In mechanical conveying classifications, which of the following is typically not listed under the division “carriers” (consider standard plant handling taxonomy)?

Introduction / Context:
Material handling devices can be grouped based on how they carry or convey bulk solids. “Carriers” commonly include equipment that physically transports material in pockets, on belts, or on pans. Knowing which equipment belongs to which category aids selection and safety analysis.

Given Data / Assumptions:

• Belt, apron, and bucket systems visibly carry material.
• Screw conveyor moves solids by internal helical conveying rather than carrying in pockets.
• Classification considered is the conventional plant operations taxonomy.

Concept / Approach:
Carriers typically feature external carrying surfaces (belt, pans, buckets). A screw conveyor transports solids using a rotating helical flight within a trough, pushing material along without discrete carriers. Thus, it is generally separated from the “carriers” subdivision.

Step-by-Step Solution:
List common carriers: belt, apron, bucket elevator.Contrast operating principle of screw conveyors (internal screw transport).Identify screw conveyor as not in the “carriers” grouping.

Verification / Alternative check:
Standard mechanical handling references group belt/apron/bucket as carriers; screws are under continuous conveyors but not “carriers.”

Why Other Options Are Wrong:
Belt/Apron/Bucket: canonical carriers.Pneumatic conveyor: not a mechanical carrier but not among the provided main “carrier” examples; however, the asked exclusion among listed mechanicals is the screw conveyor.

Common Pitfalls:
Confusing generic “conveyor” with the narrower term “carrier.”

Final Answer:
Screw conveyor