a
pressure
below
that
given
by
Sargent's
curve
for a 2-inch
tube, indicates
that
E
C02
this curve should
be
used only for
horizontal
systems. The point labeled
"Industrial explo-
SFlar.am
bl
sion"
was
reported
by
Miller
and
Penny
144)
W 4
and presumably
refers
to
a deflagration. The
..j third experimental point is discussed,
along
with the
detonation curve,
in
the section
on
to
2-
stability.
21
The
effect of
temperature on the lower limit
of
flammability
was
determined
by
White
in
a
2.5-cm tube
with
downward propagation
of
Iflame
(2).
Although
the actual
limit
values
0 10
20
30
40
50
tire not
satisfactory for our purposes, they can
ADDED
INERT,
volume-percent
be
used to
check the
applicability
of the fL-/'2
5
ratio data
presented in figure 23. The
White
Fiouaz.
58.-Limits of Flammability
of
Butene-l- ratio
of
lower
limits at 3000
and 200 C.
is
Carbon
Dioxide-Air
and
Butene-l-.Nitrogen-Air
Mixtures
at
Atmospheric Pressure
and
260 C.
2.19/2.90=0.76; the corresponding
ratio
from
10 I
air
= l00%-%
3 methyl
butene.l-%
inert
8
43
0.
E
_6--N
FiGuRE 59.-Limits
of Flamma-
N2
bility
of
3
Methyl Butene-1-
"
L-
Carbon Dioxide-Air
and
3
z
Methyl-Butene-l-Nitrogen-Air
Mixtures at Atmospheric
Pre.
M
Flammable
sure and 260
C. 01 4-
mixtures
-2
10
20
30
40
50
ADDED INERT, volume.percent
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FLAMMABILiTY
CHARACTERISTICS
55
12
1
%
air
=
100 -
butadiene
-
inert
10I
E
FGuRE
60.-Limits
of Flamma-
.
bility
of
Butadiene-Carbon
>
6-
Dioxide-Air
and Butadiene-
Nitrogen-Air
Mixtures
at At-
z
Flammble
NZ
mospheric
Pressure and
260
C.
W
mixtures
t
C 0 2
24
SI
I
I
0
10
20
30
40
50
ADDED
INERT,
volurtie-percent
"Constant
flame
temperature"
curve in
figure
The quantities
of
propylene
required
to
23
is
0.78. Accordingly,,
this
figure
should
be
prevent
flame
propagation
through
methyl-
satisfactory
for use wit
i acetylene
at
tempera- acetylene-propadiene-propylene mixtures
at
tures
in
the range
from
20'
to
3006 C.
120' C and
50 and
100
psig
have been
deter-
The lower
limit
of flammability
of methyl-
mined
in
1-,
2-, 4-,
and
12-inch
tubes (fig. 62),
acetylene
(propyne)
in air
at'
atmospheric
and
at
120'
C and
100 psig
in
a
24-inch
sphere.
pressure
is 1.7
volume-percent,
equal
to
0.34 C,,
As noted,
the
propylene
requirements
are
which
compares
favorably
with
the
value
for
strongly
affected
by temperature,
pressure,
and
acetylene
(0.32
0,,).
Upper
limit
investiga-
container
size.
As the tube
diameter
increases,
tions
have
been
conducted
bv
Fitzgerald
(59)
the
quantity
of
propylene
required
to prevent
in a
2-inch
tube at
20'
and 1200
C to
determine
flame
propagation
increases;
this
effec,
is
less
the
low-pressure
limits
or lowest
pressures
at
pronounced
in
the
larger
vessels
(diameter
which
a flame
will propagate
through
methyl-
greater
than
4 inches)
than
in
the smaller
acetylene
vapor
at these
temperatures.
He
vessels
(diameter
less than
4
inches).
The
fouwd
these
to
be 50
and
30 psig
at
20'
and
results
obtained
in
the 24-inch
sphere
were
120' C,
respectively.
In
a
4-inch
tube,
Hall
similar
to those
in the
12-inch
tube.
and
Straker
(77)
obtained
a low-pressure
limit
of 43
psig
at.
20' C. This
indicates
that
the
Limits
in
Other
Atmospheres
upper
limit
of
flammability
of
methylacetylene
in
air
is
probably
less
than
100
percent
at
200
C
Gliwitzky
(71),
and
Jones and
coworkers
and
1
atmosphere.
determined
the
effects
of
carbon
dio.-ide
and
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56
FLAMMABILTY
CHARACTERISTICS
OF COMBUSTIBLE
GASEE
AND VAPORS
400
----
,
I
1
i
I
11I
200
-Deflagration
100-
80
C,,
60
CLJ
=
40
Sargent
20
0
Miller and
Penny
(Extrapolated)
0
Industrial
explosion
A Jones
and
others
10-
NN
0.02
0.04
0.06
0.1
0.2
0.4
0.6
1
2
4
6
10
DIAMETER,
inches
FiouRI
61.-Effect
of
Tube
Diameter
on
Initial
Pressure
Requirements
for
Propagation
of
Deflagration
and
Detonation
Through
Acetylene Gas.
nitrogen, on
the limits
of
acetylene
in
air
at
gel,
or charcoal
lowered
the pipe
temperature
atmospheric
pressure
and room
temperature.
required
for
ignition
to
a 280
°
to
300'
C range.
Unfortunately,
all
measurements
were made
in
The presence
of 1
gram of potassium
hydroxide
tubes
that were
too narrow
to
give
actual
upper
lowered
tile pipe temperature
still further
to
limit
data.
Nevertheless,
the
resulting
170'
C.
The impact
of
a 0.25-inch
steel
ball
quenched-limit
data are
summarized
in figure
falling
from
a
height
of 15
inches against
a
63,
because
they
show
the
relative
effects
of
fragment
of copper
acetylide
produced
a ho t
adding
two
inert diluents to- acetylene-air spot
that
ignited the surrounding
gaseous
acety-
mixtures
in
a 2-inch-ID
tube.
lene
at
room temperature
and
3
atmospheres.
Autoignition
Burning
Rate
A summary
of
available
autoignition
tem-
The
burning
velocity
data
for
acetylene
in
perature
data
for acetylene,
acetylene-air,
and
air
obtained
by Manton
and Milliken
at
1
acetylene-oxygen
mixtures
in clean
systems
is
atmosphere
and
room
temperature
are
given
in
given
in figure
64.
They are
based
on
measure-
figure
65
(158).
The
burning
velocity
ranges
ments
by
Jones
and
Miller
(110),
by Jones
and
from
a
low
of
a
few
centimeters
per
second
near
Kennedy
in quartz
tubes
(99),
and by
Miller
the
lower
limit to
a
high of about
160 cm/sec
and
Penny
in
a
0.5-inch
steel
pipe,
15 inches
on
the rich
side
of the
stoichiometric
composi-
long (14).
Jones
and Miller
found
minimum
tion. Parker
and
Wolfhard
(164)
have
found
autoignition
temperatures
of 3050
and
2960 C
considerable
variation
in
the burning
velocity
for a
variety
of
acetylene-air
and
acetylene-
of acetylene
in
various
oxidants.
The
burning
oxygen
mixtures,
respectively,
at
atmospheric
velocities
in stoichionetric
mixtures
with
oxy-
pressure.
Miller
and Penny
report
little
waria-
gen,
nitrous
oxide,
nitric oxide,
and
nitrogen
tion
in
the autoignition temperature
of
acety- tetroxide
were
found to
be
900, 160,
87,
and
135
lene
in a clean
pipe
at 4
to
26 atmospheres
initial
cm/sec,
respectively;
for comparison,
the
burn-
pressure.
However, the
presence
of
I gram
of ing
velocity
in
a stoichiometric
acetylene-air
powdered
rust,
scale,
kieselguhr,
alumina,
silica
mixture
(fig.
65)
is 130
cm/sec.
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FLAMNMAIILTTY
C'I IAltA(Tl.Ei1STICS
57
'000
,Z
\Flammable mixtures
-
12-inch-I D bomb,l0O
psi
2-inch-I D bomb,IO0psig
'\
\- 2-inch~-i
D
~~0
I~~-inch-ID
bomb,IO0psig \ \obs~i
00
90 80 70
60 50 4 00 1
PROPYLENE, volume- percent
FIGURE
62.-Itange
of
Flamnmable
Mixtures for Mc(thy-lacety.lene-Propadienc-Propylenie
System at
1200
C and at
50 an~d 100 Psig.
The burning
velocities of acetylene-air m1ix-
required for
propagation ait
subsonic
(deflagra-
lures
were found to ibe indlependcit, of
pressure tion) and
supersonic rotes
(detonation)
into
b~et ween 0.1 and
1.0 atmnosphlere (138).
Sint- the
unhurijod gats tire giveni for
ai range of pipe
ibrly, A
'new andt 'raiffl (3)
and Parker
andi~
(I. -41er.s
i ,
''',ure
61
(185).
D~eflagration
is
WVofhard 164~)
found
U'h,
1urninq, velocities LIscussed briefly
under
Liniits
of Flan-iniability;
of stoicliioietric,
acetylene-oxygen and1
acety- dletonatio
:s dfiscussed
in
this
section.
lene-nitrous oxide inixt tires wereo
independent (of The
cuirse labeled
''Detonation''
in
figure
p)ressure
bet ween approxiimately 0,5 and
2
61 gives thle iniimui pressure required
for
atmuospheires
and~
0.03 and
I
atniospliere,
re- propagation
(of
it (detonalt on,
once
initiated,
inl
spectively.
Th'le
b~urning
velocities
(if
st
ojchio- tuibes of
0.3 to
1(0
inches
(liv
ieter.
In
ipraw-
Inetric
1cctylene-mitiic ox'ide and( acetyliene- live, at (detonat
on inay be initiated directl
11i
rogen
let rt xide iiixtures incrca:~ed slightly
front it
defla
grittion t hat hias lpropaglited throu l
o vern
thiis pressurme
range
0.03 tot
I at mospier'e
at
rat,her
ill -definied distance,
know
itsi ts
(1
((.4).
pedletInait)
0n
or
run-up)
distanimce. This
us -
Stabfitytanlce
depends
ontc
itemneritutre, pressure.
tuhbe'
Staili~r
Ijittiieter,
conidition
iof tube
watls,
and onl
As noted,
iicetyleiie
canil
propagatte
fltiie inl igilit ion-s( urce
streligtbI.
Fori exampiJle,
using
the
absence
(if
air (39, 165). The
pressures
it fulsed p~itiiui
wir-e ignit(Ir, Miller
anid P~enny
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58 FLAMMABILITY CHARACTERISTICS
OF COMBUSTIBLE GASES
AND
VAPORS
100
144)
found the predetonation
distance for
%air
100%-%
acetylene-% Inert
acetylene in a
1-inch tube
to
be
t1
feet at
51.4
psia, 22 feet at
55.9
psia,
12
feet
ot
73.5
psia,
and
2.8
to
3.2 feet at 294 psia
initial
pressure.
80 Extrapolation
of
these
data
yields
the
point
in figure
61
for a very large predetonation
distance. This point (44 psia and1-inch
diam-
eter)
lies
fairly
close
to
the detonation curve
established
by Sargent
(185).
The
maximum
A,
lenth-to-diameter
ratios
LID)
given
by
Sargent
for establishing
detonation in
acetylene
is
9plotted
against
intial
pressure in
figure 66.
Z
In
tubes, Fa
vinga
diameter greater
than
those
40
-
given along
the
top
of the
figure and having
L
mixtures
powerful
ignitors, the
LID
ratio
will
be
less
than
that
given
by
the
curve. Nevertheless,
this
figure
should be
of use
in giving
the outer
20
N2bound
of
LID
and the approximate
quenching
C02
-
diameter;
a better
value
for
the quenching
est
diameter
can be
obtained
directly
from figure
~61.
Although
predetonation distances
are diffi-
o
20
40
80
cult
to
measure
and
experimental
data
often
ADDED
INERT,
voiurre-percent
exhibit
much
scatter,
they
are
of interest
in
safety
work because
they can
be used
to evalu-
FIUnt
63.-Quenched
Limits
of Flammability
of
ate
the
maximum
pressures
likely
to
occur
in
Acetylene-Carbon
Dioxide-Air
and Acetylene-
a system
due
to cascading
or
pressure
piling.
Nitrogen-Air
Mix~'rcs at Atmospheric Pressure and
- 'bis phenomenon
presents
a sp..-:-ial
problem
26' C, Obtained
in
a
2-Inch Tube.
because
the final
pressure achieved
in
a detona-
700
1 1
I
KEY
Oxidant
Pressure
Tube
* Air 1
atm
131
cc quartz
0 Air
1atm 200 cc
quartz
600-
.L
Air
2 atrm
200
cc
quartz
0 Oxygen 1atm 131
cc quartz
None 4-26 atm -inch steel pipe
500-
FiGURa
64-Minimumn
Autoigni-
z
tion Temperatures
of
Acety-
9
lene-Air and Acetylene-oxygen
mixtures at atmospheric and
Z
elevated pressures.
4 00
-
Region of autoigntion
300I-
200
0 20
40 60
80
100
ACETYLENE,
volume-percent
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FLAMMABILITY
CHARACTERISiTICS
59
2001g
to be expected
from
a detonAtion
is
about
50
times the initial pressure.
As the pre-sure
equalizes
at
the
speed of sound
in a deflrgra-
tion, the
maximum initial
pre3sure to
be
ex-
pected
upon tranisiticn from deflagration to
a
00
150-
detonation
is approximately
1i times
the
frac-
N.
tion
of acetylene
that
has
been
burned times
E
the initial
precombustion pressure.
Fifty
times
U
this pressure
is -.ho ap'proximate
maximum
pressure
that rould be
o ;ained
when a
detona-
-
tion occur-.
'.Lo illustrate this, Sargent has
3 100 r-plotted
the final-to-initial pressure ratio
(P,/Pj)
W
~against the
predetonation distance-to -tube
>
length
for acetylene.
A siniliar
graph
is
given
z/
in
figure
67.
To
use
this graph,
the maximum
z
redetonation distance
to
be expected must
-s
be deemndfo
figure 66. Tb.-n'z
maximum final-to-initial
pressure ratio.
____
_______ ____(C.H
2
.
,)
0
5
10
1s
LiMitS
inaAir
ACETYLEJE,
volume-percent
Fso.-s,
65.-Burning VnIocity
of
Acetylcnc-Air
Nfx
The combustibles
considered in
this section
tures at
Atmospl.cric k'ressurc and Room
Tempera- are
listed
in
table 11,
with
pertinent
properties.
ture.
At
atmospheric pressure
and room
temperature,
the lower limits of
flariimabilit
ofte
aromatic
tion depends
on the initial
pressure
at
the onset
hdoabn
arap
oately 50±2 mg/l
of
detonation.
