Cleaning and Grading Equipment Questions and Answers

Answer: C

Correct answer: It is caused by oversized apertures

This is the false statement. Blinding needs something able to lodge in the aperture, so it is near-size particles, damp material and fibrous trash that cause it; an aperture too large for anything in the feed cannot plug at all. The other three statements are correct, including the use of ball trays beneath the deck as the standard remedy.

Answer: D

Correct answer: Raising the feed rate well above design capacity

Overfeeding deepens the bed so that undersize particles never reach the deck, and both recovery and effectiveness fall - it is the classic way of trading effectiveness for throughput. The other three all improve the separation: a shallower bed, an aperture shape matched to the dimension being sorted, and devices that keep the apertures open.

Answer: A

Correct answer: Stones the same size as the grain

An air screen cleaner separates on size and on terminal velocity, and a grain-sized stone matches the grain in the first and exceeds it in the second, so neither the screens nor the aspiration will take it out. It needs a destoner, which works on density. The other three all differ from sound grain in size or in aerodynamic behaviour.

Answer: B

Correct answer: Wrong: sound grain goes with it

The air velocity has to sit between the terminal velocity of what is to be removed and that of what is to be kept. Raising it above the grain’s own terminal velocity lifts the grain as well, so the chaff is certainly removed but so is the product. The correct setting is a margin below the grain’s terminal velocity.

Answer: C

Correct answer: Short material is lifted and long falls back

The pockets in the drum have a chosen depth, and a particle short enough to seat fully in one is carried round and dropped into the collecting trough, while a longer one projects, catches the bed and falls back. So the short fraction is lifted out and the long fraction stays - which is how broken kernels are separated from sound ones.

Answer: D

Correct answer: A roller mill

A roller mill grinds; it belongs to the milling process that follows cleaning, not to the cleaning line itself. The other three are all cleaning machines and all standard: a scalping screen for oversize trash, an aspirator for light material, and a destoner for dense foreign matter that nothing else will remove.

Answer: A

A cyclone never handles the grain at all; it works only on the aspiration air stream and its entrained dust. Stones are the destoner's business entirely, and the other three statements in the question are perfectly correct.

Answer: B

Correct answer: Removing stones of the same size as the grain

A colour sorter examines each particle optically and rejects it with an air jet, so it is the machine for anything that differs in appearance - discoloured, mouldy or insect-damaged kernels - and for meeting a strict appearance specification. Stones are a density problem with a well-established mechanical solution, and a destoner does the job far more cheaply.

Answer: C

Correct answer: It sorts sound produce into classes

Grading and cleaning answer different questions. Cleaning removes what should not be in the lot at all; grading takes what remains and sorts it into classes by size, weight, colour or quality for sale. Grading therefore follows cleaning, and there is no point grading material that still contains trash.

Answer: D

Correct answer: Gravity feed and no moving parts

A spiral separator is a helical chute with nothing that turns or vibrates. The material is fed at the top and descends under gravity, and the separation comes from the difference between rolling and sliding as it goes: round seeds accelerate, are thrown outward and leave over the edge, while flat ones stay on the inner track. There is nothing to drive.