A Sectional Feeder System is a bulk-material feeder split into two or more independently driven sections that meter solids out of a hopper, bin, or stockpile under separate motor control. Mining concentrators and steel mills rely on it to manage wide draw-down areas where a single drive cannot pull material evenly. Each section runs on its own gearmotor and VFD, so flow rate and bed depth get tuned per lane. The result is even hopper draw-down, no rat-holing, and metered throughput from 50 to 6,000 tonnes per hour on plants like SAG mill feed circuits.
Sectional Feeder System Interactive Calculator
Vary section count, bulk density, lane width, bed depth, and pan speed to see total feeder throughput and lane draw-down change.
Equation Used
The calculator applies the article mass-flow equation to equal-width feeder sections: each lane contributes rho_b times lane width, bed depth, and pan speed, and the total is the sum of all lanes.
FIRGELLI Automations - Interactive Mechanism Calculators.
- All feeder sections are identical and run at the same speed.
- Bulk density is constant through the hopper outlet.
- Output tonnage uses 1 kg/s = 3.6 tonnes/h.
- Design speed reference is 0.30 m/s from the article range.
How the Sectional Feeder System Works
A Sectional Feeder System sits directly under a hopper outlet, stockpile reclaim tunnel, or rail-car dump pit. The deck is split — usually into 2, 3, or 4 lanes running side by side — and each lane has its own drive, its own VFD, and its own load measurement. You set a target tonnes-per-hour for the combined output, and the control system trims each section's speed to keep the hopper drawing down evenly across its full footprint.
Why bother splitting it? Because a single wide feeder pulling from a wide hopper almost never gives you mass flow. The material in front of the drive end moves first, and you get funnel flow — a rat-hole forms over the active zone, fines segregate, and the rest of the load goes stagnant. Split the feeder into independently driven sections and each lane reclaims its own column of material. The draw-down stays flat. With apron-style sectional feeders the pans are typically 1.2 to 2.4 m wide per section, running at 0.05 to 0.30 m/s. Vibratory sectional feeders run at 950 to 1500 RPM eccentric speed with 3 to 8 mm stroke per lane.
If you get the section-to-section coordination wrong you see it immediately. Run one lane 20% faster than its neighbour and the bed depth on the slow lane builds up until the feeder skirt overflows; the fast lane runs starved and its load cells read low. Belt tracking goes off on apron sections if the chain tension differs by more than about 5% side-to-side. The most common failure mode in service is a single section's VFD tripping on overload — usually because oversize material wedged between the skirt and the pan — which then cascades because the remaining sections cannot pull the missing tonnage without exceeding their own design rating.
Key Components
- Independent Section Drives: Each lane runs on its own gearmotor, typically 15 to 75 kW for apron sections and 2.2 to 11 kW for vibratory sections. The drives must be matched within ±2% on output torque rating so that under common-mode load steps no single drive saturates first.
- Variable Frequency Drives (VFDs): One VFD per section, controlling speed from roughly 10% to 100% of rated. The VFDs sit on a common fieldbus — typically Profinet or EtherNet/IP — so the master PLC can trim section speeds in 0.1 Hz increments to balance bed depth.
- Belt Weighers or Load Cells: Each section has a dedicated weigh frame measuring instantaneous tonnage to ±0.5% of full scale. Without per-section weighing you cannot close the loop on individual lane flow, and the whole point of the system collapses to a wide single feeder.
- Section Skirts and Dividers: Steel divider walls separate the lanes from the hopper opening down to the discharge. Skirt clearance to the deck must be 6 to 10 mm — too tight and fines pack and stall the section, too loose and material spills laterally between lanes and corrupts the per-section weight readings.
- Master PLC Control Logic: Runs the section-balancing algorithm. The PLC reads each lane's tonnage, compares against the setpoint, and trims VFD frequency. Loop update rate of 100 to 250 ms is typical — slower than that and the system hunts during surge events from the hopper.
- Hopper Outlet Geometry: The hopper above must be designed for mass flow with wall angles steeper than the material's effective angle of friction (typically 60 to 70° from horizontal for run-of-mine ore). A funnel-flow hopper bolted to a sectional feeder will rat-hole regardless of how well you tune the sections.
Where the Sectional Feeder System Is Used
Sectional Feeder Systems show up wherever a wide hopper or a long reclaim tunnel needs metered flow without rat-holing. The decision to go sectional usually comes down to footprint width — once a hopper outlet exceeds about 2.5 m wide, a single feeder cannot pull mass flow reliably, and you split it. Power and control complexity goes up, but you get even draw-down, accurate per-lane tonnage, and the ability to bypass a damaged lane without shutting the plant.
- Hard Rock Mining: SAG mill feed at the Newmont Boddington concentrator in Western Australia uses sectional apron feeders pulling from the coarse ore stockpile reclaim tunnel at up to 4,000 tonnes per hour.
