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 may set upon entering a cold pump, you should heat the 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.

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 particular unit.

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 up.

WARNING

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.

Spraying

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.

Attachments

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 16-36. This equipment must be operated following the instructions, given in the manufacturer's manual.