Shaftless Screw Conveyor Selection Guide for Palm Oil Mills

Why Shaftless Screw Conveyors for Palm Oil Mills

Palm oil milling generates large volumes of fibrous waste, including empty fruit bunch (EFB) fibers, palm kernel shells, and press cake. These materials have long, tough fibers and are often mixed with high-moisture sludge. In conventional shafted screw conveyors, the center shaft becomes a wrapping point for these fibers, leading to jams, motor overload, and frequent manual disassembly for cleaning.

Shaftless screw conveyors eliminate the center shaft and use a continuous ribbon screw blade to push material along a U-shaped trough. This design removes the wrapping point entirely. For palm oil mills that need to handle fibrous waste continuously, the shaftless configuration reduces downtime and the need for manual intervention.

Key Selection Parameters

Screw Diameter and Capacity

The WLS series offers six standard sizes with screw diameters ranging from 150mm to 500mm, covering a maximum capacity of 0.5–28 m³/h. Diameter selection should be based on the material's bulk density and design flow rate: small milling lines typically use WLS200 or WLS250 for waste discharge, while large palm oil mills conveying boiler fuel often select WLS400 or WLS500.

Conveying Distance and Inclination

A single unit can convey up to 30 meters (WLS400/WLS500 sizes) at an inclination of 0°–30°. Common layouts in palm oil mills include horizontal conveying from the press shop to the boiler silo, or inclined conveying from low-level dewatering equipment to elevated storage. When operating at an incline, actual capacity is lower than in horizontal position, so a safety margin should be included during selection.

Material Selection

Palm oil mills operate under high temperature and humidity. Boiler areas produce acidic fumes, and coastal mills face additional salt spray corrosion. Stainless steel is recommended for both the trough and screw to reduce corrosion risk and extend maintenance intervals.

Typical Layout Applications

• Boiler fuel conveying: Continuous transfer of palm kernel shells and fibers from the press shop to the boiler fuel bin
• Waste discharge: Transport of press cake and wastewater sludge to the waste handling area
• Inter-stage transfer: Bridging equipment at different elevations between process stages

Selection Considerations

1. Confirm the maximum fiber length and moisture content of the material — these are the core criteria for diameter selection.
2. When inclination exceeds 20°, consider reducing the design flow rate or selecting the next larger size.
3. Seal flange joints properly when splicing multiple sections to prevent leakage of fine material and liquid.
4. Equip the drive end with overload protection to prevent motor damage from sudden jams.
5. Coastal mills should prioritize stainless steel construction and regularly rinse salt deposits from the surface.