F, r example, the
maximum
(0.050±
0.002
oz combtustible vapor
per
cubic
pressure
to be
expected
from
the deflagration foot
of
air).
of
Lcetylene
at moderatc pressures is
about 11
The
lower limit of
toluene
was
determined
times
the
initial
pressure (144);
the maximum
by
Zabetakis and coworkers
in air
at 300,
QUENCHING DIAMETER,
inches
012821
0.5
FIOURE 66.-Mlaxiimum LID ratio
.S
Rea uired for Transition
of a
Deflgration
to
a
Detonation
*:. 40-
in Acetylene Vapor
at
'*01
F C
and
from
10
to
70
Psia.
.
10
20 30
40
50
60
70
INITIAL PRESSURE.
psia
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60 FLAMMABILITY
CHARACTERISTICS OF COMBUSTIBLE GASES AND VAPORS
TABLE 1
1.-Properties
o selected
aromatic hydrocarbons
Lower limit
in
air ' Upper
limit
in air
I
C, in
net
Ali
.....
('ombustihlm
Formula
M
Sp gr air (vol /Kcal -
Wr )
pt volle
110
m
j00
L
o
I.. [Ii
PCtI pet)
Blzeee
('1,1 78.
11
2.,69)
2. 72
757.
5 1, 31
0. 48 47
7. 9
2. 9 300
"IhUe(_(
(...711,
92. 13
3.
is 2.27
101. 5 1.2
. 53
50 7.
1
3. 1 310
IE'thl
ihmnzene - ( e
116. 16 63.17 1.96
104s. 5 1. 1) 51 48 6.
7
3. 4 341)
omI-X'vn.
.... (l10
106.t 16 . 7 1.96
1045., 9 1. 1 56 53
6. 4 3.
3 320
rn-Xvmmmle
----- cjl
106.
1
:3.
67
1,96
1045.
5 1.- 1 .56 53 6. 4 3.
31
321)
p-Xl.n_--
C---- 106.
16 3. 67
1.96 1145.
7 1 1 56 53 6.
6
.
4
340
(IIinmI----------C
1 2
120. 19 4.
15
1.
72 111,.2 .8,8
.1
4S
6 5 3. 8 3170
p-Cym--en--.....--Co11,
4
134.21 4.63
1.
53 1341.8
. 85 56 51
t.5
3.6 350
I e.
147).
400 --
---.--------...
T .......
T
300
j
FiorRaE
67.--Final-lo-Initial
Pres
sunr Ratios
Decvvopied
y
Acet-
200
yeime With
I),olitiol
l1litim-
tion at Various Points Along
a
Tube.
100 ,--
0 0.2
0.4 0.6 0.8
1 0
PREDETONATION
DISTANCE/
TUBE LENGTH
1000,
and 200'
(i (235,
247); the varintion
in Their
values
rmiuge f'rin 8.8 percent (ctiinieiie
lower
limit with tonipertlikre
is
given
by eqaui- (80' (' aid
a) tii
pherie pres,.re)
(if 10.8 per-
tions (31)
and (33') derived
for parafflin h
'dro-
(,ett
ctiiniiei (I4i' ('
kiind 11) psig pressutire).
carbons,
aid the
vorresponding curves
of
filgure
23.
For
example,
jImp, rIL.3,
,. wits folund to he Limits
in
Other Atmospheres
1.07/1.24 or 0.86; the ratio predicted
by the
curve in figtire
23 is 0.87.
The
iniit ,,if flhininititilitl
,dtgiiumed hv ir.
Ihe
u )p(er litijts
of tie
irminiics
(iin.idered
g li.
(;29) mrid
lhv
r.
1
i
(.t[)) f
iur
zlmc'l-
here it
1000
(
nire inchded in t able
11 (270.
miirl)lml
di~xhNle-iir
and
eli?
'mi.-iitrmigeu-nuli
These
were
otlaiiied it
ntnisl)lierii'
fpreslr
mixilt
tires
at
tit
Iiimmli'n
jtreslilre
nllml
25
°
('
mie
iii it 2-incl-diwnietr
Itihe, oiin ait line eid. glixen
in
igtre
WS ; simiillir dall mire :ivlii
fir
Blier
nind
W~elbb
4lobtiL
ned
uppier
iliii nmiatit
i
he
last two Ililiires t 1it111,
m1hwric
pes~olrt
R
mtmilinrciil
grade
m'iieriv
(9;.1 prt
riiiet-e) 1i11ml I
1 ('
The iiertint rpqtltrm'liieit
tit
2i
;ii nir tit elevated
tenimer
ires
anm iiimmmtheic t
ire liprixhlihitek
lile
silmie 1 tihfse
if It-
milld 'el'vtted pressures
Ii
it
chim1ed
b1 111 (I. Ilexine
(fig. 33).
Agnili,
it sloi le
hi II
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FLAMMABILiTY CHARACTERXSTJCO
6
10.
.
......
%air =100 -97o
benzene
-
qV
inert
8
150
6,
25
>Ee~
z
4
Zi
r-W
N
0 10
20
30
40
50
ADDED
INERT, volume-percent
Fioiunw
6S.'--Limila of Flarnmabilitv
of Benzene-Methyl
Bromide-Air Mixttures
at 250 C and
Benzene.-Carbon
Dioxide-Air and
Bnzene-Ntrogen-Air Mixtures
at
250 and
1500 C
and
Atmospheric Pressure.
that
the methyl lbromide
datta aire
not
consistent
expressed
in mole-percent as in the
ori~ia
with
those obtained by
Hlill
(rompare figs. 28 presentation. 'Plur
system
has
no lower mit
an3), Tjhese
lattter
(lain
(80) were used
to,
mixtures,
as
a
flamie
can be
initiated
in hydrogen
construct.
thle approxitnate
(broken)
flaninma-
peroxide
vapors (186).
As a 90-weight-percent,
hility
curves
for
the
benzene-iriethyl bromide-
hydrog
en
peroxide was actually used
to
obtain
itir
system,.
these
flawinability
data, all
compositions
were
Tlhe decrease in
the
minimium oxyNgen
require-
cailculated
to)
yield values based
on a
10-cercent,
mnents
for flaine p~ropatgationi (fronti
14.2±+0.3 hydrogen per(')xidle co nten
t. This co~uld
be
done
vohiinw-percent
ait
250'
C to 1:3
1±013 volumve-
here
because
only three cemiponients
are
consid-
[)ere~ont ait 150t' in it carbon
dioxidle-air atnmrs- Pred.
Where
four
components aire considered,
phere;
fromt
1.4 ±0.3 voluine-jiercent at 250
the
flumnahiiity
6ata
can
be presented in a
C
to
10.1
-f.0.3
v'ohiine-percemit
fit
I
50,
in) at
tiiree-itnenginn
plot ; if
two
of
the
cornpo
-
initri
pgcm-air
tttJ11iO~jpher'e)
iS withilin(fhe
Irange mient
11
pear
in fixed proportions, at
triangular
predic
ted lv (flie miodified
ilurgess4-Whepeler plot (,an
Ce
used
wit It the two
compnets (for
lakw (equialion (05),
ig. 23).
exaniple,
90-weight.
Iercemit
hydrogen
peroxide)
Tlhe limlits
of 1f1ilnifilalitY of ort
Iioxvknle C40mnsid
ered ats
a sinigle c~npinemlt.
Such
a
((
df1
1
(('i,)
2
)-water-h'
dogemi peroxide hu-
plIot
is presented in figure
70
for
00-weight-
Iwres were dri crmined tit I54' C
and I
titimu14-
percent
hydroigen 1)eroxidle-4 rthoxyvilenie-forinic
l'ohere rs'weby Matrt
iiidill,
Lang, atid acid (HMUMO~) at 1540
C and
I 'atmnosphere.
4itbem skis
(1T).hle (lait
tire
pretiented
iii rhit; was
considered to) he atplane in
a
regular
it
triangular
plot.
in
figure
t19; emflposiionS
are
tetrahedIron
in
the original article and is there-
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62 FLAMMABMI1TY CHARACTERISTICS
ul,
COMBUSTIBLE
GASES
AND
VAPOUIS
100
0
80
20
Composition
line formed
with
82.6
mole
go wt )
H
2
0
2
600
200
2
oe eseo
g p d
Flammbble
mixtures
l
co
Decmpsitonof
hepeoxideloers
th
upe
eaadpr-oitos
epciey.T'
100
so
60
40
20
0
H202,
mole-percent
FimuRi
69.--Limits of
Fladsmabity of HiOrCH4 (CH3)rHO at 154i C
and
I
Atmosphere Prature.
fore
not
a regular
triangle.
As
before,
onl~y
an
-CHa
group
(24
1).
When
the
benzene
ring
upper
limit
curve
is given
because 90-weight- contains two side
groups, L, is determined
percent hydrogen peroxide is flammable.
In
first for the side
roup that yieds the largest
addition, a calculated curve based
on Le Chate-
average value and
d
o this is added
l,
,
or
lier's rule is given, as
is the upper liait curve
of
the average chain length of
the second
side
obtained with decomposed hydrogen peroxide group; (a,, and correspond to the ortho-,
Decomposition of
the
ide lowers
the
upper meta-, and
para-positions,
respectively). T-
limit appreciably
ane
o ields a system wLch
data
again fal into high- and low-temperature
has
a lower
limit of flammability
(not
deter-
regions (fig. 43).
mined in
this study).
Autoignition
Burning
Rate
Burning rates
and
detonation
velocities
of
The minimum
autoignition
temperatures
of
benzene in
air and
oxygen appear
to
be ap-
a series
of aromatic
hydrocarbons
in
air at proximately
the same
as those
of the
higher
atmospheric
pressure
are given
in
figure
71 as
paraffin hydrocarbons.
For
example,
the
re-
a
fntion oF
the correlation
parameter L
... sults
of
Golovina
and
lFyodorov
(211)
show
This parameter was
determined
by
use of that
the maximum
burning velocities of
benzene
equation
(49), treating the
benzene
ring as a in
nitrogen-oxygen mixtures
range from about
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FLAMMABILITY
CHARACTERISTICS
6
100
0
80
20
.60
4
00
Oxtdant;
ecompose
0
VaV100
100 so
60
40
20
0
90 weight-percent
H202. mole-percent
Fioun. 70-Limitaof
Flammability of 90-Weight-Paeent
IIOrCH#
.(CH3)rlICOOH
at 1540
C
and
I Atmnosphere
Pressure.
295
cm/sec
in oxygen
to 45
cm/sec
in
air;
the
table 12.
The lower
limits of flammability
in
maximum
burning velocities
of haxane in
air at atmospheric press
ire
and room
tempera-
various
nitrogen-oxygen
mixtures range
from
ture fall
in
the range
from 48 ±3mg/i
(.048
abouit
260
cm/sec
in oxygen to 40
cm/sec
in
±.003
oz combustible per
cubic foot of air).
air. Similarly,
Fraser (0 )
found
the maximum
By
volume,
this
is
equivalent to approximately
detonation
velocities
of
benzene
and
n-octane
0.55
02,,,
which
is
the
same
as
for
paraffini
iii
oxygen to
be 2,510 and
2,540 rn/see,
hydrocarbons. The
ratio of
the upper
limit
respectively,
to
C,, appears
to increase
with molecular
weight.
ALICYCLIC HYDROCARBONS
According
to Jones
(40),
the
lower limit
of
(CA.,,)
cyclohexane
in
air
at
atmospheric
pressure
and
260 C determined
in a 2.0-inch
tube is
1.26
Limita
in Air voluine-percent.
Under
thea
same
conditions,
Burgoyne
and
Neale
(26)
found the
lower
limit
A summary of
the pertinent properti&; of
to be 1.34 volume-percent,
using
a 2.5-inch
some of
the
members
of the series is
given
in
tube. Matson
and Dufour (141) found
the
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64 FlAML4DIITY
CHARACTER18TICS OF COMBUSTiBLE
GAGES AND
VAPORS
57-
-1
~~CH
2
CHH-H
ICH
a-wH
C
3
CCH3
02475
-
F-
0H
CH -CH-CH
3
S425
CH3-H
3
-H3-C
2
H
37
-
CH
375
1
C2H5
1
0
12
3
4 5
6
L
av g
Fiaunu
71.-Minimum Autoignition Temperatures of Aromatic Hydrocarbons
in
Air as
a
Function
of
Correlation
Parameter L.,..
TABLE
12.-Properties;of
selected
alicyclic
hydrocarbons
Net J....... limit In air Upper limit in air
S9 r, C.0
k.0l
Combustible Formula M (Au) inair
mole ) L. LM L U,, U
(Vol
pet)
(Vol * ~(mg) Ref. (vol Un
mg)
Rat,
pe)
T
pot)
C.,
C
corpn
------- Cas.. 4208 1.48 4.45 465 2,4 1
0.54
46 (107) 10.4
2.3 220
(107)
Cy lb(ae-
----
11. .- -----
.10
A'94
3.37 1'600 1,8 .5 46
(1) ---- - ---- -- -
C eoAnse_.-----
lo
--
I... - 70.13
2
42
2.72
740.8 1.'5
.M
48 (I)6
-i
C
coeae----
--
- (:11------
84.16
2.91 2.27
81. 7
1.
.6
7
49
(40)
-7.8
3.4
32
0
Eflif1eycobutane--
---
lhg. 84.
10
2. l
'2.27 MW) 1.2
.53
41
(40) 7.
7 3.4
310
(40
lower
limit
to
be
1.12
volume-percent,
tit
21'
C cordingly, the
data
of
Jones and
of Burgoyne
in
a 12-inch diamieter
chamber
about 15
inches and Neale
are used here.
long:
however, there
is
evidence
that
they did
not use
the same criteria
of flammability am did
Limits in
Other Atmospheres
the
other
authors; only
one
observation window
was
provided at
the to
p
of a
rather squatty The
limits
of flammability of
cyclopropane-
chamber,
whereas
with
the
glas's tubes used by
carbon dioxide-air, cyclopropaiie-nitrogen-air,
Jones
and
by Burgoyne and
Neole the flame and cyclopropanc-helium-air mixtures at
250
C~
could
be observed along the entire tube. Ac- and atmospheric
pressure
are given
in figure
LI
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FLAW&ADILITY
CHARACTERISTICS
0
%
air
100O%-% cyclopropane-%
inert
10-
E
FiGUaRE
72.-Liits
of
Flamma-
Flmae
bility
of
Cy
clopropane-
Carbon
Flmal
IDioxide-Air,
Cyclopropane-Ni-
U36 mixtures
trugen-Air,
and
Cyclopropane-
z
1Iihum-Air
Mixturcs
at 250
and Atniospheric Pressurc 0
-
01020 30
40
50
ADDED
INERT,
volume-percent
72
(106). The first two curves are
similar
to
ALICOHOLS
(0
5
H
2
.+
1
0H)
those
obtained
with
naraffin
hydrocarbons (fig.
