necessary to preheat the circulating system to ensure thatthe first material to enter the pump is not to be chilledsufficiently to stop the pump. A portable burner isavailable for this purpose. An opening in the circulatingsystem housing at the rear, near the bottom of thehousing, is provided for the burner.Normally, 150 gallons per minute (gpm) is the bestloading speed. Light materials or heavy materials atspraying temperature may be loaded at faster pumpspeeds. Check the filling line as well as the pumpdischarge 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 orif emulsion was used in the previous load becausefoaming could occur. A liquid compound, Dow CorningDC-200, can be used to prevent foaming.HEATING BITUMEN IN THE DISTRIBU-TOR.— When you are heating bitumen in a distributorwith low-pressure atomizing burners, using clean,moisture-free fuel is important; therefore, use kerosene,fuel oil, or diesel fuel. DO NOT USE GASOLINE. Tostart the blower, disengage the engine clutch, engage theblower drive clutch, then engage the engine clutch.Air pressure should be sufficient to raise the airrelief valve slightly. Excessive engine speed will raisethe relief valve too much. The correct air pressure touse is 1 1/2 to 2 psi.Fuel pressure should not be excessive. High fuelpressure will make the needle valve adjustments moresensitive. The correct fuel pressure to use is 10 to 20psi. Pressure is determined by a relief valve, locatedunder the fuel tank. An adjusting screw and locknut areinside the dome-shaped cap.Do not light the burners unless you are sure the fluesare covered with 6 inches of material the full length ofthe tank. On tanks having high-low flues, it is necessaryto cover only the lower flue when using the lower burner.Open the stack cover.To light the burners, you should turn the air butterflyvalves to the START position, light the torch, and holdit under the burner tip.Then turn the valve aboutone-half turn. The burner should ignite immediately. Ifit does not, turn off the needle valve and wait until thegas is exhausted from the flues, then try again.NOTE: The correct amount to turn the needle valveis determined by the fuel pressure. Experience is theonly way you can determine the correct amount for aparticular unit.At first, the flame will be yellow and smokey.Adjust the fuel valve so that the flame is bright orangewith slight color in the exhaust. More adjustment to thefuel will be needed as the flues and tank contents heatup.WARNINGWhen the burner goes out, you should turnoff the fuel valve immediately and do NOTattempt to relight until the gas vapors areexhausted from the flues.For larger flames, increase the air butterfly valveopening and the fuel valve opening in equal increments.Always keep a mix that produces an exhaust that has aslight color. The nozzle of the burner is adjustable forthe amount of secondary air desired. Light the burnerand turn this nozzle until you secure the type of flameyou desire. Further adjustment is not necessary. DoNOT leave the burners unattended. Do NOT heat to atemperature over the maximum spraying temperaturerecommended by the supplier. To shut off the burners,turn the fuel off before stopping the blower or turningoff the air.SprayingCorrect spraying cannot be obtained unless thebitumen is heated to the proper spraying temperature.When using 1/8-inch nozzles, set the governor from 120to 180 gpm for a 12-foot spray bar. In the NCF, a ruleof thumb for GPM is 10 gallons per minute for everyfoot of bar length. Example: 10-foot bar length =10 GPM. Higher pump speeds cause excessive foggingof the spray. Lower pump speeds cause the bitumenspraying fan, as shown in figure 16-33, to sag with heavyedges. Also, when the fans have heavy edges, the causecould be that the material is too cold or the pump speedis too slow.At the end of the day, be sure to flush out the pumpand circulating system. Performing this easy drainingand cleaning operation prevents the pump andcirculating system from clogging up because of bitumensetting up and hardening in the system.AttachmentsSome areas cannot be reached with the spray bar;therefore, it is sometimes necessary to apply asphalt byanother means. In such cases, spraying can be done byhand with a spray hose and gun, as shown in figure16-30
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