Cleaning and Grading Equipment Questions and Answers

Answer: C

Correct answer: None; an optical sorter would be needed

Every mechanical separator works on some physical difference - size, length, density, shape, aerodynamic behaviour - and two fractions identical in all of them present no handle for any of these machines. What remains is appearance, so an optical or colour sorter, which examines each particle and rejects it with an air jet, is the only route.

Answer: D

Correct answer: The aspirator, at 85 of 130

The question asks for the largest share of what arrives, not the largest absolute quantity. The aspirator removes 85 kg/h of the 130 present at its inlet, about 65 per cent. The scalping screen removes more in absolute terms, 70 kg/h, but from an inlet of 200, which is 35 per cent, and the two later stages remove smaller fractions still.

Answer: A

Both rows use a four millimetre hole, but the closer pitch packs more of them into the same area and lifts capacity by a fifth. The limit on how far the pitch can be tightened is the strength left in the remaining metal.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is why the order matters. Straw, string and stems would thread through and plug the finer apertures downstream, so the coarse screen goes first to take them out while they can still be removed easily. The sequence of a cleaning line is generally coarse to fine for exactly this reason.

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the geometry. A screen presents each particle to an aperture and sorts on the dimension the aperture measures, which is width for a round hole and thickness for a slot. A broken kernel differs from a sound one in length alone, so neither aperture can tell them apart, and a length-sorting machine is required.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. Air rising through the perforated deck fluidises the bed so that the particles can move relative to one another; the dense ones then sink into contact with the deck and are carried up its slope by the vibration, while the light ones float on top and flow down. Without the air the bed would not stratify at all.

Answer: A

Correct answer: A is false but R is true

The reason is true and it defeats the assertion. Raising the feed rate deepens the bed and effectiveness falls, so beyond a point the mass of undersize actually recovered falls too - more material is presented but a smaller fraction of it reaches an aperture. There is an optimum feed rate, and pushing past it loses product to the oversize stream.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the design rule. Dust and chaff are abrasive and would erode an impeller running at high tip speed, so the cyclone is placed on the suction side to take the particles out before the air reaches the fan. The fan then handles clean air, and its life is measured in years rather than months.

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the cause. A spiral separator is simply a helical chute: round seeds accelerate as they roll and are thrown outward over the edge into an outer collector, while flat or irregular ones slide and stay on the inner track. Nothing moves but the material, so there is no motor and nothing to wear.

Answer: D

The reason is correct and it condemns the assertion: above the grain's own terminal velocity the product is carried away with the trash. The setting must sit somewhere between the two terminal velocities and nowhere else.