Definition of screen efficiency in particle sizing\nIn industrial screening, “screen efficiency” is best described as which of the following?

Introduction / Context:
Screen efficiency is a key performance metric for sizing operations in mining, aggregates, and chemicals. While different texts present slightly different forms (sometimes defining “effectiveness” using both streams), the most common, practical definition of efficiency focuses on the recovery of the desired size class to its designated product stream.

Given Data / Assumptions:

• A single-deck screen separates undersize (through) and oversize (retained).
• “Undersize” is the material smaller than the screen aperture.

Concept / Approach:
Efficiency may be defined for either stream. The most often used is the undersize recovery: the mass of true undersize in the undersize product divided by the total mass of true undersize in the feed, expressed as a percentage. This captures the screen’s ability to pass the material that should pass. A complementary metric is oversize recovery to oversize (rejection), and a combined measure sometimes called “effectiveness” considers both simultaneously. However, the question asks specifically for “screen efficiency,” for which the undersize recovery definition is the standard in many QA calculations.

Step-by-Step Solution:

Verification / Alternative check:
Plant data sheets and vendor performance guarantees commonly specify minimum undersize recovery (efficiency) at given feed conditions and apertures.

Why Other Options Are Wrong:

• Rejection concerns the oversize stream; useful but not the usual “efficiency” in QA sheets.
• Recovery/rejection or averages are not standard definitions and can mislead.
• “None” is incorrect because a clear, accepted definition exists.

Common Pitfalls:
Confusing “efficiency” with “effectiveness” (which blends both recoveries); always state which stream you are referencing.

Final Answer:
Recovery: percentage of undersize material correctly reporting to the undersize stream