Cleaning and Grading Equipment Questions and Answers

Answer: A

Correct answer: Statement I is incorrect but Statement II is correct

Statement I is incorrect, and inverts the setting. The air velocity must be below the terminal velocity of sound grain, or the grain itself would be lifted and lost with the chaff.

Statement II is correct and is what makes the separation possible: chaff, dust and shrivelled grain have terminal velocities far below that of sound grain - perhaps \( 2.5 \) against \( 9.0 \) m/s - so a velocity set between the two lifts the one and leaves the other. The wider the gap, the more forgiving the setting.

Answer: B

Correct answer: Both Statement I and Statement II are correct

Both statements are correct and the second explains the first. Two fruits of identical diameter can differ appreciably in mass if one is hollow, under-filled, dehydrated or internally damaged.

A size grader, sorting on diameter alone, cannot distinguish them and passes the defective fruit into the premium class. Weight grading catches it, which is why the two methods are used together for crops where internal defects are common - and why weight grading, though slower and more complex, earns its place.

Answer: C

Correct answer: 2, 1, 3, 4

The order works from coarsest contaminant to finest. Scalping comes first (2), removing oversize trash that would blind everything downstream. Aspiration follows (1), lifting away light chaff and dust before they interfere with the screens.

Grading on sizing screens (3) then sorts the cleaned grain, and destoning (4) removes the dense foreign matter that has passed every previous stage - stones being of grain size and heavier than grain, so neither the screens nor the air can catch them.

Answer: D

Correct answer: 2, 1, 3, 4

The sequence follows a rotation of the cylinder. Seed enters the rotating cylinder (2) and forms a bed in the bottom. As the wall rises, the indents carry seeds up with it; the short ones sit fully within the indents and are lifted clear of the bed (1), while the long ones project and fall back as soon as the wall tilts (3).

The short seeds are carried further round until they too fall, into a collecting trough set at the height where only they reach (4). Trough height is the adjustment that sets the separation.

Answer: A

Correct answer: 2, 1, 3, 4

The order runs from the simplest geometric property to the most abstract. A screen separates on width (2), the most direct size measure. An indented cylinder separates on length (1), still a dimension but one no screen can address.

A gravity table separates on density (3), a bulk physical property rather than a dimension at all. A colour sorter separates on reflected light (4), a surface appearance carrying no information about size or mass. Each step addresses material the previous stage cannot distinguish.

Answer: B

Correct answer: 1, 2, 3, 4

The chain runs from operating decision to lost product. Feed rate is raised beyond design capacity (1), so the bed on the deck deepens (2).

In a deep bed the undersize particles lower down cannot reach the screen surface within their travel along the deck (3), so they leave with the oversize and effectiveness falls (4). The loss is of good material into the reject stream, which is why pushing a screen for throughput is usually a false economy.

Answer: C

Correct answer: 1, 2, 3, 4

The air follows this path. It is drawn through the falling grain curtain (1), where the separation actually happens, and the light material - chaff, dust, shrivelled grain - is entrained and carried upward (2).

The laden air passes to a cyclone, which separates the entrained material from it by centrifugal action (3), dropping the solids to a collection point. The cleaned air then passes to the fan and to discharge (4). Placing the fan last keeps the abrasive dust out of it, which matters greatly for wear.

Answer: D

Correct answer: Only three

Three pairs are right. An indented cylinder exploits length, an aspirator exploits terminal velocity, and a gravity table exploits density.

The fourth is wrong. A spiral separator exploits shape and rolling behaviour, not colour: round seeds accelerate down the helical flight and are thrown outward, while flat or irregular seeds stay on the inner track. Colour is exploited by an optical sorter, which is a quite different machine.

Answer: A

Correct answer: Only three

Three pairs are right. A destoner removes stones and dense foreign matter, a magnetic separator removes ferrous tramp metal, and a scalping screen removes oversize trash.

The fourth is wrong. A cyclone does not touch the grain stream at all: it sits in the air circuit, separating the dust and chaff that aspiration has entrained so that the material can be collected and the air discharged clean. Stones are far too heavy to be lifted by aspiration in the first place.

Answer: B

Correct answer: Only three

Three pairs are right. Round perforations sort on width, since a particle cannot turn to advantage in a round hole and its width governs. Slotted perforations sort on thickness, since a particle can present itself edge-on. Square mesh, like round holes, sorts effectively on width.

The fourth is wrong. Slots do not sort on length - a long thin particle passes a slot as readily as a short one of the same thickness. Length separation requires an indented cylinder or a disc separator.