to document the asphalt temperatures during production. Caltrans also requires, when a recording type temperature indicator is used, it shall be maintained in a working condition. Recorded data shall be retained for the duration of the contract and submitted to the Resident Engineer on request. The Plant Inspector should make it a habit to examine each day’s record for excessive temperatures and report any concerns to the Resident Engineer.
Asphalt Metering Systems The asphalt meter measures the liquid asphalt flow and nothing else. Asphalt pumps move the asphalt through the piping to the mixer. The control valve adjusts the rate of flow after receiving a signal from the controller telling it to do so. The asphalt meter must automatically compensate for changes in asphalt temperature (i.e., temperature corrected to 60 F), unless the meter is of the mass flow, coriolis effect, type. The asphalt meter must be interlocked so that the rates of feed will be adjusted automatically (at all production rates and production changes) to maintain the specified bitumen ration. The asphalt pump, piping and meter must be free of leaks. Most typically, the pump packing will be the first place to look for leaks. If the packing is leaking, the plant operator should tighten the packing flange bolts which should stop the leak. If this doesn’t help, the packing may have to be replaced and retightened multiple times until a good seal is created.
During any day’s run, the temperature of asphalt binder may not vary more than 50 F. The meter and lines shall be heated and insulated. There are many different types of asphalt meters, but only a few have been type approved for use by the State of California, Department of Agriculture, Division of Measurement Standards.
The following is a list of asphalt meters that are type approved for use in the State of California.
Brooks (Broodie) - This is an all mechanical meter and includes the automatic
temperature compensator (ATC).
A temperature corrected signal is sent
B & S Industries DigiFlow - This meter uses the same principle as an asphalt pump, but the liquid asphalt is being pushed through it. A gear on top of the unit, drives an impulse generator, which in turn sends a signal to an electronics card. The signal is electronically adjusted and temperature compensated, then displayed at the control panel. The correct specific gravity of the asphalt binder is required for this system to function properly.
Standard Havens DigiFlow - This meter utilizes the same meter as the Brooks (Brodie) B-43 meter. A gear on top of the unit, drives an impulse generator, which in turn sends a signal to an electronics card. The signal is electronically adjusted and temperature compensated, then displayed at the control panel. The correct specific gravity of the asphalt binder is required for this system to function properly.