Asphalt Plant Cold Feed and Dosing Automation

Production in an asphalt plant starts at the cold feed bins. Aggregate fractions of different sizes are released from separate bins at set speeds onto the collecting belt and travel to the dryer drum. If this first step is set wrong, nothing downstream fully recovers: one hot bin overflows while another runs empty, weighing waits, and the plant runs below capacity. This page explains the logic of an asphalt plant dosing system and how automation keeps it in balance.

How does the cold feed work?

Each fraction has a bin and a feeder underneath it (usually a belt feeder). The feeder speed determines how much material is drawn from that fraction per hour. Feeders drop the material onto a common collecting belt, which carries the aggregate to the drum. A typical plant keeps fractions such as 0-5, 5-12, 12-19 and 19-38 mm in separate bins; their proportions follow the grading of the mix being produced.

Feeder speed and frequency control

Feeder motors are usually driven by frequency inverters. The automation sets each feeder’s speed according to the recipe proportion and the plant’s target capacity. Two points matter:

Calibration: how many tonnes per hour a given feeder speed delivers must be measured for each material. Sand and coarse aggregate carry different amounts at the same speed.
Moisture: cold aggregate is wet. Dosing is based on wet material, so proportions shift after rain and the operator needs to be able to correct the speeds.

Empty bins and material flow

When a bin runs empty or the material bridges and stops flowing, that fraction goes missing from the mix. Until the operator notices, the hot bins get out of balance. Showing empty-bin signals on screen immediately — and stopping the feed if needed — prevents faulty production.

How dosing relates to the rest of the plant

The cold feed has to match the pace of the hot side. Too much feed and the hot bins overflow and material is wasted through the screen overflow; too little and weighing waits and the batch time grows. The drum and burner also work according to how much material enters the drum. That is why dosing, burner control and the weighing system must be considered together.

Priority sequence: no gate before the belt runs

The start order in the dosing line is critical. If feeders run before the collecting belt and the drum, material piles up on the belt and the belt jams or breaks. Stopping works in reverse: feed is cut first, belts stop after they have emptied. Letting the software enforce this sequence leaves no room for the operator to forget.

How DKT APlants handles dosing

DKT APlants provides separate dosing control for the 0-5, 5-12, 12-19 and 19-38 fractions; feeder speeds are set from the screen and empty-bin signals are displayed. Thanks to the machine priority system, a machine cannot start before the machine it depends on: no gate opens before the belt runs. Every motor’s thermal fault is monitored separately.

Frequently asked questions

How are cold feed proportions determined in an asphalt plant?

By the grading of the mix to be produced. The laboratory’s mix proportions give each fraction’s share of the total; feeder speeds are set to these shares and the plant’s target capacity.

Why does dosing change after rain?

Cold aggregate is fed by volume without being weighed wet. When moisture rises, the belt carries less dry material at the same speed, so proportions and burner load need correcting.

What causes one hot bin to overflow constantly?

Usually that fraction’s cold feed exceeds what the recipe needs, or the feeder calibration has drifted. Feeder speeds and calibration should be checked.

Do I need to replace my frequency inverters?

No. The existing drives stay in place; the automation software sends speed references and run commands through the PLC.

Send us your plant’s IO list

The plant’s input/output list and PLC model are enough. We check compatibility together, set up DKT APlants for your plant and show it running in simulation. WhatsApp: +90 547 909 99 90