Screen Efficiency (Two-Product Formula)
How well a screen deck separates at its aperture, from three sieve assays.
Example
You enter
- Feed: % finer than the aperture 40
- Oversize product: % finer than the aperture 8
- Undersize product: % finer than the aperture 98
- Feed rate (short tons per hour, blank to skip) 200
You get
- Overall efficiency (%) 86.08
- Undersize recovery (%) 87.11
- Undersize stph 71.11
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeThe percent finer than the opening in the feed, the oversize, and the undersize. With 40% fines in the feed, 8% left in the oversize, and 98% in the undersize, 35.6% of the feed passes, 87.1% of the fines are recovered, 98.8% of the coarse stays on the deck, and the overall efficiency is 86.1%. Fines in the oversize are the usual loss (a short or overloaded deck, near-size grains, blinding). Dry solids. A screen; plant sampling governs.
Formula or tableWith f, o, u the fraction finer than the aperture in feed, oversize, undersize: U/F = (f - o)/(u - o); fines recovery Eu = u (f - o)/(f (u - o)); oversize efficiency Eo = (1 - o)(u - f)/((1 - f)(u - o)); overall E = Eu x Eo.
Source and editionScreen efficiency by the two-product formula, a steady-state mass balance on the fraction finer than the aperture (as in Wills' Mineral Processing Technology), by name.
Free accessA mass balance on the user's own sieve assays; no published data is bundled.
What governsEstimate. AHJ and licensed professional govern.
API field namesfeed_undersize_pct, oversize_undersize_pct, undersize_undersize_pct, feed_stph, overall_efficiency_pct, undersize_recovery_pct, undersize_stph
- Undersize split U/F = (f - o)/(u - o)mass balance; Wills
- Efficiency fines recovery x oversize efficiencyWills