lifted and the aggregate on it is weighed. This will givethe weight per square yard of aggregate being spread.ASPHALT DISTRIBUTORThe asphalt distributor (fig. 16-33) is a unitconsisting of an insulated storage and heating tank, anopen flame heating system, an asphalt pump, alow-pressure air blower, and a circulating and sprayingsystem. Power to operate the components is PTOdriven.NOTE: The operation of this truck requires theabsolute need for experienced personnel only. Mishaps,resulting in loss of man-days and equipment, are a directresult of this factor being overlooked.Heating SystemThe air blower provides low-pressure air to atomizefuel for the burners. The burners heat the tubes, locatedin the tank. An asphalt covering must be maintainedover the fire tubes to prevent them from overheating andcausing a fire or explosion. Because the distributor ismobile, care must be taken to ensure that heating isperformed in a level area that is well-ventilated and thatthe distributor truck is not moving at all and is at aCOMPLETE HALT. Whenever you are heatingcutbacks, the asphalt must be circulating at all times.This is a must to prevent any chance of volatile liquidsoverheating around the flues, which can be verydangerous.Spray SystemThe spray system consists of necessary piping, aseries of hand-operated valves to control the flow ofbitumen, and an adjustable length spray bar, capable ofproviding coverage from 4 to 14 feet wide. The spraybar may be the full-circulating or the noncirculatingtype, depending on the model of the distributor. Thespray bar may be equipped with either 1/8-inch nozzlesor 3/8-inch nozzles; the 1/8-inch nozzles are used formost applications. The application rate is controlled bythe length of the spray bar, the pump output, and theforward speed of the distributor truck.Spray Bar AdjustmentsFor normal use, the spray bar of the distributorshould be adjusted, so the vertical axes of the nozzlesare perpendicular to the roadway. Also, each nozzle onthe spray bar should be set at the same angle. The angleset for each should be between 15 degrees to 30 degreesof the horizontal axis of the spray bar (fig. 16-34) oraccording to manufacturer’s specifications. This actionprevents the fan-shaped spray patterns of the nozzlesfrom interfering with each other.Another adjustment that is essential for uniformprime or tack coat coverage is the adjustment of theheight of the spray bar. As shown in figure 16-35, thefan-shaped spray patterns from the nozzles overlap todifferent degrees, depending on the distance betweenthe spray bar and the surface to be covered. The spraybar should be set high enough, usual] y 10 to 12 inchesabove the roadway for the surface to receive tripleFigure 16-33.-Asphalt distributor.16-28
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