The wear point of greatest concern in a pneumatic line is
Answer: A
Particles are thrown against the outer wall wherever the flow changes direction, so bends erode long before straight pipe does. Long radius bends and replaceable wear backs are the standard answers. Velocity is the other lever, since wear rises steeply with it.
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State whether the following is true or false.
Screw conveyors are well suited to abrasive materials such as quartz.
Answer: B
The flight rubs continuously against the trough and the material, so an abrasive charge wears both quickly. Belt conveyors, which carry rather than drag, are preferred where the material is hard and the distance is long.
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Respirable crystalline silica is a hazard specifically in
Answer: C
Only particles small enough to reach the deep lung cause silicosis, and they are generated by dry handling and cleaning rather than by the material at rest. Wet processing and enclosed transfer are the primary controls.
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All of the following control dust at a transfer point EXCEPT
Answer: D
Dry sweeping puts settled dust back into the air, which is why vacuum or wet methods are required instead. The other three all stop the dust being generated or capture it at source. Housekeeping method is as much a control as the plant design.
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Assertion (A): Compressed air must not be used to blow dust off clothing or plant.
Reason (R): It re-entrains settled respirable dust into the breathing zone at high concentration.
Answer: A
Both are true and the reason gives the hazard: the practice converts a harmless settled deposit into an airborne exposure in seconds, and it is prohibited in every modern dust control regime. Vacuum equipment rated for fine dust is the sanctioned alternative.
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A silo of 6 metres diameter and 12 metres cylindrical height holds a powder of bulk density 1.2 tonnes per cubic metre. Roughly what mass does the cylindrical section hold when full?
Answer: B
The volume is pi times three squared times twelve, which is about three hundred and thirty-nine cubic metres, and multiplying by one point two gives about four hundred and seven tonnes. Confusing radius with diameter is the usual error here.
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Bulk density quoted for a silo calculation should be
Answer: C
Material at the bottom of a deep silo is compressed by everything above it, so it is denser than a poured sample and much denser than the loose figure suggests. Using the wrong one underestimates both the mass stored and the wall loads.
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State whether the following is true or false.
The true density of a mineral and its bulk density in a silo are usually close to each other.
Answer: D
Bulk density counts the air between particles as well as the solid, so it is commonly between a third and two thirds of the true density. The two are used for entirely different calculations and are never interchangeable.
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First in first out stock rotation matters most for
Answer: A
A deflocculant or a prepared body that ages, or a hygroscopic salt that cakes, has a shelf life and must be used in the order received. Tonnage and price do not by themselves make rotation necessary. A dated label on every pallet is what makes the rule workable.
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Consider the following statements about bulk bag handling.
1. Bags should be lifted by all four loops together.
2. Stacked bags can lean and topple if the fill is uneven.
3. An emptied bag may be reused for a different material without cleaning.
Answer: B
The first two are correct. The third invites cross-contamination, which in a ceramic body can mean an iron speck or an unexpected flux appearing in a fired ware with no traceable cause. A bag once used should be marked for that material only.
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