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Varec SerieS 5000/5010 Flame arreSter
InstructIon, operatIon and maIntenance manual
cONStructION
the standard unit is constructed of a heavy
cast housing containing a removable multiplate
bank assembly with aluminum extensible
frame. a fixed 316 S.S. frame is also available.
Working pressure rating is 10 Psig (69.0 kPa).
For material selection see tables 4 and 6.
practIcal lIMItatIONS
While flame arresters decrease the possibility
of flame propagation in a system, certain
variables must be evaluated to ensure safety.
the relative fire hazard of flammable mixtures
can be judged by the upper and lower explosive
limits. these limits are expressed as percent by
volume of the gas or vapor in air. the explosive
range is that span of concentrations lying
between the lower and upper limits. the upper
limit is the point at which the mixture is too rich
to burn, i.e., contains too little oxygen to support
combustion. the broader the explosive range,
the easier it is to create an air-gas explosive
mixture. Conversely, when the explosive range
is narrow, the chance of developing a hazardous
air-gas mixture decreases.
table 1 gives the approximate limits of
flammability of some single gases, vapors
and industrial mixtures in air at common
temperatures and at atmospheric pressure.
table 1 - FlaMMabIlIty lIMIt OF gaSeS aND VapOr
limits in air pressure
product
lower
acetyldehyde
acetone
acetylene
ammonia
Benzene
Benzine
Blast furnace gas
Butadiene
Butane
Butylene
Carbon Disulphide
Carbon monoxide
Cyclohexane
Cyclopropane
Decane
ethane
ethyl-acentate
reference: Bureau of mines bulletin 503, limits of flammability of gases and vapors, 1952
WarNINg
In all cases where the ratio of upper limit/lower
limit exceeds 10, the use of flame arresters is
not recommended. Also, the presence of any O
is dangerous because of the lack of homogeneity
which is possible in gas mixtures. Any surplus of
oxygen provides the potential for rapid explosion.
OperatION
Flame arresters do not prevent ignition of
flammable mixtures, but do prevent the
propagation of a flame. the Varec 5000/5010
Series flame arresters stop flame propagation
by absorbing and dissipating heat through
the surface area of the bank sheets. Heat
is absorbed as ignited gas attempts to pass
through the small passages within the bank
assembly. this action lowers the temperature
of the gas below its ignition point and quenches
the flame.
Higher
4.1
55
ethyl-alcohol
3
11
ethyl-Bromide
2.5
81
ehtyl-Chloride
15
28
ethyl-ether
1.4
7.1
ethyl-Formate
1.1
ethylene
35
74
Furfural
2
11.5
Gasoline
1.9
8.5
Hexane
2
9.6
Heptane
1.25
44
Hydrocyanic acid
12.5
74
Hydrogen
1.3
8
Hydrogen-Sulhide
2.4
10.4
isobutane
0.8
5.4
isopentane
3
12.5
isopropyl-alcohol
2.5
9
methane
limits in air pressure
product
lower
4.3
6.7
3.8
1.9
2.7
3.1
2.1
1.4
1.2
1.2
6
4
4.3
1.8
1.4
2
5.3
2
Higher
product
19
methyl-alcohol
11.3
methyl-Chloride
15.4
methyl-ethyl-Ketone
48
methyl-Formate
13.5
methyl-Proply-Ketone
32
Natural gas
Noriane
7.6
Octane
7.5
Pentane
6.7
Propane
41
Propyl-alcohol
75
Propylene
5
Pyridine
8.4
Styrene
7.6
toluene
12
Water gas
14
Xylene
limits in air percent
lower
Higher
7.3
36
10.7
17.4
1.8
10
5.9
20
1.5
8
3.8
17
0.8
1
1.5
7.8
2.1
9.5
2.1
13.5
2.4
10.3
1.8
12.4
1.1
6.1
1.4
6.7
7
72
1
6
2
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