Cleaning and Grading Equipment Questions and Answers

Answer: C

Correct answer: Only three

Three pairs are right. A higher feed rate deepens the bed and lowers effectiveness; a larger open area raises capacity; and near-size sticky particles blind the apertures.

The fourth is wrong and reverses the effect. A steeper deck inclination makes material travel faster, so residence time is shorter, not longer - which raises capacity but reduces the chance for every undersize particle to find an aperture. Inclination is one of the levers by which capacity is traded against effectiveness.

Answer: D

Correct answer: Only three

Three pairs are right. Cleaning is the removal of foreign and damaged material; grading is the sorting of acceptable produce into classes; and blinding is the plugging of apertures.

The fourth is wrong. Effectiveness measures how completely each fraction is recovered - the product of oversize and undersize recovery - and is a measure of separation quality. Mass throughput per unit screen area is capacity, a quite different quantity, and the two trade against each other in operation.

Answer: A

Correct answer: Gravity table

A screen sorts on width or thickness, an indented cylinder on length, and a disc separator on length as well - all geometric dimensions. A gravity table works on density, using an upward air flow to fluidise the bed so that dense particles sink to the deck and are conveyed one way while light ones float and go the other. Size plays no part in it.

Answer: B

Correct answer: Diverging belt sizer

Cleaning removes what should not be there; grading sorts what should. An aspirator, a destoner and a magnet all remove foreign matter - chaff, stones and tramp metal respectively. A diverging belt sizer takes sound fruit and sorts it into size classes, which is grading, and it is normally placed after cleaning is complete.

Answer: C

Correct answer: A larger aperture than the feed particles

Blinding is the plugging of apertures, and it needs something that can lodge in them: near-size particles that wedge, sticky material that adheres, or fibrous trash that threads through the mesh. An aperture larger than anything in the feed cannot be plugged - though such a screen would separate nothing either, which is why aperture choice is always a compromise.

Answer: D

Correct answer: Cyclone

A cyclone handles the air leaving the aspiration system, spinning it so that the entrained dust and chaff are thrown to the wall and drop out while the cleaned air passes on to the fan. The other three all act on the grain itself - removing stones, sorting on length, or scalping off oversize trash.

Answer: A

Correct answer: Raising the feed rate well above design

Overfeeding deepens the bed on the deck, so undersize particles buried in it never reach the surface of the screen and leave with the oversize. Both recovery and effectiveness fall. The other three all help: ball trays keep the apertures clear, a shallower bed gives every particle a chance at the deck, and the right aperture shape separates on the right dimension.

Answer: B

Correct answer: The destoner or magnet

Rolls are broken by hard dense objects - stones and tramp metal - and neither is a matter of the foreign matter percentage that the trade specification measures. A single stone that passes every screen because it is grain-sized will still wreck a roll, which is why a destoner and a magnet are fitted regardless of what the analysis says.

Answer: C

Correct answer: An indented cylinder

A broken kernel is shorter than a sound one but no narrower, so a screen sorting on width or thickness passes both alike however carefully it is set. Separating them needs a machine that works on length, and that is the indented cylinder: its pockets lift the short pieces out of the bed while the long ones fall back.

Answer: D

With size and density both matched, the only remaining difference is how the particles roll, and shape separators exploit exactly that. Round seeds roll away downhill while irregular ones are carried along by the belt.