The vibrating screen and hot bins are what make a batch plant precise. After drying, all the aggregate is mixed together and hot. The screen splits it back into sizes, the hot bins store each size, and the scales take exactly what each batch needs.

How the system works

Step Equipment What happens
1 Hot elevator Lifts hot aggregate from the drum to the top of the tower
2 Vibrating screen Multi-deck screen separates sizes; oversize rejected
3 Hot bins Each size fraction stored in its own compartment
4 Bin gates Open to release the weight called for by the recipe
5 Aggregate scale Weighs fractions cumulatively for the batch
6 Overflow chutes Take excess from full bins away

Why it matters for quality

Stockpiles vary — from load to load, from the top of a pile to the bottom. The cold feed proportions the sizes approximately. The screen and hot bins then separate the hot aggregate again so each batch is built from measured amounts of each size. That second step is why many highway and airport specifications favor batch plants — see when a drum plant is enough.

Choosing mesh sizes

Mesh openings are chosen so the fractions match the gradation bands of your main mixes. A plant producing mainly fine wearing courses needs different decks from one producing base courses. When your main mix changes for a long period, changing meshes can improve bin balance.

Keeping the bins in balance

Symptom Likely cause What to do
One bin always overflowing Too much of that size in the cold feed Adjust cold feed proportions to the recipe
One bin running empty Too little of that size; mesh blinded Adjust feed; clean or replace mesh
Coarse material in a fine bin Hole in a mesh Replace mesh
Fines in coarse bins Blinded mesh; overloaded screen Clean mesh; check feed rate
Waiting for a bin to fill Feed out of balance Recalibrate feeders — see calibration

Overflow means heated aggregate — and the fuel used to heat it — going to waste.

Screen meshes, springs and bearings, and hot bin gates, are regular maintenance items — see hot elevator and screen maintenance.

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