- Steel Production: Sinter plant raw material bins at ArcelorMittal Dofasco in Hamilton use 3-section vibratory feeders to dose iron ore fines, coke breeze, and limestone into the sinter strand at controlled ratios.
- Cement Manufacturing: Clinker reclaim from longitudinal storage halls at Lafarge plants uses sectional belt feeders with 4 to 6 lanes pulling from under a 100 m long pile.
- Coal Fired Power: Coal bunker discharge at the Drax Power Station in the UK historically used sectional feeders below each mill bunker to meter pulveriser feed at 40 to 80 tonnes per hour per section.
- Grain and Agribulk: Rail-car dump pits at Cargill terminals on the Mississippi use 2-section apron feeders to reclaim wheat and corn at 600 to 1,200 tonnes per hour while keeping the pit floor clean.
- Aggregate and Quarry: Primary crusher feed at Lehigh Hanson quarries uses sectional vibrating grizzly feeders to scalp fines and meter oversize to a jaw crusher at 800 tonnes per hour.
The Formula Behind the Sectional Feeder System
The core sizing question for a Sectional Feeder System is total mass flow rate as the sum of each section's contribution. What changes across the operating range is bed depth and section speed — at the low end of the range each lane runs slow with a thin bed and you risk segregation, at the high end the bed packs deep and skirt drag dominates the drive load. The sweet spot for most mineral feeders sits at 50 to 70% of design speed with a bed depth roughly 2 to 3 times the top size of the material.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Qtotal | Total mass flow rate from all sections combined | kg/s (or tonnes/h) | lb/s (or tons/h) |
| ρb | Bulk density of the material being fed | kg/m³ | lb/ft³ |
| Wi | Width of section i | m | ft |
| hi | Bed depth on section i above the deck | m | ft |
| vi | Linear belt or pan speed of section i | m/s | ft/s |
Worked Example: Sectional Feeder System in a copper concentrator SAG mill feed circuit
A copper concentrator in northern Chile is sizing a 3-section apron feeder under a coarse ore stockpile reclaim tunnel feeding a 38-foot SAG mill. Each section is 1.8 m wide. Ore bulk density is 1,900 kg/m³. The plant wants 3,600 tonnes per hour combined nominal feed, with the ability to turn down to 50% and surge to 120% of nominal during operating swings.
Given
- ρb = 1900 kg/m³
- Wi = 1.8 m (each of 3 sections)
- hnom = 0.30 m bed depth at nominal
- vnom = 0.108 m/s pan speed at nominal
- Qtarget = 3600 tonnes/h
Solution
Step 1 — compute the per-section nominal mass flow at design speed and bed depth:
Step 2 — sum across the 3 sections to get total nominal throughput, then convert to tonnes per hour:
That lands within 0.3% of the 3,600 tonnes per hour target — good enough that you tune the final tonnage with a small VFD trim rather than re-cutting steel.
Step 3 — at the low end of the operating range, run each section at 50% speed (0.054 m/s) with bed depth dropping to roughly 0.22 m as the hopper draws thinner:
That is 37% of nominal — the mill is barely fed, and at this rate you will start seeing fines segregation on the deck because the bed is too shallow to keep coarse and fines mixed. Run here only during plant ramp-up, not steady state.
Step 4 — at the high end push to 120% speed (0.130 m/s) with bed packing up to about 0.36 m:
You can hit it on the math, but skirt drag rises with bed depth squared, and at 0.36 m you are within 50 mm of the apron deflection limit on a 1.8 m wide pan. Run there for surge handling, not as a continuous setpoint, or you will be replacing chain links inside 6 months.
Result
Nominal combined throughput is 3,590 tonnes per hour across all 3 sections — effectively the 3,600 tonnes per hour target. At the low-end 50% setpoint each lane delivers around 440 tonnes per hour with thin bed and noticeable fines segregation, while at the 120% surge setpoint the system reaches roughly 5,180 tonnes per hour but with skirt drag and apron deflection both running near their limits. If you measure 3,200 tonnes per hour when the calculation says 3,590, look first at bed depth — a 0.27 m bed instead of 0.30 m drops you exactly into that range and usually means hopper draw-down is non-uniform and one section is starving. Second cause is VFD speed mismatch where one drive is back-trimmed by the master PLC because its motor current is running 10% above the others, often from a wedged tramp rock against the section skirt. Third is bulk density drift — wet ore at 2,050 kg/m³ instead of dry 1,900 kg/m³ throws your weigh-frame calibration and the indicated tonnage reads low even though physical flow is correct.