35).LiisiAr
& ~~~Thp
imits of
flainmability of cyclopropane-LiisiAr
heliumn-oxygen and
cyclopropane-nitrous
oxide-
The alcohols considered here are listed
in
oxygen
mixtuires
at
25' C and atmospheric pres- table 13 together with L~s.
and
U
2
6.. The
sare
are
given
in
figure
731 (106). The
latter
ratios
Lzso/C., are
approximately
0,5. How-
clurvn diffctrs from
the
former,
as
both
additives ever,
the
L (mg/i) values
decrease
with increase
are oxidants
(oxygen
andl
nitrous oxide). in molecular
weight. If L* is
taken
to be the
The limits o
flammability
of
cyclopro
pane-
weight
of combustible material
(exclusive
of
the
lielirnt-ii~itrons
oxide
initires
at
25' C
and
oxygen in
the molecule)
per liter
of air, then
for
atinospherie.
pressure are
giren
in
figure
74 (106).
the
simple
alcohols:
Hlere
the
minimum
oxidant,
concentration
*LM-
16
(4
(nitrous
oxide)
required for
flame
propagation
L*~ M.(4
is
approximately twice the corresponding
con-
centration of oxygen in
the
systems
cyclo- This
eqkuation gives
the value,; listed in paren-
propane.-heliumi-air (fig.
7-2)
and ('yclopropane- theses in the mg/I coluimn; these are
in fair
helium-oxygen
(fig.
73).
agreement
with the
values obtained
for the
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66
FLAMMABILITY
CHARACTERISTICS OF COMBUSTIBLE
GASES AND VAPORS
--
p
n
eo2
corresponding
L*. from
figure
19
for
ethyl
oxygen
-
00c-%
lopropne-(
He,
or
N20)
alcohol
(M=-46)
is 2.2
volume-percent. Then,
from
equation (54), L is 3.4 volume-percent; the
50
-
iN
2
0
measured
value
is
3.3
volume-porcent.
The
lower
limits of
methyl alcohol
have been
determined
by
Scott
and
coworkars
at
25',
100',
and 2000
C (192).
The values
at
these three
40
temperatures are
6.7, 6.5, and 5.9 volume-per-
ent,
respectively.
rhe
calculated
values
ob-
tained
from
the
modified
Burgess-Wheeler
law
Flammable
He
(fig.
23) at
1000
and
2000
C
are
6.4
and
5.8
I3
mxtue
volme-percent,
respectively.
Limits
in
Other
Atmospheres
20-
C
5
1 (in
02
+ N
2
0)
The
limits
of flammability
of methyl
alcohol-
carbon dioxide-air and metnyl alcohol-nitrogen-
air mixtures at
atmospheric pressure and 25'
o
cal
(in 02
and
50'
C
are
given
in
figure
75;
flammability
determinations
on
mixtures
containing
more
I
than 15
percent methyl
alcohol
vapor
were
I
conducted
at
50
°
C. The
maximum amounts
S 20 40 60
1 of carbon
dioxide
and nitrogen required to
20 40 6o
s
loo prevent
flame
propagation in these inixtures
NITROGEN OR
NITROUS OXIDE,
volume-percent
40
FIGuRa
73.-Limits of
Flammability of Cyclopropane-
%
] =
i
t
Helium-Oxygen
and Cyclopropane-Nitrous
Oxide-
X air
100%-%
methyl
alcohol-%
inert
Oxygen
Mixtures
at
250
C and
Atmospheric Pressure.
40 I I35
N
2
0 = 100%-% cyclopropane-%
He
30-
30
V
\k
E2
Min N20
6= 25-\
21\ \
uz
20-
o
Flammable
>
20\
10
i
smixturesS
Flammable \ XSaturated
at
10
mixtures 25' C and 1 atm.
C s.CO
C02
10 -
0 20
40 60 80
HELIUM, volume-percent
FiGURE 74.-Limits
of
Flammability
of C clo ropane- 5
flelium-Nitrous
Oxide
Mixtures
at
250
JandAtmos-
pherio
Pressure.
saturated hydrocarbons.
Approximate L
(mg/
i 0
3 4
I)
values can be obtained
from
the
higher
DE10 20
30
40
50
hydrocarbon
values given
in
figure
22 by
ADDED
INERT, voiume-percent
multiplying these
by
the
ratio
M/(M-16).
Further,
figure
19
can be
used
to
obtain L*
and
FIGURE 75.-Limits
of Flammability
of Methyl Alcohol-
Carbon Dioxide-Air
and Methyl Alcohol-Nitrogen-
values
in
volume-percent.
For
example,
at
Air Mixtures
at
25*
C
and Atmospheric
Pressure.
250
C, L"
is about
47 mg/1 from figure 22; the (Broken
curve
at
500
C and
atmospheric pressure.)
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i
FLAMMABILITY
CHARACTERISTICS
67
TABLE
13.-Propertesoj 8elected simple akohols
Lower
limit
In
air Upper
limit In air
NetalHe
Combustible
Formula
Al (AirI
in
ai
jj uLu,
U
(Vol
pct)
(vol
. ,g Ref. (Vol
Ref
pet)
C.,
/
pct)
Methyl alcohol----- S.......H
_-- 82.04
1.11
12.25
IN1 8.7
0.65
1103
(40) '31 2.0 ,
f5
Ethyl
alcohol
.............
CH OH
........ 46.07
1.59 6.58
306
3.3 .5 70
(40)
'11
2.
9
1 )(086)
n-Propylalcohol ........
CHF
O- ........
60.09 2.07 4.48 448
'2.2
.49 1460
(40) 814
3.2
420 j (4
n-Butyi alcohol
--------- CiHoOH
....... 74.12 2. M 3.37
e
41.7 .50 87 I
(S) 412 -------------- ()
pri-n-Amyl
alcohol-...
C&IIIsOH
----- 83.15 3.04 2.72 742 '1.4
.51 {
VO (6)
10
.................
n.-..exyl
alcohol.-- ------ -
102.17
3.53
2.27
888 1.2 .53
............
t
L..
-
.
t-100
e
C.
M*Fgures compied
by
Explosivu Re. Center, Federal Bureau of
it60 .
Min
o.
t
saturation
temperature.
I Calculated
value.
were
compared with
the
corresponding
maxima
60
T
for
paraffin
hydrocarbons
(figs. 28-35);
it was
a r
-100%-%
methyl alcohol-
wa
\
found
that
appreciably
more inert
is required
to
make mixtures
containing methyl
alcohol non-
so
flammable. Conversely, methyl
alcohol
re-
400
C
quires less
oxygen
to form
flammable
mixtures,
2W C
at
a given temperature
and pressure, than
paraf-
40
fin hydrocarboni
do.
This may
be due in
part
to the
oxygen
of
the alcohol
molecule.
For the
-
simple
alcohols,
we
have:
30
C.H,,OH+
1.5nO
2
--
*nCO
3
+
(n
+
I )H
2
0.
(55)
C
20
-
Flamrmable
Thus, the
ratio
of oxygen
required
for complete
mixtures
combustion
of an
alcohol
to
that for complete
rz
combustion
of
the
corresponding
paraffin,
10
equation
(22), is:
(56)
0 L
20
30 40
5O
60
WATER
APOR,olume.percent
When
n--
1,
this
ratio is 0.75.
The correspond-
FIGURE
76.-Limits of
Flammability
of Methyl
Alcohol-
ing
ratios
of
the
experimental
minimum
oxygen Water
Vapor-Air
Mixtures
at 1000,
2000, and 4000
C
values
from figures
75 and
28 are 0.82
with
and Atmospheric
Pressure.
carbon
dioxide
and 0.85
with nitrogen
as inert.
The
limits
of
flammability of
methyl
alcohol-
ity data
for
the systems
tert-butyl alcohol-
water vapor-air
were
obtained
by Scott
(192)
carbon
dioxide-oxygen
and 2-ethylbutanol-
in a
2-inch-ID
cylindrical
tube
at 1000
and nitrogen-oxygen
are given
in figures
79-81.
200'
C
and in
a
'4.9-liter cylindrical
bomb at
4000 C and
I atmosphere
(fig.
76). Similar
Autoignition
data
were
obtained by
Dvorak
and Reiser
in a
2.2-liter
apparatus
at 1000 C (58).
The minimum
autoignition temperatures
in
The
limits of flammability
of
ethyi
alcohol-
air
and oxygen of
a number
of
alcohols at
carbon
dioxide-air
and ethyl
alcohol.nitrogen-
atmospheric
pressure
are given in
appendix
A.
air
mixtures
were
obtained
at
25'
C
and Comparison
of these values
with those
of
the
atmospheric,
or
one-half
atmosphere,
pressure
as
corresponding
paraffins (methyl
alcohol and
noted (fig.
77).
Additional
flammability
data,
methane;
ethyl alcohol
and
ethane,
etc.),
obtained
for ethyl
alcohol at
100'
C 'and
I shows
that the AlT
values
of the alcohols are
atmosphere
are given
in
figure
78. Flammabil-
generally lower.
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68 FLAMMABILITY
CHARACTrERISTICS
OF COMBUSTIBLE GIASES AND
VAPORS
15It
air
m
100%-%
ethyl alcohcl-%
Inr
air an
l00%-% alcohol-% water vapor
vkq"2-
'13.8%
10- Flammable8
Flammable
0
C02
mixtures
0 10 20
30L 40
so 8 s
ADDED INERT, volume-percent
_
Fiounia
77.-Limits
of Flammability
of Ethyl Alcohol-
0
Carbon Dioxide-Air
and
Ethyl
Alcohol-Nitrogen-Air
t
24
Mixtures
at
250
C
and
Atmospheric
Pressure.
P
(Broken curves at one-half atmosphere.)
251
III
air
-100%-%
ethyl
alcohol-%
water
0
10
20
30
40
WATER VAPOR, volume-percent
*20
Fioumz
79.-Limits
of Flammability
of
ter-Butyl
Alcohol-Water Vapor-Air Mixtures at
1500 C and
Atmospheric
Pressure.
E
iO
601
15Mi.3 oxygen 100
- 1\alcohol-% C02
50-
0
Flammable
nmlbe
0
400
WaX Vao-i
Mixure
at100CadAmop2i
5rsre
and
Cacote
or
rnge o
mixtue comositios
Alchol-Cros
Dixd-xge
itrs
t1 0
ate
apC;-the
mxmmturni
0
nveloispwereinctoshrcPrsue
fosutre
5.
n
14c/e
1
rsetvl
8.Thes
invesotiaos
o
otland
th
hlt
00
CRO
he
IDEximumves
were
72.
burning velocities
of methyl and n-propyl
alco- and
64.8
cm/sec, respectively.
These
values
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FLAMMtABILU/Y
CHARCTERISTICS
89
60
-----
40
T
"
I
ygsk'plt
a
le•i
tenoI-.%
n
%
air 100%-%
ether-%
Inert
Cool
flames
40-
t
20
0
2
30
5
400
0
FlammF
oble
8
- t
o\ a
i o
D m h
2Ner
.1mixtures
9.3%9
920-
C-st
ADDED
INERT,
volume-percent
10-
FiauaE
82.-imxits
of
Flammability
of
Dimethyl
Ether-
Carbon Dioxide-Air
and
Dimethyl
Ether-Nitrogen-
*Air
Mixtures
at
250
C
and Atmospheric
Pressure.
0 20
40 60
80
100
40 [ I
1
i
NITROGEN,
volume-percent
air
-
100%-%
ether-%
inrt
FiOuRs
81.-Limits
of Flammability
of
2-Ethyl-
§
butanol-Nitrogen-Oxygen
Mixtures
at
1500
C and
K
Atmospheric
Pressure.
4 30
Cool
flames
are
in fair
agreement
with
the
corresponding
-
values
of
the
paraffin
hydrocarbons.
Q:
The
methyl
alcohol
liquid-burning
rate ob-
20-
tained
from
equation
(53)
is in
fair agreement
a
with
that obtained
experimentalir
(fig.
52).
FlammbIe
N2
The
relatively
low AHeIL
JJ.
atios
.or
the alco-
mixtures
hols
indicates
that
they
should
be
characterized
o
C02
by
low-burning
rates
in large
pools.
t
ETHO
S (CUH,. , .OCAj)
0iit
1n0i
20
30
40
50
Liitsn
r
ADDED
INERT,
volume-percent
The
properties
of
a few
common
ethers
are
FIGURE
83.--Limits
of Flammability
of
Diethyl
Ether-
listed
in
table
14.
Unfortunately,
the
limits
Carbon
Dioxide-Air
and
Diethyl
Ether-Nitrogen-Air
data
show
appreciable
scatter,
so it
is
difficult
Mixtures
at 250
C
and
Atmospheric
Pressure.
to
establish
any
general
rules
with
the given
data.
However,
as
a first
approximation,
the
limit
of
the
cool
flame
region
in air
is
48.4 vol-
L/C,,
is about
0.5 for
the simple
ethers.
ume-percent,
according
to Burgoyne
and Neale
(26).
The
limits
of
the
systems
diethyl
ether-
Limits
in
Other
Atmosphereo
helium-oxygen
and
diethyl
ether-nitrous
oxide-
oxygen
are given
in figure
84
and
the
limits
of
Because
of
the
importance
of
ethers
as
anes-
diethyl
ether-helium-nitrous
oxide
are
given
in
thetics,
limits
of flammability
were
determined
figure
85
(106).
Again,
as with
the
alcohols,
in several
atmospheres.
The
limits
of
the sys-
more
inert
is needed
to assure
the
formation
of
tems dimethyl
ether-Freon-12 (CCI
2
F2)-air
nonflammable
mixtures
than
is
needed for
the
dimethyl
ether-carbon
dioxide-air,
and
dimethyl
corresponding
paraffin
hydrocarbons.
Also,
ether-nitrogen-air
obtained
by Jones
and
co-
cool
flames
are
encountered
at lower
tempera-
workers
are
given
in
figure
82
(114);
the
tures
and pressures.
limits
of
the
systems
diethyl
ether-carbon
di-
Comparison
of
curves
in
figures
84
and
85
oxide-air
and
diethyl
ether-nitrogen-air
are
shows
that
the
minimum
oxidant
requirement
given
in figure
83 (26,
166,
108),
Cool
flames
for the
formation
of
flammable
diethyl
ether-
exist
above
the upper
limit
as noted;
the
upper
helium-oxidant
mixtures
is
approximately
twice
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70
FLAMMABILITY CHARACTERISTICS
OF
COMBUSTIBLE
GASES AND
VAPORS
TABLE 14.-Properties
Of 8elected ethers
- -Lower
limit in aW Upper
limit ill
air
orml,
is
Ls
L
Tin
Us
Comba~lbeomula
M ~ (Vol pct)
moe
(vol
C. )
,\ elf. (vol
K)ig
Ref.
pet)
pet)
0
Dimetllyl
ether
........ C~igOCH
.... 4&.
07
1.
50 6.
83 0.16 3.4 0.562
{
7 1 1
4.1 760
(114)
Dletliyl
ether----------Cils-
74. 12 2.N6 3.37
608 1.9 . 56
(
4
40) g 6
11
1,880 (40)
Eth~yl propyl
ether---- CiHsOCa,, - 88.
8&15
3.
28 2.
72 5 760
1.7
.62
68
}
3.)
M0
(8)
Dl-t-propyi ether-....C~I1,OCI,?--102.17
3.53
2.27
'900 1.4
.87
1501 (40)
7.9 3.
291)
(40)
Dlvtnyl
ether----------...CillOCifla
...
