asphalt pavement planing
Asphalt planing refers to the act of mechanically removing asphalt by way of a pavement planing machine. This description refers to an industry standard modern cold planing model, though many different sizes and types of planers exist. An asphalt cold planing or milling machine consists of the following primary components: The milling drum, the milling drum housing, the engine, the conveyor belt, water tank, crawler tracks, and operator’s platform.
The milling drum is a steel structure with replaceable carbide teeth that grind and rip into the asphalt to remove it and send it onto the conveyor. The teeth will eventually wear out with use and can even be broken if they come in contact with unseen structures such as manholes or castings. The milling drum is typically concealed by housing that covers the drum from view for safety and operation.
The following are standard specifications for an average sized crawler cold planing machine. The engine is typically a water cooled, 4-8 cylinder, 500-700 horsepower, combustible fuel-powered, engine. The capacity of the fuel tank is typically about 300-400 gallons and the machine will consume approximately 30-35 gallons an hour at full capacity. The conveyor belt is typically 2-3′ wide and can move 400-450cy per hour at peak capacity. The water tank is used to control dust and heat in the drum housing and can carry approximately 900-950 gallons of water. The crawler tracks allow such a massive and heavy piece of equipment to both move and work efficiently. The shipping weight of the machine is about 13-15 tons. The machine can mill approximately 6′-6″ wide and 12″ depth max. From the operators platform, the operator will control the milling depth, vertical and horizontal angle of the conveyor, speed of the conveyor, and speed of the machine. A typical milling crew consists of 4-6 workers; a foreman, 1-2 laborers, and 2-3 operators. The equipment typically required for an asphalt milling operation will be a cold planing machine, a sweeping machine, and a backhoe. Typically one operator can run the mill. The operator will adjust the drum to remove the material at the correct depth. He then adjusts the conveyor vertically and horizontally to unload material appropriately into the trucks in front of the machine.
After the mill makes its final pass over a surface, a backhoe operator will typically follow behind and remove any excess debris not removed by the mill. Then the sweeper will make several passes over the surface the clean and prepare the surface for tack or prime coats if the surface will receive paving. The mill must be careful for structures and obstructions in the asphalt such as manholes, castings, water and gas valve boxes, electrical pull boxes, and anything else in the way. Because the mill cannot reach these tight areas surrounding obstructions, they require additional attention after the milling work such as trimming with a small mill machine or jack hammering and removal, though most often the latter as such structures will require adjustment to meet the new pavement grade anyway.