Drum Plants Construction1 HMA Production Senior/Graduate HMA Course.

Construction 1Drum Plants

HMA Production

Senior/GraduateHMA Course

Construction 2Drum Plants

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

Construction 3Drum Plants

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

Construction 4Drum Plants

Construction 5Drum Plants

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.

Construction 6Drum Plants

Construction 7Drum Plants

Cold Feed Proportioning

Variation in material flow from individual bins:

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

minimum and maximum flow

Construction 8Drum Plants

Cold Feed Proportioning

• 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

Construction 9Drum Plants

Construction 10Drum Plants

Cold Feed Gradation Control

Many styles of feeder controls found in field.

All can perform satisfactory proportioning.

Construction 11Drum Plants

Construction 12Drum Plants

Asphalt Binder Proportioning

Asphalt binder must proportion to aggregate flow.

First step in asphalt binder proportioning is measuring aggregate flow.

Belt scale is used.

Construction 13Drum Plants

Construction 14Drum Plants

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

Construction 15Drum Plants

Construction 16Drum Plants

Construction 17Drum Plants

Asphalt Binder Proportioning

Asphalt binder must proportion to aggregate flow.

Second step is regulating asphalt binder flow.

Asphalt binder pumping / metering unit is used.

Construction 18Drum Plants

Construction 19Drum Plants

Construction 20Drum Plants

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

Construction 21Drum Plants

Construction 22Drum Plants

Plant Automation

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

Construction 23Drum Plants

Construction 24Drum Plants

QUESTIONS ?