Suggested Spraying Temperatures

Suggested spraying temperatures are given in table 16-3 for various types and grades of asphalts commonly used for prime coating and tack coating.

WARNING

Application temperatures may, in some cases, be above the flash points of some materials. Care must be given to prevent fire or _explosion. The maximum temperature (cutback asphalt) shall be below that at which fogging occurs.

Below are the formulas used for distributor truck operations.

Table 16-3.-Suggested Spraying Temperature Ranges for Prime and Tack Coat

Figure 16-36.-Hand-spray application.

To compute truck application speed ^{in feet per} minute (FPM):

To compute truck application speed in miles per hour:

To compute the length of spread in feet:

Where

^L= Length of spread in feet

^T= Total gallons in distributor

^W= Sprayed width of roadway in feet

^{ROA =} Rate of application in gallons per square yard.

ASPHALT KETTLE

The asphalt kettle shown in figure 16-37 is equipped for hand-spraying bituminous materials for dressing stretches of road or runway shoulders, filling surface cracks, and spray-coating areas for asphalt repairs, surface treatment, or seal coating.

The trailer-mounted tank consists of an outer shell with a 165-gallon capacity storage and melting tank

Figure 16-37.-Asphalt kettle.

mounted inside. A removable fuel burner, mounted inside the kettle outer shell, provides heat to the melting tank through a baffle. A flue stack located on the forward end of the melting tank over the top of the baffle and burner assembly, provides an escape for exhaust gases. A thermometer, inserted through an insulated pipe into the interior of the melting tank indicates the temperature reading of the bituminous material being heated. When the bituminous material is overheated, a fire or explosion can result.

A two-cylinder gasoline engine provides power for the bitumen pumping system. When you shift the clutch shifter lever, the engine is engaged to the pump assembly that provides the pressure for all pumping operations. A flexible, metal spray hose, which connects the pump to the hand-held spray bar assembly, is used to convey bitumen to the surface being repaired.