automatically correct the height of the spray bar, as this
change occurs.
The uniform application of asphalt prime and tack
coat is essential.
Transverse spread should not be
allowed to vary more than 15 percent, and the
longitudinal spread should not vary more than 10
percent. To ensure the correct application, you must
calibrate the distributor before it is used. Then the
transverse and longitudinal spread rate variations should
be checked periodically to determine when the
distributor is operating within these limits. A procedure
for checking these spread variations in the field has been
standardized by ASTM D 2995, published by the
American Society for Testing and Materials.
FILLING TANKS AND DISTRIBUTORS.—
Always use a manhole strainer when filling tanks and
distributors unless you are filling them with emulsions.
When you do not want material to enter the pump and
circulating system, ensure the intake valve lever is in the
UP position. When the tank is full of hot bitumen that
Figure 16-34.-Proper angling of nozzles.
coverage.
This height varies according to the nozzle
may set upon entering a cold pump, you should heat the
spacing of the spray bar. Under heavy wind conditions
or depending on the nozzle spacing, it maybe necessary
to lower the bar farther down so that the surface only
receives double coverage.
On some distributors, as asphalt is sprayed (and the
load lightens), the truck rear springs of the truck rise,
raising the distributor and changing the height of the
spray bar. Mechanical devices are usually available that
pump and circulating system before starting to circulate
the bitumen to prevent it from freezing in the pump. A
portable burner is available to use if the pump is cold.
When you are filling lines using a pump, always use
a strainer in the filling line except when using emulsions.
Be sure that all connections between the distributor and
source of supply are tight. Because air leaks reduce
vacuum and slow down the heavier bitumens, it may be
Figure 16-35.-Spray bar height and coverage.
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