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CHARACTERISTICS OF GAS FUELS
Each of the four types of gas has a specific boiling point (see Figure 1-2). The
boiling point
is
referred to as the temperature where gas turns from a liquid to a gas at atmospheric pressure. If
temperatures fall below the freezing point (32˚F), the liquid will not turn into a gas, and there will
be no flame.
By itself, gas cannot be ignited. Fuel, oxygen, and heat are necessary for combustion to occur.
Remove one of these, and combustion cannot take place (see Figure 1-3).
200
100
32
– 44
–100
– 200
– 300
Zero
Butane
Propane
L.P.
Natural
Mixed
Manufactured
FahrenheitDegrees
BOILING POINT OF GAS
FUEL
OXYGEN
HEAT
THE COMBUSTION PROPERTIES
Figure 1-2
Figure 1-3
Gases will ignite at temperatures between 900˚F and 1200˚F.
A proper mixture, or ratio, of gas and air is needed to produce a flame. If the air-to-gas ratio is not
correct, incomplete combustion, or an improper flame, will result. The ratio needed to ignite natural
gas (10:1) is shown in Figure 1-4, and the ratio for L.P. gas (24:1) is shown in Figure 1-5.
Figure 1-4
Figure 1-5
1 cu.ft.
Gas
1000 BTU Heat
Natural Gas (10:1)
10 cu. ft. Air To 1 cu.ft. Gas
10 cu.ft.
Air
1 cu.ft.
Gas
1000 BTU Heat
L.P. Gas (24:1)
24 cu. ft. Air To 1 cu.ft. Gas
24 cu.ft.
Air