Choosing the Sectional Feeder System: Pros and Cons
Sectional Feeder Systems compete with single wide feeders and with multiple parallel narrow feeders. The right choice depends on hopper width, required turndown, and how much you care about per-lane tonnage accuracy.
| Property | Sectional Feeder System | Single Wide Apron Feeder | Multiple Parallel Standalone Feeders |
|---|---|---|---|
| Throughput range (tonnes/h) | 50 to 6,000 | 20 to 4,500 | Sum of individual units, typically 100 to 8,000 |
| Turndown ratio | 10:1 typical | 4:1 typical | 10:1 per unit |
| Hopper draw-down uniformity | Mass flow across width up to 7 m | Funnel flow above 2.5 m width | Mass flow but with dead zones between feeders |
| Per-lane tonnage accuracy | ±0.5% with section weigh frames | ±1% total only, no per-zone data | ±0.5% per unit |
| Capital cost (relative) | 1.0× baseline | 0.6 to 0.7× | 1.3 to 1.5× including separate hopper outlets |
| Control complexity | High — master PLC + per-section VFDs | Low — single drive | Medium — independent control loops |
| Maintenance interval (chain or spring) | 8,000 to 12,000 h per section | 6,000 to 10,000 h | 8,000 to 12,000 h per unit |
| Single-point failure tolerance | Plant runs at 66% on 1 of 3 lanes down | Full plant stop | Plant runs at reduced rate per unit |
Frequently Asked Questions About Sectional Feeder System
Hunting between lanes almost always means the control loop update rate is slower than the surge frequency from the hopper. If your hopper drops a slug of material onto section 2, the lane sees a tonnage spike, the PLC trims that section down, and by the time it responds the slug has cleared and the lane is now running starved. The neighbouring section then catches the next slug and the oscillation walks back and forth.
Check your loop scan rate first. Anything slower than 250 ms on a sectional feeder will hunt under typical mining hopper surge conditions. Drop the integral gain on the per-section PID by half as a quick fix, then look at whether the hopper outlet geometry is actually delivering mass flow — funnel flow above the deck is the root cause more often than the loop tuning.
The most common cause is bulk density drift you are not accounting for. Sectional feeders are sized on a nominal density figure — say 1,900 kg/m³ — but when ore comes in wet from the stockpile after rain, density jumps to 2,050 or 2,100 kg/m³. Your motor sees the higher mass flow as higher torque demand, and one of the three drives — usually the one with the most worn chain — saturates first and trips on overload.
Put a moisture probe on the reclaim conveyor and have the PLC apply a density correction to the speed setpoint. A 10% density swing needs a 9% speed reduction to keep motor load constant.
Run the mass-flow check on each option. With 2 sections at 2.25 m width each, you are right on the edge of where funnel flow starts to develop within a single lane for typical run-of-mine ore. With 3 sections at 1.5 m width each, every lane is comfortably in mass-flow territory.
The deciding factor is usually material top size. If your top size is above about 300 mm, the 1.5 m sections start choking on bridging because the lane width is only 5× top size. Go with the 2-section design for coarse ore and accept the funnel-flow risk, or step up to 3 sections at wider 2.0 m centres with offset inlet geometry.
Yes, and this is one of the main reasons plants choose sectional in the first place. With one of three lanes locked out, you can typically run the remaining two at up to 110% of their individual rating to recover about 73% of plant tonnage. The constraint is not the feeder itself — it is the hopper above. With one lane stopped you create an asymmetric draw-down, and the material column over the dead lane goes stagnant.
Run the lockout for less than 8 hours where possible. Beyond that, the stagnant column compacts and when you restart the lane you will trip on overload pulling the consolidated material loose.
This is expected and is exactly what you bought the sectional system to detect. Identical speed never gives identical tonnage because the bed depth above each lane differs based on hopper geometry, material angle of repose, and any bridging events upstream. A 15 to 25% spread between lanes at fixed speed is normal on a fresh stockpile draw.
What you actually do is invert the logic — set the target tonnage per section, and let the PLC trim each VFD to whatever speed delivers it. If the spread exceeds 40%, then look at hopper outlet symmetry or a developing rat-hole over one section.
For 25 mm minus material, set skirt-to-deck clearance at 8 to 10 mm. The general rule is 30 to 40% of the d50 particle size, not the top size. Set it tighter than that and fines wedge between the skirt and the deck and either stall the drive or wear a groove in the skirt liner inside a few weeks.
The diagnostic check: pull the section out for inspection after 200 operating hours. If the skirt liner shows uniform polish, your clearance is right. If it shows a ploughed groove with packed fines, open the clearance by 2 mm. If material is escaping laterally between sections and corrupting your weigh data, close it by 1 mm and check again.
Cold-weather current rise on apron-style feeders comes from two places. First, the chain lubricant viscosity climbs sharply below 0 °C — most apron feeder chain greases are rated for service down to about -20 °C, and below that the chain articulates against grease that is acting more like a solid. Second, frozen fines pack into the pan articulation joints and into the head and tail sprocket pockets, adding mechanical drag.
If you are seeing a consistent 30% current rise, look at chain lubricant spec first. A switch to a synthetic chain oil rated to -40 °C typically recovers 15 to 20% of that. The remaining draw is real frozen-material drag and you handle it with sprocket pocket heaters or by running a dry-cycle at startup before introducing material.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
