Vibrating Screen Deck Capacity and Feed Check

Capacity is a base rate times a chain of correction factors, and because the chain is multiplicative the errors compound rather than average. An 8 by 20 ft deck at 3.5 TPH per square foot, with an oversize factor of 1.10, a halfsize factor of 1.15, a second-deck factor of 0.90, wet screening at 1.25 and 0.95 for efficiency, carries a combined multiplier of 1.352 and a capacity of 757 TPH. Feed it 400 TPH and it is at 53% -- so oversize in the product is not an area problem and the crew should look elsewhere. WATCH HOW THE FACTORS COMPOUND. Drop the halfsize factor from 1.15 to 0.80 -- which is what happens when the crusher upstream is set tighter and the feed loses its fines -- and capacity falls to 527 TPH, a 30% loss from one factor. The screen did not change; the feed did. That is why a deck comfortable on one gradation blinds and floods on another from the same pit. And when a deck IS over capacity, the bed is too deep for particles to reach the wire: the symptom is oversize in the product with no mechanical fault anywhere, and knowing that stops a crew chasing stroke, slope, and wire tension for a problem none of them can fix. A capacity estimate using the multiplicative factor method. The base capacity and every factor come from the screen manufacturer's published tables and differ between manufacturers and between media types; this does not ship them and results are only as good as the values entered. It does not size the drive, select stroke, speed, or slope, choose screen media, or evaluate blinding and pegging, which are material-property problems -- clay, moisture, flaky particles, near-size material -- that no capacity formula predicts. It does not compute screening efficiency or the recirculating load in a closed circuit, both of which change the tonnage the deck actually sees, and structural capacity and the deck's rated load are separate limits. The screen manufacturer's selection data and the plant designer govern.

capacity TPH = screen area x base capacity for the opening x the PRODUCT of the oversize, halfsize, deck position, wet screening and efficiency factors; the area a feed requires = feed rate / (base capacity x the combined multiplier).

The multiplicative factor method by name. Every factor and the base capacity come from the screen manufacturer's published tables, differ between manufacturers and media types, and are entered rather than shipped. The manufacturer's selection data and the plant designer govern.

Multiplication on factors the user reads off the manufacturer's tables; no capacity table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: deck_width_ft, deck_length_ft, base_capacity_tph_per_sqft, oversize_factor, halfsize_factor, deck_factor, wet_factor, efficiency_factor, actual_feed_tph, screen_area_sqft, combined_multiplier, capacity_tph, percent_of_capacity, area_required_sqft

• The factors multiply, so errors compound and the halfsize and oversize factors dominate the chainscreen manufacturer data
• Oversize with no fault is an AREA problem the bed is too deep for particles to reach the wirescreening practice
• A tighter crusher can starve a screen fewer fines is a lower halfsize factor and a large capacity lossscreening practice