70.00 2.42 4.02
31,770 1.7
.42 54 11)
2 6. 7
1,160 (97)
IVLM-16
I
Calculated
value.
V---
'cool
fiames: Ua.'>16
vol
pot.
'Cool
flsmes:
tVag-53
vol
pot.
I
Ref.
(165).
100
300%-
dity
ete-%H
o
2)3
%
02=
10%-%diehyl
he-
1
% e o N20
~
100 -
diethy
ether-% He
',
20
E
0
K
Flammable
Min
N20
E
6
wmixtures22
401
5
~N20
Csf~n
02+
N0)
HELUMvolume-percent
Csj in
2)
,,
FioTTasE
85.-Limits of
Flammability
of Diethyl
Ether-
-
Nitrous
Oxide-Helium
Mixtures at
250 C
and
At-
0
20
40 60
80 100
mospheric
Pressure.
HELIUM
OR NITROUS OXIDE, volume-percent
Fzouaai
84.-imits
of Flammability
of
Diethyl Ether-
Since
the ethers
tend
to formn peroxides
under
Helium-Oxygen
and
Diethyl Ether-Nitrou's Oxide-
a -variety
of conditions, they inay
appear
to be
Oxygen
Mixtures at 25' C and
Atmospheric
Pressure,
unstable
at
room
temperature (238).
as
great
with
nitrous
oxide
as
with
oxygen.ES
RS(n
n_0
C H . I
However, if
.1 mole of
nitrous oxide
furnishes
The properties
of
several
esters are listed in
one-half mole of
oxygen during
combustion,
table 15.
The ratio of the lower limit
at 25' C
then
the
minimum
oxygen contents in
the
two to the
stoichiometric
concentration is
about
0.55
cases
are otearly equa. Unfortunately, the
for many of these
compounds.
This
is tile
available
data are too meager
to
permit a more
same
ratio
as in equation (21) for
paraffin
detailed comparison,
hydrocarbons. The
lower
limit values
ex-
pressed in terms of
the
weight
of combustible
Autclinitioper
liter of
air (see section
about alcohols)
are
AuFistetdo
in
parei.these,3
under
L(mng/1).
These
ore
In genere.l, ethers
are
readily ignited
by
hot
larger
than
thle
corresponding
values
for the
surfaces. These
combustibles usually
hlave a hydrocarbons
and alcohols. The inert require-
lower ignition temperature
in
air and in
oxygen nients and minimum
oxygen
requirements
for
than
do the
corresponding
paraffin,;
and
the firs,.t member of
the series,
methyl
formate,
alcohols. The
available
at'toigraion
temipera-
tire neI4
rly
the
same as for mnethyl
alcohol and
ture
data are
included
in app-ndix
A. diniethyl' ether (figs.
76,
82,
86).
This is not
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FLAMMABILrITY CHARACTERISTICS
71
TABLE 15.-Properties
of
selected
esters
Lower
limit
in
air Upper
limit
in
ir
Sp.
gr.
C.,
Net ll,
(omlunstibh"
Formula
M
(Air-1) in air
cal
L2
&
L
U., [ U
(vol
pct) \i0
)(vol ( g Re. (vol (ng\
Ref.
pet)
I.T
pet)
\I
Methyl formate-...... II('OOCJI ... 60.05 2.07 9,48 219 5.0 0.53 142
1
(,,,) 23.0 2.4 800 t111)
Ethyl foruate. .........
|COO( ,ii
.... 4.08
2.
b0 5,65
307 2.8 .50 {
M (40)
16.0 2.8
630
(40)
n-Buty1 forniate ......... OOCI,n.....
102.13
3.53
3.12 2650
1.7
.M 1
7
(40)
8.2
2.6
410
(40)
Methyl acetoe-.........
CIICOOCIh, . 74.08
2,50
L.65 358 3.2 .57 (146
0) 16.0 2.8 630
(40)
Ethyl acetate
......... CICOOC11,..
88.10
3.04
4.02
504
2.2 .55 I M
(40)
11.0
510
(176)
n-Propyl acetato ......
CII3COOCsII?..
102.13 3.53
3.12
1650
1.6
.58
( 57
(40) 8.0
2.6
400 (40)
n-Butyl acetate ........
('1COOC4lt,..
116.16 4.01
2.55
...........
'14 .55 {73 (')
'8.0
3.1
450
(6)
n-Amyl acetate
.........
CIICOOC,1j .
130,18
4.50 2.16 ----
1.0 .51
1
40 5 ) '
7.1
3.3
440 (')
Methyl
proplonate
......
HCOOCIIs..
88.10 3.04
4.02
........
2.4
.60
7 (0)
13.0
'5.2
580 (40)
Ethyl propionate .......
C 11COOC,21.
102.13 3 53 3.12 2650
1.8 .58
(40) 11.0 3.5
510
4 ))
L-
LM
32
4
1=100 C.
M
L--
a
Figures
eompled
by Explosives Res.
Center, Federal Bureau
of Mines.
Calculated value.
6P-0.5 atm.
t=90'
C.
true of the othei' members
for which
data
The
autoignition
temperatures
of
many esters
compiled at
the
Explosives
Research
Center are in air and
oxygen
at
atmospheric
pressure are
avaialable--.isobutyl
formate and methyl acetate
given
in
appendix A.
In
general, the
AIT
(figs.
87, 88).
Accordingly,
it
is
rather
difficult values of
the esters are lower
than
are those
of
to
make additional
generalizations
for this series, the
corresponding paraffins.
25
-n1---
I
5% ir
= 100 -
methyl
formate-%
inert
20
FIGURE
86.-Limits of
Flamma- 0
F
bility
of
Methyl
Formate-Carbon
F
Dioxide-Air and
Methyl Formate-
W
mixtures
Nitrogen-Air Mixtures.
5-
0
10
20
30
40
50
ADDED INERT,
volume-percent
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FLAMMABWLITY
niiRACTXHISTIC3
or
COMBUSTIBLE
GAOVI
AND
VAPORA
10T
air
m
100 -
isobutyl
formate
aH
81
C0 2
Fioun.
87.--LUmite
of
Flimrabfl-
tj
Flammable
N2
ity
of Isobutyl Formato'-Carbon
C
mixtures
Dioldde-Air
and lonbutyl
For-
a
ia 4eNltrogn-.AIr
Mixtures.
0
4&¥
0
10
20
30 40
50
ADDED
INERT, volume-percent
20T
""I
air
100%,-%
methyl
acetate-%
inert
U 10-
Flammable
Fsolua 88.-ALmlit
o
Flamnmabil-
t
M2
Ity
of
Methyl
Aoetate-Carbon
t
mixtures
Dioxide-Air
and Methyl
Aoetate-
Nitrogen-Air Mixture. -j
C C0
0
10
20 30 40
50
ADDED
INERT,
volume-percent
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IP
FLAMMABILITY
CHIARACTERISTICS 73
20~ ~n-
I~- --
i - ------- r r~
____
Flammable
mixtures
E
70.5
mole
MEK +
29.5
mole %u
oene
0
C')
AtmospericiPessure
Fgive
i tablEe 1.Thto
of
eprte Lower
Limits
on,
amity sown -tat
he sytues
MnEK-
atDHY
E
50
KEO E (C.
irOimi
he s1ici0n-ri
Ccpstoosen
hd THFo
en
oe vlueChitler
is
approximately
0.5.
law,
equation
(46).
Calculated
and
experi-
Zabe
takis, Cooper,
and Furno found
that
the mental values for the
preceding systems in air
lower
limits
of
wethyl ethyl
ketone (MEK) and are iven
in figures 91
and
92.
MEK-toluene
mixtures
vary
linearly with Te
limitsoth systems acetone-carboD
temperature
between room
temperature
and
dioxide-air,
acetone-nitrogen-air,
MEK-chlorc-
20
0
C (36.
A summary of these data is bromomethane (CBM)
-air,
MEK-carbon
di-
given in
figure 89;
broken curves in
this
figure
oxide-air,
and MEK-nitrogen-air are given
in
were
obtained
from the modified
Burgess-
figures
93
and
94. The data
in
these ftgurcs
Wheeler law, equation (33),
taking the lower
were
obtained by Jones and
coworkers
(2588).
TABLE I
6.-Pro ertim
of
8e.ected aldehydes
and kcet ones
NLA.
Lower
limit
lo
air
Upper
limit
In
air
Combustible Formula
Ai (Ag - 1)
inA
i
14
LIDU U
mole)
(
IL
)
.
U
Vol
pet)
(Vol
E/g\
Ref. (voi C,,
/f-g\ Rof.
pet)
'kJ
pet) k.
Aretaldehyde..........
.I1aCIIO.
. 44.051
L.62 7.73 264 4 0
0.52 82 (M9) ' 36
4.7
1,100
(961)
Pmopionuidehyde. .-
CS1tCHO. . &S.
8
2.01 497
409 2.9
.69
7
(9)
*14 2.8 420 (96)
1'mraidehy~de
.... (CIIiCHO)s,_.132.16
4. 8 2.72 .. 1.3
.49 78
40)_ j
_i
Acetone
(lC I, 8.08 2.01
4.97 403
2.6
.52
70
(98) Ii
2.6
Niethyl ethyl
ketone. C 113CC
.
,c-
72.10 2,49 3 67 648 1.9 .52 62 (U3) 10
2.7 360 (19#3
hiethyl
prcpyl
ketone M.sC~I 813 2.97 2.90 692
1.6 .55
63
40) 8.2 2.8 340 40,
a(011CCVI PA.13 2.'J
2 90 592 I'6
.65
63
(1)
- . .
Nfethyl butyl ketone
CII,3COC,1it
100.16
3 4A
2,40 840 '1. 4
.58 64
40)
'8.0
3.3
390
(40)
ICool
flameL:
U-f0
Vol
pet.
' Cool Barnes:
Via-17
vol pot.
I CalculatA~
t'Clue.
*f-60 C.
I 100 C.
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74
A
1
A
~
~
cR
CVT~
1
I
S
M
S
CO
USSTI
L
r,
G
X~
VI
ND
VA
?O
BS
2.0
Flammable
Mixt'Ures
THE
GD
1.8
6
70.5
mote-%
HE+
29.5
mo~e%
toluen~e
'14
35.6
mol%
~l-lV
*
6
.4m
%
oluenle
00
204
1.2U
0
40
60IA
.
EMP~ailt
of
T
Fo
ue
n
MlitureB
in
Air
at
T
h
eec
ati
T
r
r
P
e
r
t
e
s
o
v
a
i
u
Sfi
L
S
A
N
D
n
m
L
E
O
de
und
'kili
u
no
onrd
i
teme
rtre
s
of
endIO
.
Fuis
used
for
not
co
eed
aatigpOiS
lowe
an
inad
d
here(tble1
aldehy
~
~
a5ueaeg~e
ln
those
t
e
nIaae
O
P
at
os
hei
vr
lues
are
low
r
at
e
e
t~
f5
r
of
r-1
h
'-
para
us.
A
m
o
iy
n
,(
I
)
~
.'
a
of
sulfu
copud
adusnlren
pCflb0
4
,I7
This
theytyl
avei
T
h
eM
n
d
I
S
e
rzin
e
(
N2')
'
m
o
n
arerie
give
nfu
apo
zse
N,9
di
mNle
A)ti
en
I
aegni-
theoyi
formCS)S
lammable
ixtuire
s
es
ppae
1
,
g
l
i
,
,l
o
carb
o
n
an
o
h
r
M
.
i
a
v
r
I
o
f
co
lcen
tr
ia
a
n
tab~t
A8
nedr
water
ti
o
f,
Vht
e
and
an
lv
r
n
e
ase
xi
at
s
in
.
a
n
i
ncae
n
wide
el
am
uerp
en
i
-.
fr
carboan
an
o
ra
.
doa
be
19
N
~
widn
disk
d~
~%
m
r
a
d
a
r'
aon
O
v
n
ton
a
noted
in
t
a
n,
us
,(1) re
o
Fl
ar
n
s
4
with
car
bo
4dair
f
9
5)
that
Fue
-
..
hy
r
crbo
s
r,1 ie
s
vicarbo
nl
iodfor
in
t
an
d
roge
7)fi
e-
(lor
g*an
ethe
rfa
m
b
e
~
t
fa
l
em
F
rt
er
r
iniia
d]
meeapanwit
horl
,,
(17
(fg.
7)
thet
trie
1
ne
raige.
axrre
in
with
chlo
inar
,Eich
O%
j
oet
an
e
n
h
t
it
shows
not
press
t
a
h
In
e
us
n
wth
erfoun
qguof
car11bon
disulfd
e
essentially
c
th
'a2.
larnt
l
rang
fcr.ie
topetthe
guatj:e
of
inert
requr
teperature.
t~~
o
p
r
e
e
n
T
A
L
t
1
7
.
-
P
r
O
P
e
"
6
oJ
.e
e
c e
d
s
n
jflr
v
n
~
n
d
p
e
o
i
-
P
-3
0213
231
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FLAMMABILM'
Y' CIHARACTERISTICS
75
2.0-r-------
--- -
0
Experimental
points
1.8
-
Calculated
300C
0
9.
0
Flammable
mixtures
E
~1.6-
0
CL
LU
0
0
20
4
08
0
MEK, mole-percent
FioUREI
91.-Effect
of
Liquid
Composition
on Lower
Limits of Flammability of
MIEK-Toluene Mixture-s
in
Air
at 300
and 2000 C.
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76
FLAMMABILITY
CHARACTERISTICS OF COMBUSTIBLE GASES AND VAPORS
2.0
I
0 Experimental
points
-
Calculated
Flammable mixtures
E0
~1.6-
0
U0
~1.4-
C,,
1.0
0 20 40 60
8 0
THF,
mole-percent
Fioug,
92.-Effect
of Liquid
Composition on
Lower Limits of Flammability
of THF-Toluexte
Mixtures
in Air
at
300
and 2000
C.
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FLAMMABILY CLARACTERISTICS 77
14
1 f
a
ir -
100 - acetone-% inert
12
10
a-
E
.-
Flammable
Fiovas
9&.-Limita of
Flammabil-
mixtures
N2 ity
of
Aoetone-Carbon
Dioxide-
ti
Air
and Aeetone-Nitrogen-Air
z
Mixtures.
Cs,, C02
4-
-
2 I
0 10 20 30
40
50
ADDED INERT,
volume-percent
TABLE
18.-Properties
of
selected fue. and
uel blend.
Not Aem limit In air Upper limit
In
air
I ., /
.8a
Combustible
Formula AV (22i) iNCS AH -MOWG -aLu-U
(oPa)(Vol
C
I (o
~
( j\ Ia
Pet)
IS
pot)19'
Ammonia
------------.-.-- --..- 7..
7.08 0.0 21.58
..........
1
0.0 134
(16, 2 1.8
800
(181)
Hydrasine
............... N-.-'".- 2 06 I 17.32- ......... 4.7 .27 70 -880- .3 (...
?eonomtyl b draem NuCi.:: 46.07
1.:80 7.73------4 .82
so
(18)_ ----5'.
