How many stages are in a wheat cleaning line?

Nine to eleven depending on whether wet cleaning, length grading and a second scourer are included. A standard dry line has nine.

Can I skip pre-cleaning if the wheat looks clean?

No. Pre-cleaning protects the machines downstream. A single rope entering a vibrating screen can wrap a shaft and stop the line for a day.

Cluster article

Wheat Cleaning Process Flow: The Ten Stages and Why the Order Is Fixed

The complete wheat cleaning flow for a flour mill, stage by stage, with the machine at each step, the impurity each removes, and what happens when stages are reordered or omitted.

By Haiyun engineering desk Updated 2026-11-07 8 min read

Key takeaways

Ten stages in a fixed order: coarse, size, density, surface, length, wet, temper, magnets, aspiration.
Reordering two stages typically blinds a screen or sends stones into a roll.
Cleaning capacity is roughly one third of the pre-cleaning figure on the same machine datasheet.

The ten stages

#	Stage	Machine	Removes	Skip it and…
1	Intake & weighing	Weighbridge, scale	Nothing — measures	You cannot control wheat cost
2	Coarse pre-cleaning	Drum sieve	Straw, rope, cob, plastic	Ropes wrap shafts; screens blind
3	Size grading	Vibrating screen	Large and small impurities	Sand enters the destoner and reduces its efficiency
4	Density separation	Gravity destoner	Stones, glass, mud balls	Stones reach the rolls and the flour
5	Surface scouring	Horizontal scourer	Dirt, beard, smut, bacteria	Ash rises 0.03–0.06 points
6	Length grading (optional)	Indent cylinder	Broken, shrivelled, diseased kernels	Ash rises at the top end
7	Wet cleaning (optional)	Washer-destoner-dryer	Crease dirt, residue, stones	Residue limits may not be met
8	Dampening	Automatic dampener	Nothing — adds water	Bran shatters, extraction falls
9	Magnetic separation	Plate / drum magnets	Ferrous metal	Roll damage and recall risk
10	Aspiration	Aspirator	Final chaff and beard	Contaminants enter the mill

Why the order is fixed

Four physical rules govern the sequence:

Coarse before fine. Large material must leave before any fine screen, otherwise it bridges and blinds.

Dry before wet. Wet cleaning makes wheat sticky. Running a wet stream through a dry screen destroys separation.

Size before density. A destoner works on material of similar size. Un-graded wheat with large stones and fine sand cannot be stratified properly.

Magnets last. You want to catch wear particles generated by the machines upstream, not just the ones that arrived in the truck.

Cleaning versus pre-cleaning capacity

Every machine datasheet shows two numbers. On a TQLZ100×150 they are 50 t/h and 12 t/h.

The first is how fast you can scalp coarse material. The second is how fast you can actually clean. The ratio is roughly 4:1 because real cleaning requires far longer residence time on the deck.

Size on the cleaning figure. This is the most common specification error in the industry.

Where the flow differs by capacity

Capacity	Scourer passes	Length grader	Wet cleaning	Magnets
20 t/d	1	Optional	Rare	3
30 t/d	1–2	Optional	Optional	3–4
60 t/d	2	Common	Common	4–5
100 t/d	2 + brush	Standard	Standard	5–6
300 t/d+	2 + brush	Standard	Standard	6–7

Below 30 t/d most plants omit wet cleaning and length grading. Above 60 t/d both become standard because the quality delta is worth more than the capital.