Screening practice: the capacity of vibrating screens is commonly expressed in tons per (ft²·mm mesh size). What is the typical capacity range for such screens under industrial conditions?

Introduction / Context:
Vibrating screens are sized using empirical capacity charts that relate throughput to screen area and aperture (mesh size). A convenient way to normalize is tons per (ft²·mm). Familiarity with typical capacity ranges helps engineers quickly estimate screen area and select the number of decks for a given duty.

Given Data / Assumptions:

• Throughput basis: tons per (ft²·mm mesh size).
• Industrial screens with standard throw and frequency.
• Moderate moisture and near-size content; single deck assumption.

Concept / Approach:
As aperture increases (mm), capacity per area rises approximately proportionally for similar material conditions. Industrial experience places the normalized capacity within a midrange that avoids plugging and accommodates typical bed depths. Values far above that range imply unrealistic bed velocities or excessive carryover; values far below indicate inefficient use of area.

Step-by-Step Solution:
Identify the normalized metric: tons per (ft²·mm).Recall empirical range used in vendor charts: ~5–25.Choose the interval that reflects common practice without extreme assumptions.

Verification / Alternative check:
Back-of-the-envelope: If a 4 mm aperture screen handles ~60–80 t/h on ~3–4 m² area (≈32–43 ft²), normalized capacity is roughly 60 / (32*4) ≈ 0.47 t/(ft²·mm) = 9.4 when expressed per mm—consistent with the 5–25 band depending on material and setup.

Why Other Options Are Wrong:
0.2–0.8: far too low for vibrating screens in continuous service.50–100 and 100–250: unrealistically high for normalized capacity; would imply excessive carryover and poor separation.

Common Pitfalls:
Ignoring near-size fraction and moisture; both can drastically reduce effective capacity below nameplate charts, requiring derating.

Final Answer:
5 to 25