Unspunmetrl
NH*(CHs)s. 60.10
2 OR 4.07..... .2 .40 .6 10.1....
onmtylyn
ln..
N E
a....4 0
.0i
??
.....
mn ........
Ddioa...
..........
......
.27.09
...
88
478 .8
.12 10
(11
8.
1..I ........ 16)
Tetra
..........
.....
.
1 4
&
7
4 1........
----
0----
Pentaborane ........... B
...........
17
2,18
8 308 .
.12
12
............
Deosorae........Da.u . 12.: 4.2 ..--------- 2 .11
It
I
............. U ..... ..... . 7 2 ............. ........ ........
viation
Be
P-
... .............................
(141)....38
Aviation
letuel
.1P-I
........................
............
...........
1.4............. 1
71
-
viation etfuelJ P-4....
.1.2
.........
.
?
8 .
Aviation
jet tuel J P-4.........................-.---..-............,......
... .. .
Aydron .............
Ht
............
2.0
0 298
87.3
4.--
---
8. (40)
7
.84
270.
Calculated
value. I-u100. 0.
't-30
0.
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Fp
FLAMMABILITY
CHARACTERISTICS
79
507
20-
1
air
-
100%-%
carbon
disulfide-%
Inert
air
=
100 -
ethyl
mcrcaptan-%
inert
40 - 1
SF-22
(CH
CI
172)
6..
CHcCl 172)
3
0
\o
I-
Flammable
ixtures
=
Flammable
\
M
0
mixtures
min
02
C
10-
C0 2
0
5
10
15
20
ADDED
INERT,
volume-percent
Fioumm
97.-Limits
of
Flammability
of Ethyl
Mereap-
0
20
40
60
80
tan-F-12-Air
and
Ethyl Mercaptan-F-22-Air
Mixtures
ADDED
INERT,
volume.percent
at Atmospheric
Pressure
and
270
C.
FiouRE
95.-Limits
of
Flammability
of
Carbon
Disul-
mixture
NO
2
*-NO
2
NO
4
)
is
given
in
figure
fide-Carbon
Dioxide-Air,
Carbon
Dioxide-Nitrogen-
100;
short
horizontal
lines
indicate
th
un-
Air
Mixtures
at
250 C
and
Atmospheric
Pressure,
and
Carbon
Disulfide-Water
Vapor-Air
at
1000
C and
certainty
in
N0
2
*
concentrations.
These
ma-
Atmospheric
Pressure.
terials
may
ignite
spontaneously
at
room
temperature
with
relatively
small
NO
2
* con-
50
1
centrations
in the air;
at 250
C,
liquid
UDMH
%
air 1009-%
hydrogen
sulfid. -
C02
ignites
in
N02*-air
atmospheres
that
contain
more
than
about
8 volume-percent
NOa*;
MM H
I
and
hydrazine
ignite
in
atmospheres
that
contain
more
than
about
11
and
14 volume-
40-
-
percent
NO
2
*,
respectively.
In
general,
even
smaller
concentrations
of
N0
2
* produce
spon-
taneous
ignition
of
these
combustibles
at
higher
initial
combustible
liquid
temperatures.
30--
Mi
02
The
effect
of
the
hydrazine
liquid
temperature
11.6%
on
the
spontaneous
ignition
temperature
in
*
,
NO
2
*-airatmospheres
is
illustrated
in
figure
101.
0_
Similar
data
are
given
in
figures
102
and
103
Flammable
Flmmatue
for
MMH
and
UDMH;
there
is an
apparent
' 20
mixtures
Zanomal*
in
the
data obtained
with
ivi1il at
36
55
,
and 67'
C.
0=
0
The
use
of
various
helium-oxygen
atmos-
pheres
in place of
air results
in the spontaneous
S10-
Igniton temperature
curves
given
in
figure
104
for
UDMH.
Comparison
of
curve
B
of
this
set
with
curve A
of
figure 100
indicates
that the
spontaneous
ignition
temperature
of
UDMH
in
S
I
I
NO
2
*-He-O.
atmospheres
is
the
same
as
that
0
10
20
30
40
obtained
in
N
2
-air
atmospheres.
Ignition
temperature
data
obtained
with
ARBON
DIOXIDE,
volumepercent
tTDMH
in NO
2
*-air
mixtures
at
15
and
45
psia
FIwRE
96.--Limits
of Flammability
of Hydrogen
Sul-
are
summarized
in
figure
105.
These
indicate
fide-Carbon
I)ioxide-Air
Mixtures
at
25'
C and
that
although
the
spontaneous
ignition
tem-
Atmospheric
Pressure.
perature
of
UDMII
in
air
is
not
affected
ap-
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80
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND VAPORS
760
1
1
1
100
600
-Ammonia
Upper
-78.9
- ~limit
400-
-DH52.6
E
E 200 -Flammable-
26.3
E
-d Cs,
mixtures 0
Flovitz
9S.-ljznits
of
FlamIna-
CO 100:
1.
t
7
of Ammonia
UD MH, CO0.
MMIH,
and Hydrazine
at At-
W8
o
niOSPheric Presaure
in Saturated
cr
and
Near-Saturated
vapor.Akr
0.
60
Cst
-7.9
>
ixtures.
C
51
-
w
40-
Lower
-5.
Jt
-limit
-
I~
20-
Hydrazine
-2.6 2
0
MMH
10L
1.
150O
-100 -50
0
50
100
150
200
TEMPERATURE,
OC
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FLAMMABILITY
CHARACTERISTICS
81
100
10
90
20
0
0
0
30
0
00
70
%30
4000
60o
0KEY
mFlammable
50 mixtures
50
016
8
0
4
60
4
X
70
30
0
KEY
80 ~0 Flammable 2
HEPTANE-VAPOR,
volume-percent
F URN99.-oFlammable
Mixture
Compositions of
20ydrazine-Heptane-Air
t 125* C
and
Approximately
Atmospheric
Pressure.
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82 FLAMMABILITY
CHARACTP.RISTICS
OF
COMBUSTIBLE
GASES AN) VAPORS
300
I
Boron
Hydrides
This
series
includes diborane
(B2H,), tetra-
a
UOMH borane
(B
4
Ho),
pentaborane
(B '),
and deca-
b MMH
borane (B
1
oH
4
).
However,
reliable
tipper
and
c
Hydrazine lower
limit
data
are available only
on the first
250
member of this series
at the present time.
These were obtained
by
Parker
and Wclfhard
168)
who
determined the
limits of flammability
of
diborane in air in
a 5-cm-diameter tube at
an
initial
pressure of 300 mm
Hg;
this
combustible
200
forms flammable
mixtures
in air in the
range
Region of
spontaneous
ignition
from 0.8 to
87.5
volume-percent.
A pale blue
egogflame
propagated throughout
the
tube
at, the
upper limit;
luminous iltmes were not
visible
above 79 volume-perccnt. Limit
of flamma-
bility
curves for the system
diborrnie-ethane-air
S150
are presented in rectangular
coordinates
in
figure
107.
Except for the slight dip to the
ethine-
axis (zero diborane)
in
the
area in which ethane
forms
flammable
mixtures
in air, these curves
E
are
rather
similar to those
obtained
with
other
100.
combustible-oxidant-inert
systems. Burning
velocities in excess of
500 cm/sec were
measured
in
this
same
study for fuel-rich diborane-air
mixtures.
Berl and
Renich have
prepared
a summary
report
about boron
hydrides
(9). It
includes
50 -data
obtained by these
and
other
authors; they
a
h
C
25*
C
found
the
lower
limit
of
pentaborane
in
air to
be 0.42
volume-percent.
The
autoignition temperature
of diborane in
Dew
point line
of NO* air
is
apparently
quite low.
Price
obtained
a
0
-
value
of
135'
C at
16.1
mm
Hg (169); that
of
pentaborane is 30'
C at about
8
mm
Hg
(9).
0
5
10
is
20
25 30
Gasolines,
Diesel
and
Jet
Fuels
NOI CONCENTRATION,
volume-percent
Fuels
considered
in this section
are blends
FicVRu 100.-Minimum Spontaneous
Ignition Tern- that contain a
wide variety of hydrocarbons
peratures
of
Liquid Hydrazine, MMH,
and UDMH
and
additives. Accordingly,
their
flammability
at an Initirl Temperature of 25* C in Contact
With characteristics arc governed
by the method used
NO,*-Air Mixtures at
740± 10 mm
Hg
as
a Function
of NO,* Concentration.
to
extract a vapor
sample
as
well
as by the
history of
the liquid. For example, since
the
preciably
by
this
pressure
change, it
is affected lower limit
of
flammability,
expressed in
in
a
range of
NO,*-air
mixtures.
volume-percent,
is inversely
proportional
to
The
data
presented
in figures
100 to 105 were
the molecular
weight of
the
combustible
vap(,r,
obtained with
liquid
fuel
in
contact
with apor- equation (28),
the
first vapors to come from a
ized
NO*
;n
air.
Similar data
obtained
with blend, such as gasoline,
give a higher
lower
vaporized UDMH-air in
contact
with NO*
limit
value
than the
completely
vaporit.sd
are given in
figure
106.
This
figure indicates sample. Conversely, the
heavy fractions or
that
LTDMH-air
mixtures
that
contain
more
residue
give a
smaller lower linit
value. For
than 9 volume-percent
UDMH will ignite spon- this reason,
there
is some disagreement aboutI
taneously
on
contact with
NO*;
UDMH-air the limits
of
flammability
of
blends such
as
mixtures
that contain more than
approximately gasoline
and
the
diesel and jet fuels. These
2 volume-percent
UDMH
can be
ignited
by an fuels
are,
in
general, characterized by a wide
ignition
source
under the
same
conditions (166).
distillation range;
the ASTM
distillation
curves
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FLAMMABILITY
C H A R A C T E R I S T I C S ~
83
300
I
200
Lj
M
Region of
spontaneous
ignition
000
100-
36*
770
670
I
x
0
0
15
20
NO
CONCENTRATION, volume-percent
FiGuRE 101.-Miniiui
Spontaneous Ignition
Temperatures
of Liquid Il:3drazine at Vafious Initial Temperatures
in
NO,*-Air
Mixtures
at 740±
10
mmn
lg
as
a
Fuikction of
N0
2
* Concentration.
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84
FLAMMABILITY CHARACTERISTICS OF
COMBUSTIBLE GASES
AND
VAPORS
200
x
,.*
/
67"
C100
-
"36
Region
of spontaneous
ignition
0o
/
-1
05
10
15
20
25
NO*
CONCENTRATION, volume-percent
FhG'RE
102.- Miiniml
111
Spontneous
lgniitioii
Tiperaturv of Liqih'
\IN1\ :t tr ius
Initil] "
tih-ir
trci
iil
N( ) -Air
M[ixtizrtus at
740 10 min
lig
as a Iwt otionof
N02*
'onceittratioth.
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FLAMMABILITY
CHARACTERISTICS
85
200
S
SRegion
of
spontaneous
ignition
w
D
x
36* and 55*
-
x
0
5
10
15
20
NO*
CONCENTRATiON,
volume-percent
FIGURE 103.-Minimum Spontaneous
lgtition
Temperatures
of Liquid
UDMlf at
Various
Initial
Temperatures
in N)3*-Air Mixtures
at 740:_ 10 mm
lig as a Function
of
N0*
Concentration.
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86
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES
AND VAPORS
400
-
I
Curve
He/0
2
a
0.0/100
b
100/25
C 100/6.50
d 100/1.70
300
U 100/0.30
f
100/0.00
P
V
Region
of
spontaneous
ignition
-200
-
we
V
cc
FIGURE
104.-Minimum
Spon-
%
taneous
Ignition
Temperatures
Ratios.
100
-
'i
of 0.05 cc of
Liquid
UD MNHn
Atmosphere
for
Various
He/O
2
-a
ob
line
of
N*
2
~
.
-
-
-
-
--
_
__
-
-
0
5
10
15
20
25
NO*
CONCENTRATION,
volume-percent
22
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FLAMMABILrTY CHARACTERISTI(
5
87
300
. .
.
-
. . 250
---T-T T -T-----T-- iF
a
15
psia
b
45
psia
_
200
200-
Region of
spontaneous ignition
Region
of spontaneous
;gnition
i
0 150
I J
100
1
100
Lower
limit of flammability
of
UDMH in
air
I ] ] 50I
0 5 10
15
20
NO*
CONCENTRATION,
volume-percent
Dew
point
line
FiouRx 105.-Minimum
Spontaneous
Ignition Tern-
""
peraturep of 0.05 cc of Linuid UDNIH in NO,*-Air
Mixtures
at
15 and 45 Psia
as a Function of
NO,*
I I I
Concentration.
0 4
8
12 16 20
of
two
gasolines
and
three
jet
fuels
considered
UDMH
CONCENTRATION,
volume-percent
here are
given
in
figure
108.
Unfortunately,
FIGURE
106.-Minimum
Spontaneous
Ignition Tem-
such curves
give
only
an approximate
measure peratures of Vaporized
UDMH-Air Mixtures in Con-
of
the volatile
constituents in
the liquid
blend.
tact With 100 pct
NO; at 250 C
and
740±
10
mm
Even
relatively
nonvolatile
high-flashpoint,
oils
Hg
as
a Iunction
of UDMH
Concentration
in
Air.
may liberate
flammable vapors at
such a slow
rate that the
closed vapor space
above
the
grade JP-4 (fig. 110). Combustible
vapor-air-
liquid
may
be made flammable
at reduced
carbon
dioxide
and
vapor-air-nitrogen mixtures
temperatures.
Gasolines
can produce flam-
at
about
25' C and atmospheric
pressure are
mable saturated vapor-air mixture at tempera-
considered for each. Similar data are given in
tures
below
-65'
C (241),
although the flash
figure 14
for
the gasoline vapor-air-water
vapor
points of such
fuels are considered
to be
about system
at 21' and 100'
C;
the effect
of
pressure
-45' C (158). An
apparent
discrepancy thus
on limits
of
flammability
of volatile constituents
exists
if flashpoint data
are
used
to
predict
of
JP-4 vapor
in air
are discussed
in connection
the
lowest
temperature
at which flammable
with figure 12.
mixtures
can
be formed
in a
closed
vapor
space Minimum autoignition
temperatures of gaso-
above a blend in
long-term
storage.
lines
and
jet fuels
considered here
are
given in
As
noted earlier, the limits
of
flammability
of
compilations by Zabetakis,
Kuchta,
and
co-
hydrocarbon
fuels are
not
strongly dependent
workers
(126,
237). These
data are included
on molecular weight
when
the
limits
are
ex-
in
table
20.
pressed by weight. However,
since results Setchkin
(194)
determined the
AIT values
of
measured by a
volume
are
perhaps more
widely four diesel fuels
with
cetane numbers
of 41,
55 ,
used
than
those measured by
weight,
typical
60
and
68.
These
data
are included
in
table 20.
flammability curves are presented by
volume Johnson, Crellin,
and Carhart 92, 93)
obtained
for
the
light fractions
from
aviation'
gasoline,
values that. were larger than
those
obtained
by
grade 115/145 (fig. 109), and
aviation jet fuel,
Setchkin, using a
smaller apparatus.
