necessary to preheat the circulating system to ensure that
the first material to enter the pump is not to be chilled
sufficiently to stop the pump. A portable burner is
available for this purpose. An opening in the circulating
system housing at the rear, near the bottom of the
housing, is provided for the burner.
Normally, 150 gallons per minute (gpm) is the best
loading speed. Light materials or heavy materials at
spraying temperature may be loaded at faster pump
speeds. Check the filling line as well as the pump
discharge strainer periodically and clean as needed.
When the distributor is to be filled with hot bitumen,
proceed cautiously if there is any moisture in the tank or
if emulsion was used in the previous load because
foaming could occur. A liquid compound, Dow Corning
DC-200, can be used to prevent foaming.
HEATING BITUMEN IN THE DISTRIBU-
TOR. When you are heating bitumen in a distributor
with low-pressure atomizing burners, using clean,
moisture-free fuel is important; therefore, use kerosene,
fuel oil, or diesel fuel. DO NOT USE GASOLINE. To
start the blower, disengage the engine clutch, engage the
blower drive clutch, then engage the engine clutch.
Air pressure should be sufficient to raise the air
relief valve slightly. Excessive engine speed will raise
the relief valve too much. The correct air pressure to
use is 1 1/2 to 2 psi.
Fuel pressure should not be excessive. High fuel
pressure will make the needle valve adjustments more
sensitive. The correct fuel pressure to use is 10 to 20
psi. Pressure is determined by a relief valve, located
under the fuel tank. An adjusting screw and locknut are
inside the dome-shaped cap.
Do not light the burners unless you are sure the flues
are covered with 6 inches of material the full length of
the tank. On tanks having high-low flues, it is necessary
to cover only the lower flue when using the lower burner.
Open the stack cover.
To light the burners, you should turn the air butterfly
valves to the START position, light the torch, and hold
it under the burner tip.
Then turn the valve about
one-half turn. The burner should ignite immediately. If
it does not, turn off the needle valve and wait until the
gas is exhausted from the flues, then try again.
NOTE: The correct amount to turn the needle valve
is determined by the fuel pressure. Experience is the
only way you can determine the correct amount for a
At first, the flame will be yellow and smokey.
Adjust the fuel valve so that the flame is bright orange
with slight color in the exhaust. More adjustment to the
fuel will be needed as the flues and tank contents heat
When the burner goes out, you should turn
off the fuel valve immediately and do NOT
attempt to relight until the gas vapors are
exhausted from the flues.
For larger flames, increase the air butterfly valve
opening and the fuel valve opening in equal increments.
Always keep a mix that produces an exhaust that has a
slight color. The nozzle of the burner is adjustable for
the amount of secondary air desired. Light the burner
and turn this nozzle until you secure the type of flame
you desire. Further adjustment is not necessary. Do
NOT leave the burners unattended. Do NOT heat to a
temperature over the maximum spraying temperature
recommended by the supplier. To shut off the burners,
turn the fuel off before stopping the blower or turning
off the air.
Correct spraying cannot be obtained unless the
bitumen is heated to the proper spraying temperature.
When using 1/8-inch nozzles, set the governor from 120
to 180 gpm for a 12-foot spray bar. In the NCF, a rule
of thumb for GPM is 10 gallons per minute for every
foot of bar length. Example: 10-foot bar length =
10 GPM. Higher pump speeds cause excessive fogging
of the spray. Lower pump speeds cause the bitumen
spraying fan, as shown in figure 16-33, to sag with heavy
edges. Also, when the fans have heavy edges, the cause
could be that the material is too cold or the pump speed
is too slow.
At the end of the day, be sure to flush out the pump
and circulating system. Performing this easy draining
and cleaning operation prevents the pump and
circulating system from clogging up because of bitumen
setting up and hardening in the system.
Some areas cannot be reached with the spray bar;
therefore, it is sometimes necessary to apply asphalt by
another means. In such cases, spraying can be done by
hand with a spray hose and gun, as shown in figure