Gravity-fed vibratory screeners receive material from above through a hopper or chute and are the standard choice for approximately 85% to 90% of screening applications. Inline pneumatic screeners are installed directly in pneumatic conveying lines and are the right choice when material is already being moved by air pressure or vacuum and breaking the conveying line would add unnecessary cost or complexity.
The feeding method affects screener design, installation requirements, maintenance access, and cost. This guide explains both methods and provides clear guidance on when to use each.
How Does a Gravity-Fed Vibratory Screener Work?
In a gravity-fed configuration, material enters the screener from above through a center feed inlet. The material drops onto the screen surface, either directly onto the mesh or through a distribution cone that spreads it evenly. Gravity provides the downward force while the vibration motor drives horizontal and rotational movement.
Gravity-fed screeners are typically positioned below a hopper, bin, mixer, reactor, or conveyor discharge point. All ScreenerKing complete screener units--the SiftPro 18", SiftPro 24", SiftPro 30", SiftPro 48 (48"), and SiftPro 60--are designed for gravity-fed operation as standard.
How Does an Inline Pneumatic Screener Work?
An inline pneumatic screener is installed directly in a pneumatic conveying pipeline. Material arrives carried by an air stream, either under positive pressure or vacuum. The screener housing is sealed to contain system pressure. Good product passes through the screen and continues in the conveying line, while oversize material is diverted to a reject discharge.
Inline pneumatic screeners require pressure-rated housings, sealed inlet and outlet connections, pressure-relief provisions, and gaskets rated for the conveying system pressure.
How Do the Two Approaches Compare?
| Factor | Gravity-Fed Screener | Inline Pneumatic Screener |
|---|---|---|
| Material delivery | Falls by gravity from above | Carried by air stream in pipeline |
| Housing design | Standard (atmospheric pressure) | Sealed, pressure-rated |
| Dust containment | Requires lid or dust cover | Fully enclosed by design |
| Multi-deck capability | Yes (1 to 5 decks) | Usually single-deck only |
| Equipment cost | Lower | 30%-60% higher |
| Screen change time | 10-30 minutes | 20-45 minutes |
| Prevalence | 85%-90% of installations | 10%-15% (specialty) |
When Should You Choose a Gravity-Fed Screener?
Gravity-fed is the default choice. Choose it when:
- Material is available from above (hopper, bin, conveyor, process vessel)
- You have sufficient headroom for the screener below the feed point
- You need multi-deck separation (multiple fractions)
- You want the simplest, lowest-cost installation
- You are replacing an existing gravity-fed screener from Sweco, Kason, or Midwestern Industries
ScreenerKing replacement screens are available in 304 SS, 316 SS, and T-430 from 18 to 60 inches, compatible with all major round separator brands.
When Should You Choose an Inline Pneumatic Screener?
- Material is already pneumatically conveyed: Avoid the cost of breaking the line, adding a receiver, and re-entraining material.
- Floor space and headroom are severely limited: Inline screeners fit within the pipeline footprint.
- Complete dust containment is required: Fully sealed within the conveying line for hazardous or explosive powders.
- You need to screen at a specific point in a conveying system: Before packaging, after blending, or at the receiver discharge.
What About Hybrid Approaches?
Many facilities use a hybrid approach: material is pneumatically conveyed to a cyclone or receiver, then gravity-fed into a standard vibratory screener below the receiver. This uses a less expensive gravity-fed screener while keeping pneumatic conveying for transport. It also allows multi-deck separation, which is difficult with inline pneumatic screeners.
Contact ScreenerKing for help selecting the right feeding configuration for your application.
Frequently Asked Questions
What is a gravity-fed vibratory screener?
A gravity-fed vibratory screener receives material from above, typically from a hopper, bin, or conveyor. Material drops by gravity into the screener's feed inlet. This is the most common feeding method for round vibratory separators.
Can I use a standard gravity-fed screener in a pneumatic line?
No. A standard gravity-fed screener is not sealed for pneumatic pressure. Inline pneumatic screening requires a screener specifically designed for pressurized operation.
Which feeding method is more common?
Gravity feeding is used in approximately 85% to 90% of vibratory screening installations. Pneumatic inline screening is a specialty application for facilities already using pneumatic conveying.