Drum Plants Construction1 HMA Production Senior/Graduate HMA Course.

Construction 1Drum Plants

HMA Production

Senior/GraduateHMA Course


What you will learn….

• How gradation is controlled in a drum-mixer• How asphalt is controlled in a drum-mixer• Different styles of drum-mixers• Using RAP with a drum plant


Drum-Mix Production

Hot Mix Asphalt production characterized by:

• Gradation Control at Cold Feed• Measure aggregate flow with belt scale• Meter asphalt binder to aggregate flow• Produce HMA continuously


Cold Feed Proportioning

Composite gradation is controlled at cold feed by proportioning material from individual bins.

Gradation and quality of the individual materials is controlled at the quarry.



Variation in material flow from individual bins:

• Based on variable speed motor on belt• Adjustable manual gates help control

minimum and maximum flow



• Accomplished by calibrating the feeders• Material output is charted against belt speed

in calibration charts• Different charts are created for different gate

settings on the same feeder


Cold Feed Gradation Control

Many styles of feeder controls found in field.

All can perform satisfactory proportioning.


Asphalt Binder Proportioning

Asphalt binder must proportion to aggregate flow.

First step in asphalt binder proportioning is measuring aggregate flow.

Belt scale is used.


How a Belt Scale Works

• Weigh bridge measures weight of aggregate.• Speed sensor measures speed of belt.• “Integrator / Totalizer” calculates aggregate

flow in ton (tonnes) per hour• “Integrator / Totalizer” reports flow rate to

plant control system


Asphalt Binder Proportioning

Asphalt binder must proportion to aggregate flow.

Second step is regulating asphalt binder flow.

Asphalt binder pumping / metering unit is used.


How the Asphalt Binder Proportioning System Works

• Controls system reads wet aggregate flow from belt scale.• Controls accepts moisture content entered by operator to

establish dry flow rate of aggregate• Control system accepts target asphalt content entered by

operator.• Control system drives pumping/metering unit flow control

device.• Control system adjusts asphalt binder flow control system

based on signal received back from meter


Plant Automation

Many types of systems and levels of complexity found in the field.


QUESTIONS ?

Drum Plants Construction1 HMA Production Senior/Graduate HMA Course.

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