Belt Feeder Volumetric Capacity and Density Check

ScopeThe material sits in a hopper and the belt pulls a ribbon out from under it whose cross-section is fixed by the gate opening, so output is linear in speed -- which is what makes a feeder controllable -- and linear in the opening, which is what makes it adjustable. A conveyor, by contrast, carries whatever is put on it in a surcharged profile, and its capacity formula does not apply here at all. A 36 in feeder with an 8 in gate at 60 fpm on 100 pcf material moves 7,200 cu ft an hour, or 360 TPH. To reach 400 TPH the belt goes to 67 fpm, or the gate opens to 8.9 in at the original speed. THE DENSITY CHECK IS THE ONE WORTH RUNNING IN THE FIELD. Put 160 pcf ore through that same feeder at the same setting and it delivers 576 TPH -- 60% more tonnage with nothing touched. A feeder calibrated on one material is not calibrated on another, and a plant that changes feed and keeps the setpoint has silently changed its rate. The failure the arithmetic does not capture is RATHOLING. A feeder that draws from only part of the hopper opening creates a flow channel while the rest stays static, and the static material eventually consolidates into an arch that stops flow entirely. The fix is an interface that increases in cross-section in the direction of travel so the belt draws progressively along the whole opening, and it is a design feature rather than an adjustment. Volumetric capacity for a fixed rectangular opening. It assumes the material fills the opening uniformly and flows freely, which is exactly what does not happen with wet, sticky, or cohesive material: arching, ratholing, and flushing depend on the material's shear properties and the hopper's geometry and are resolved by a flow-properties test and a hopper design, not by this formula. The belt pull and drive power a feeder requires are much higher than a conveyor's, because the belt is shearing material under a full hopper load, and undersizing them is a common error; the Belt Feeder Load, Pull and Power calculator computes them. The feeder manufacturer, a material flow-properties test, and the plant designer govern.

Formula or tablevolumetric flow = opening width x opening height x belt speed x 60; tonnage = that volume x bulk density / 2,000; the belt speed for a target tonnage and the gate opening for it invert the same relation.

Source and editionThe metering relation for a fixed rectangular gate by name -- a FEEDER's relation, not a conveyor's surcharged-profile one. The feeder manufacturer, a material flow-properties test, and the plant designer govern.

Free accessVolume and density arithmetic on the user's own geometry and material; no manufacturer table is reproduced.

What governsEstimate. AHJ and licensed professional govern.

API field namesopening_width_in, opening_height_in, belt_speed_fpm, bulk_density_pcf, target_tph, alternative_density_pcf, volumetric_cfh, tph, required_speed_fpm, required_opening_in, alternative_tph, density_change_pct

• A feeder is not a conveyor its capacity is a fixed gate cross-section, not a surcharged profilebulk material handling practice
• Density changes tonnage with nothing touched a feeder calibrated on one material is not calibrated on anotherbulk material handling practice
• Feeder drive power is much higher than a conveyor's the belt shears material under a full hopper load; a common undersizing errorfeeder manufacturer data