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calibrated at 30%, 60% and 100% of the feed capacity. When calibrating bins, individual aggregate sizes are run over a belt scale until the reading appears

constant. along an format.

These points are then plotted "X" and "Y" axis in a graph Usually, tons per hour and

feeder speed percentage are the used for each leg of the graph.

values Once

the bins have been calibrated, the openings should be marked and checked frequently for movement.

gate then

Cold feed bin gate openings must be

calibrated.

Bin

calibration

is

the

responsibility of the contractor, but the AC plant inspector should be familiar

This panel controls the feed rates (TPH) of the cold feed bins manually or automatically.

with

the

calibration

charts.

Proper

calibration will insure correct proportions for the different sized aggregates being delivered to the drier drum.

AC plant inspectors should know the gradings for each individual cold feed bin. Then, if a bin change is required at the cold feed, the Plant Inspector can perform calculations using the proposed bin percentages and determine whether the new combined grading is going to work.

Feeder controls (pictured above) regulate the amount of material flowing from each bin. Each cold feed bin can be controlled by this device as well as the combined aggregate rate for all bins being used to produce any asphalt mixture.

When the aggregate stream is decreased by more than

30 percent, the paddle pictured above will drop and send a signal to the plant controller.

down

be e q u ed Each of the aggregate feeders i p p determine the rate of feed (TPH, RPM, etc.) while the plant is in full with devices must that

production. This system, when functioning properly, provides a continuous and uniform flow of aggregates to the plant.

Caltrans between

requires a device for each the troughing rollers.

belt The

feeder, which will monitor the Device, commonly referred

depth

of

aggregate

to as

a

low-flow

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