The cold feed system is where every ton of mix begins. It takes each aggregate size from its own bin and sends it, in the right proportion, to the drying drum. In a batch plant the hot screen refines the gradation later; in a drum plant, the cold feed is the only proportioning step.

The parts

Part Role
Cold bins Hold each aggregate size; loaded by wheel loader
Bin gates Set the opening height under each bin
Belt feeders Variable-speed belts that meter material out of each bin
No-flow sensors Detect an empty or bridged bin
Bin vibrators (sand bins) Help wet fines flow
Collecting belt Gathers all sizes under the feeders
Scalping screen (often) Removes oversize and debris before the drum
Inclined belt Carries aggregate up to the drum
Weighing belt (drum plants, some batch plants) Measures total flow

Number and size of bins

Plant size Typical bins
Small (60–80 t/h) 4 bins
Mid (120–160 t/h) 4–5 bins
Large (240–400 t/h) 6 bins

Our RMX-C series, for example, runs from 4 × 8 m³ on the RMX-C80 to 6 × 18 m³ on the RMX-C400. Bigger bins mean fewer loader trips and steadier feed.

How proportioning works

  1. The recipe gives the share of each size
  2. The control system calculates each feeder’s flow from the total feed rate
  3. Calibration curves convert flow to belt speed — see calibration
  4. Feeders run at those speeds; no-flow sensors watch for interruptions
  5. In batch plants, hot bin levels show whether cold feed proportions match the recipe — see screen and hot bins

Common problems

Problem Cause Fix
Sand bin stops flowing Wet fines bridging Vibrator; drier sand; cover stockpile
Hot bins out of balance Feed proportions off Recalibrate; adjust recipe feed
Oversize in the drum Contaminated stockpile Scalping screen; cleaner loading
Belts wandering Misalignment, spillage Tracking; clean-up

Good loading practice starts at the stockpile — see stockpile management.

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