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88 FLAMMAI3ILIT
CHARACTERISTICS
OF COMBUSTIBLE GASES AND
VAPORS
100
S air
100 -% diban@-X
ethane
S
air
100X- X psolIne- S inert
lmF lammable
wimm~ mixtures
0
Luminous
20-
flame
(cltio\\a
0 to
20
3 40
0
I
i
I
ADDED INERT. volume-percent
0 20
40
60
so
1W.
Fzoaui
109.-Limit. of Flammability
of
Aviation
ETHANE. volume-percent Gasoline
Grades
115/145
Vapor-Carbon
Dioxide-Air
and
115/145
Vapor-Nitrogen-Air, at
27" C and At-
Fnouzz
107.-Limits
of
Flammability
of
Diborane- mospherlc Pressure.
Ethane-Air
Mixtures at Laboratory
Temperatures
and 300 mm Hg Initial
Pressure.
10
1
460-
i
r00%-% JP4-
inert
- 6-
420
-/
"8
380- -
N
340
/4-
Flammable
3407
It
mixture
L
C02"
02
-
S260-
, 0 10 20
30
40 50
l'-
ADDED
INERT,. volume-percent
220-
Fiouaz
110.-Limits of
Flammability
of
JP-4
Vapor-
Carbon Dioxide-Air
and JP-4 Vapor-Nitrogen-Air
/ -Mixtures
at 270
C and
Atmospheric Pressure.
180-/
,
TABLE
20.-Autoignition temperature ialues
of
various
fuels
in
air
at
1
atmosphere
Fuel:
140
Aviation gasoline:
AlT,
-c
100/130--------------------------
440
115/145
--------------------------
471
Aviation jet fuel:
I00
I I
JP-1
----------------------------
228
0
20
40
60
80 100
JP-3
-------------------------
238
DISTILLED, ercent
JP-4
---------------------------- 242
JS-6
n----------------------.------
232
FJouaz
108.-ASTM
Distillation Curves for, A, Avis-
)iesel fuel:
tion Gasoline, Grade 100/130; B, Aviation
Gasoline,
41 eetane
-----------
------------ 233
Grade
115/145;
C, Aviation Jet
Fuel, Grade JP-I;
55 cetane -----------------------
230
D, Aviation
Jet Fuel, Grade JP-3; and F, Aviation
00 cetane------------------
225
Jet Fuel,
Grade
JP-4.
68 cetane
-------- _----------------
226
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g0
FLAMMABILITY CHARACTERISTICS OF
COMBUSTIBLE
OASES AND VAPORS
100 0
KEY
*
Flammable
mixture
0 Nonflammable
mixture
so
20
40 NO,
mleecen
Fiouiaz 112.-Limits of
Flammability
of
HrNt).';2 at
Approximately
280 C
ane
I Atmosphere,
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A..AMMABILITY
CHARACTERISTICS
91
100
0
KEY
*
Flammable
mixture
o
Nonflammable
mixture
80
20
A
Coward and
Jones,
Bureau
of
Mines
o3
Smith
and
Linnett,
JCS
(London),
1953,
pp.
37-43
20
80
0
10 0
100
80
60
40
20
0
N
2
0, mole-percent
FIGURE
113.-Limits
of
Flammaubility
of Ilr-N20-Air
at
Approximately
280
C
and
1
Atmosphere.
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92
FLAMIMABILIT
CHARACTERISTICS OF
COMBUSTIBLE
GASES
AND
VAPOR$
100
0
KEY
* Flammable
mixture
*
Nonflammable
mixture
80
20
A
Coward and Jones,
Bureau of Mines
Bull.
50 3
60
40
1
00
0
-100
10
80 60
40
20
0
AIR,
mole-percent
FIOL'Rz 114.-Limits of Flammability
Of HrNO..Air at
Approximately 280
C
and I Atmosphere.
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FLAM"MABILITY
CHARACTERISTICS
93
Start
of liquid
transfer
to Dewar
10
1 T
- -T
-
T
- '
a-
.
.-
(Film and nucleate
boiling limited)
E
I: Theoretical
(conduction
limited)
IAI
2
-
Region
i
_of
vilent
boiling
F--1-
Quiet
vaporization
0
1I I I I1 1 1
1 1 1
-20 0 20 40 60 80 100 120 140 160
ELAPSED
TIME,
seconds
FxoUiuE
115.-Rate of
Vaporization of Liquid Hydrogen From
Parafin
in a 2.8-Inch Dewar
Flask: Initial
Liquid
Depth-6.7 Inches.
0.4 I I I I
.3
2
• 040
60 80 100
120
140
1'60
ELAPSED TIME, seconds
FiOURs 116.-Theoretical Liquid Regression Rates Following Spillage
of
Liquid
Hydrogen
Onto, A,
an A\'trage
,oil; B, Moist Sandy
Soil
(8
Pet.
Moisture); and
C, Dry Sandy Soil,
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FLAMMABILITY CHARACTERISTICS
95
flames that
resulted
following
spillage
of
7.8
liters
of
liquid hydrogen and
subsequent
ignition
of
vapors above
the
spill
area. Th e
height and width
of fireballs that resulted
from
ignition
of
vapors
produced by rapid
vaporiza-
tion of about
3 to 90 liters o?
liquid
hydrogen
are
given
in
figure
120.
The
data are repre-
sented
fairly
well by the
equation
Hm.=
Wym,= ./)V
feet= 17.8V M
feet,
(56)
where H..
and
W. are the
maximum flame
height
and
width, respectively,
V
is
the volume
of
liquid hydrogen in liters, and
M is
the mass
of this
volume in pounds.
The
burning
rate of
a 6-inch
pool of
liquid
hydrogen
in
air is given
as the regression
of the
.375
liquid
level
in
figure 121;
burning
rate
data
for
liquid
methane
are included for
comparison.
An
extrapolated
value
of
burning
rate
for
large
pools
of
liquid hydrogen
is
included
in figure
52.
Approximate quantity-distance relationships
can
be
established
for
the storage
of liquid hy-
&-ogen
near
inhabited buildings and
other stor-
age
sites f certain
assumptions are made
(83,
2o0
160, ,34).
Additional
work is
required to
establish such distances
for
very
large quantities
15-
of
liquid.
The detonation velocity
and the static
and
10-
W
reflected
pressures
developed
by
a
detonation
3
.
wave propagating
through
hydrogen-oxygen
V)
mixtures are
given
in
figure
i6. The
predeto-
0-1
nation
distance
in
horizontal
pipes is reportedly
proportional
to the
square
root
of
the
pipe
diameter
(229); this
is presamably
applicable
to
results obtained
with a
mild
ignition
source,
since
a
shock
front
can
establish
a
detonation
at
essentially zero runup distance.
Numerous
investigators
have examined this
and related
problems
in recent years (11--8, 65,
155-137,
'161).
.3 HYDRAULIC
FLUIDS AND ENGINE
OILS
Both
mineral oil derivad and
synthetic
hy-
draulic
fluids
and engine
oils
are
presently in
common use (148).
These materials are
often
used at elevated
temperatures
and
pressures
and
contain additives
designed to improve
qta-
bility, viscosity,
load-bearing characteristics,
etc.
Such
additives affect flammability
char-
acteristics of the
base fluid.
However, the base
.364
Floun ll.-Motion
Picture Sequence
(16 Frames
per
Second)
of Visible Clouds and
Flames Resulting
From Rapid
Spillage
of 7.8 Liters
of Liquid
Hydrogen
on
a Gravel Surface
at 180
C.
Ignition
Source:
20
Inches
Above
Gravel.
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96
FLAMMABILITY CHARACTERISTICS OF
COMBUSTIBLE GASE4'
AND VAPOJ%3
100-r-T--r-F--F-r
I
I
1F-
i1-
60- Flame height
- -
I-
Flame
width
0
ME0
2
20
FiounE 120.-Maimurn
riane
height and
widtk. pitcd-c'd
by
gnitioni
U vapor-air
mixtures0
formed by sudden spillage of
10
1
II
IL I
I I IL
2.8
to 89 liters
of liquid
hy-
2
4 6
8 10
20
40
60 80 100
drogen
(VI).
VI,
liters
5-
U
.4-
00
Hydrogen
0
z
Methane
0
2
FG URE
121.-Burning rates
of w
liquid
hydrogun
%nd of liquid
0
methane
at
the boiling
points
in
W
6-inch-Pyrex
Dear
flasks.
1i
10
20
30
40
50
60
ELAPSED
TIME,
minutes
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FLAMMABILiTY
CHARACrERISTIL"S
97
fluid generally
plays
a predominant
role iii
de-
ambient
temperatures
can
lead
to
the auto-
ternining
limits
of
flammability
and ignition
ignition
oi ,t
mineral
oil
lubricant
(curve
5) if
tAmperaturo
of
a particular
fluid.
For exam-
sufficient
vapo'
or
mist
is in the
system.
In
the
pie,
many
of
the
oil-based
fluids
have
lover
same
pressure range, only elevated
initial
limits
of
flammability
that
fall
in
the
ranges
temperatures
could lead
to
the
autoignition
of
a
given
in figure
22
for
paraffin
hydrocarbons.
phosphate
ester (curve
4).
If the
initial pressure
Further,
those
that have
minimumn
autoignition
is increased
to
10
atmospheres,
autoignition
temperatures
in the
lower
temperature
ranges
cin oo-ur
at lower
air-intake
temperatures
in
considered
in fiugres
43 and
71 are
not affected
every
case
(248).
appreciably
by oxygen
concentration
of
the
atmotsphere
and by ambient and
fluid-injec'ion
M C]
M OUS
pressures;
those
that,
have
minimum
autoigni-
tion
temperatures
in
the
higher
temperature
The
flammability
characteristics
of a number
ranges
do
not
follow these
generblizat
ions
(287).
of miscellaneous
combustibles
not considered
Since these
fluids
are
designed
for
use at ele-
elsewhere,
are
discussed
in this
section.
These
vated
temperatures
and pressures,
they are nor-
include
carbon
monoxide,
n-propyl
nitrate, and
mally
made
up
of
high -molecular
weight
mate-
the
halogenated
hydrocarbons.
The
properties
tials.
Accordingly,
they
are
flammable
at
of
these
and
a
geat
variety of
other materials
ordinary
temperatures
and
ressures
as mists
are
included
in
Appendix
A.
and
foams.
Burgoyne
and
his
coworkers
(27)
The
limits of
flammability
of the
systems
car-
found
that,
lubricating-oi mists
were
flrmma-
bon
monoxide-carbon
dioxide-air
and carbon
ble in
air
but
not in
carbon
dioxide-air
mix-
monoxide-nitrogen-air
are
presented
in figure
ture,:
that
contained
about
28
,volume-percent
126. These
curves were
constructed
from
the
carbon
dioxide
(fig.
1i5).
At
elevated
temper-
flammability
data
obtained
by
Jones in
a
2-inch
Otnre4,
the ,A ,
vapors
cracked
Rnd
produced
vertical
glass
tube
with upward
flame propaga-
acetylene
and hydrogen,
which
affected
the
tion
(11);
other
representations
may be found
flarmmability
of the
resultant
mixture;
the
va- in
the
original
reference
and in the
compilation
pors
are
often
unstable
at
elevated
tempera-
prepared
by
Coward
and
Jones
(40).
tures.
Chiantella,
Affens.
and
Johnson
have
Materials
that
are
oxidized
or
decomposed
determined
the
effect
of elevated
temperatures
readily
may
yield
erratic
flammability
data
on
the stability
and
ignition
properties
of
three
under
certain
conditions.
This
effect
i
illus-
commercial
triaryl
phosphate
fluids
(36).
trated
in
figure
127
which
summarizes
the
Zabetakis,
Scott,
and
Kennedy
have
deter-
lower-limits
data obtained
by
Zabetakis,
Mason
mined
the
effect
of
pressure
on
the autoignition
and
Van
Dolah
with n-propyl
nitrate
(NPN)
in
temperatures
of
commercial
lubricants
(248).
air at
various temperatures
and
pressures
(248).
Figure
122
gives
the
minimunm
autoignition
An
increase
in temperature
from
750
to 1250 C
temperatures
for
four
commercial
phosphate
is accompanied
by
a decrease
in the
lower-limit
ester-base
fluids
(curves
1-4)
and three values;
a
further
increase in
temperature
to
mineral
oils
(curves
5-7).
In
each
case,
the
1500
C results
in
a
further
lowering
of the lower
minimum
autoignition
temperature
was
found
limit at pressures
below 100
psig,
but
not
at the
to
decrease
with increase
in pressure
over
most higher
pressures.
An increase
in the
tempera-
of the
pressure
range
considered.
A
plot
of
the
ture to
1700
C
results
in an
apparent
increase
in
logarithm
of
the
initial
pressure
to temperature
the lower-limit
value
because
of
the
slow
oxida-
ratio
versus
the
reciprocal
of the
temperature
tion of
NPN.
A complete
flammability
dia-
is given
for
curves
1 to
7 in
figure
123.
The
gram
has
been
constructed
for
the NPN
vapor
resultant
curves
are
linear
over
P limited
tern-
system
in figure
128; a
single
lower
limit
curve
perature
range.
and two
upper
limit
curves
are
given here
tc
The ratio
of the
final
temperature
attained
by
show
the
effect
of
pressure
on
the
flammable
air in
an adiabatic
compression
process
to
the range
of
a vapor-air
system.
initial
temperature
is given
in
figure
124
as a
The
spontaneous
ignition
of
NPN
in air
was
function
of both
the final-to-initial
pressure
considered
earlier
at 1,000
psig
(figs.
3, 4).
The
ratio and
initial-to-final
volume
ratio.
If a
explosion
pressures
obtained
at
this
initial
pres-
lubricating
oil
is exposed
to high
temperatures
sure
in
air
and
in
a
10
volume-percent
oxygen
during
a compression
process,
autoignition
may +90-volume-percent
nitrogen
atmosphere
at
occur if
the
residence
or
contact
time
is
ade-
various NPN concentrations
are
presented
in
quate. Such
high
temperatures
do occur
in
figure
129.
A summary
of the
minimum
spon-
practice
and
have been
kLown
to cause
disas-
taneous
ignition
and decomposition
tempera-
trous
explosions
(68,
146,
149,
27,
2 1).
The tures
obtained
with
NPN
in ir
and
nitrogen
curves
ii
ligure
125
show
that
in
the
compression
respectively
are given
in
figure
130.
The data
pressure
range
1
to
10 atmospheres
(initial
given
in this
figure
exhibit
a
behavior
that
is
praesure=l
atmosphere),
a wide
range
of typical
of
that
found
with
other
combustibles
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98
FLAMMABILITY
CHARACTIEISTICS
OF COMBUSTIBLE. GASES
AND) tAPORS
6.50
.T-. ............ -T--
r
-
-T-T
-TT
-1
00
C0
autignti1
IV~
0:500
£
0.
