Storage Engineering Questions and Answers

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both statements are correct and the second explains the first. Produce arrives from the field carrying substantial heat, and respiration roughly doubles for every ten degree rise, so warm produce consumes its reserves and ages rapidly.

Removing that field heat quickly slows respiration, water loss, ripening and microbial growth together, which is what extends storage life. The emphasis on speed is important: hours at field temperature cost days of shelf life, and the loss cannot be recovered by cooling later.

Answer: B

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

Statement I is incorrect. Fumigation depends entirely on how well the structure is sealed - a leaky store loses gas faster than it can act.

Statement II is correct and is why: the kill depends on holding a lethal concentration for the whole exposure period, which for phosphine means several days, because the gas must penetrate the bulk and reach eggs and pupae as well as adults. A partial exposure kills the susceptible individuals and leaves the resistant ones to breed, so poor sealing actively selects for resistance.

Answer: C

Correct answer: 2, 1, 4, 3

The order follows the logic of preparation. Cleaning comes first (2), because trash, fines and damaged grain carry the moisture, insect eggs and mould spores that cause trouble, and removing them also improves airflow through the bulk.

Drying to the safe moisture content follows (1), since storage stability depends on it. The store is then filled and the surface levelled (4) - levelling matters because a peaked surface gives very uneven airflow. Finally aeration cools and equalises the bulk (3), which is a continuing operation rather than a single step.

Answer: D

Correct answer: 1, 2, 3, 4

The chain begins with a local anomaly: a pocket of damp or damaged grain respires more rapidly than the surrounding bulk (1). Because grain is a poor conductor and the interstitial air moves slowly, the heat and moisture that respiration produces accumulate locally rather than dispersing (2).

The warm damp pocket is then ideal for moulds and insects, which multiply and respire in their turn (3) - a positive feedback. The spot grows, and the moisture and mould growth cause the grain to cake into a solid mass (4). Temperature probes exist to catch the sequence at step 2.

Answer: A

Correct answer: 2, 1, 4, 3

The chain follows the produce. Harvest and grading come first (2), since only sound produce is worth cooling. Precooling to remove field heat follows immediately (1) - the sooner the better, because respiration at field temperature is consuming storage life.

The produce is then held at the recommended temperature and humidity (4), and finally the cold chain must be maintained in transit (3) to the market. The last step is the one most often broken, and a break there undoes the benefit of everything before it.

Answer: B

The dose follows from the volume, the seal must be proved before the gas goes in, and the hold period is what actually kills the insects. Ventilation before re-entry is a safety requirement rather than part of the treatment.

Answer: C

Correct answer: 1, 2, 3, 4

Cost per tonne rises with the sophistication of the environmental control. A traditional farm structure (1) is cheapest, built of local materials and needing no power. An aerated bulk silo (2) adds a structure, a fan and a plenum but only a small electrical load.

A controlled atmosphere store (3) needs a gas-tight envelope with generators, scrubbers and instrumentation, and a refrigerated cold store (4) adds a complete refrigeration plant with a continuous and substantial energy demand. Each step is justified only by a commodity whose value can bear it.

Answer: D

Correct answer: Only three

Three pairs are right. Aeration controls temperature and, by removing gradients, moisture migration; fumigation controls insect infestation; and hermetic sealing controls the oxygen available to insects, since respiration in a sealed space depletes it.

The fourth is wrong. Precooling controls the temperature of harvested produce, removing field heat to slow respiration. It has nothing to do with the moisture content of grain - indeed it applies to perishables rather than to grain at all.

Answer: A

Correct answer: Only three

Three pairs are right. A bag store gives easy stock identification but costly handling, since every sack is moved individually; a metal silo is cheap and quick to erect but thermally responsive, following ambient swings closely; and a concrete silo's thermal mass evens those swings out.

The fourth is wrong, and reverses the principle. A hermetic structure must be sealed, not ventilated: its whole action depends on respiration depleting the oxygen inside, and any ventilation admitting fresh air would defeat it entirely.

Answer: B

Correct answer: Only three

Three pairs are right. The product load is the heat removed in cooling the produce from its arrival temperature; the respiration load is the metabolic heat the living produce generates; and the transmission load is heat conducted through walls, floor and roof.

The fourth is wrong. Infiltration load is heat and moisture entering with outside air through doors and openings, which is why door discipline and air curtains matter. Compressor heat is rejected outside the cold space at the condenser and is not part of the room's load at all.