Heating asphalt binder always constitutes some degree of hazard, with the exception perhaps of emulsions. The most hazardous are cutback asphalts because of the highly volatile solvents used. Extreme care must be taken not to allow open flames to come in contact with the cutback asphalt or the gases from hot cutback asphalt. When working with asphalt cement, the major safety concern is related to the high temperature of the binder. Contact with asphalt cement at 300°F will cause severe burns.

When switching from one type of asphalt binder to another in the same asphalt distributor, thoroughly flush or clean out the previous binder from the system. This will minimize contamination of the new binder and enhance safety of the seal coat operation. When switching from emulsion to AC, the distributor should not be filled to more than half full for the first two or three asphalt shots to minimize foaming and possible overflow via the manhole of the tank. Emulsion in the spray bar is sufficient to cause foaming and tank overflow when the hot asphalt cement is circulated through the spray bar. Switching from cutback asphalt to AC can create a potential explosion hazard, and extreme caution should be exercised.

The distributor must be filled from the heater unit, booster tank, asphalt storage tank, or transporter as shown in Figure 8‑5.

When the distributor is full, the number of gallons must be recorded. A strap stick should be used to measure the gallons as described in .

The asphalt temperature in the distributor must be checked to ensure that it is within the recommended application temperature range. If the temperature is low, the operator should light the burners of the heater unit and start the pump to circulate the asphalt through the pipes. It is also important for the spray bar to be hot. Circulating the asphalt through the system should heat the bar adequately.

The operator should increase the pump speed to make certain the correct pressure is set for the asphalt to be applied. This is important on the first shot of the project, even though the distributor was inspected earlier. It should also be done on the first shot each morning.