80 20 416810
0 0
INT2450SSR,
t
FIUR 12.Vrai4i0i0umAtintoiTmeaur
ihPesr t(omnrh
hsht s
a2
Miea
iiurcnsi
i na40-cSaiesSellonj
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FLAMMABILrrY
CHARACTERISTICS
9
TEMPERATURE,
-C
650
550
450
400
350
300
250
200
175
.6
-
M n
a l
Phosphate
3
ol
.4
esters0
A
-X
Regioo
of
outoignition
.10
.08
0D6
0
be
.04-
FIGUIC~
123.-togarithm
of
Ini-
I-,
tial
Prpe~ura-AIT
Ratio
of
E
Seven
Fluids
in
Air
for
Various
Reciproca~lTemperatureb.
Data.
-
from
Figure
122.
.02-
.0i-
.008-
.006-
.004
.002
V11
VI
I.
.40I
1.8
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100
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE GASES
AND VAPORS
2.4
2.2-
V,
2.0-
v-
1.8-
Pf
FiouUm 124.-Variation
in T,/T,
i
of Air With V
4
/Vt
and With
PIPi in
an
Adiabatic
Corn- 1.6-
preaion
Procen.
1.4
1.2
1 2 3 4
5 6 7 8 9 10
vi Pf
vf P,
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FLAMM4ABILITY CHARACTERISTICS
101
500
Om
Re( ion
of
500-
autoignition
Fiouaa 125.-Variation
In
Air
11A;
rIemperature
With P,/P, in
an
Adiabatic
Compnression
Proces3
Tepea
30
-/I-t
for
Five
Initial
Air
Tepr
<~~0P
t
tures
(00, 250,
5O*,
750,
and
MAIT
1000
C).
Regions
of autoignl-
tion
for lubricants
TV and
Vat CL
0.
P,/P,
Between
1 and
10 Atmos-
2
phere and
P,
of Between 1 and W
10
Atmospheres.
20
-P-1
t
P,,i100
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102
FLAMMABILITY CHARACTERISTICS
OF COMBUSTIBLE GASES AND VAPORS
80 at elevated pressures; the minimum spontaneous
ignition
temperature first decreases with ini-
air
1009-
carbon
monoxide-
Inert tial
increase
in pressure
and
then
increases
as
the
pressure
is
increased still
further
(120,
60 248).
Burning velocities
were found
to
range
from
I20
cm/sec
to
110
cm/sec in
NPN-air
mixtures
containing 3.0
to
7.2
volume-percent
NPN.
id
Flammable
Detonations
were
obtained
in
saturated
NPN
0 40- mixtures
vapor-air
mixtures from 300
to
650 C and 1
atmosphere
pressure;
the
detonation
velocit
0
_,,
st
C02
/
was
from
1,500
to
2,000
meters
per
second
S N2Stable
detonations
were
obtained
with
liquid
z
NPN
at
900
C;
the
detonation
velocity
was
cc - from 4,700
to
5,100 meters per second.
5Although
many of
the halogenated
hydro-
carbons are
known to be
flammable
(40)
still
others such
as
methyl bromide,
methylene
F
chloride,
and
trichloroethylene
(TCE)
have
0
20 40 60 80
been
considered to
be
nonflammable or essential-
ADDED
INERT,
volume-percent
ly
nonflammable
in air. As noted
in
connection
witb the methyl bromide
data given in figure
Frounn 126.-Limits
of Flammability of
Carbon
Mo- 28 Hill found methyl bromide to
be
flammable
novide-Carbon
Dioxide-Air
and
Carbon
Monoxide-
. H
Nitrogen-Air
Mixtures
at
Atmospheric
Pressure
and
in
air at
1 atmosphere
pressure
(84); the
re-
2W'
C. ported limits of flammability
were from
10 to
5
Flammable mixtures
0
0 2
--
1700C
(3 hr
heating
time)
-
> /75C /170C
(2
hr heating time)
0
- -
- - - -
-
-
-
-
z
1.500C
.1250C
Z
I
I
0
100
200 300 400
500 600
700 800
900 1,000
PRESSURE,
psig
FIGUaz 127.-Lower Linitq
of Flammability
of NPN
Vapor-Air
Mixtures
river
the
l'r,ssijrv
Range I.-roi t
1,000 Psig at 75',
125', 150
o
, and 170" C.
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FLAMMABILrrY
CHARACTERISTICS
103
100
15
volume-percent
methyl bromide.
At
an
initial pressure
of
100
psig,
the flammable
range
was found
to
extend from 6 to 25 volume-per-
90 --
cent. Similarly, methylene
chloride and tri-
chloroethane
were
found to be flammable in air
at
ambient
temperatures although
the flam-
mable ranges
were not determined. In
general,
so -
much
higher
source
energies
are required
with
Impossible vapor-air
these
combustibles than are required
to
ignite
mixtures
at T &I25
"C
methane-air mixtures.
70
An
approximate
flammability diagram
was
prepared by
Scott
for trich oroethylene-air
60
mixtures
(190);
a
modification
is
reproduced
in
60
.figure131. The
lower
limit
data
were obtained
in
a vertical
7-inch-diameter flammabil~ty
tube
and
the upper limit data in an 8-inch-diameter
0 50-
glass
sphere with
upward
propagation
of
flame.
lammable
mixtures of
TCE and air were also
0
obtained between
10.5
and
41
volume-percent
a40
TCE at,
I atmosphere
and 1000 C
in
an
8-inch-
>
diameter glass
sphere. Under the
same con-
Z
ditions,
flammable
mixtures
of
TCE
and
z
oxygen
were obtained between
7.5 and
90
30
volume-percent
TCE.
However,
additional
work must
be conducted
with
this
and the
other halogenated
hydrocarbons to
determine
20 Saturated vapor-oir
the
effect
of
vessel size,
ignition source strength,
mixtures T 1250C
temperature
and
pressure on
their flammability
characteristics.
1o
Other useful
flammability
data
may be found
T-50o6C
for
various
miscellaneous combustibles in many
..
Flammable
of the
publications
listed in
the bibliography
" , ,(40,
154,
200,
208-214, 118). These
include
0
200
400
600
800 1,000
data on the gases
produced when metals react
PRESSURE,
psig
with
water
(56)
and
sulfur
reacts
with
various
hydrocarbons
(62).
Still other
references con-
1"1OURE
128.-Flammable
NPN
Vapor-Air
Mixtures
sider
the hazards
associated
with
the
production
Formed Over
the l'ressure Range
From
0
to 1,000 of
unstable peroxides (142,
157, 187,
238)
,and
Psig
at 50
°
and 1250 C.
other reactive
materials (66,
74,
80,
139).
,.S
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104
FLAMMABILITY
CHARACTERISTICS
OF COMBUSTIBLE
GASES AND VAPORS
5,000--
In
ct
4,000-
o3,000-
a-
z 2,000-
0
Q.
1,000-0
Ai
X
~0-10%
02
+ 90
N
2
0
0.3 0.6 0.9 1.2 1.5
1.8 2.1
NPN VAPOR,
volume-percent
FIOURZ
129.-Variation
of Explosion
Pressure
Following
Spontaneous
Ignition With NPN Concentration,
Initial
Pressure
1,000 Psig.
2
4
0C
11T
_
T
Regions of
spontaneous
ignition
and
220-
spontaneous
decomposition
~
Dcoposition
in N
2
0
0
400
800
1,200
1,600
2,000 2,400 2,800 3,200
3,600
4,000
INITIAL
PRESSURE,
psig
FIGURE 130.-Minimum
Spontaneous
Ignition
and
Decomposition
Temporatures of n-Propyl Nitrate in
Air
as
a
Function
ofPressure,
Type
347)
Stainless
Steel Test
Chamber,
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FLAMMABILITY
CHARACTERISTICS
105
TEMPERATURE. "C
0
10
20
30 40 50 60
70
80 90
100
1,o000
, r , , I
T -F..
.
800
-- 1O
-90
600
L80
-
60 /
400
5
30
Upper
limit
4
E
300
-
-440 "
Impossible
mixtures
0 >
200
Flammable mixtures
E
E
i, i0
_-e,/,r
ower
limit
420
60-
40-10
30-
Nonflammable
mixtures
u
10
I
0
,
0
50
100
150
200
250
TEMPERATURE,
F
FIouRE 131.-Flammability of
Trichloroethylene-Air
Mixtures.
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0,es
4 sort,
Laburator.
led,
arid Eng.
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v.
15:3,
lizrs9.
lvll
n.(ono)
90
I 5
WI
,il)lr).
4t0A
-
4 2A.
tu
1
).ios9.
viniI.0
ofad
h
nl r
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E .
C
.,
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It
.
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Explosive
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nd
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acq i
r-Sotlv
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io
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e
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APPENDIX
A
11 5
Limits of flam-
Limits of
flam-
Imability
(volume-
inability
(volume-
Combustible percent)
TL
AIT
Combustible peicent) TL AIT
(00C)
(0
C)
I__
_- (_
(0 C)
) (0 C)
Los Ulf
Lot
U.
Dip
henyl ether
.......
40.8 .........
620 Methyl chloride -------
4
7
-
----- -----
Diphenyl
methane .
7---------------- 485 Methyl
cyclohexane_
1. 1 6.7 -------
250
DiN~
yl ether -------- -1.7 27----------
Methyl cyclopenta-
n-Do( ecane
---------- .
.60---------
4 205 diene--------------
1.1..3 1 7.6 49
445
Ethan ---------------
30
12.4 -130 515 Methyl
ethyl ketone. 1.9 10
.............
Ethyl
acetate ---------
2 11
------------
Methyl ethyl ketone
Ethyl alcohol---------
3.
3
1119
..
365
peroxide ----------------------- -
40 390
Ethyl amine--------- -3.5.---------------
385
Methyl
formate ......
5.0 23 ------ 465
Ethyl
benzene ------
'1. 0
1 6. 7
------
430 Methyl cyclohexanok_ ' 1.0 -------- ------
295
Ethyl 12hloride------- 3.
8
--------
---- " ----- Methyl isobutyl
car-
Ethyl
cyclobatane
---
1.
2
7. 7.--------210 binol------------
--
1.
2--------
440
-
Ethyi yclohexane_.
142.
0
146.
6
------ 260 Methyl isopropenyl
E thyl cyclopertane_.
1. 1
6.7
..---
260
ketone
-------------
1.8
'9.
0
-----------
Ethyl
formate------- -2.8
16
------ 455
Methyl lactate--------- 1 2. 2
-
-----------
Ethyl
lactate-
---------
1.5 ---------.
400
a-Methyl naphthalee ' .8
-......-.....-- 530
Ethyl met captan ....
2.
8 18 I--.. 300
2,
Methyl
pentane_--_ 41.2 -------------------
Ethyl nitrate
----------
4
0 ---------
Methyl propionate.--- 2.
4 13 -----------
Elhyl nitrite- . 3.
0 50
----------
Methyl propyl
ketone-,
1.6
8-2 ----------
Ethyl
propionate - - 1.8
11 ... 440 Methyl
.tyrene ------- 41.0 --------
/ 49 495
Ethyl
propyl
ether
- - 1
7
9 - -----
Methyl vinyl
ether.
__
2.
6
39
------
Ethylele ......---- 2. 7
36
-
490
Methylene chloride--- --------
--------- ------ 615
Ethyleneimine ---------
3. 6 46
--
.320 Monoisopropyl bicy-
Ethylene glycol- . 3.5 --------------
400
clohexy-
- -
,52 " 4. 1
124 230
.2hylene
oxide------- 3.
6
100
-----
----- 2-Monoisopropyl
Furfural
alcohol-----,
-1.8 in 16
72
390 biphenyl --------- 1) 53
3. 2
141
435
Gasoline- Monoinethylhydra-
100/130------------1.3
7. 1 ------.
440
zinc------------------
115/145 ---------
1.
2
7. 1 ------. 470
Naphthalene
-------
1
88 20
5.9
lycei.------- ---- -------- -------------- -- 370
Nicotine --------------- 1,751-..
"
-----------
n-itcIptane
---------
1.05 6.
7 -- 4 215 Nitroethaie ------------
3.
4
--------- 30
7-1leXIlecalI-- ----- -
.
43
------
126 205 Nitro
nethane-----------.
3
--------- - 33
-
-llexatle
-- --------- 1.2 7.4
-26 225 1-Nitropropane ----- 2. 2
---
34
n-llexvI
alcohol---. -I 1. 2
..............
2-Nitropropane
-------
2.
5
-- 27
,-ll l
ether
. . .6
.4. 185
n-,oan ---
-
21. .
-----------
3 205
1llyhazie.
.4.
7
100
----------:
n-Octane ------------
0. 95
---------
-
13
220
l
,drogil........ 4. 0
5
400
l'araldehyde ------------
1.
3 --- - --.... --
llvdrogen cyaii(ie___ 5.6
46
-- - -Pentahorane
-.......
42
------
--- -- --
...... .4
4-
-....
...
.
1.4 7. 8 -A8
260
lsa-It anl
ti't 1. 1 1 7. 1 25 360
'entaon.tilene
I- I
lsoialn
ii(tl]
I
,.
I .I
350 eol-.....--------
335
lolta. ,.. --
81
401
Plitlalic aiodridc
. 2 2
Is(ohilvi llvolol . 1. 7 '11
.........- 3-Picoline
------------
4 1.4------- ----------
5t0
[SlAt
vl
hiW llo( -6
9,
43- - 0
i
l.l.allt
-- ------------------ 23 . 74
23 7. 2
Iulit
vi fu-lia,
2.
0 S.
9
- 'ropadicniw, .
1-
2.
16
Isb
vi',
. ,
1. 8 1. . . . .. .
l'ro
_ ...
... . . . 2. 1 .,5 1 )2 450
lsfn-r,-
I. 4 . . . .
1,2-1'ropanditl I
'2.5
.
- - .
410
--- -- ---... .. . .U l /-}'ropiolaetoie
2. ii
4,, . .I
r
i tlhhyd.
2. 9 17
:dd
l . 2 .. .t-I
yl
acetiate._ 1.
I,.
pr()o
'l
tdhilil iyl
4 .
j
It. . . t 1
-Prop~y
l' h
l
_l
1.2. '2 '
1.1
- '
w o.1
.vI fi
l: l 'rp
It ttiine ,
ii
i.:
,
_ 210 l'rj, yl
,hlori,ic-_
2.
4_
6ii _
-230 t-Kj,'l
nitrate-
I 8 100 21
175
K .,si .
.
-
. 2111 i'r,+
l 1h11
.
" . 1 .4 460
M' i1.i 1
187 54 0 rou; I.
],
hi
3. 1
\h- 110 v,.All 3. 1 ;4_
.'ri,,
nl
i.
tyol
:
2.
4i
Nio
'li v,',' Ir.
.
..II Ou
I
i'
.-
',
-
i
,.
. '1 .0 ;7 . . .
N11" 11
I
i
hIA t-
0 NA
1
, 2
17
,h0 ;N-1'
..,~
,.u
1
12
McI
i i
t
1111w
4- 2 1 - I2
- - .. . ..
.
