Destoner vs Gravity Separator: What Each Machine Actually Removes
Stones or damaged kernels? The two machines look similar and do completely different jobs. Here is the difference, why the order in the line matters, and how to test which one you need.
Buyers often ask for one machine to "clean everything". In practice stones and damaged kernels are opposite problems: one is heavier than grain, the other is lighter. No single machine separates both well, which is why a proper line has both.
The short answer
- Destoner: removes material heavier than grain — stones, glass, metal, mud balls.
- Gravity separator: removes material lighter than good grain — shrivelled, sprouted, mouldy and insect-damaged kernels.
Why the order matters
Run the destoner first. A gravity separator set for grain has a deck working with close air control, and a stone that reaches it can jam or damage the deck. Stones also wear screens and flights downstream. Removing them early protects everything after.
The usual order in a cleaning line is: intake and pre-clean (air-screen) → destoner → gravity separator → magnet → dust collection. Each stage gets easier because the previous one removed the interference.
How to tell which one you need
- Take a 1 kg sample of the grain as it arrives.
- Spread it on a white sheet and pick out everything that is not grain.
- Put the picked-out material in a glass of water. What sinks is stone-type contamination (destoner job). What floats, plus what looks like grain but is thin or discoloured, is light contamination (gravity separator job).
Most real samples contain both. That is why the answer is usually "both machines", not "one bigger machine".
Where the money goes
If your grain goes to a mill and the mill only penalises visible stones and dust, a destoner plus an air-screen cleaner may be enough. If you sell seed, or sell grain on grade and appearance, the gravity separator is what earns the premium. Spend where the price difference is decided.
For lines with moderate capacity, a single-deck gravity separator often does the job; for high capacity or strict seed standards, double deck is worth the difference.
Ask before you order
Send us a photo of the contamination on a white sheet, the material and your target cleanliness. We will tell you which machine in the line needs to change — sometimes the honest answer is that your existing machine only needs to be set up properly.
Tell us the material and the rate
Send the material, the hourly rate, the target cleanliness and the site conditions. We reply with what is still missing before a real price.
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