650 W. Industrial Blvd.
Cleburne, TX 76033
682-356-6200
877-664-2687
Bulk Material Handling Equipment
Orthman screw feeders control how much bulk material moves from storage into your process. Each feeder is designed around your material, required feed rate and hopper or bin outlet, then manufactured in Cleburne, Texas.
From sand and cement to grain and wood chips, the right feeder starts with understanding your application.
A screw feeder is a screw conveyor designed to meter bulk material out of a hopper, bin or silo at a controlled, repeatable rate. Because its inlet runs completely full of material, the rotating screw governs how much product leaves the opening. Changing the screw speed adjusts how much material is delivered to the next part of the process.
Common Point of Confusion
Material has to be withdrawn from a bin, hopper or silo at a controlled rate; the process needs a specific dosage; flow has to start and stop cleanly; or the material will not discharge reliably on its own and needs mechanical help at the outlet.
Material is already being delivered at a known rate and simply has to be moved from one point to another. The conveyor is sized for the load it will be handed, not for setting that load. Many systems use both — a feeder to set the rate, then a screw conveyor to move it.
Configurations
A screw with uniform flight spacing can draw material primarily from one end of a long hopper opening, leaving other areas stagnant. Stepped-pitch screw feeders increase flight spacing in defined stages along the inlet, creating additional capacity as material moves toward the discharge. When properly designed, these pitch changes encourage more even withdrawal along the hopper opening, helping reduce stagnant areas and support consistent feeding.
Cone screw feeders are particularly useful for long hopper inlets, where material needs to be drawn evenly across an extended opening. A tapered center cone decreases in diameter toward the discharge and works with progressively increasing flight pitch to create additional capacity along the inlet. When properly designed, this arrangement encourages material withdrawal along the full length of the hopper opening rather than primarily from one end, helping reduce stagnant areas and support consistent feeding.
Live bottom feeders use two, three, or four screws arranged side by side beneath a wide bin or hopper outlet. Where a single screw may leave material stagnant along the sides, multiple screws encourage withdrawal across the full width of the opening, helping reduce stagnant areas and support consistent discharge.
Orthman commonly builds live bottom feeders for wide slot outlets, large silos, and materials that do not flow reliably on their own. The number, size, and arrangement of screws are selected to match the bin outlet dimensions, material characteristics, and required feed rate.
Where They Run
Questions
A screw feeder controls the rate at which bulk material is discharged from a hopper, bin, or silo into a process. Its inlet operates flood-loaded, meaning material covers the screw beneath the vessel outlet. Screw geometry and operating speed regulate material withdrawal, while the actual feed rate also depends on the material’s density and flow characteristics.
The main differences are function and inlet loading. A screw conveyor transfers material supplied at a controlled rate and typically operates with a partly filled trough. A screw feeder withdraws material from a flood-loaded inlet and controls discharge to downstream equipment. Feeders often use shorter or changing flight pitch, lower operating speeds, and drives selected for the higher torque needed to start beneath a loaded hopper.
Feed rate is commonly adjusted by changing screw speed with a variable frequency drive (VFD). This is volumetric feeding: the amount delivered depends on screw speed, geometry, and consistent material filling. A calibrated speed setting can target a weight-based rate, but it does not automatically compensate for changes in bulk density.
Variable-pitch screw feeders increase flight spacing progressively along the inlet. Stepped-pitch screw feeders use sections of constant pitch that increase in defined stages. Both arrangements can create additional capacity toward the discharge, helping distribute material withdrawal when the pitch changes are properly positioned beneath the hopper opening.
A live bottom feeder uses two or more screws arranged side by side beneath a wide bin or hopper outlet. This arrangement helps distribute material withdrawal across the opening, reducing areas that may remain inactive with a single screw. Live bottoms are commonly used for large outlets and materials that tend to pack or bridge. Screw quantity, size, and arrangement are selected around the outlet dimensions, material characteristics, and required feed rate.
Yes, when the feeder and hopper are designed for the material. Difficult materials may require a live bottom, increasing-capacity screw geometry, a larger outlet, suitable hopper wall finishes or liners, or a dedicated agitation system.
A screw feeder alone does not guarantee that bridging or ratholing will be eliminated. Consistent feeding depends on maintaining material flow into the screws through a properly designed hopper-and-feeder arrangement.
Sizing starts with the required feed-rate range, bulk density, particle size, and material flow characteristics. Hopper outlet dimensions, material height above the inlet, feeder length, incline, and available installation space also influence the selection. Startup conditions must be considered when sizing the drive.
Send your material information, required feed-rate range, and hopper or layout drawings to Orthman’s engineering team for application review and sizing.
Send your material information, required feed-rate range, and hopper or layout drawings to Orthman’s engineering team for application review and sizing.