.N(l' It-
i
i ._(------ 2 ,
t ~ .- E{(
'p1 t]L-IV I
-lc-)ht . '. 53.
5
it rtii
1-
...
1 (I........
3-
M
,vI vl
I [ ,I ..n I~ I
1 5
1 St
v I,.-
" I.
. .
1. , %1 '
,ut kelm w), 1. 2 0 S.1
.
illfi,
l
'2.
0 -
2.17
, jj
,'i )1\,,
7 2. 5
"2(
...
3"'11
,-T
.orl~ ,\I _
v.
)
.
. ...
;
,
,.L 'I vIo ).l '," v -
it, kt -tr ll.,. . : *.5
. _.
2
i 1 I '. . .
1.
7
-
. . 46
I
11%
''
,
\,1h',,filralc .
. 2
(0
.,ithi IthYl
,th.r
_ 2. 2 . ------.
rait........... ...
- 5. o
71 315
s,, iii I/tntes
ti
t
end of table.
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116
FLAMMABILITY
CHARACTERISTICS
OF
COMBUSTIBLE
GASES
AND VAPORS
TABLE
A-I.
Summary of limits
of flamma-
bility, lower temperature
limits (TL) and
minimum autoignition temperatures (AIT)
of
individual
gaves and
vapors
rn
airat atmospheric
pressure-
Contiaued
Limits of
flam-
mability (volume-
Combusible
percent) T,
AIT
(0C)
(
0
C)
L,.. U,__
,2,3,3-Tetrmnethyl
pentane ----------- 0.
8 ---------------
430
Tetramethylene
gly-
col ...
---------
------
390
Toluene
------------ 1.2
'.7.1 -------
480
Trichloro~thane
------
---------
I ----------- 500
Trichlo=oethylene
-_-- 24 2
26 40 30
420
Triethyl
amine
------
1.2
8. 0 ....--
Triethylene glycol.
. 9 2 9.2
------------
2,2,3-Trimethyl bu-
tane ...------------
1.0 --------------
420
Trimeth;yl amine
.... 2. 0
12 -----------
2,2,4-Trimethyl pen-
tane --------------
.95 --------------
415
Trimethylene glycol
- 1.7 --------------
400
Trioxane ------------ 3.2
---------------
-----
Turpentine
------.. '.7 ............
Unsymmetrical
di-
methylhydrazine_-
2. 0 95
-----------
Vinyl
acetate
--------
2. 6
-------------------
Viniyl chloride -------
&
6
33 ..----......
m-Xylene
----------- 1.1
3.4 ------- 530
o-Xyene------------
11.1
16.4------
465
p-Xylene
-----------
'
1.1
'6.6 -------
530
1
:100* C, 1:1-0:
C.
t-:43*
C.
i-47*C. 12g.-530 C.
Ug195* C.
8tm75*
C.
C.
t~
-
1
60
o
C.
4
Calclated.
.
t-130
C.
24-96
C.
t-60* C.
1 1-72* C. Ist70O
C.
4t-850
C.
Is
t-117
o
C.
U
9 29 C.
1- 140. C.
9T 125o C. C
.-
247
o
C.
'1-160O
C.
"t-200
0
C.
"-0 C.
t-110.
C. "-78o
C. 1-203
°
C.
"t-17*6
C.
t-122* C.
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APPENDIX
B
STOICHIOMETRIC
COMPOSITION
N,
0
0.25 0.50 0.75
The
stoichiometric composition (C,,)
of
a ..
-
-
combustible vapor CnH.O\Fk in air may be ------------
1. 87 1. 83 1.
79
1. 75
obtained
from
the equation
12------------- 1. 72 1.
68
1.
65 1.62
13 1.59
1,56
1.53 1.50
m
k2X14
---------------
1. 47
1,45 1.42
1.40
CH OxFFk±+
+
A
2
O CCO
2
15------ 1.
38 1.36
1.33
1. 31
16 ------------- 1.29 1.27
1.25
1. 24
17------------- 1.
22 1.20 1.18 1. 7
rn-k
18
--------------
1. 15
1. 13
1.12 1. 10
H
2
O+kHF.
19....------------
1.
09
1.
08
1.
06 1. 05
20-------------
1.04
1.02 1.01
1.00
21 -------------.
99 .98 .97
.
95
22
-------------.
94 .93 .92 .91
100
23
-------------.
90
.89
.88
.87
Thus,
C,,= - -
volume-per-
24
-------------.
87
.86
.85 .84
1_
A.73
n k-2X )
25
-------------
83 .82
.81
.81
1+4.773
4
26--------------. 80 .79 .78
.78
27 -------------
.77 .76
.76
75
cent,
where
4,773
is he
reciprocal
of 0.2095,
28
-----------.
74
.74
.73
72
the molar concentration of oxygen in dry air.
29 -------------. 72 .71 .71
.70
The following table lists the
values
of C,,
for 30
------------- . 69 .69 .68 68
a
range of (
m-k-2X)
values
from
0.5 to m-k-2
I I I Ihe
30.75:
4
1
N-n+ 4 ; where
n, m,
X,
and
k
are
the
number of
carbon,
hydrogen,
oxygen,
and halogen
atoms,
N
1
0
0.25
0.50
respectively,
in
he
combustible.
___-- -For
example, the stoichiometric
mixture com-
------------------
29.53 121.83
position
of
acetyl
chloride (C
2
H
3
0CI)
in
air
1--------------17.
32
14.
35
12.
25
10.
69
may
be
found
by
noting
that
2 -------------
9.48
8.52 7. 73 7.08
3 ------------- 6.53 6.05 5.65 5.29
n
m
-k-2X
3-1-2
4-------------- 4.97 4. 70 4.45 4.22
N=n+.
20
5
-------------- 4.02 3.84 3.67 3.51 2=4
6
--------------
3.
37
3. 24
3.12
3.01
7
-------------
2.
90
2. 81 2. 72 2.
63
The entry for
N=2.0 in the preceding table
is
8
--------------
2.55 2. 48 2.40 2. 34
9--------------2.
27
2.
21
2. 16
2. 10
9.48 volume-percent,
which
is
the
value of C,,
10.------------- 2. 05 2.
00 1.96 1.91
for this combustible
in air.
117
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APPENDIX C
HEAT CONTENTS
OF
GASES
(Kcalimole
I)
T, - K CO,
H,O
O, N,
298.
16
0 0
0
0
300 .017
.014 .013 .013
400
.941 .823 .723 .709
500 1.986 1.653
1.4541 1.412
600 3. 085
2.
508
2. 2094 2.
125
700
4.
244
3.
389
2.
9873
2, 52
800
5. 452
4. 298
3.
7849 3.
595
900
6.700 . 238 4.5990
4.354
1,000 7.
983 6. 208 5. 4265
5. 129
1,100 9.293 7.208
6.265 5.917
1,200 10.630 8
238 7.
14 6.717
1,300
11.987 9.297
7.970
7.529
1.400
lM
360
10. 382 &
834
8.
349
1,500 14.749 11.494
9.705 9.
178
1,600 16. 150
12.627 10.582
10.014
1,700
17. 563
13.
785
11.464 10. 857
1,800
1& 985
14. 962 12. 353 11. 705
1,900
20.
416
16. 157
13. 248
12.
559
2,000 21.
855
17.
372 14. 148
13.
417
2,100
23. 301 18. 600 15.
053
14.
278
2,200
24. 753 19.
843
15.
965
15.
144
2,300
26.210 21.
101 16. 881 16.012
2. 400 27. 672 22.
371 17. 803 16.
884
2.500
29. 140
23.
652 18.
731
17.
758
IGordon,
J. S. Thermodynamics
of High
Temperature
Gas Mix-
tuuan-d
Application
to
Combustion
Problemn.
WADC
Technical
Report
57-33,
3anuary
1967, 172 pp.
118
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APPENDIX
D
DEFINITIONS
OF
PRINCIPAL
Symbol:
filcuaigtiUof
SYMBOLS M-----Mach number.
No,--,----Equilibrium
mixture
of NO
2
and
Symbol: Definition
NO at
a
specified temperature
*A--------Constant.
and pressure.
*'--------Avea.
n
---------- Number of moles.
a ---------- Velocity
of sound. P----lresmire.
B--------- Constant.
P
---------
Maximum
pressure.
C., ------- tStoichiometric
composition. n~P-------Pressure ise.
-H------Heat
f combustion.
p ----------
Partial
pressure.
K
--------- Ratio of
duct
area to
vent area.S-----
Burning
velocity.
k
--------
T
hermal conductivity.
T
--------
Absolute
temperature.
L
-------- Lower limit of flammability.
t----------T-
emperature.
-*-----Mo dified
ower limit
value.
r- -- -- -
--
Tme delay before ignition.
LA Average
carbon
chain length for
U-------- Upper limit
of
flammability.
paraffin
hydrocarbons arnd
correla-
U --------
Upper limit of flammability at
P
C.
tion
parameter for
aromatic hy-
V
--------
Volume.
drocarbons.
V'--------Critical
approach
velocity.
-
----
Lowe(r limit of flammability
at io C.
v ---------
Liquid
regression
rate.
/ID
------
Length to
diameter ratio.
------- Specific
heat ratio.
119
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SUBJECT
INDEX
A
PaeHPg
Acetaldehyde ---------------------------
73
Hlalogenated hydrocarbons
-------------- 102
AkaietIIIV hydrocarbons ------------------------
53 He~at of formation-_
- -- ------------------
51
Airf1'1 _ ratio--------------------------------- 21
Pi-lleptane
------------------------------
21.25, 35
Alcohols-----------------------
------------- 6(5 Heterogeneous mixtures----------
------------- 3
Aldehydes -------------------
-----------------
73
n-llexadecanm-------------------------------21,
25
Ammonia------------------------------------
77
Yi-llexano -------------------------------
21, 25.,34
n-Ainyl
alcohol -------------------------------
67 n-ll&'Xy.l
floo------------------7
Aromatic hydrocarbons------------------------
511 Hydraulic
fluids
---------------------------
9
Autoignitlon------------------------------
4,32,41 Hiydrogen
----------------------------------
77,
89)
B
Hydrogen
peroxide.---------------------------1
Barrcades-----------------------------------
17
1
Blast pressure---------
-----------------------
16 Ignition ----------------------------------
Burgess-Wheeler
law ------------------
--------
22
Ignition. temperature
--------------
------------
4
Burnling
velocity.---------------
-
-- - - -4 ,
45 Ignitihility
limits
-------------------------------
Butadiwne
---------------------------------
48,53
Inertial
is------------------1
n-Butane
-------------------------------
21, 25, 32 Isobutylene-----------------------------------
48
Butene-1-------------------------------48,50,52
n-Butyl
alcohol-------------------------------
671
tert-Butyl
alcohol-----------------------------
68
JP-4-------------------------------------
11,88
o
K
Carbon
chain---------------------------------
41
Kerosine--------------------------------------
7
Carbon monoxide
----------------------------
97
Ketones-------------------------------------
73
Combustion equations--------------------
21,
117
Contact
time_---------------------------------4
L
Cool flames
----------
------------------------
28
Layering
-------
------------------------------
3
Copper
acetylide ------------------------------
56 Le Chatelier's
law -----------------------------
31
Critical CIN----------------------------------11
Limits
of
flammability
-------------------------
2
Cyclopropane
---------------------------------
64 Liquid mixtures
-------------------------------
31
Lower
limit ----------------------------------
2
D
Low
pressure
limits -------------------------
12,89
n-Decane----------------------------------
21,25
Decane-dodecane blends
---------------------
32,
43
M
Deco.nposition--------------------------------
5A
Methane
-------------
----------------------
9,21
Deflagration
---------------------------------
15
Methyl acetylene
--- _--------------------------5)
Detonation --------------------------------
16,
57
Methyl
alcohol
---------------------------
-
6i)7
Dimethyl
ether -------------------------------
70
Methyl bromide-------------------------
--- 21N,
1
n-Dodccane
-------------------------------
21,25
3-Methyl
butene-1 ----------------------------
48
E
Mehyl formate
------------------------------
71
JE
Methylene
bistearamide
------------------------
7
Enigine oils -----------------------------------
95 Mlethylene
chloride--------------------------
102
Esters - -
------------------------------------
70
Minimum oxygen
value-------_.-
--.- -- ------
1
Ethane
--------------------------------
21,
25, 28
Mists
--------------------------------------
3, 6
Ethers--------------------------------------
69
M Iixer--------------------------- -----------
4,7
Eth'
alcohol
---------------------------------
67
2-Ethyl butanol ------------------------------
67
N
Ethylene-----------------------------------
48, 52 Natural
gas------------- -------------------
27,
30
F
n-Nonane
---------------------------------
21, 25
Flame arrestors
-------------------------------
18
0
Flame caps
-----------------------------------
2 n-Octane ----------------------------------
21,
25
Flame
extinction
-------------
_----------------29
Flammability
characteristics
------------------- 20
Foam
---------
-------------------------------
Paraffin
hydrocarbons
-----------------------
2(0,
3
Formic
acid
------------
----------------------
61 n-Pentadecane
----------
----------------------
21
Freon-12 ------------------------------------
69
?entane-----------------------
-------------- 24
Fuel-air ratio --------------------------------- 21 n-Pentane ------------------------------ 21, 25,
33
Fuel blends ----------------------------------
74 Perfluo-ometha---
--------------------------
28
Perfluoropropane
-----------------------------
28
G
Peroxides-------------------------------
53, 70, 103
Gas freeing---------------------------------
13
Predetonation
distance----------------------
57
Gas
mixtures
---------------------------------
3
Pressure piling -
- - ----------------------------
58
Gasoline----------------------------------
13, 82
Propadiene --------------
--------------------
48
120
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SUBJECT
INDEX
121
Page
Page
Propane
..........................
-------
1, 25, 31 Sulfw
compounds
-----.
. . . . . 74
Isopropyl
alcohol ----------........ ..........
115
Sulfur hexafluoride ------......................
28
n-irropyl
alcohiol
-----------------------------
67
n-Propyl
nitrate
-------.---------------------
97
T
Propylene
----------.------------------------
48,51 Temperature
limit ---------------------------
11
n-Tctradecane
----------------------....-
---- 21
Q
Tetralin ------------------------------------
7
Time
delay-
........
..--------
4
Quantity-distance
relationships
---------------
95
Town gas--------------.------------------
19
Triangular
diagram--------------------------
9
Trlchloroethylene
-----------------------------
102
R
n-Tridecane---------------------------------
21
Raoult's
law-----------.--------------------
31
Tube
diameter
------------------------- 3,53,57
Rectangular diagra
------------------------
9
Rc.gression
rate- -..------.--------------------
44
U
Relief
diaphragms
--------------------------
18 n- Undecane
------------------------------
21
Unsaturated
hydrocarbons
...---------------
47
S
Upper
limit
--------------------------
2, 23,
26
Shock
wave -------------------------------
17
W
Spark-energy requirements
-------------------
3
Wall
quenching -----------------------------
3
Spontaneous
ignition --------------------------
3
Spray injection -----------------------------
97
X
Sprays ..---------------------------
------
6
o-Xylene
-----------------------------------
60